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android / toolchain / jdk / jdk9_hotspot / refs/tags/jdk-9+181 / . / src / share / vm / gc / g1 / g1CollectedHeap.cpp
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/*
* Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "classfile/metadataOnStackMark.hpp"
#include "classfile/stringTable.hpp"
#include "classfile/symbolTable.hpp"
#include "code/codeCache.hpp"
#include "code/icBuffer.hpp"
#include "gc/g1/bufferingOopClosure.hpp"
#include "gc/g1/concurrentG1Refine.hpp"
#include "gc/g1/concurrentG1RefineThread.hpp"
#include "gc/g1/concurrentMarkThread.inline.hpp"
#include "gc/g1/g1Allocator.inline.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1CollectionSet.hpp"
#include "gc/g1/g1CollectorPolicy.hpp"
#include "gc/g1/g1CollectorState.hpp"
#include "gc/g1/g1EvacStats.inline.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1HeapSizingPolicy.hpp"
#include "gc/g1/g1HeapTransition.hpp"
#include "gc/g1/g1HeapVerifier.hpp"
#include "gc/g1/g1HotCardCache.hpp"
#include "gc/g1/g1MarkSweep.hpp"
#include "gc/g1/g1OopClosures.inline.hpp"
#include "gc/g1/g1ParScanThreadState.inline.hpp"
#include "gc/g1/g1Policy.hpp"
#include "gc/g1/g1RegionToSpaceMapper.hpp"
#include "gc/g1/g1RemSet.inline.hpp"
#include "gc/g1/g1RootClosures.hpp"
#include "gc/g1/g1RootProcessor.hpp"
#include "gc/g1/g1StringDedup.hpp"
#include "gc/g1/g1YCTypes.hpp"
#include "gc/g1/heapRegion.inline.hpp"
#include "gc/g1/heapRegionRemSet.hpp"
#include "gc/g1/heapRegionSet.inline.hpp"
#include "gc/g1/suspendibleThreadSet.hpp"
#include "gc/g1/vm_operations_g1.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.inline.hpp"
#include "gc/shared/gcTimer.hpp"
#include "gc/shared/gcTrace.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "gc/shared/generationSpec.hpp"
#include "gc/shared/isGCActiveMark.hpp"
#include "gc/shared/preservedMarks.inline.hpp"
#include "gc/shared/referenceProcessor.inline.hpp"
#include "gc/shared/taskqueue.inline.hpp"
#include "logging/log.hpp"
#include "memory/allocation.hpp"
#include "memory/iterator.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/init.hpp"
#include "runtime/orderAccess.inline.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/stack.inline.hpp"
size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
// INVARIANTS/NOTES
//
// All allocation activity covered by the G1CollectedHeap interface is
// serialized by acquiring the HeapLock. This happens in mem_allocate
// and allocate_new_tlab, which are the "entry" points to the
// allocation code from the rest of the JVM. (Note that this does not
// apply to TLAB allocation, which is not part of this interface: it
// is done by clients of this interface.)
// Local to this file.
class RefineCardTableEntryClosure: public CardTableEntryClosure {
bool _concurrent;
public:
RefineCardTableEntryClosure() : _concurrent(true) { }
bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL);
// This path is executed by the concurrent refine or mutator threads,
// concurrently, and so we do not care if card_ptr contains references
// that point into the collection set.
assert(!oops_into_cset, "should be");
if (_concurrent && SuspendibleThreadSet::should_yield()) {
// Caller will actually yield.
return false;
}
// Otherwise, we finished successfully; return true.
return true;
}
void set_concurrent(bool b) { _concurrent = b; }
};
class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
private:
size_t _num_dirtied;
G1CollectedHeap* _g1h;
G1SATBCardTableLoggingModRefBS* _g1_bs;
HeapRegion* region_for_card(jbyte* card_ptr) const {
return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
}
bool will_become_free(HeapRegion* hr) const {
// A region will be freed by free_collection_set if the region is in the
// collection set and has not had an evacuation failure.
return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
}
public:
RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
_num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
HeapRegion* hr = region_for_card(card_ptr);
// Should only dirty cards in regions that won't be freed.
if (!will_become_free(hr)) {
*card_ptr = CardTableModRefBS::dirty_card_val();
_num_dirtied++;
}
return true;
}
size_t num_dirtied() const { return _num_dirtied; }
};
void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
}
void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
// The from card cache is not the memory that is actually committed. So we cannot
// take advantage of the zero_filled parameter.
reset_from_card_cache(start_idx, num_regions);
}
// Returns true if the reference points to an object that
// can move in an incremental collection.
bool G1CollectedHeap::is_scavengable(const void* p) {
HeapRegion* hr = heap_region_containing(p);
return !hr->is_pinned();
}
// Private methods.
HeapRegion*
G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
while (!_secondary_free_list.is_empty() || free_regions_coming()) {
if (!_secondary_free_list.is_empty()) {
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
"secondary_free_list has %u entries",
_secondary_free_list.length());
// It looks as if there are free regions available on the
// secondary_free_list. Let's move them to the free_list and try
// again to allocate from it.
append_secondary_free_list();
assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
"empty we should have moved at least one entry to the free_list");
HeapRegion* res = _hrm.allocate_free_region(is_old);
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
"allocated " HR_FORMAT " from secondary_free_list",
HR_FORMAT_PARAMS(res));
return res;
}
// Wait here until we get notified either when (a) there are no
// more free regions coming or (b) some regions have been moved on
// the secondary_free_list.
SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
}
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
"could not allocate from secondary_free_list");
return NULL;
}
HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
"the only time we use this to allocate a humongous region is "
"when we are allocating a single humongous region");
HeapRegion* res;
if (G1StressConcRegionFreeing) {
if (!_secondary_free_list.is_empty()) {
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
"forced to look at the secondary_free_list");
res = new_region_try_secondary_free_list(is_old);
if (res != NULL) {
return res;
}
}
}
res = _hrm.allocate_free_region(is_old);
if (res == NULL) {
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
"res == NULL, trying the secondary_free_list");
res = new_region_try_secondary_free_list(is_old);
}
if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
// Currently, only attempts to allocate GC alloc regions set
// do_expand to true. So, we should only reach here during a
// safepoint. If this assumption changes we might have to
// reconsider the use of _expand_heap_after_alloc_failure.
assert(SafepointSynchronize::is_at_safepoint(), "invariant");
log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
word_size * HeapWordSize);
if (expand(word_size * HeapWordSize)) {
// Given that expand() succeeded in expanding the heap, and we
// always expand the heap by an amount aligned to the heap
// region size, the free list should in theory not be empty.
// In either case allocate_free_region() will check for NULL.
res = _hrm.allocate_free_region(is_old);
} else {
_expand_heap_after_alloc_failure = false;
}
}
return res;
}
HeapWord*
G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
uint num_regions,
size_t word_size,
AllocationContext_t context) {
assert(first != G1_NO_HRM_INDEX, "pre-condition");
assert(is_humongous(word_size), "word_size should be humongous");
assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
// Index of last region in the series.
uint last = first + num_regions - 1;
// We need to initialize the region(s) we just discovered. This is
// a bit tricky given that it can happen concurrently with
// refinement threads refining cards on these regions and
// potentially wanting to refine the BOT as they are scanning
// those cards (this can happen shortly after a cleanup; see CR
// 6991377). So we have to set up the region(s) carefully and in
// a specific order.
// The word size sum of all the regions we will allocate.
size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
assert(word_size <= word_size_sum, "sanity");
// This will be the "starts humongous" region.
HeapRegion* first_hr = region_at(first);
// The header of the new object will be placed at the bottom of
// the first region.
HeapWord* new_obj = first_hr->bottom();
// This will be the new top of the new object.
HeapWord* obj_top = new_obj + word_size;
// First, we need to zero the header of the space that we will be
// allocating. When we update top further down, some refinement
// threads might try to scan the region. By zeroing the header we
// ensure that any thread that will try to scan the region will
// come across the zero klass word and bail out.
//
// NOTE: It would not have been correct to have used
// CollectedHeap::fill_with_object() and make the space look like
// an int array. The thread that is doing the allocation will
// later update the object header to a potentially different array
// type and, for a very short period of time, the klass and length
// fields will be inconsistent. This could cause a refinement
// thread to calculate the object size incorrectly.
Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
// Next, pad out the unused tail of the last region with filler
// objects, for improved usage accounting.
// How many words we use for filler objects.
size_t word_fill_size = word_size_sum - word_size;
// How many words memory we "waste" which cannot hold a filler object.
size_t words_not_fillable = 0;
if (word_fill_size >= min_fill_size()) {
fill_with_objects(obj_top, word_fill_size);
} else if (word_fill_size > 0) {
// We have space to fill, but we cannot fit an object there.
words_not_fillable = word_fill_size;
word_fill_size = 0;
}
// We will set up the first region as "starts humongous". This
// will also update the BOT covering all the regions to reflect
// that there is a single object that starts at the bottom of the
// first region.
first_hr->set_starts_humongous(obj_top, word_fill_size);
first_hr->set_allocation_context(context);
// Then, if there are any, we will set up the "continues
// humongous" regions.
HeapRegion* hr = NULL;
for (uint i = first + 1; i <= last; ++i) {
hr = region_at(i);
hr->set_continues_humongous(first_hr);
hr->set_allocation_context(context);
}
// Up to this point no concurrent thread would have been able to
// do any scanning on any region in this series. All the top
// fields still point to bottom, so the intersection between
// [bottom,top] and [card_start,card_end] will be empty. Before we
// update the top fields, we'll do a storestore to make sure that
// no thread sees the update to top before the zeroing of the
// object header and the BOT initialization.
OrderAccess::storestore();
// Now, we will update the top fields of the "continues humongous"
// regions except the last one.
for (uint i = first; i < last; ++i) {
hr = region_at(i);
hr->set_top(hr->end());
}
hr = region_at(last);
// If we cannot fit a filler object, we must set top to the end
// of the humongous object, otherwise we cannot iterate the heap
// and the BOT will not be complete.
hr->set_top(hr->end() - words_not_fillable);
assert(hr->bottom() < obj_top && obj_top <= hr->end(),
"obj_top should be in last region");
_verifier->check_bitmaps("Humongous Region Allocation", first_hr);
assert(words_not_fillable == 0 ||
first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
"Miscalculation in humongous allocation");
increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
for (uint i = first; i <= last; ++i) {
hr = region_at(i);
_humongous_set.add(hr);
_hr_printer.alloc(hr);
}
return new_obj;
}
size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
}
// If could fit into free regions w/o expansion, try.
// Otherwise, if can expand, do so.
// Otherwise, if using ex regions might help, try with ex given back.
HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
_verifier->verify_region_sets_optional();
uint first = G1_NO_HRM_INDEX;
uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
if (obj_regions == 1) {
// Only one region to allocate, try to use a fast path by directly allocating
// from the free lists. Do not try to expand here, we will potentially do that
// later.
HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
if (hr != NULL) {
first = hr->hrm_index();
}
} else {
// We can't allocate humongous regions spanning more than one region while
// cleanupComplete() is running, since some of the regions we find to be
// empty might not yet be added to the free list. It is not straightforward
// to know in which list they are on so that we can remove them. We only
// need to do this if we need to allocate more than one region to satisfy the
// current humongous allocation request. If we are only allocating one region
// we use the one-region region allocation code (see above), that already
// potentially waits for regions from the secondary free list.
wait_while_free_regions_coming();
append_secondary_free_list_if_not_empty_with_lock();
// Policy: Try only empty regions (i.e. already committed first). Maybe we
// are lucky enough to find some.
first = _hrm.find_contiguous_only_empty(obj_regions);
if (first != G1_NO_HRM_INDEX) {
_hrm.allocate_free_regions_starting_at(first, obj_regions);
}
}
if (first == G1_NO_HRM_INDEX) {
// Policy: We could not find enough regions for the humongous object in the
// free list. Look through the heap to find a mix of free and uncommitted regions.
// If so, try expansion.
first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
if (first != G1_NO_HRM_INDEX) {
// We found something. Make sure these regions are committed, i.e. expand
// the heap. Alternatively we could do a defragmentation GC.
log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
word_size * HeapWordSize);
_hrm.expand_at(first, obj_regions, workers());
g1_policy()->record_new_heap_size(num_regions());
#ifdef ASSERT
for (uint i = first; i < first + obj_regions; ++i) {
HeapRegion* hr = region_at(i);
assert(hr->is_free(), "sanity");
assert(hr->is_empty(), "sanity");
assert(is_on_master_free_list(hr), "sanity");
}
#endif
_hrm.allocate_free_regions_starting_at(first, obj_regions);
} else {
// Policy: Potentially trigger a defragmentation GC.
}
}
HeapWord* result = NULL;
if (first != G1_NO_HRM_INDEX) {
result = humongous_obj_allocate_initialize_regions(first, obj_regions,
word_size, context);
assert(result != NULL, "it should always return a valid result");
// A successful humongous object allocation changes the used space
// information of the old generation so we need to recalculate the
// sizes and update the jstat counters here.
g1mm()->update_sizes();
}
_verifier->verify_region_sets_optional();
return result;
}
HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_humongous(word_size), "we do not allow humongous TLABs");
uint dummy_gc_count_before;
uint dummy_gclocker_retry_count = 0;
return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
}
HeapWord*
G1CollectedHeap::mem_allocate(size_t word_size,
bool* gc_overhead_limit_was_exceeded) {
assert_heap_not_locked_and_not_at_safepoint();
// Loop until the allocation is satisfied, or unsatisfied after GC.
for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
uint gc_count_before;
HeapWord* result = NULL;
if (!is_humongous(word_size)) {
result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
} else {
result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
}
if (result != NULL) {
return result;
}
// Create the garbage collection operation...
VM_G1CollectForAllocation op(gc_count_before, word_size);
op.set_allocation_context(AllocationContext::current());
// ...and get the VM thread to execute it.
VMThread::execute(&op);
if (op.prologue_succeeded() && op.pause_succeeded()) {
// If the operation was successful we'll return the result even
// if it is NULL. If the allocation attempt failed immediately
// after a Full GC, it's unlikely we'll be able to allocate now.
HeapWord* result = op.result();
if (result != NULL && !is_humongous(word_size)) {
// Allocations that take place on VM operations do not do any
// card dirtying and we have to do it here. We only have to do
// this for non-humongous allocations, though.
dirty_young_block(result, word_size);
}
return result;
} else {
if (gclocker_retry_count > GCLockerRetryAllocationCount) {
return NULL;
}
assert(op.result() == NULL,
"the result should be NULL if the VM op did not succeed");
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
}
}
ShouldNotReachHere();
return NULL;
}
HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
AllocationContext_t context,
uint* gc_count_before_ret,
uint* gclocker_retry_count_ret) {
// Make sure you read the note in attempt_allocation_humongous().
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
"be called for humongous allocation requests");
// We should only get here after the first-level allocation attempt
// (attempt_allocation()) failed to allocate.
// We will loop until a) we manage to successfully perform the
// allocation or b) we successfully schedule a collection which
// fails to perform the allocation. b) is the only case when we'll
// return NULL.
HeapWord* result = NULL;
for (int try_count = 1; /* we'll return */; try_count += 1) {
bool should_try_gc;
uint gc_count_before;
{
MutexLockerEx x(Heap_lock);
result = _allocator->attempt_allocation_locked(word_size, context);
if (result != NULL) {
return result;
}
if (GCLocker::is_active_and_needs_gc()) {
if (g1_policy()->can_expand_young_list()) {
// No need for an ergo verbose message here,
// can_expand_young_list() does this when it returns true.
result = _allocator->attempt_allocation_force(word_size, context);
if (result != NULL) {
return result;
}
}
should_try_gc = false;
} else {
// The GCLocker may not be active but the GCLocker initiated
// GC may not yet have been performed (GCLocker::needs_gc()
// returns true). In this case we do not try this GC and
// wait until the GCLocker initiated GC is performed, and
// then retry the allocation.
if (GCLocker::needs_gc()) {
should_try_gc = false;
} else {
// Read the GC count while still holding the Heap_lock.
gc_count_before = total_collections();
should_try_gc = true;
}
}
}
if (should_try_gc) {
bool succeeded;
result = do_collection_pause(word_size, gc_count_before, &succeeded,
GCCause::_g1_inc_collection_pause);
if (result != NULL) {
assert(succeeded, "only way to get back a non-NULL result");
return result;
}
if (succeeded) {
// If we get here we successfully scheduled a collection which
// failed to allocate. No point in trying to allocate
// further. We'll just return NULL.
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
} else {
if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
// The GCLocker is either active or the GCLocker initiated
// GC has not yet been performed. Stall until it is and
// then retry the allocation.
GCLocker::stall_until_clear();
(*gclocker_retry_count_ret) += 1;
}
// We can reach here if we were unsuccessful in scheduling a
// collection (because another thread beat us to it) or if we were
// stalled due to the GC locker. In either can we should retry the
// allocation attempt in case another thread successfully
// performed a collection and reclaimed enough space. We do the
// first attempt (without holding the Heap_lock) here and the
// follow-on attempt will be at the start of the next loop
// iteration (after taking the Heap_lock).
result = _allocator->attempt_allocation(word_size, context);
if (result != NULL) {
return result;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
"retries %d times", try_count);
}
}
ShouldNotReachHere();
return NULL;
}
void G1CollectedHeap::begin_archive_alloc_range() {
assert_at_safepoint(true /* should_be_vm_thread */);
if (_archive_allocator == NULL) {
_archive_allocator = G1ArchiveAllocator::create_allocator(this);
}
}
bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
// Allocations in archive regions cannot be of a size that would be considered
// humongous even for a minimum-sized region, because G1 region sizes/boundaries
// may be different at archive-restore time.
return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
}
HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
assert_at_safepoint(true /* should_be_vm_thread */);
assert(_archive_allocator != NULL, "_archive_allocator not initialized");
if (is_archive_alloc_too_large(word_size)) {
return NULL;
}
return _archive_allocator->archive_mem_allocate(word_size);
}
void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
size_t end_alignment_in_bytes) {
assert_at_safepoint(true /* should_be_vm_thread */);
assert(_archive_allocator != NULL, "_archive_allocator not initialized");
// Call complete_archive to do the real work, filling in the MemRegion
// array with the archive regions.
_archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
delete _archive_allocator;
_archive_allocator = NULL;
}
bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
assert(ranges != NULL, "MemRegion array NULL");
assert(count != 0, "No MemRegions provided");
MemRegion reserved = _hrm.reserved();
for (size_t i = 0; i < count; i++) {
if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
return false;
}
}
return true;
}
bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
assert(!is_init_completed(), "Expect to be called at JVM init time");
assert(ranges != NULL, "MemRegion array NULL");
assert(count != 0, "No MemRegions provided");
MutexLockerEx x(Heap_lock);
MemRegion reserved = _hrm.reserved();
HeapWord* prev_last_addr = NULL;
HeapRegion* prev_last_region = NULL;
// Temporarily disable pretouching of heap pages. This interface is used
// when mmap'ing archived heap data in, so pre-touching is wasted.
FlagSetting fs(AlwaysPreTouch, false);
// Enable archive object checking in G1MarkSweep. We have to let it know
// about each archive range, so that objects in those ranges aren't marked.
G1MarkSweep::enable_archive_object_check();
// For each specified MemRegion range, allocate the corresponding G1
// regions and mark them as archive regions. We expect the ranges in
// ascending starting address order, without overlap.
for (size_t i = 0; i < count; i++) {
MemRegion curr_range = ranges[i];
HeapWord* start_address = curr_range.start();
size_t word_size = curr_range.word_size();
HeapWord* last_address = curr_range.last();
size_t commits = 0;
guarantee(reserved.contains(start_address) && reserved.contains(last_address),
"MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
p2i(start_address), p2i(last_address));
guarantee(start_address > prev_last_addr,
"Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
p2i(start_address), p2i(prev_last_addr));
prev_last_addr = last_address;
// Check for ranges that start in the same G1 region in which the previous
// range ended, and adjust the start address so we don't try to allocate
// the same region again. If the current range is entirely within that
// region, skip it, just adjusting the recorded top.
HeapRegion* start_region = _hrm.addr_to_region(start_address);
if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
start_address = start_region->end();
if (start_address > last_address) {
increase_used(word_size * HeapWordSize);
start_region->set_top(last_address + 1);
continue;
}
start_region->set_top(start_address);
curr_range = MemRegion(start_address, last_address + 1);
start_region = _hrm.addr_to_region(start_address);
}
// Perform the actual region allocation, exiting if it fails.
// Then note how much new space we have allocated.
if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
return false;
}
increase_used(word_size * HeapWordSize);
if (commits != 0) {
log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
HeapRegion::GrainWords * HeapWordSize * commits);
}
// Mark each G1 region touched by the range as archive, add it to the old set,
// and set the allocation context and top.
HeapRegion* curr_region = _hrm.addr_to_region(start_address);
HeapRegion* last_region = _hrm.addr_to_region(last_address);
prev_last_region = last_region;
while (curr_region != NULL) {
assert(curr_region->is_empty() && !curr_region->is_pinned(),
"Region already in use (index %u)", curr_region->hrm_index());
curr_region->set_allocation_context(AllocationContext::system());
curr_region->set_archive();
_hr_printer.alloc(curr_region);
_old_set.add(curr_region);
if (curr_region != last_region) {
curr_region->set_top(curr_region->end());
curr_region = _hrm.next_region_in_heap(curr_region);
} else {
curr_region->set_top(last_address + 1);
curr_region = NULL;
}
}
// Notify mark-sweep of the archive range.
G1MarkSweep::set_range_archive(curr_range, true);
}
return true;
}
void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
assert(!is_init_completed(), "Expect to be called at JVM init time");
assert(ranges != NULL, "MemRegion array NULL");
assert(count != 0, "No MemRegions provided");
MemRegion reserved = _hrm.reserved();
HeapWord *prev_last_addr = NULL;
HeapRegion* prev_last_region = NULL;
// For each MemRegion, create filler objects, if needed, in the G1 regions
// that contain the address range. The address range actually within the
// MemRegion will not be modified. That is assumed to have been initialized
// elsewhere, probably via an mmap of archived heap data.
MutexLockerEx x(Heap_lock);
for (size_t i = 0; i < count; i++) {
HeapWord* start_address = ranges[i].start();
HeapWord* last_address = ranges[i].last();
assert(reserved.contains(start_address) && reserved.contains(last_address),
"MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
p2i(start_address), p2i(last_address));
assert(start_address > prev_last_addr,
"Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
p2i(start_address), p2i(prev_last_addr));
HeapRegion* start_region = _hrm.addr_to_region(start_address);
HeapRegion* last_region = _hrm.addr_to_region(last_address);
HeapWord* bottom_address = start_region->bottom();
// Check for a range beginning in the same region in which the
// previous one ended.
if (start_region == prev_last_region) {
bottom_address = prev_last_addr + 1;
}
// Verify that the regions were all marked as archive regions by
// alloc_archive_regions.
HeapRegion* curr_region = start_region;
while (curr_region != NULL) {
guarantee(curr_region->is_archive(),
"Expected archive region at index %u", curr_region->hrm_index());
if (curr_region != last_region) {
curr_region = _hrm.next_region_in_heap(curr_region);
} else {
curr_region = NULL;
}
}
prev_last_addr = last_address;
prev_last_region = last_region;
// Fill the memory below the allocated range with dummy object(s),
// if the region bottom does not match the range start, or if the previous
// range ended within the same G1 region, and there is a gap.
if (start_address != bottom_address) {
size_t fill_size = pointer_delta(start_address, bottom_address);
G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
increase_used(fill_size * HeapWordSize);
}
}
}
inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
uint* gc_count_before_ret,
uint* gclocker_retry_count_ret) {
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_humongous(word_size), "attempt_allocation() should not "
"be called for humongous allocation requests");
AllocationContext_t context = AllocationContext::current();
HeapWord* result = _allocator->attempt_allocation(word_size, context);
if (result == NULL) {
result = attempt_allocation_slow(word_size,
context,
gc_count_before_ret,
gclocker_retry_count_ret);
}
assert_heap_not_locked();
if (result != NULL) {
dirty_young_block(result, word_size);
}
return result;
}
void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
assert(!is_init_completed(), "Expect to be called at JVM init time");
assert(ranges != NULL, "MemRegion array NULL");
assert(count != 0, "No MemRegions provided");
MemRegion reserved = _hrm.reserved();
HeapWord* prev_last_addr = NULL;
HeapRegion* prev_last_region = NULL;
size_t size_used = 0;
size_t uncommitted_regions = 0;
// For each Memregion, free the G1 regions that constitute it, and
// notify mark-sweep that the range is no longer to be considered 'archive.'
MutexLockerEx x(Heap_lock);
for (size_t i = 0; i < count; i++) {
HeapWord* start_address = ranges[i].start();
HeapWord* last_address = ranges[i].last();
assert(reserved.contains(start_address) && reserved.contains(last_address),
"MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
p2i(start_address), p2i(last_address));
assert(start_address > prev_last_addr,
"Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
p2i(start_address), p2i(prev_last_addr));
size_used += ranges[i].byte_size();
prev_last_addr = last_address;
HeapRegion* start_region = _hrm.addr_to_region(start_address);
HeapRegion* last_region = _hrm.addr_to_region(last_address);
// Check for ranges that start in the same G1 region in which the previous
// range ended, and adjust the start address so we don't try to free
// the same region again. If the current range is entirely within that
// region, skip it.
if (start_region == prev_last_region) {
start_address = start_region->end();
if (start_address > last_address) {
continue;
}
start_region = _hrm.addr_to_region(start_address);
}
prev_last_region = last_region;
// After verifying that each region was marked as an archive region by
// alloc_archive_regions, set it free and empty and uncommit it.
HeapRegion* curr_region = start_region;
while (curr_region != NULL) {
guarantee(curr_region->is_archive(),
"Expected archive region at index %u", curr_region->hrm_index());
uint curr_index = curr_region->hrm_index();
_old_set.remove(curr_region);
curr_region->set_free();
curr_region->set_top(curr_region->bottom());
if (curr_region != last_region) {
curr_region = _hrm.next_region_in_heap(curr_region);
} else {
curr_region = NULL;
}
_hrm.shrink_at(curr_index, 1);
uncommitted_regions++;
}
// Notify mark-sweep that this is no longer an archive range.
G1MarkSweep::set_range_archive(ranges[i], false);
}
if (uncommitted_regions != 0) {
log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
}
decrease_used(size_used);
}
HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
uint* gc_count_before_ret,
uint* gclocker_retry_count_ret) {
// The structure of this method has a lot of similarities to
// attempt_allocation_slow(). The reason these two were not merged
// into a single one is that such a method would require several "if
// allocation is not humongous do this, otherwise do that"
// conditional paths which would obscure its flow. In fact, an early
// version of this code did use a unified method which was harder to
// follow and, as a result, it had subtle bugs that were hard to
// track down. So keeping these two methods separate allows each to
// be more readable. It will be good to keep these two in sync as
// much as possible.
assert_heap_not_locked_and_not_at_safepoint();
assert(is_humongous(word_size), "attempt_allocation_humongous() "
"should only be called for humongous allocations");
// Humongous objects can exhaust the heap quickly, so we should check if we
// need to start a marking cycle at each humongous object allocation. We do
// the check before we do the actual allocation. The reason for doing it
// before the allocation is that we avoid having to keep track of the newly
// allocated memory while we do a GC.
if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
word_size)) {
collect(GCCause::_g1_humongous_allocation);
}
// We will loop until a) we manage to successfully perform the
// allocation or b) we successfully schedule a collection which
// fails to perform the allocation. b) is the only case when we'll
// return NULL.
HeapWord* result = NULL;
for (int try_count = 1; /* we'll return */; try_count += 1) {
bool should_try_gc;
uint gc_count_before;
{
MutexLockerEx x(Heap_lock);
// Given that humongous objects are not allocated in young
// regions, we'll first try to do the allocation without doing a
// collection hoping that there's enough space in the heap.
result = humongous_obj_allocate(word_size, AllocationContext::current());
if (result != NULL) {
size_t size_in_regions = humongous_obj_size_in_regions(word_size);
g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
return result;
}
if (GCLocker::is_active_and_needs_gc()) {
should_try_gc = false;
} else {
// The GCLocker may not be active but the GCLocker initiated
// GC may not yet have been performed (GCLocker::needs_gc()
// returns true). In this case we do not try this GC and
// wait until the GCLocker initiated GC is performed, and
// then retry the allocation.
if (GCLocker::needs_gc()) {
should_try_gc = false;
} else {
// Read the GC count while still holding the Heap_lock.
gc_count_before = total_collections();
should_try_gc = true;
}
}
}
if (should_try_gc) {
// If we failed to allocate the humongous object, we should try to
// do a collection pause (if we're allowed) in case it reclaims
// enough space for the allocation to succeed after the pause.
bool succeeded;
result = do_collection_pause(word_size, gc_count_before, &succeeded,
GCCause::_g1_humongous_allocation);
if (result != NULL) {
assert(succeeded, "only way to get back a non-NULL result");
return result;
}
if (succeeded) {
// If we get here we successfully scheduled a collection which
// failed to allocate. No point in trying to allocate
// further. We'll just return NULL.
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
} else {
if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
// The GCLocker is either active or the GCLocker initiated
// GC has not yet been performed. Stall until it is and
// then retry the allocation.
GCLocker::stall_until_clear();
(*gclocker_retry_count_ret) += 1;
}
// We can reach here if we were unsuccessful in scheduling a
// collection (because another thread beat us to it) or if we were
// stalled due to the GC locker. In either can we should retry the
// allocation attempt in case another thread successfully
// performed a collection and reclaimed enough space. Give a
// warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
"retries %d times", try_count);
}
}
ShouldNotReachHere();
return NULL;
}
HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
AllocationContext_t context,
bool expect_null_mutator_alloc_region) {
assert_at_safepoint(true /* should_be_vm_thread */);
assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
"the current alloc region was unexpectedly found to be non-NULL");
if (!is_humongous(word_size)) {
return _allocator->attempt_allocation_locked(word_size, context);
} else {
HeapWord* result = humongous_obj_allocate(word_size, context);
if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
collector_state()->set_initiate_conc_mark_if_possible(true);
}
return result;
}
ShouldNotReachHere();
}
class PostMCRemSetClearClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
ModRefBarrierSet* _mr_bs;
public:
PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
_g1h(g1h), _mr_bs(mr_bs) {}
bool doHeapRegion(HeapRegion* r) {
HeapRegionRemSet* hrrs = r->rem_set();
_g1h->reset_gc_time_stamps(r);
if (r->is_continues_humongous()) {
// We'll assert that the strong code root list and RSet is empty
assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
assert(hrrs->occupied() == 0, "RSet should be empty");
} else {
hrrs->clear();
}
// You might think here that we could clear just the cards
// corresponding to the used region. But no: if we leave a dirty card
// in a region we might allocate into, then it would prevent that card
// from being enqueued, and cause it to be missed.
// Re: the performance cost: we shouldn't be doing full GC anyway!
_mr_bs->clear(MemRegion(r->bottom(), r->end()));
return false;
}
};
void G1CollectedHeap::clear_rsets_post_compaction() {
PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
heap_region_iterate(&rs_clear);
}
class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
UpdateRSOopClosure _cl;
public:
RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
_cl(g1->g1_rem_set(), worker_i),
_g1h(g1)
{ }
bool doHeapRegion(HeapRegion* r) {
if (!r->is_continues_humongous()) {
_cl.set_from(r);
r->oop_iterate(&_cl);
}
return false;
}
};
class ParRebuildRSTask: public AbstractGangTask {
G1CollectedHeap* _g1;
HeapRegionClaimer _hrclaimer;
public:
ParRebuildRSTask(G1CollectedHeap* g1) :
AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
void work(uint worker_id) {
RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
_g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
}
};
class PostCompactionPrinterClosure: public HeapRegionClosure {
private:
G1HRPrinter* _hr_printer;
public:
bool doHeapRegion(HeapRegion* hr) {
assert(!hr->is_young(), "not expecting to find young regions");
_hr_printer->post_compaction(hr);
return false;
}
PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
: _hr_printer(hr_printer) { }
};
void G1CollectedHeap::print_hrm_post_compaction() {
if (_hr_printer.is_active()) {
PostCompactionPrinterClosure cl(hr_printer());
heap_region_iterate(&cl);
}
}
bool G1CollectedHeap::do_full_collection(bool explicit_gc,
bool clear_all_soft_refs) {
assert_at_safepoint(true /* should_be_vm_thread */);
if (GCLocker::check_active_before_gc()) {
return false;
}
STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
gc_timer->register_gc_start();
SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
GCIdMark gc_id_mark;
gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
SvcGCMarker sgcm(SvcGCMarker::FULL);
ResourceMark rm;
print_heap_before_gc();
print_heap_regions();
trace_heap_before_gc(gc_tracer);
size_t metadata_prev_used = MetaspaceAux::used_bytes();
_verifier->verify_region_sets_optional();
const bool do_clear_all_soft_refs = clear_all_soft_refs ||
collector_policy()->should_clear_all_soft_refs();
ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
{
IsGCActiveMark x;
// Timing
assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
GCTraceCPUTime tcpu;
{
GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
TraceCollectorStats tcs(g1mm()->full_collection_counters());
TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
G1HeapTransition heap_transition(this);
g1_policy()->record_full_collection_start();
// Note: When we have a more flexible GC logging framework that
// allows us to add optional attributes to a GC log record we
// could consider timing and reporting how long we wait in the
// following two methods.
wait_while_free_regions_coming();
// If we start the compaction before the CM threads finish
// scanning the root regions we might trip them over as we'll
// be moving objects / updating references. So let's wait until
// they are done. By telling them to abort, they should complete
// early.
_cm->root_regions()->abort();
_cm->root_regions()->wait_until_scan_finished();
append_secondary_free_list_if_not_empty_with_lock();
gc_prologue(true);
increment_total_collections(true /* full gc */);
increment_old_marking_cycles_started();
assert(used() == recalculate_used(), "Should be equal");
_verifier->verify_before_gc();
_verifier->check_bitmaps("Full GC Start");
pre_full_gc_dump(gc_timer);
#if defined(COMPILER2) || INCLUDE_JVMCI
DerivedPointerTable::clear();
#endif
// Disable discovery and empty the discovered lists
// for the CM ref processor.
ref_processor_cm()->disable_discovery();
ref_processor_cm()->abandon_partial_discovery();
ref_processor_cm()->verify_no_references_recorded();
// Abandon current iterations of concurrent marking and concurrent
// refinement, if any are in progress.
concurrent_mark()->abort();
// Make sure we'll choose a new allocation region afterwards.
_allocator->release_mutator_alloc_region();
_allocator->abandon_gc_alloc_regions();
g1_rem_set()->cleanupHRRS();
// We may have added regions to the current incremental collection
// set between the last GC or pause and now. We need to clear the
// incremental collection set and then start rebuilding it afresh
// after this full GC.
abandon_collection_set(collection_set());
tear_down_region_sets(false /* free_list_only */);
collector_state()->set_gcs_are_young(true);
// See the comments in g1CollectedHeap.hpp and
// G1CollectedHeap::ref_processing_init() about
// how reference processing currently works in G1.
// Temporarily make discovery by the STW ref processor single threaded (non-MT).
ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
// Temporarily clear the STW ref processor's _is_alive_non_header field.
ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
ref_processor_stw()->enable_discovery();
ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
// Do collection work
{
HandleMark hm; // Discard invalid handles created during gc
G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
}
assert(num_free_regions() == 0, "we should not have added any free regions");
rebuild_region_sets(false /* free_list_only */);
// Enqueue any discovered reference objects that have
// not been removed from the discovered lists.
ref_processor_stw()->enqueue_discovered_references();
#if defined(COMPILER2) || INCLUDE_JVMCI
DerivedPointerTable::update_pointers();
#endif
MemoryService::track_memory_usage();
assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
ref_processor_stw()->verify_no_references_recorded();
// Delete metaspaces for unloaded class loaders and clean up loader_data graph
ClassLoaderDataGraph::purge();
MetaspaceAux::verify_metrics();
// Note: since we've just done a full GC, concurrent
// marking is no longer active. Therefore we need not
// re-enable reference discovery for the CM ref processor.
// That will be done at the start of the next marking cycle.
assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
ref_processor_cm()->verify_no_references_recorded();
reset_gc_time_stamp();
// Since everything potentially moved, we will clear all remembered
// sets, and clear all cards. Later we will rebuild remembered
// sets. We will also reset the GC time stamps of the regions.
clear_rsets_post_compaction();
check_gc_time_stamps();
resize_if_necessary_after_full_collection();
// We should do this after we potentially resize the heap so
// that all the COMMIT / UNCOMMIT events are generated before
// the compaction events.
print_hrm_post_compaction();
if (_hot_card_cache->use_cache()) {
_hot_card_cache->reset_card_counts();
_hot_card_cache->reset_hot_cache();
}
// Rebuild remembered sets of all regions.
uint n_workers =
AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
workers()->active_workers(),
Threads::number_of_non_daemon_threads());
workers()->update_active_workers(n_workers);
log_info(gc,task)("Using %u workers of %u to rebuild remembered set", n_workers, workers()->total_workers());
ParRebuildRSTask rebuild_rs_task(this);
workers()->run_task(&rebuild_rs_task);
// Rebuild the strong code root lists for each region
rebuild_strong_code_roots();
if (true) { // FIXME
MetaspaceGC::compute_new_size();
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
// Discard all rset updates
JavaThread::dirty_card_queue_set().abandon_logs();
assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
// At this point there should be no regions in the
// entire heap tagged as young.
assert(check_young_list_empty(), "young list should be empty at this point");
// Update the number of full collections that have been completed.
increment_old_marking_cycles_completed(false /* concurrent */);
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
_verifier->verify_after_gc();
// Clear the previous marking bitmap, if needed for bitmap verification.
// Note we cannot do this when we clear the next marking bitmap in
// G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
// objects marked during a full GC against the previous bitmap.
// But we need to clear it before calling check_bitmaps below since
// the full GC has compacted objects and updated TAMS but not updated
// the prev bitmap.
if (G1VerifyBitmaps) {
GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
_cm->clear_prev_bitmap(workers());
}
_verifier->check_bitmaps("Full GC End");
// Start a new incremental collection set for the next pause
collection_set()->start_incremental_building();
clear_cset_fast_test();
_allocator->init_mutator_alloc_region();
g1_policy()->record_full_collection_end();
// We must call G1MonitoringSupport::update_sizes() in the same scoping level
// as an active TraceMemoryManagerStats object (i.e. before the destructor for the
// TraceMemoryManagerStats is called) so that the G1 memory pools are updated
// before any GC notifications are raised.
g1mm()->update_sizes();
gc_epilogue(true);
heap_transition.print();
print_heap_after_gc();
print_heap_regions();
trace_heap_after_gc(gc_tracer);
post_full_gc_dump(gc_timer);
}
gc_timer->register_gc_end();
gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
}
return true;
}
void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
// Currently, there is no facility in the do_full_collection(bool) API to notify
// the caller that the collection did not succeed (e.g., because it was locked
// out by the GC locker). So, right now, we'll ignore the return value.
bool dummy = do_full_collection(true, /* explicit_gc */
clear_all_soft_refs);
}
void G1CollectedHeap::resize_if_necessary_after_full_collection() {
// Include bytes that will be pre-allocated to support collections, as "used".
const size_t used_after_gc = used();
const size_t capacity_after_gc = capacity();
const size_t free_after_gc = capacity_after_gc - used_after_gc;
// This is enforced in arguments.cpp.
assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
"otherwise the code below doesn't make sense");
// We don't have floating point command-line arguments
const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
const double maximum_used_percentage = 1.0 - minimum_free_percentage;
const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
const double minimum_used_percentage = 1.0 - maximum_free_percentage;
const size_t min_heap_size = collector_policy()->min_heap_byte_size();
const size_t max_heap_size = collector_policy()->max_heap_byte_size();
// We have to be careful here as these two calculations can overflow
// 32-bit size_t's.
double used_after_gc_d = (double) used_after_gc;
double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
// Let's make sure that they are both under the max heap size, which
// by default will make them fit into a size_t.
double desired_capacity_upper_bound = (double) max_heap_size;
minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
desired_capacity_upper_bound);
maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
desired_capacity_upper_bound);
// We can now safely turn them into size_t's.
size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
// This assert only makes sense here, before we adjust them
// with respect to the min and max heap size.
assert(minimum_desired_capacity <= maximum_desired_capacity,
"minimum_desired_capacity = " SIZE_FORMAT ", "
"maximum_desired_capacity = " SIZE_FORMAT,
minimum_desired_capacity, maximum_desired_capacity);
// Should not be greater than the heap max size. No need to adjust
// it with respect to the heap min size as it's a lower bound (i.e.,
// we'll try to make the capacity larger than it, not smaller).
minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
// Should not be less than the heap min size. No need to adjust it
// with respect to the heap max size as it's an upper bound (i.e.,
// we'll try to make the capacity smaller than it, not greater).
maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
if (capacity_after_gc < minimum_desired_capacity) {
// Don't expand unless it's significant
size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
"Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
expand(expand_bytes, _workers);
// No expansion, now see if we want to shrink
} else if (capacity_after_gc > maximum_desired_capacity) {
// Capacity too large, compute shrinking size
size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
"Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
shrink(shrink_bytes);
}
}
HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
AllocationContext_t context,
bool do_gc,
bool clear_all_soft_refs,
bool expect_null_mutator_alloc_region,
bool* gc_succeeded) {
*gc_succeeded = true;
// Let's attempt the allocation first.
HeapWord* result =
attempt_allocation_at_safepoint(word_size,
context,
expect_null_mutator_alloc_region);
if (result != NULL) {
assert(*gc_succeeded, "sanity");
return result;
}
// In a G1 heap, we're supposed to keep allocation from failing by
// incremental pauses. Therefore, at least for now, we'll favor
// expansion over collection. (This might change in the future if we can
// do something smarter than full collection to satisfy a failed alloc.)
result = expand_and_allocate(word_size, context);
if (result != NULL) {
assert(*gc_succeeded, "sanity");
return result;
}
if (do_gc) {
// Expansion didn't work, we'll try to do a Full GC.
*gc_succeeded = do_full_collection(false, /* explicit_gc */
clear_all_soft_refs);
}
return NULL;
}
HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
AllocationContext_t context,
bool* succeeded) {
assert_at_safepoint(true /* should_be_vm_thread */);
// Attempts to allocate followed by Full GC.
HeapWord* result =
satisfy_failed_allocation_helper(word_size,
context,
true, /* do_gc */
false, /* clear_all_soft_refs */
false, /* expect_null_mutator_alloc_region */
succeeded);
if (result != NULL || !*succeeded) {
return result;
}
// Attempts to allocate followed by Full GC that will collect all soft references.
result = satisfy_failed_allocation_helper(word_size,
context,
true, /* do_gc */
true, /* clear_all_soft_refs */
true, /* expect_null_mutator_alloc_region */
succeeded);
if (result != NULL || !*succeeded) {
return result;
}
// Attempts to allocate, no GC
result = satisfy_failed_allocation_helper(word_size,
context,
false, /* do_gc */
false, /* clear_all_soft_refs */
true, /* expect_null_mutator_alloc_region */
succeeded);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
}
assert(!collector_policy()->should_clear_all_soft_refs(),
"Flag should have been handled and cleared prior to this point");
// What else? We might try synchronous finalization later. If the total
// space available is large enough for the allocation, then a more
// complete compaction phase than we've tried so far might be
// appropriate.
assert(*succeeded, "sanity");
return NULL;
}
// Attempting to expand the heap sufficiently
// to support an allocation of the given "word_size". If
// successful, perform the allocation and return the address of the
// allocated block, or else "NULL".
HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
assert_at_safepoint(true /* should_be_vm_thread */);
_verifier->verify_region_sets_optional();
size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
word_size * HeapWordSize);
if (expand(expand_bytes, _workers)) {
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
return attempt_allocation_at_safepoint(word_size,
context,
false /* expect_null_mutator_alloc_region */);
}
return NULL;
}
bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
aligned_expand_bytes = align_size_up(aligned_expand_bytes,
HeapRegion::GrainBytes);
log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
expand_bytes, aligned_expand_bytes);
if (is_maximal_no_gc()) {
log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
return false;
}
double expand_heap_start_time_sec = os::elapsedTime();
uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
assert(regions_to_expand > 0, "Must expand by at least one region");
uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
if (expand_time_ms != NULL) {
*expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
}
if (expanded_by > 0) {
size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
g1_policy()->record_new_heap_size(num_regions());
} else {
log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
// The expansion of the virtual storage space was unsuccessful.
// Let's see if it was because we ran out of swap.
if (G1ExitOnExpansionFailure &&
_hrm.available() >= regions_to_expand) {
// We had head room...
vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
}
}
return regions_to_expand > 0;
}
void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
size_t aligned_shrink_bytes =
ReservedSpace::page_align_size_down(shrink_bytes);
aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
HeapRegion::GrainBytes);
uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
if (num_regions_removed > 0) {
g1_policy()->record_new_heap_size(num_regions());
} else {
log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
}
}
void G1CollectedHeap::shrink(size_t shrink_bytes) {
_verifier->verify_region_sets_optional();
// We should only reach here at the end of a Full GC which means we
// should not not be holding to any GC alloc regions. The method
// below will make sure of that and do any remaining clean up.
_allocator->abandon_gc_alloc_regions();
// Instead of tearing down / rebuilding the free lists here, we
// could instead use the remove_all_pending() method on free_list to
// remove only the ones that we need to remove.
tear_down_region_sets(true /* free_list_only */);
shrink_helper(shrink_bytes);
rebuild_region_sets(true /* free_list_only */);
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
}
// Public methods.
G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
CollectedHeap(),
_collector_policy(collector_policy),
_g1_policy(create_g1_policy()),
_collection_set(this, _g1_policy),
_dirty_card_queue_set(false),
_is_alive_closure_cm(this),
_is_alive_closure_stw(this),
_ref_processor_cm(NULL),
_ref_processor_stw(NULL),
_bot(NULL),
_hot_card_cache(NULL),
_g1_rem_set(NULL),
_cg1r(NULL),
_g1mm(NULL),
_refine_cte_cl(NULL),
_preserved_marks_set(true /* in_c_heap */),
_secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
_old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
_humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
_humongous_reclaim_candidates(),
_has_humongous_reclaim_candidates(false),
_archive_allocator(NULL),
_free_regions_coming(false),
_gc_time_stamp(0),
_summary_bytes_used(0),
_survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
_old_evac_stats("Old", OldPLABSize, PLABWeight),
_expand_heap_after_alloc_failure(true),
_old_marking_cycles_started(0),
_old_marking_cycles_completed(0),
_in_cset_fast_test(),
_gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
_gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
_workers = new WorkGang("GC Thread", ParallelGCThreads,
/* are_GC_task_threads */true,
/* are_ConcurrentGC_threads */false);
_workers->initialize_workers();
_verifier = new G1HeapVerifier(this);
_allocator = G1Allocator::create_allocator(this);
_heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
_humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
// Override the default _filler_array_max_size so that no humongous filler
// objects are created.
_filler_array_max_size = _humongous_object_threshold_in_words;
uint n_queues = ParallelGCThreads;
_task_queues = new RefToScanQueueSet(n_queues);
_evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
for (uint i = 0; i < n_queues; i++) {
RefToScanQueue* q = new RefToScanQueue();
q->initialize();
_task_queues->register_queue(i, q);
::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
}
// Initialize the G1EvacuationFailureALot counters and flags.
NOT_PRODUCT(reset_evacuation_should_fail();)
guarantee(_task_queues != NULL, "task_queues allocation failure.");
}
G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
size_t size,
size_t translation_factor) {
size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
// Allocate a new reserved space, preferring to use large pages.
ReservedSpace rs(size, preferred_page_size);
G1RegionToSpaceMapper* result =
G1RegionToSpaceMapper::create_mapper(rs,
size,
rs.alignment(),
HeapRegion::GrainBytes,
translation_factor,
mtGC);
os::trace_page_sizes_for_requested_size(description,
size,
preferred_page_size,
rs.alignment(),
rs.base(),
rs.size());
return result;
}
jint G1CollectedHeap::initialize() {
CollectedHeap::pre_initialize();
os::enable_vtime();
// Necessary to satisfy locking discipline assertions.
MutexLocker x(Heap_lock);
// While there are no constraints in the GC code that HeapWordSize
// be any particular value, there are multiple other areas in the
// system which believe this to be true (e.g. oop->object_size in some
// cases incorrectly returns the size in wordSize units rather than
// HeapWordSize).
guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
size_t init_byte_size = collector_policy()->initial_heap_byte_size();
size_t max_byte_size = collector_policy()->max_heap_byte_size();
size_t heap_alignment = collector_policy()->heap_alignment();
// Ensure that the sizes are properly aligned.
Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
_refine_cte_cl = new RefineCardTableEntryClosure();
jint ecode = JNI_OK;
_cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode);
if (_cg1r == NULL) {
return ecode;
}
// Reserve the maximum.
// When compressed oops are enabled, the preferred heap base
// is calculated by subtracting the requested size from the
// 32Gb boundary and using the result as the base address for
// heap reservation. If the requested size is not aligned to
// HeapRegion::GrainBytes (i.e. the alignment that is passed
// into the ReservedHeapSpace constructor) then the actual
// base of the reserved heap may end up differing from the
// address that was requested (i.e. the preferred heap base).
// If this happens then we could end up using a non-optimal
// compressed oops mode.
ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
heap_alignment);
initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
// Create the barrier set for the entire reserved region.
G1SATBCardTableLoggingModRefBS* bs
= new G1SATBCardTableLoggingModRefBS(reserved_region());
bs->initialize();
assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
set_barrier_set(bs);
// Create the hot card cache.
_hot_card_cache = new G1HotCardCache(this);
// Also create a G1 rem set.
_g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
// Carve out the G1 part of the heap.
ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
G1RegionToSpaceMapper* heap_storage =
G1RegionToSpaceMapper::create_mapper(g1_rs,
g1_rs.size(),
page_size,
HeapRegion::GrainBytes,
1,
mtJavaHeap);
os::trace_page_sizes("Heap",
collector_policy()->min_heap_byte_size(),
max_byte_size,
page_size,
heap_rs.base(),
heap_rs.size());
heap_storage->set_mapping_changed_listener(&_listener);
// Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
G1RegionToSpaceMapper* bot_storage =
create_aux_memory_mapper("Block Offset Table",
G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
G1BlockOffsetTable::heap_map_factor());
ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
G1RegionToSpaceMapper* cardtable_storage =
create_aux_memory_mapper("Card Table",
G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
G1SATBCardTableLoggingModRefBS::heap_map_factor());
G1RegionToSpaceMapper* card_counts_storage =
create_aux_memory_mapper("Card Counts Table",
G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
G1CardCounts::heap_map_factor());
size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
G1RegionToSpaceMapper* prev_bitmap_storage =
create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
G1RegionToSpaceMapper* next_bitmap_storage =
create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
_hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
g1_barrier_set()->initialize(cardtable_storage);
// Do later initialization work for concurrent refinement.
_hot_card_cache->initialize(card_counts_storage);
// 6843694 - ensure that the maximum region index can fit
// in the remembered set structures.
const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
g1_rem_set()->initialize(max_capacity(), max_regions());
size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
"too many cards per region");
FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
_bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
{
HeapWord* start = _hrm.reserved().start();
HeapWord* end = _hrm.reserved().end();
size_t granularity = HeapRegion::GrainBytes;
_in_cset_fast_test.initialize(start, end, granularity);
_humongous_reclaim_candidates.initialize(start, end, granularity);
}
// Create the G1ConcurrentMark data structure and thread.
// (Must do this late, so that "max_regions" is defined.)
_cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
if (_cm == NULL || !_cm->completed_initialization()) {
vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
return JNI_ENOMEM;
}
_cmThread = _cm->cmThread();
// Now expand into the initial heap size.
if (!expand(init_byte_size, _workers)) {
vm_shutdown_during_initialization("Failed to allocate initial heap.");
return JNI_ENOMEM;
}
// Perform any initialization actions delegated to the policy.
g1_policy()->init(this, &_collection_set);
JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
SATB_Q_FL_lock,
G1SATBProcessCompletedThreshold,
Shared_SATB_Q_lock);
JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
DirtyCardQ_CBL_mon,
DirtyCardQ_FL_lock,
(int)concurrent_g1_refine()->yellow_zone(),
(int)concurrent_g1_refine()->red_zone(),
Shared_DirtyCardQ_lock,
NULL, // fl_owner
true); // init_free_ids
dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
DirtyCardQ_CBL_mon,
DirtyCardQ_FL_lock,
-1, // never trigger processing
-1, // no limit on length
Shared_DirtyCardQ_lock,
&JavaThread::dirty_card_queue_set());
// Here we allocate the dummy HeapRegion that is required by the
// G1AllocRegion class.
HeapRegion* dummy_region = _hrm.get_dummy_region();
// We'll re-use the same region whether the alloc region will
// require BOT updates or not and, if it doesn't, then a non-young
// region will complain that it cannot support allocations without
// BOT updates. So we'll tag the dummy region as eden to avoid that.
dummy_region->set_eden();
// Make sure it's full.
dummy_region->set_top(dummy_region->end());
G1AllocRegion::setup(this, dummy_region);
_allocator->init_mutator_alloc_region();
// Do create of the monitoring and management support so that
// values in the heap have been properly initialized.
_g1mm = new G1MonitoringSupport(this);
G1StringDedup::initialize();
_preserved_marks_set.init(ParallelGCThreads);
_collection_set.initialize(max_regions());
return JNI_OK;
}
void G1CollectedHeap::stop() {
// Stop all concurrent threads. We do this to make sure these threads
// do not continue to execute and access resources (e.g. logging)
// that are destroyed during shutdown.
_cg1r->stop();
_cmThread->stop();
if (G1StringDedup::is_enabled()) {
G1StringDedup::stop();
}
}
size_t G1CollectedHeap::conservative_max_heap_alignment() {
return HeapRegion::max_region_size();
}
void G1CollectedHeap::post_initialize() {
ref_processing_init();
}
void G1CollectedHeap::ref_processing_init() {
// Reference processing in G1 currently works as follows:
//
// * There are two reference processor instances. One is
// used to record and process discovered references
// during concurrent marking; the other is used to
// record and process references during STW pauses
// (both full and incremental).
// * Both ref processors need to 'span' the entire heap as
// the regions in the collection set may be dotted around.
//
// * For the concurrent marking ref processor:
// * Reference discovery is enabled at initial marking.
// * Reference discovery is disabled and the discovered
// references processed etc during remarking.
// * Reference discovery is MT (see below).
// * Reference discovery requires a barrier (see below).
// * Reference processing may or may not be MT
// (depending on the value of ParallelRefProcEnabled
// and ParallelGCThreads).
// * A full GC disables reference discovery by the CM
// ref processor and abandons any entries on it's
// discovered lists.
//
// * For the STW processor:
// * Non MT discovery is enabled at the start of a full GC.
// * Processing and enqueueing during a full GC is non-MT.
// * During a full GC, references are processed after marking.
//
// * Discovery (may or may not be MT) is enabled at the start
// of an incremental evacuation pause.
// * References are processed near the end of a STW evacuation pause.
// * For both types of GC:
// * Discovery is atomic - i.e. not concurrent.
// * Reference discovery will not need a barrier.
MemRegion mr = reserved_region();
// Concurrent Mark ref processor
_ref_processor_cm =
new ReferenceProcessor(mr, // span
ParallelRefProcEnabled && (ParallelGCThreads > 1),
// mt processing
ParallelGCThreads,
// degree of mt processing
(ParallelGCThreads > 1) || (ConcGCThreads > 1),
// mt discovery
MAX2(ParallelGCThreads, ConcGCThreads),
// degree of mt discovery
false,
// Reference discovery is not atomic
&_is_alive_closure_cm);
// is alive closure
// (for efficiency/performance)
// STW ref processor
_ref_processor_stw =
new ReferenceProcessor(mr, // span
ParallelRefProcEnabled && (ParallelGCThreads > 1),
// mt processing
ParallelGCThreads,
// degree of mt processing
(ParallelGCThreads > 1),
// mt discovery
ParallelGCThreads,
// degree of mt discovery
true,
// Reference discovery is atomic
&_is_alive_closure_stw);
// is alive closure
// (for efficiency/performance)
}
CollectorPolicy* G1CollectedHeap::collector_policy() const {
return _collector_policy;
}
size_t G1CollectedHeap::capacity() const {
return _hrm.length() * HeapRegion::GrainBytes;
}
void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
hr->reset_gc_time_stamp();
}
#ifndef PRODUCT
class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
private:
unsigned _gc_time_stamp;
bool _failures;
public:
CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
_gc_time_stamp(gc_time_stamp), _failures(false) { }
virtual bool doHeapRegion(HeapRegion* hr) {
unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
if (_gc_time_stamp != region_gc_time_stamp) {
log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
region_gc_time_stamp, _gc_time_stamp);
_failures = true;
}
return false;
}
bool failures() { return _failures; }
};
void G1CollectedHeap::check_gc_time_stamps() {
CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
heap_region_iterate(&cl);
guarantee(!cl.failures(), "all GC time stamps should have been reset");
}
#endif // PRODUCT
void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
_hot_card_cache->drain(cl, worker_i);
}
void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
size_t n_completed_buffers = 0;
while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
n_completed_buffers++;
}
g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
dcqs.clear_n_completed_buffers();
assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
}
// Computes the sum of the storage used by the various regions.
size_t G1CollectedHeap::used() const {
size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
if (_archive_allocator != NULL) {
result += _archive_allocator->used();
}
return result;
}
size_t G1CollectedHeap::used_unlocked() const {
return _summary_bytes_used;
}
class SumUsedClosure: public HeapRegionClosure {
size_t _used;
public:
SumUsedClosure() : _used(0) {}
bool doHeapRegion(HeapRegion* r) {
_used += r->used();
return false;
}
size_t result() { return _used; }
};
size_t G1CollectedHeap::recalculate_used() const {
double recalculate_used_start = os::elapsedTime();
SumUsedClosure blk;
heap_region_iterate(&blk);
g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
return blk.result();
}
bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
switch (cause) {
case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
case GCCause::_update_allocation_context_stats_inc: return true;
case GCCause::_wb_conc_mark: return true;
default : return false;
}
}
bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
switch (cause) {
case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
case GCCause::_g1_humongous_allocation: return true;
default: return is_user_requested_concurrent_full_gc(cause);
}
}
#ifndef PRODUCT
void G1CollectedHeap::allocate_dummy_regions() {
// Let's fill up most of the region
size_t word_size = HeapRegion::GrainWords - 1024;
// And as a result the region we'll allocate will be humongous.
guarantee(is_humongous(word_size), "sanity");
// _filler_array_max_size is set to humongous object threshold
// but temporarily change it to use CollectedHeap::fill_with_object().
SizeTFlagSetting fs(_filler_array_max_size, word_size);
for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
// Let's use the existing mechanism for the allocation
HeapWord* dummy_obj = humongous_obj_allocate(word_size,
AllocationContext::system());
if (dummy_obj != NULL) {
MemRegion mr(dummy_obj, word_size);
CollectedHeap::fill_with_object(mr);
} else {
// If we can't allocate once, we probably cannot allocate
// again. Let's get out of the loop.
break;
}
}
}
#endif // !PRODUCT
void G1CollectedHeap::increment_old_marking_cycles_started() {
assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
_old_marking_cycles_started == _old_marking_cycles_completed + 1,
"Wrong marking cycle count (started: %d, completed: %d)",
_old_marking_cycles_started, _old_marking_cycles_completed);
_old_marking_cycles_started++;
}
void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
// We assume that if concurrent == true, then the caller is a
// concurrent thread that was joined the Suspendible Thread
// Set. If there's ever a cheap way to check this, we should add an
// assert here.
// Given that this method is called at the end of a Full GC or of a
// concurrent cycle, and those can be nested (i.e., a Full GC can
// interrupt a concurrent cycle), the number of full collections
// completed should be either one (in the case where there was no
// nesting) or two (when a Full GC interrupted a concurrent cycle)
// behind the number of full collections started.
// This is the case for the inner caller, i.e. a Full GC.
assert(concurrent ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 2),
"for inner caller (Full GC): _old_marking_cycles_started = %u "
"is inconsistent with _old_marking_cycles_completed = %u",
_old_marking_cycles_started, _old_marking_cycles_completed);
// This is the case for the outer caller, i.e. the concurrent cycle.
assert(!concurrent ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 1),
"for outer caller (concurrent cycle): "
"_old_marking_cycles_started = %u "
"is inconsistent with _old_marking_cycles_completed = %u",
_old_marking_cycles_started, _old_marking_cycles_completed);
_old_marking_cycles_completed += 1;
// We need to clear the "in_progress" flag in the CM thread before
// we wake up any waiters (especially when ExplicitInvokesConcurrent
// is set) so that if a waiter requests another System.gc() it doesn't
// incorrectly see that a marking cycle is still in progress.
if (concurrent) {
_cmThread->set_idle();
}
// This notify_all() will ensure that a thread that called
// System.gc() with (with ExplicitGCInvokesConcurrent set or not)
// and it's waiting for a full GC to finish will be woken up. It is
// waiting in VM_G1IncCollectionPause::doit_epilogue().
FullGCCount_lock->notify_all();
}
void G1CollectedHeap::collect(GCCause::Cause cause) {
assert_heap_not_locked();
uint gc_count_before;
uint old_marking_count_before;
uint full_gc_count_before;
bool retry_gc;
do {
retry_gc = false;
{
MutexLocker ml(Heap_lock);
// Read the GC count while holding the Heap_lock
gc_count_before = total_collections();
full_gc_count_before = total_full_collections();
old_marking_count_before = _old_marking_cycles_started;
}
if (should_do_concurrent_full_gc(cause)) {
// Schedule an initial-mark evacuation pause that will start a
// concurrent cycle. We're setting word_size to 0 which means that
// we are not requesting a post-GC allocation.
VM_G1IncCollectionPause op(gc_count_before,
0, /* word_size */
true, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
cause);
op.set_allocation_context(AllocationContext::current());
VMThread::execute(&op);
if (!op.pause_succeeded()) {
if (old_marking_count_before == _old_marking_cycles_started) {
retry_gc = op.should_retry_gc();
} else {
// A Full GC happened while we were trying to schedule the
// initial-mark GC. No point in starting a new cycle given
// that the whole heap was collected anyway.
}
if (retry_gc) {
if (GCLocker::is_active_and_needs_gc()) {
GCLocker::stall_until_clear();
}
}
}
} else {
if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
// Schedule a standard evacuation pause. We're setting word_size
// to 0 which means that we are not requesting a post-GC allocation.
VM_G1IncCollectionPause op(gc_count_before,
0, /* word_size */
false, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
cause);
VMThread::execute(&op);
} else {
// Schedule a Full GC.
VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
VMThread::execute(&op);
}
}
} while (retry_gc);
}
bool G1CollectedHeap::is_in(const void* p) const {
if (_hrm.reserved().contains(p)) {
// Given that we know that p is in the reserved space,
// heap_region_containing() should successfully
// return the containing region.
HeapRegion* hr = heap_region_containing(p);
return hr->is_in(p);
} else {
return false;
}
}
#ifdef ASSERT
bool G1CollectedHeap::is_in_exact(const void* p) const {
bool contains = reserved_region().contains(p);
bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
if (contains && available) {
return true;
} else {
return false;
}
}
#endif
bool G1CollectedHeap::obj_in_cs(oop obj) {
HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
return r != NULL && r->in_collection_set();
}
// Iteration functions.
// Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
class IterateOopClosureRegionClosure: public HeapRegionClosure {
ExtendedOopClosure* _cl;
public:
IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
bool doHeapRegion(HeapRegion* r) {
if (!r->is_continues_humongous()) {
r->oop_iterate(_cl);
}
return false;
}
};
// Iterates an ObjectClosure over all objects within a HeapRegion.
class IterateObjectClosureRegionClosure: public HeapRegionClosure {
ObjectClosure* _cl;
public:
IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
bool doHeapRegion(HeapRegion* r) {
if (!r->is_continues_humongous()) {
r->object_iterate(_cl);
}
return false;
}
};
void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
IterateObjectClosureRegionClosure blk(cl);
heap_region_iterate(&blk);
}
void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
_hrm.iterate(cl);
}
void
G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
uint worker_id,
HeapRegionClaimer *hrclaimer,
bool concurrent) const {
_hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
}
void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
_collection_set.iterate(cl);
}
void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
_collection_set.iterate_from(cl, worker_id, workers()->active_workers());
}
HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
HeapRegion* result = _hrm.next_region_in_heap(from);
while (result != NULL && result->is_pinned()) {
result = _hrm.next_region_in_heap(result);
}
return result;
}
HeapWord* G1CollectedHeap::block_start(const void* addr) const {
HeapRegion* hr = heap_region_containing(addr);
return hr->block_start(addr);
}
size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
HeapRegion* hr = heap_region_containing(addr);
return hr->block_size(addr);
}
bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
HeapRegion* hr = heap_region_containing(addr);
return hr->block_is_obj(addr);
}
bool G1CollectedHeap::supports_tlab_allocation() const {
return true;
}
size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
}
size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
return _eden.length() * HeapRegion::GrainBytes;
}
// For G1 TLABs should not contain humongous objects, so the maximum TLAB size
// must be equal to the humongous object limit.
size_t G1CollectedHeap::max_tlab_size() const {
return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
}
size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
AllocationContext_t context = AllocationContext::current();
return _allocator->unsafe_max_tlab_alloc(context);
}
size_t G1CollectedHeap::max_capacity() const {
return _hrm.reserved().byte_size();
}
jlong G1CollectedHeap::millis_since_last_gc() {
// See the notes in GenCollectedHeap::millis_since_last_gc()
// for more information about the implementation.
jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
_g1_policy->collection_pause_end_millis();
if (ret_val < 0) {
log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
". returning zero instead.", ret_val);
return 0;
}
return ret_val;
}
void G1CollectedHeap::prepare_for_verify() {
_verifier->prepare_for_verify();
}
void G1CollectedHeap::verify(VerifyOption vo) {
_verifier->verify(vo);
}
class PrintRegionClosure: public HeapRegionClosure {
outputStream* _st;
public:
PrintRegionClosure(outputStream* st) : _st(st) {}
bool doHeapRegion(HeapRegion* r) {
r->print_on(_st);
return false;
}
};
bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
const HeapRegion* hr,
const VerifyOption vo) const {
switch (vo) {
case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
default: ShouldNotReachHere();
}
return false; // keep some compilers happy
}
bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
const VerifyOption vo) const {
switch (vo) {
case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
case VerifyOption_G1UseMarkWord: {
HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
return !obj->is_gc_marked() && !hr->is_archive();
}
default: ShouldNotReachHere();
}
return false; // keep some compilers happy
}
void G1CollectedHeap::print_heap_regions() const {
Log(gc, heap, region) log;
if (log.is_trace()) {
ResourceMark rm;
print_regions_on(log.trace_stream());
}
}
void G1CollectedHeap::print_on(outputStream* st) const {
st->print(" %-20s", "garbage-first heap");
st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
capacity()/K, used_unlocked()/K);
st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
p2i(_hrm.reserved().start()),
p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
p2i(_hrm.reserved().end()));
st->cr();
st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
uint young_regions = young_regions_count();
st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
(size_t) young_regions * HeapRegion::GrainBytes / K);
uint survivor_regions = survivor_regions_count();
st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
(size_t) survivor_regions * HeapRegion::GrainBytes / K);
st->cr();
MetaspaceAux::print_on(st);
}
void G1CollectedHeap::print_regions_on(outputStream* st) const {
st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
"HS=humongous(starts), HC=humongous(continues), "
"CS=collection set, F=free, A=archive, TS=gc time stamp, "
"AC=allocation context, "
"TAMS=top-at-mark-start (previous, next)");
PrintRegionClosure blk(st);
heap_region_iterate(&blk);
}
void G1CollectedHeap::print_extended_on(outputStream* st) const {
print_on(st);
// Print the per-region information.
print_regions_on(st);
}
void G1CollectedHeap::print_on_error(outputStream* st) const {
this->CollectedHeap::print_on_error(st);
if (_cm != NULL) {
st->cr();
_cm->print_on_error(st);
}
}
void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
workers()->print_worker_threads_on(st);
_cmThread->print_on(st);
st->cr();
_cm->print_worker_threads_on(st);
_cg1r->print_worker_threads_on(st); // also prints the sample thread
if (G1StringDedup::is_enabled()) {
G1StringDedup::print_worker_threads_on(st);
}
}
void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
workers()->threads_do(tc);
tc->do_thread(_cmThread);
_cm->threads_do(tc);
_cg1r->threads_do(tc); // also iterates over the sample thread
if (G1StringDedup::is_enabled()) {
G1StringDedup::threads_do(tc);
}
}
void G1CollectedHeap::print_tracing_info() const {
g1_rem_set()->print_summary_info();
concurrent_mark()->print_summary_info();
}
#ifndef PRODUCT
// Helpful for debugging RSet issues.
class PrintRSetsClosure : public HeapRegionClosure {
private:
const char* _msg;
size_t _occupied_sum;
public:
bool doHeapRegion(HeapRegion* r) {
HeapRegionRemSet* hrrs = r->rem_set();
size_t occupied = hrrs->occupied();
_occupied_sum += occupied;
tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
if (occupied == 0) {
tty->print_cr(" RSet is empty");
} else {
hrrs->print();
}
tty->print_cr("----------");
return false;
}
PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
tty->cr();
tty->print_cr("========================================");
tty->print_cr("%s", msg);
tty->cr();
}
~PrintRSetsClosure() {
tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
tty->print_cr("========================================");
tty->cr();
}
};
void G1CollectedHeap::print_cset_rsets() {
PrintRSetsClosure cl("Printing CSet RSets");
collection_set_iterate(&cl);
}
void G1CollectedHeap::print_all_rsets() {
PrintRSetsClosure cl("Printing All RSets");;
heap_region_iterate(&cl);
}
#endif // PRODUCT
G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
size_t eden_capacity_bytes =
(g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
VirtualSpaceSummary heap_summary = create_heap_space_summary();
return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
eden_capacity_bytes, survivor_used_bytes, num_regions());
}
G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
stats->unused(), stats->used(), stats->region_end_waste(),
stats->regions_filled(), stats->direct_allocated(),
stats->failure_used(), stats->failure_waste());
}
void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
const G1HeapSummary& heap_summary = create_g1_heap_summary();
gc_tracer->report_gc_heap_summary(when, heap_summary);
const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
gc_tracer->report_metaspace_summary(when, metaspace_summary);
}
G1CollectedHeap* G1CollectedHeap::heap() {
CollectedHeap* heap = Universe::heap();
assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
return (G1CollectedHeap*)heap;
}
void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
// always_do_update_barrier = false;
assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
// Fill TLAB's and such
accumulate_statistics_all_tlabs();
ensure_parsability(true);
g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
}
void G1CollectedHeap::gc_epilogue(bool full) {
// we are at the end of the GC. Total collections has already been increased.
g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
// FIXME: what is this about?
// I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
// is set.
#if defined(COMPILER2) || INCLUDE_JVMCI
assert(DerivedPointerTable::is_empty(), "derived pointer present");
#endif
// always_do_update_barrier = true;
resize_all_tlabs();
allocation_context_stats().update(full);
// We have just completed a GC. Update the soft reference
// policy with the new heap occupancy
Universe::update_heap_info_at_gc();
}
HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
uint gc_count_before,
bool* succeeded,
GCCause::Cause gc_cause) {
assert_heap_not_locked_and_not_at_safepoint();
VM_G1IncCollectionPause op(gc_count_before,
word_size,
false, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
gc_cause);
op.set_allocation_context(AllocationContext::current());
VMThread::execute(&op);
HeapWord* result = op.result();
bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
assert(result == NULL || ret_succeeded,
"the result should be NULL if the VM did not succeed");
*succeeded = ret_succeeded;
assert_heap_not_locked();
return result;
}
void
G1CollectedHeap::doConcurrentMark() {
MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
if (!_cmThread->in_progress()) {
_cmThread->set_started();
CGC_lock->notify();
}
}
size_t G1CollectedHeap::pending_card_num() {
size_t extra_cards = 0;
JavaThread *curr = Threads::first();
while (curr != NULL) {
DirtyCardQueue& dcq = curr->dirty_card_queue();
extra_cards += dcq.size();
curr = curr->next();
}
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
size_t buffer_size = dcqs.buffer_size();
size_t buffer_num = dcqs.completed_buffers_num();
// PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
// in bytes - not the number of 'entries'. We need to convert
// into a number of cards.
return (buffer_size * buffer_num + extra_cards) / oopSize;
}
class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
private:
size_t _total_humongous;
size_t _candidate_humongous;
DirtyCardQueue _dcq;
// We don't nominate objects with many remembered set entries, on
// the assumption that such objects are likely still live.
bool is_remset_small(HeapRegion* region) const {
HeapRegionRemSet* const rset = region->rem_set();
return G1EagerReclaimHumongousObjectsWithStaleRefs
? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
: rset->is_empty();
}
bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
assert(region->is_starts_humongous(), "Must start a humongous object");
oop obj = oop(region->bottom());
// Dead objects cannot be eager reclaim candidates. Due to class
// unloading it is unsafe to query their classes so we return early.
if (heap->is_obj_dead(obj, region)) {
return false;
}
// Candidate selection must satisfy the following constraints
// while concurrent marking is in progress:
//
// * In order to maintain SATB invariants, an object must not be
// reclaimed if it was allocated before the start of marking and
// has not had its references scanned. Such an object must have
// its references (including type metadata) scanned to ensure no
// live objects are missed by the marking process. Objects
// allocated after the start of concurrent marking don't need to
// be scanned.
//
// * An object must not be reclaimed if it is on the concurrent
// mark stack. Objects allocated after the start of concurrent
// marking are never pushed on the mark stack.
//
// Nominating only objects allocated after the start of concurrent
// marking is sufficient to meet both constraints. This may miss
// some objects that satisfy the constraints, but the marking data
// structures don't support efficiently performing the needed
// additional tests or scrubbing of the mark stack.
//
// However, we presently only nominate is_typeArray() objects.
// A humongous object containing references induces remembered
// set entries on other regions. In order to reclaim such an
// object, those remembered sets would need to be cleaned up.
//
// We also treat is_typeArray() objects specially, allowing them
// to be reclaimed even if allocated before the start of
// concurrent mark. For this we rely on mark stack insertion to
// exclude is_typeArray() objects, preventing reclaiming an object
// that is in the mark stack. We also rely on the metadata for
// such objects to be built-in and so ensured to be kept live.
// Frequent allocation and drop of large binary blobs is an
// important use case for eager reclaim, and this special handling
// may reduce needed headroom.
return obj->is_typeArray() && is_remset_small(region);
}
public:
RegisterHumongousWithInCSetFastTestClosure()
: _total_humongous(0),
_candidate_humongous(0),
_dcq(&JavaThread::dirty_card_queue_set()) {
}
virtual bool doHeapRegion(HeapRegion* r) {
if (!r->is_starts_humongous()) {
return false;
}
G1CollectedHeap* g1h = G1CollectedHeap::heap();
bool is_candidate = humongous_region_is_candidate(g1h, r);
uint rindex = r->hrm_index();
g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
if (is_candidate) {
_candidate_humongous++;
g1h->register_humongous_region_with_cset(rindex);
// Is_candidate already filters out humongous object with large remembered sets.
// If we have a humongous object with a few remembered sets, we simply flush these
// remembered set entries into the DCQS. That will result in automatic
// re-evaluation of their remembered set entries during the following evacuation
// phase.
if (!r->rem_set()->is_empty()) {
guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
"Found a not-small remembered set here. This is inconsistent with previous assumptions.");
G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
HeapRegionRemSetIterator hrrs(r->rem_set());
size_t card_index;
while (hrrs.has_next(card_index)) {
jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
// The remembered set might contain references to already freed
// regions. Filter out such entries to avoid failing card table
// verification.
if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
*card_ptr = CardTableModRefBS::dirty_card_val();
_dcq.enqueue(card_ptr);
}
}
}
assert(hrrs.n_yielded() == r->rem_set()->occupied(),
"Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
hrrs.n_yielded(), r->rem_set()->occupied());
r->rem_set()->clear_locked();
}
assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
}
_total_humongous++;
return false;
}
size_t total_humongous() const { return _total_humongous; }
size_t candidate_humongous() const { return _candidate_humongous; }
void flush_rem_set_entries() { _dcq.flush(); }
};
void G1CollectedHeap::register_humongous_regions_with_cset() {
if (!G1EagerReclaimHumongousObjects) {
g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
return;
}
double time = os::elapsed_counter();
// Collect reclaim candidate information and register candidates with cset.
RegisterHumongousWithInCSetFastTestClosure cl;
heap_region_iterate(&cl);
time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
cl.total_humongous(),
cl.candidate_humongous());
_has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
// Finally flush all remembered set entries to re-check into the global DCQS.
cl.flush_rem_set_entries();
}
class VerifyRegionRemSetClosure : public HeapRegionClosure {
public:
bool doHeapRegion(HeapRegion* hr) {
if (!hr->is_archive() && !hr->is_continues_humongous()) {
hr->verify_rem_set();
}
return false;
}
};
uint G1CollectedHeap::num_task_queues() const {
return _task_queues->size();
}
#if TASKQUEUE_STATS
void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
st->print_raw_cr("GC Task Stats");
st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
}
void G1CollectedHeap::print_taskqueue_stats() const {
if (!log_is_enabled(Trace, gc, task, stats)) {
return;
}
Log(gc, task, stats) log;
ResourceMark rm;
outputStream* st = log.trace_stream();
print_taskqueue_stats_hdr(st);
TaskQueueStats totals;
const uint n = num_task_queues();
for (uint i = 0; i < n; ++i) {
st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
totals += task_queue(i)->stats;
}
st->print_raw("tot "); totals.print(st); st->cr();
DEBUG_ONLY(totals.verify());
}
void G1CollectedHeap::reset_taskqueue_stats() {
const uint n = num_task_queues();
for (uint i = 0; i < n; ++i) {
task_queue(i)->stats.reset();
}
}
#endif // TASKQUEUE_STATS
void G1CollectedHeap::wait_for_root_region_scanning() {
double scan_wait_start = os::elapsedTime();
// We have to wait until the CM threads finish scanning the
// root regions as it's the only way to ensure that all the
// objects on them have been correctly scanned before we start
// moving them during the GC.
bool waited = _cm->root_regions()->wait_until_scan_finished();
double wait_time_ms = 0.0;
if (waited) {
double scan_wait_end = os::elapsedTime();
wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
}
g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
}
class G1PrintCollectionSetClosure : public HeapRegionClosure {
private:
G1HRPrinter* _hr_printer;
public:
G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
virtual bool doHeapRegion(HeapRegion* r) {
_hr_printer->cset(r);
return false;
}
};
bool
G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
assert_at_safepoint(true /* should_be_vm_thread */);
guarantee(!is_gc_active(), "collection is not reentrant");
if (GCLocker::check_active_before_gc()) {
return false;
}
_gc_timer_stw->register_gc_start();
GCIdMark gc_id_mark;
_gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
SvcGCMarker sgcm(SvcGCMarker::MINOR);
ResourceMark rm;
g1_policy()->note_gc_start();
wait_for_root_region_scanning();
print_heap_before_gc();
print_heap_regions();
trace_heap_before_gc(_gc_tracer_stw);
_verifier->verify_region_sets_optional();
_verifier->verify_dirty_young_regions();
// We should not be doing initial mark unless the conc mark thread is running
if (!_cmThread->should_terminate()) {
// This call will decide whether this pause is an initial-mark
// pause. If it is, during_initial_mark_pause() will return true
// for the duration of this pause.
g1_policy()->decide_on_conc_mark_initiation();
}
// We do not allow initial-mark to be piggy-backed on a mixed GC.
assert(!collector_state()->during_initial_mark_pause() ||
collector_state()->gcs_are_young(), "sanity");
// We also do not allow mixed GCs during marking.
assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
// Record whether this pause is an initial mark. When the current
// thread has completed its logging output and it's safe to signal
// the CM thread, the flag's value in the policy has been reset.
bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
// Inner scope for scope based logging, timers, and stats collection
{
EvacuationInfo evacuation_info;
if (collector_state()->during_initial_mark_pause()) {
// We are about to start a marking cycle, so we increment the
// full collection counter.
increment_old_marking_cycles_started();
_cm->gc_tracer_cm()->set_gc_cause(gc_cause());
}
_gc_tracer_stw->report_yc_type(collector_state()->yc_type());
GCTraceCPUTime tcpu;
FormatBuffer<> gc_string("Pause ");
if (collector_state()->during_initial_mark_pause()) {
gc_string.append("Initial Mark");
} else if (collector_state()->gcs_are_young()) {
gc_string.append("Young");
} else {
gc_string.append("Mixed");
}
GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
workers()->active_workers(),
Threads::number_of_non_daemon_threads());
workers()->update_active_workers(active_workers);
log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
// If the secondary_free_list is not empty, append it to the
// free_list. No need to wait for the cleanup operation to finish;
// the region allocation code will check the secondary_free_list
// and wait if necessary. If the G1StressConcRegionFreeing flag is
// set, skip this step so that the region allocation code has to
// get entries from the secondary_free_list.
if (!G1StressConcRegionFreeing) {
append_secondary_free_list_if_not_empty_with_lock();
}
G1HeapTransition heap_transition(this);
size_t heap_used_bytes_before_gc = used();
// Don't dynamically change the number of GC threads this early. A value of
// 0 is used to indicate serial work. When parallel work is done,
// it will be set.
{ // Call to jvmpi::post_class_unload_events must occur outside of active GC
IsGCActiveMark x;
gc_prologue(false);
increment_total_collections(false /* full gc */);
increment_gc_time_stamp();
if (VerifyRememberedSets) {
log_info(gc, verify)("[Verifying RemSets before GC]");
VerifyRegionRemSetClosure v_cl;
heap_region_iterate(&v_cl);
}
_verifier->verify_before_gc();
_verifier->check_bitmaps("GC Start");
#if defined(COMPILER2) || INCLUDE_JVMCI
DerivedPointerTable::clear();
#endif
// Please see comment in g1CollectedHeap.hpp and
// G1CollectedHeap::ref_processing_init() to see how
// reference processing currently works in G1.
// Enable discovery in the STW reference processor
if (g1_policy()->should_process_references()) {
ref_processor_stw()->enable_discovery();
} else {
ref_processor_stw()->disable_discovery();
}
{
// We want to temporarily turn off discovery by the
// CM ref processor, if necessary, and turn it back on
// on again later if we do. Using a scoped
// NoRefDiscovery object will do this.
NoRefDiscovery no_cm_discovery(ref_processor_cm());
// Forget the current alloc region (we might even choose it to be part
// of the collection set!).
_allocator->release_mutator_alloc_region();
// This timing is only used by the ergonomics to handle our pause target.
// It is unclear why this should not include the full pause. We will
// investigate this in CR 7178365.
//
// Preserving the old comment here if that helps the investigation:
//
// The elapsed time induced by the start time below deliberately elides
// the possible verification above.
double sample_start_time_sec = os::elapsedTime();
g1_policy()->record_collection_pause_start(sample_start_time_sec);
if (collector_state()->during_initial_mark_pause()) {
concurrent_mark()->checkpointRootsInitialPre();
}
g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
evacuation_info.set_collectionset_regions(collection_set()->region_length());
// Make sure the remembered sets are up to date. This needs to be
// done before register_humongous_regions_with_cset(), because the
// remembered sets are used there to choose eager reclaim candidates.
// If the remembered sets are not up to date we might miss some
// entries that need to be handled.
g1_rem_set()->cleanupHRRS();
register_humongous_regions_with_cset();
assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
// We call this after finalize_cset() to
// ensure that the CSet has been finalized.
_cm->verify_no_cset_oops();
if (_hr_printer.is_active()) {
G1PrintCollectionSetClosure cl(&_hr_printer);
_collection_set.iterate(&cl);
}
// Initialize the GC alloc regions.
_allocator->init_gc_alloc_regions(evacuation_info);
G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
pre_evacuate_collection_set();
// Actually do the work...
evacuate_collection_set(evacuation_info, &per_thread_states);
post_evacuate_collection_set(evacuation_info, &per_thread_states);
const size_t* surviving_young_words = per_thread_states.surviving_young_words();
free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
eagerly_reclaim_humongous_regions();
record_obj_copy_mem_stats();
_survivor_evac_stats.adjust_desired_plab_sz();
_old_evac_stats.adjust_desired_plab_sz();
// Start a new incremental collection set for the next pause.
collection_set()->start_incremental_building();
clear_cset_fast_test();
guarantee(_eden.length() == 0, "eden should have been cleared");
g1_policy()->transfer_survivors_to_cset(survivor());
if (evacuation_failed()) {
set_used(recalculate_used());
if (_archive_allocator != NULL) {
_archive_allocator->clear_used();
}
for (uint i = 0; i < ParallelGCThreads; i++) {
if (_evacuation_failed_info_array[i].has_failed()) {
_gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
}
}
} else {
// The "used" of the the collection set have already been subtracted
// when they were freed. Add in the bytes evacuated.
increase_used(g1_policy()->bytes_copied_during_gc());
}
if (collector_state()->during_initial_mark_pause()) {
// We have to do this before we notify the CM threads that
// they can start working to make sure that all the
// appropriate initialization is done on the CM object.
concurrent_mark()->checkpointRootsInitialPost();
collector_state()->set_mark_in_progress(true);
// Note that we don't actually trigger the CM thread at
// this point. We do that later when we're sure that
// the current thread has completed its logging output.
}
allocate_dummy_regions();
_allocator->init_mutator_alloc_region();
{
size_t expand_bytes = _heap_sizing_policy->expansion_amount();
if (expand_bytes > 0) {
size_t bytes_before = capacity();
// No need for an ergo logging here,
// expansion_amount() does this when it returns a value > 0.
double expand_ms;
if (!expand(expand_bytes, _workers, &expand_ms)) {
// We failed to expand the heap. Cannot do anything about it.
}
g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
}
}
// We redo the verification but now wrt to the new CSet which
// has just got initialized after the previous CSet was freed.
_cm->verify_no_cset_oops();
// This timing is only used by the ergonomics to handle our pause target.
// It is unclear why this should not include the full pause. We will
// investigate this in CR 7178365.
double sample_end_time_sec = os::elapsedTime();
double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
size_t total_cards_scanned = per_thread_states.total_cards_scanned();
g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
MemoryService::track_memory_usage();
// In prepare_for_verify() below we'll need to scan the deferred
// update buffers to bring the RSets up-to-date if
// G1HRRSFlushLogBuffersOnVerify has been set. While scanning
// the update buffers we'll probably need to scan cards on the
// regions we just allocated to (i.e., the GC alloc
// regions). However, during the last GC we called
// set_saved_mark() on all the GC alloc regions, so card
// scanning might skip the [saved_mark_word()...top()] area of
// those regions (i.e., the area we allocated objects into
// during the last GC). But it shouldn't. Given that
// saved_mark_word() is conditional on whether the GC time stamp
// on the region is current or not, by incrementing the GC time
// stamp here we invalidate all the GC time stamps on all the
// regions and saved_mark_word() will simply return top() for
// all the regions. This is a nicer way of ensuring this rather
// than iterating over the regions and fixing them. In fact, the
// GC time stamp increment here also ensures that
// saved_mark_word() will return top() between pauses, i.e.,
// during concurrent refinement. So we don't need the
// is_gc_active() check to decided which top to use when
// scanning cards (see CR 7039627).
increment_gc_time_stamp();
if (VerifyRememberedSets) {
log_info(gc, verify)("[Verifying RemSets after GC]");
VerifyRegionRemSetClosure v_cl;
heap_region_iterate(&v_cl);
}
_verifier->verify_after_gc();
_verifier->check_bitmaps("GC End");
assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
ref_processor_stw()->verify_no_references_recorded();
// CM reference discovery will be re-enabled if necessary.
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
gc_epilogue(false);
}
// Print the remainder of the GC log output.
if (evacuation_failed()) {
log_info(gc)("To-space exhausted");
}
g1_policy()->print_phases();
heap_transition.print();
// It is not yet to safe to tell the concurrent mark to
// start as we have some optional output below. We don't want the
// output from the concurrent mark thread interfering with this
// logging output either.
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
print_heap_after_gc();
print_heap_regions();
trace_heap_after_gc(_gc_tracer_stw);
// We must call G1MonitoringSupport::update_sizes() in the same scoping level
// as an active TraceMemoryManagerStats object (i.e. before the destructor for the
// TraceMemoryManagerStats is called) so that the G1 memory pools are updated
// before any GC notifications are raised.
g1mm()->update_sizes();
_gc_tracer_stw->report_evacuation_info(&evacuation_info);
_gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
_gc_timer_stw->register_gc_end();
_gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
}
// It should now be safe to tell the concurrent mark thread to start
// without its logging output interfering with the logging output
// that came from the pause.
if (should_start_conc_mark) {
// CAUTION: after the doConcurrentMark() call below,
// the concurrent marking thread(s) could be running
// concurrently with us. Make sure that anything after
// this point does not assume that we are the only GC thread
// running. Note: of course, the actual marking work will
// not start until the safepoint itself is released in
// SuspendibleThreadSet::desynchronize().
doConcurrentMark();
}
return true;
}
void G1CollectedHeap::remove_self_forwarding_pointers() {
G1ParRemoveSelfForwardPtrsTask rsfp_task;
workers()->run_task(&rsfp_task);
}
void G1CollectedHeap::restore_after_evac_failure() {
double remove_self_forwards_start = os::elapsedTime();
remove_self_forwarding_pointers();
SharedRestorePreservedMarksTaskExecutor task_executor(workers());
_preserved_marks_set.restore(&task_executor);
g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
}
void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
if (!_evacuation_failed) {
_evacuation_failed = true;
}
_evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
_preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
}
bool G1ParEvacuateFollowersClosure::offer_termination() {
G1ParScanThreadState* const pss = par_scan_state();
start_term_time();
const bool res = terminator()->offer_termination();
end_term_time();
return res;
}
void G1ParEvacuateFollowersClosure::do_void() {
G1ParScanThreadState* const pss = par_scan_state();
pss->trim_queue();
do {
pss->steal_and_trim_queue(queues());
} while (!offer_termination());
}
class G1ParTask : public AbstractGangTask {
protected:
G1CollectedHeap* _g1h;
G1ParScanThreadStateSet* _pss;
RefToScanQueueSet* _queues;
G1RootProcessor* _root_processor;
ParallelTaskTerminator _terminator;
uint _n_workers;
public:
G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
: AbstractGangTask("G1 collection"),
_g1h(g1h),
_pss(per_thread_states),
_queues(task_queues),
_root_processor(root_processor),
_terminator(n_workers, _queues),
_n_workers(n_workers)
{}
void work(uint worker_id) {
if (worker_id >= _n_workers) return; // no work needed this round
double start_sec = os::elapsedTime();
_g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
{
ResourceMark rm;
HandleMark hm;
ReferenceProcessor* rp = _g1h->ref_processor_stw();
G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
pss->set_ref_processor(rp);
double start_strong_roots_sec = os::elapsedTime();
_root_processor->evacuate_roots(pss->closures(), worker_id);
G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
// We pass a weak code blobs closure to the remembered set scanning because we want to avoid
// treating the nmethods visited to act as roots for concurrent marking.
// We only want to make sure that the oops in the nmethods are adjusted with regard to the
// objects copied by the current evacuation.
size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
pss->closures()->weak_codeblobs(),
worker_id);
_pss->add_cards_scanned(worker_id, cards_scanned);
double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
double term_sec = 0.0;
size_t evac_term_attempts = 0;
{
double start = os::elapsedTime();
G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
evac.do_void();
evac_term_attempts = evac.term_attempts();
term_sec = evac.term_time();
double elapsed_sec = os::elapsedTime() - start;
_g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
_g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
_g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
}
assert(pss->queue_is_empty(), "should be empty");
if (log_is_enabled(Debug, gc, task, stats)) {
MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
size_t lab_waste;
size_t lab_undo_waste;
pss->waste(lab_waste, lab_undo_waste);
_g1h->print_termination_stats(worker_id,
(os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
strong_roots_sec * 1000.0, /* strong roots time */
term_sec * 1000.0, /* evac term time */
evac_term_attempts, /* evac term attempts */
lab_waste, /* alloc buffer waste */
lab_undo_waste /* undo waste */
);
}
// Close the inner scope so that the ResourceMark and HandleMark
// destructors are executed here and are included as part of the
// "GC Worker Time".
}
_g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
}
};
void G1CollectedHeap::print_termination_stats_hdr() {
log_debug(gc, task, stats)("GC Termination Stats");
log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
}
void G1CollectedHeap::print_termination_stats(uint worker_id,
double elapsed_ms,
double strong_roots_ms,
double term_ms,
size_t term_attempts,
size_t alloc_buffer_waste,
size_t undo_waste) const {
log_debug(gc, task, stats)
("%3d %9.2f %9.2f %6.2f "
"%9.2f %6.2f " SIZE_FORMAT_W(8) " "
SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
term_ms, term_ms * 100 / elapsed_ms, term_attempts,
(alloc_buffer_waste + undo_waste) * HeapWordSize / K,
alloc_buffer_waste * HeapWordSize / K,
undo_waste * HeapWordSize / K);
}
class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
private:
BoolObjectClosure* _is_alive;
int _initial_string_table_size;
int _initial_symbol_table_size;
bool _process_strings;
int _strings_processed;
int _strings_removed;
bool _process_symbols;
int _symbols_processed;
int _symbols_removed;
public:
G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
AbstractGangTask("String/Symbol Unlinking"),
_is_alive(is_alive),
_process_strings(process_strings), _strings_processed(0), _strings_removed(0),
_process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
_initial_string_table_size = StringTable::the_table()->table_size();
_initial_symbol_table_size = SymbolTable::the_table()->table_size();
if (process_strings) {
StringTable::clear_parallel_claimed_index();
}
if (process_symbols) {
SymbolTable::clear_parallel_claimed_index();
}
}
~G1StringSymbolTableUnlinkTask() {
guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
"claim value %d after unlink less than initial string table size %d",
StringTable::parallel_claimed_index(), _initial_string_table_size);
guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
"claim value %d after unlink less than initial symbol table size %d",
SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
log_info(gc, stringtable)(
"Cleaned string and symbol table, "
"strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
"symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
strings_processed(), strings_removed(),
symbols_processed(), symbols_removed());
}
void work(uint worker_id) {
int strings_processed = 0;
int strings_removed = 0;
int symbols_processed = 0;
int symbols_removed = 0;
if (_process_strings) {
StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
Atomic::add(strings_processed, &_strings_processed);
Atomic::add(strings_removed, &_strings_removed);
}
if (_process_symbols) {
SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
Atomic::add(symbols_processed, &_symbols_processed);
Atomic::add(symbols_removed, &_symbols_removed);
}
}
size_t strings_processed() const { return (size_t)_strings_processed; }
size_t strings_removed() const { return (size_t)_strings_removed; }
size_t symbols_processed() const { return (size_t)_symbols_processed; }
size_t symbols_removed() const { return (size_t)_symbols_removed; }
};
class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
private:
static Monitor* _lock;
BoolObjectClosure* const _is_alive;
const bool _unloading_occurred;
const uint _num_workers;
// Variables used to claim nmethods.
CompiledMethod* _first_nmethod;
volatile CompiledMethod* _claimed_nmethod;
// The list of nmethods that need to be processed by the second pass.
volatile CompiledMethod* _postponed_list;
volatile uint _num_entered_barrier;
public:
G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
_is_alive(is_alive),
_unloading_occurred(unloading_occurred),
_num_workers(num_workers),
_first_nmethod(NULL),
_claimed_nmethod(NULL),
_postponed_list(NULL),
_num_entered_barrier(0)
{
CompiledMethod::increase_unloading_clock();
// Get first alive nmethod
CompiledMethodIterator iter = CompiledMethodIterator();
if(iter.next_alive()) {
_first_nmethod = iter.method();
}
_claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
}
~G1CodeCacheUnloadingTask() {
CodeCache::verify_clean_inline_caches();
CodeCache::set_needs_cache_clean(false);
guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
CodeCache::verify_icholder_relocations();
}
private:
void add_to_postponed_list(CompiledMethod* nm) {
CompiledMethod* old;
do {
old = (CompiledMethod*)_postponed_list;
nm->set_unloading_next(old);
} while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
}
void clean_nmethod(CompiledMethod* nm) {
bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
if (postponed) {
// This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
add_to_postponed_list(nm);
}
// Mark that this thread has been cleaned/unloaded.
// After this call, it will be safe to ask if this nmethod was unloaded or not.
nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
}
void clean_nmethod_postponed(CompiledMethod* nm) {
nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
}
static const int MaxClaimNmethods = 16;
void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
CompiledMethod* first;
CompiledMethodIterator last;
do {
*num_claimed_nmethods = 0;
first = (CompiledMethod*)_claimed_nmethod;
last = CompiledMethodIterator(first);
if (first != NULL) {
for (int i = 0; i < MaxClaimNmethods; i++) {
if (!last.next_alive()) {
break;
}
claimed_nmethods[i] = last.method();
(*num_claimed_nmethods)++;
}
}
} while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
}
CompiledMethod* claim_postponed_nmethod() {
CompiledMethod* claim;
CompiledMethod* next;
do {
claim = (CompiledMethod*)_postponed_list;
if (claim == NULL) {
return NULL;
}
next = claim->unloading_next();
} while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
return claim;
}
public:
// Mark that we're done with the first pass of nmethod cleaning.
void barrier_mark(uint worker_id) {
MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
_num_entered_barrier++;
if (_num_entered_barrier == _num_workers) {
ml.notify_all();
}
}
// See if we have to wait for the other workers to
// finish their first-pass nmethod cleaning work.
void barrier_wait(uint worker_id) {
if (_num_entered_barrier < _num_workers) {
MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
while (_num_entered_barrier < _num_workers) {
ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
}
}
}
// Cleaning and unloading of nmethods. Some work has to be postponed
// to the second pass, when we know which nmethods survive.
void work_first_pass(uint worker_id) {
// The first nmethods is claimed by the first worker.
if (worker_id == 0 && _first_nmethod != NULL) {
clean_nmethod(_first_nmethod);
_first_nmethod = NULL;
}
int num_claimed_nmethods;
CompiledMethod* claimed_nmethods[MaxClaimNmethods];
while (true) {
claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
if (num_claimed_nmethods == 0) {
break;
}
for (int i = 0; i < num_claimed_nmethods; i++) {
clean_nmethod(claimed_nmethods[i]);
}
}
}
void work_second_pass(uint worker_id) {
CompiledMethod* nm;
// Take care of postponed nmethods.
while ((nm = claim_postponed_nmethod()) != NULL) {
clean_nmethod_postponed(nm);
}
}
};
Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
class G1KlassCleaningTask : public StackObj {
BoolObjectClosure* _is_alive;
volatile jint _clean_klass_tree_claimed;
ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
public:
G1KlassCleaningTask(BoolObjectClosure* is_alive) :
_is_alive(is_alive),
_clean_klass_tree_claimed(0),
_klass_iterator() {
}
private:
bool claim_clean_klass_tree_task() {
if (_clean_klass_tree_claimed) {
return false;
}
return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
}
InstanceKlass* claim_next_klass() {
Klass* klass;
do {
klass =_klass_iterator.next_klass();
} while (klass != NULL && !klass->is_instance_klass());
// this can be null so don't call InstanceKlass::cast
return static_cast<InstanceKlass*>(klass);
}
public:
void clean_klass(InstanceKlass* ik) {
ik->clean_weak_instanceklass_links(_is_alive);
}
void work() {
ResourceMark rm;
// One worker will clean the subklass/sibling klass tree.
if (claim_clean_klass_tree_task()) {
Klass::clean_subklass_tree(_is_alive);
}
// All workers will help cleaning the classes,
InstanceKlass* klass;
while ((klass = claim_next_klass()) != NULL) {
clean_klass(klass);
}
}
};
// To minimize the remark pause times, the tasks below are done in parallel.
class G1ParallelCleaningTask : public AbstractGangTask {
private:
G1StringSymbolTableUnlinkTask _string_symbol_task;
G1CodeCacheUnloadingTask _code_cache_task;
G1KlassCleaningTask _klass_cleaning_task;
public:
// The constructor is run in the VMThread.
G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
AbstractGangTask("Parallel Cleaning"),
_string_symbol_task(is_alive, process_strings, process_symbols),
_code_cache_task(num_workers, is_alive, unloading_occurred),
_klass_cleaning_task(is_alive) {
}
// The parallel work done by all worker threads.
void work(uint worker_id) {
// Do first pass of code cache cleaning.
_code_cache_task.work_first_pass(worker_id);
// Let the threads mark that the first pass is done.
_code_cache_task.barrier_mark(worker_id);
// Clean the Strings and Symbols.
_string_symbol_task.work(worker_id);
// Wait for all workers to finish the first code cache cleaning pass.
_code_cache_task.barrier_wait(worker_id);
// Do the second code cache cleaning work, which realize on
// the liveness information gathered during the first pass.
_code_cache_task.work_second_pass(worker_id);
// Clean all klasses that were not unloaded.
_klass_cleaning_task.work();
}
};
void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
bool process_strings,
bool process_symbols,
bool class_unloading_occurred) {
uint n_workers = workers()->active_workers();
G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
n_workers, class_unloading_occurred);
workers()->run_task(&g1_unlink_task);
}
void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
bool process_strings, bool process_symbols) {
{ // Timing scope
G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
workers()->run_task(&g1_unlink_task);
}
}
class G1RedirtyLoggedCardsTask : public AbstractGangTask {
private:
DirtyCardQueueSet* _queue;
G1CollectedHeap* _g1h;
public:
G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
_queue(queue), _g1h(g1h) { }
virtual void work(uint worker_id) {
G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
RedirtyLoggedCardTableEntryClosure cl(_g1h);
_queue->par_apply_closure_to_all_completed_buffers(&cl);
phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
}
};
void G1CollectedHeap::redirty_logged_cards() {
double redirty_logged_cards_start = os::elapsedTime();
G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
dirty_card_queue_set().reset_for_par_iteration();
workers()->run_task(&redirty_task);
DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
dcq.merge_bufferlists(&dirty_card_queue_set());
assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
}
// Weak Reference Processing support
// An always "is_alive" closure that is used to preserve referents.
// If the object is non-null then it's alive. Used in the preservation
// of referent objects that are pointed to by reference objects
// discovered by the CM ref processor.
class G1AlwaysAliveClosure: public BoolObjectClosure {
G1CollectedHeap* _g1;
public:
G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
bool do_object_b(oop p) {
if (p != NULL) {
return true;
}
return false;
}
};
bool G1STWIsAliveClosure::do_object_b(oop p) {
// An object is reachable if it is outside the collection set,
// or is inside and copied.
return !_g1->is_in_cset(p) || p->is_forwarded();
}
// Non Copying Keep Alive closure
class G1KeepAliveClosure: public OopClosure {
G1CollectedHeap* _g1;
public:
G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
void do_oop(oop* p) {
oop obj = *p;
assert(obj != NULL, "the caller should have filtered out NULL values");
const InCSetState cset_state = _g1->in_cset_state(obj);
if (!cset_state.is_in_cset_or_humongous()) {
return;
}
if (cset_state.is_in_cset()) {
assert( obj->is_forwarded(), "invariant" );
*p = obj->forwardee();
} else {
assert(!obj->is_forwarded(), "invariant" );
assert(cset_state.is_humongous(),
"Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
_g1->set_humongous_is_live(obj);
}
}
};
// Copying Keep Alive closure - can be called from both
// serial and parallel code as long as different worker
// threads utilize different G1ParScanThreadState instances
// and different queues.
class G1CopyingKeepAliveClosure: public OopClosure {
G1CollectedHeap* _g1h;
OopClosure* _copy_non_heap_obj_cl;
G1ParScanThreadState* _par_scan_state;
public:
G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
OopClosure* non_heap_obj_cl,
G1ParScanThreadState* pss):
_g1h(g1h),
_copy_non_heap_obj_cl(non_heap_obj_cl),
_par_scan_state(pss)
{}
virtual void do_oop(narrowOop* p) { do_oop_work(p); }
virtual void do_oop( oop* p) { do_oop_work(p); }
template <class T> void do_oop_work(T* p) {
oop obj = oopDesc::load_decode_heap_oop(p);
if (_g1h->is_in_cset_or_humongous(obj)) {
// If the referent object has been forwarded (either copied
// to a new location or to itself in the event of an
// evacuation failure) then we need to update the reference
// field and, if both reference and referent are in the G1
// heap, update the RSet for the referent.
//
// If the referent has not been forwarded then we have to keep
// it alive by policy. Therefore we have copy the referent.
//
// If the reference field is in the G1 heap then we can push
// on the PSS queue. When the queue is drained (after each
// phase of reference processing) the object and it's followers
// will be copied, the reference field set to point to the
// new location, and the RSet updated. Otherwise we need to
// use the the non-heap or metadata closures directly to copy
// the referent object and update the pointer, while avoiding
// updating the RSet.
if (_g1h->is_in_g1_reserved(p)) {
_par_scan_state->push_on_queue(p);
} else {
assert(!Metaspace::contains((const void*)p),
"Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
_copy_non_heap_obj_cl->do_oop(p);
}
}
}
};
// Serial drain queue closure. Called as the 'complete_gc'
// closure for each discovered list in some of the
// reference processing phases.
class G1STWDrainQueueClosure: public VoidClosure {
protected:
G1CollectedHeap* _g1h;
G1ParScanThreadState* _par_scan_state;
G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
public:
G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
_g1h(g1h),
_par_scan_state(pss)
{ }
void do_void() {
G1ParScanThreadState* const pss = par_scan_state();
pss->trim_queue();
}
};
// Parallel Reference Processing closures
// Implementation of AbstractRefProcTaskExecutor for parallel reference
// processing during G1 evacuation pauses.
class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
private:
G1CollectedHeap* _g1h;
G1ParScanThreadStateSet* _pss;
RefToScanQueueSet* _queues;
WorkGang* _workers;
uint _active_workers;
public:
G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
G1ParScanThreadStateSet* per_thread_states,
WorkGang* workers,
RefToScanQueueSet *task_queues,
uint n_workers) :
_g1h(g1h),
_pss(per_thread_states),
_queues(task_queues),
_workers(workers),
_active_workers(n_workers)
{
g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
}
// Executes the given task using concurrent marking worker threads.
virtual void execute(ProcessTask& task);
virtual void execute(EnqueueTask& task);
};
// Gang task for possibly parallel reference processing
class G1STWRefProcTaskProxy: public AbstractGangTask {
typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
ProcessTask& _proc_task;
G1CollectedHeap* _g1h;
G1ParScanThreadStateSet* _pss;
RefToScanQueueSet* _task_queues;
ParallelTaskTerminator* _terminator;
public:
G1STWRefProcTaskProxy(ProcessTask& proc_task,
G1CollectedHeap* g1h,
G1ParScanThreadStateSet* per_thread_states,
RefToScanQueueSet *task_queues,
ParallelTaskTerminator* terminator) :
AbstractGangTask("Process reference objects in parallel"),
_proc_task(proc_task),
_g1h(g1h),
_pss(per_thread_states),
_task_queues(task_queues),
_terminator(terminator)
{}
virtual void work(uint worker_id) {
// The reference processing task executed by a single worker.
ResourceMark rm;
HandleMark hm;
G1STWIsAliveClosure is_alive(_g1h);
G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
pss->set_ref_processor(NULL);
// Keep alive closure.
G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
// Complete GC closure
G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
// Call the reference processing task's work routine.
_proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
// Note we cannot assert that the refs array is empty here as not all
// of the processing tasks (specifically phase2 - pp2_work) execute
// the complete_gc closure (which ordinarily would drain the queue) so
// the queue may not be empty.
}
};
// Driver routine for parallel reference processing.
// Creates an instance of the ref processing gang
// task and has the worker threads execute it.
void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
assert(_workers != NULL, "Need parallel worker threads.");
ParallelTaskTerminator terminator(_active_workers, _queues);
G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
_workers->run_task(&proc_task_proxy);
}
// Gang task for parallel reference enqueueing.
class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
EnqueueTask& _enq_task;
public:
G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
AbstractGangTask("Enqueue reference objects in parallel"),
_enq_task(enq_task)
{ }
virtual void work(uint worker_id) {
_enq_task.work(worker_id);
}
};
// Driver routine for parallel reference enqueueing.
// Creates an instance of the ref enqueueing gang
// task and has the worker threads execute it.
void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
assert(_workers != NULL, "Need parallel worker threads.");
G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
_workers->run_task(&enq_task_proxy);
}
// End of weak reference support closures
// Abstract task used to preserve (i.e. copy) any referent objects
// that are in the collection set and are pointed to by reference
// objects discovered by the CM ref processor.
class G1ParPreserveCMReferentsTask: public AbstractGangTask {
protected:
G1CollectedHeap* _g1h;
G1ParScanThreadStateSet* _pss;
RefToScanQueueSet* _queues;
ParallelTaskTerminator _terminator;
uint _n_workers;
public:
G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
AbstractGangTask("ParPreserveCMReferents"),
_g1h(g1h),
_pss(per_thread_states),
_queues(task_queues),
_terminator(workers, _queues),
_n_workers(workers)
{
g1h->ref_processor_cm()->set_active_mt_degree(workers);
}
void work(uint worker_id) {
G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
ResourceMark rm;
HandleMark hm;
G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
pss->set_ref_processor(NULL);
assert(pss->queue_is_empty(), "both queue and overflow should be empty");
// Is alive closure
G1AlwaysAliveClosure always_alive(_g1h);
// Copying keep alive closure. Applied to referent objects that need
// to be copied.
G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
ReferenceProcessor* rp = _g1h->ref_processor_cm();
uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
uint stride = MIN2(MAX2(_n_workers, 1U), limit);
// limit is set using max_num_q() - which was set using ParallelGCThreads.
// So this must be true - but assert just in case someone decides to
// change the worker ids.
assert(worker_id < limit, "sanity");
assert(!rp->discovery_is_atomic(), "check this code");
// Select discovered lists [i, i+stride, i+2*stride,...,limit)
for (uint idx = worker_id; idx < limit; idx += stride) {
DiscoveredList& ref_list = rp->discovered_refs()[idx];
DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
while (iter.has_next()) {
// Since discovery is not atomic for the CM ref processor, we
// can see some null referent objects.
iter.load_ptrs(DEBUG_ONLY(true));
oop ref = iter.obj();
// This will filter nulls.
if (iter.is_referent_alive()) {
iter.make_referent_alive();
}
iter.move_to_next();
}
}
// Drain the queue - which may cause stealing
G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
drain_queue.do_void();
// Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
assert(pss->queue_is_empty(), "should be");
}
};
void G1CollectedHeap::process_weak_jni_handles() {
double ref_proc_start = os::elapsedTime();
G1STWIsAliveClosure is_alive(this);
G1KeepAliveClosure keep_alive(this);
JNIHandles::weak_oops_do(&is_alive, &keep_alive);
double ref_proc_time = os::elapsedTime() - ref_proc_start;
g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
}
void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
// Any reference objects, in the collection set, that were 'discovered'
// by the CM ref processor should have already been copied (either by
// applying the external root copy closure to the discovered lists, or
// by following an RSet entry).
//
// But some of the referents, that are in the collection set, that these
// reference objects point to may not have been copied: the STW ref
// processor would have seen that the reference object had already
// been 'discovered' and would have skipped discovering the reference,
// but would not have treated the reference object as a regular oop.
// As a result the copy closure would not have been applied to the
// referent object.
//
// We need to explicitly copy these referent objects - the references
// will be processed at the end of remarking.
//
// We also need to do this copying before we process the reference
// objects discovered by the STW ref processor in case one of these
// referents points to another object which is also referenced by an
// object discovered by the STW ref processor.
double preserve_cm_referents_time = 0.0;
// To avoid spawning task when there is no work to do, check that
// a concurrent cycle is active and that some references have been
// discovered.
if (concurrent_mark()->cmThread()->during_cycle() &&
ref_processor_cm()->has_discovered_references()) {
double preserve_cm_referents_start = os::elapsedTime();
uint no_of_gc_workers = workers()->active_workers();
G1ParPreserveCMReferentsTask keep_cm_referents(this,
per_thread_states,
no_of_gc_workers,
_task_queues);
workers()->run_task(&keep_cm_referents);
preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
}
g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
}
// Weak Reference processing during an evacuation pause (part 1).
void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
double ref_proc_start = os::elapsedTime();
ReferenceProcessor* rp = _ref_processor_stw;
assert(rp->discovery_enabled(), "should have been enabled");
// Closure to test whether a referent is alive.
G1STWIsAliveClosure is_alive(this);
// Even when parallel reference processing is enabled, the processing
// of JNI refs is serial and performed serially by the current thread
// rather than by a worker. The following PSS will be used for processing
// JNI refs.
// Use only a single queue for this PSS.
G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
pss->set_ref_processor(NULL);
assert(pss->queue_is_empty(), "pre-condition");
// Keep alive closure.
G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
// Serial Complete GC closure
G1STWDrainQueueClosure drain_queue(this, pss);
// Setup the soft refs policy...
rp->setup_policy(false);
ReferenceProcessorStats stats;
if (!rp->processing_is_mt()) {
// Serial reference processing...
stats = rp->process_discovered_references(&is_alive,
&keep_alive,
&drain_queue,
NULL,
_gc_timer_stw);
} else {
uint no_of_gc_workers = workers()->active_workers();
// Parallel reference processing
assert(no_of_gc_workers <= rp->max_num_q(),
"Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
no_of_gc_workers, rp->max_num_q());
G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
stats = rp->process_discovered_references(&is_alive,
&keep_alive,
&drain_queue,
&par_task_executor,
_gc_timer_stw);
}
_gc_tracer_stw->report_gc_reference_stats(stats);
// We have completed copying any necessary live referent objects.
assert(pss->queue_is_empty(), "both queue and overflow should be empty");
double ref_proc_time = os::elapsedTime() - ref_proc_start;
g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
}
// Weak Reference processing during an evacuation pause (part 2).
void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
double ref_enq_start = os::elapsedTime();
ReferenceProcessor* rp = _ref_processor_stw;
assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
// Now enqueue any remaining on the discovered lists on to
// the pending list.
if (!rp->processing_is_mt()) {
// Serial reference processing...
rp->enqueue_discovered_references();
} else {
// Parallel reference enqueueing
uint n_workers = workers()->active_workers();
assert(n_workers <= rp->max_num_q(),
"Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
n_workers, rp->max_num_q());
G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
rp->enqueue_discovered_references(&par_task_executor);
}
rp->verify_no_references_recorded();
assert(!rp->discovery_enabled(), "should have been disabled");
// If during an initial mark pause we install a pending list head which is not otherwise reachable
// ensure that it is marked in the bitmap for concurrent marking to discover.
if (collector_state()->during_initial_mark_pause()) {
oop pll_head = Universe::reference_pending_list();
if (pll_head != NULL) {
_cm->grayRoot(pll_head);
}
}
// FIXME
// CM's reference processing also cleans up the string and symbol tables.
// Should we do that here also? We could, but it is a serial operation
// and could significantly increase the pause time.
double ref_enq_time = os::elapsedTime() - ref_enq_start;
g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
}
void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
double merge_pss_time_start = os::elapsedTime();
per_thread_states->flush();
g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
}
void G1CollectedHeap::pre_evacuate_collection_set() {
_expand_heap_after_alloc_failure = true;
_evacuation_failed = false;
// Disable the hot card cache.
_hot_card_cache->reset_hot_cache_claimed_index();
_hot_card_cache->set_use_cache(false);
g1_rem_set()->prepare_for_oops_into_collection_set_do();
_preserved_marks_set.assert_empty();
}
void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
// Should G1EvacuationFailureALot be in effect for this GC?
NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
// InitialMark needs claim bits to keep track of the marked-through CLDs.
if (collector_state()->during_initial_mark_pause()) {
double start_clear_claimed_marks = os::elapsedTime();
ClassLoaderDataGraph::clear_claimed_marks();
double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
}
double start_par_time_sec = os::elapsedTime();
double end_par_time_sec;
{
const uint n_workers = workers()->active_workers();
G1RootProcessor root_processor(this, n_workers);
G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
print_termination_stats_hdr();
workers()->run_task(&g1_par_task);
end_par_time_sec = os::elapsedTime();
// Closing the inner scope will execute the destructor
// for the G1RootProcessor object. We record the current
// elapsed time before closing the scope so that time
// taken for the destructor is NOT included in the
// reported parallel time.
}
double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
phase_times->record_par_time(par_time_ms);
double code_root_fixup_time_ms =
(os::elapsedTime() - end_par_time_sec) * 1000.0;
phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
}
void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
// Process any discovered reference objects - we have
// to do this _before_ we retire the GC alloc regions
// as we may have to copy some 'reachable' referent
// objects (and their reachable sub-graphs) that were
// not copied during the pause.
if (g1_policy()->should_process_references()) {
preserve_cm_referents(per_thread_states);
process_discovered_references(per_thread_states);
} else {
ref_processor_stw()->verify_no_references_recorded();
process_weak_jni_handles();
}
if (G1StringDedup::is_enabled()) {
double fixup_start = os::elapsedTime();
G1STWIsAliveClosure is_alive(this);
G1KeepAliveClosure keep_alive(this);
G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
}
g1_rem_set()->cleanup_after_oops_into_collection_set_do();
if (evacuation_failed()) {
restore_after_evac_failure();
// Reset the G1EvacuationFailureALot counters and flags
// Note: the values are reset only when an actual
// evacuation failure occurs.
NOT_PRODUCT(reset_evacuation_should_fail();)
}
_preserved_marks_set.assert_empty();
// Enqueue any remaining references remaining on the STW
// reference processor's discovered lists. We need to do
// this after the card table is cleaned (and verified) as
// the act of enqueueing entries on to the pending list
// will log these updates (and dirty their associated
// cards). We need these updates logged to update any
// RSets.
if (g1_policy()->should_process_references()) {
enqueue_discovered_references(per_thread_states);
} else {
g1_policy()->phase_times()->record_ref_enq_time(0);
}
_allocator->release_gc_alloc_regions(evacuation_info);
merge_per_thread_state_info(per_thread_states);
// Reset and re-enable the hot card cache.
// Note the counts for the cards in the regions in the
// collection set are reset when the collection set is freed.
_hot_card_cache->reset_hot_cache();
_hot_card_cache->set_use_cache(true);
purge_code_root_memory();
redirty_logged_cards();
#if defined(COMPILER2) || INCLUDE_JVMCI
DerivedPointerTable::update_pointers();
#endif
g1_policy()->print_age_table();
}
void G1CollectedHeap::record_obj_copy_mem_stats() {
g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
_gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
create_g1_evac_summary(&_old_evac_stats));
}
void G1CollectedHeap::free_region(HeapRegion* hr,
FreeRegionList* free_list,
bool skip_remset,
bool skip_hot_card_cache,
bool locked) {
assert(!hr->is_free(), "the region should not be free");
assert(!hr->is_empty(), "the region should not be empty");
assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
assert(free_list != NULL, "pre-condition");
if (G1VerifyBitmaps) {
MemRegion mr(hr->bottom(), hr->end());
concurrent_mark()->clearRangePrevBitmap(mr);
}
// Clear the card counts for this region.
// Note: we only need to do this if the region is not young
// (since we don't refine cards in young regions).
if (!skip_hot_card_cache && !hr->is_young()) {
_hot_card_cache->reset_card_counts(hr);
}
hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
free_list->add_ordered(hr);
}
void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
FreeRegionList* free_list,
bool skip_remset) {
assert(hr->is_humongous(), "this is only for humongous regions");
assert(free_list != NULL, "pre-condition");
hr->clear_humongous();
free_region(hr, free_list, skip_remset);
}
void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
const uint humongous_regions_removed) {
if (old_regions_removed > 0 || humongous_regions_removed > 0) {
MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
_old_set.bulk_remove(old_regions_removed);
_humongous_set.bulk_remove(humongous_regions_removed);
}
}
void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
assert(list != NULL, "list can't be null");
if (!list->is_empty()) {
MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
_hrm.insert_list_into_free_list(list);
}
}
void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
decrease_used(bytes);
}
class G1ParScrubRemSetTask: public AbstractGangTask {
protected:
G1RemSet* _g1rs;
HeapRegionClaimer _hrclaimer;
public:
G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
AbstractGangTask("G1 ScrubRS"),
_g1rs(g1_rs),
_hrclaimer(num_workers) {
}
void work(uint worker_id) {
_g1rs->scrub(worker_id, &_hrclaimer);
}
};
void G1CollectedHeap::scrub_rem_set() {
uint num_workers = workers()->active_workers();
G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
workers()->run_task(&g1_par_scrub_rs_task);
}
class G1FreeCollectionSetTask : public AbstractGangTask {
private:
// Closure applied to all regions in the collection set to do work that needs to
// be done serially in a single thread.
class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
private:
EvacuationInfo* _evacuation_info;
const size_t* _surviving_young_words;
// Bytes used in successfully evacuated regions before the evacuation.
size_t _before_used_bytes;
// Bytes used in unsucessfully evacuated regions before the evacuation
size_t _after_used_bytes;
size_t _bytes_allocated_in_old_since_last_gc;
size_t _failure_used_words;
size_t _failure_waste_words;
FreeRegionList _local_free_list;
public:
G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
HeapRegionClosure(),
_evacuation_info(evacuation_info),
_surviving_young_words(surviving_young_words),
_before_used_bytes(0),
_after_used_bytes(0),
_bytes_allocated_in_old_since_last_gc(0),
_failure_used_words(0),
_failure_waste_words(0),
_local_free_list("Local Region List for CSet Freeing") {
}
virtual bool doHeapRegion(HeapRegion* r) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
g1h->clear_in_cset(r);
if (r->is_young()) {
assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
"Young index %d is wrong for region %u of type %s with %u young regions",
r->young_index_in_cset(),
r->hrm_index(),
r->get_type_str(),
g1h->collection_set()->young_region_length());
size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
r->record_surv_words_in_group(words_survived);
}
if (!r->evacuation_failed()) {
assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
_before_used_bytes += r->used();
g1h->free_region(r,
&_local_free_list,
true, /* skip_remset */
true, /* skip_hot_card_cache */
true /* locked */);
} else {
r->uninstall_surv_rate_group();
r->set_young_index_in_cset(-1);
r->set_evacuation_failed(false);
// When moving a young gen region to old gen, we "allocate" that whole region
// there. This is in addition to any already evacuated objects. Notify the
// policy about that.
// Old gen regions do not cause an additional allocation: both the objects
// still in the region and the ones already moved are accounted for elsewhere.
if (r->is_young()) {
_bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
}
// The region is now considered to be old.
r->set_old();
// Do some allocation statistics accounting. Regions that failed evacuation
// are always made old, so there is no need to update anything in the young
// gen statistics, but we need to update old gen statistics.
size_t used_words = r->marked_bytes() / HeapWordSize;
_failure_used_words += used_words;
_failure_waste_words += HeapRegion::GrainWords - used_words;
g1h->old_set_add(r);
_after_used_bytes += r->used();
}
return false;
}
void complete_work() {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
_evacuation_info->set_regions_freed(_local_free_list.length());
_evacuation_info->increment_collectionset_used_after(_after_used_bytes);
g1h->prepend_to_freelist(&_local_free_list);
g1h->decrement_summary_bytes(_before_used_bytes);
G1Policy* policy = g1h->g1_policy();
policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
}
};
G1CollectionSet* _collection_set;
G1SerialFreeCollectionSetClosure _cl;
const size_t* _surviving_young_words;
size_t _rs_lengths;
volatile jint _serial_work_claim;
struct WorkItem {
uint region_idx;
bool is_young;
bool evacuation_failed;
WorkItem(HeapRegion* r) {
region_idx = r->hrm_index();
is_young = r->is_young();
evacuation_failed = r->evacuation_failed();
}
};
volatile size_t _parallel_work_claim;
size_t _num_work_items;
WorkItem* _work_items;
void do_serial_work() {
// Need to grab the lock to be allowed to modify the old region list.
MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
_collection_set->iterate(&_cl);
}
void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
HeapRegion* r = g1h->region_at(region_idx);
assert(!g1h->is_on_master_free_list(r), "sanity");
Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
if (!is_young) {
g1h->_hot_card_cache->reset_card_counts(r);
}
if (!evacuation_failed) {
r->rem_set()->clear_locked();
}
}
class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
private:
size_t _cur_idx;
WorkItem* _work_items;
public:
G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
virtual bool doHeapRegion(HeapRegion* r) {
_work_items[_cur_idx++] = WorkItem(r);
return false;
}
};
void prepare_work() {
G1PrepareFreeCollectionSetClosure cl(_work_items);
_collection_set->iterate(&cl);
}
void complete_work() {
_cl.complete_work();
G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
policy->record_max_rs_lengths(_rs_lengths);
policy->cset_regions_freed();
}
public:
G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
AbstractGangTask("G1 Free Collection Set"),
_cl(evacuation_info, surviving_young_words),
_collection_set(collection_set),
_surviving_young_words(surviving_young_words),
_serial_work_claim(0),
_rs_lengths(0),
_parallel_work_claim(0),
_num_work_items(collection_set->region_length()),
_work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
prepare_work();
}
~G1FreeCollectionSetTask() {
complete_work();
FREE_C_HEAP_ARRAY(WorkItem, _work_items);
}
// Chunk size for work distribution. The chosen value has been determined experimentally
// to be a good tradeoff between overhead and achievable parallelism.
static uint chunk_size() { return 32; }
virtual void work(uint worker_id) {
G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
// Claim serial work.
if (_serial_work_claim == 0) {
jint value = Atomic::add(1, &_serial_work_claim) - 1;
if (value == 0) {
double serial_time = os::elapsedTime();
do_serial_work();
timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
}
}
// Start parallel work.
double young_time = 0.0;
bool has_young_time = false;
double non_young_time = 0.0;
bool has_non_young_time = false;
while (true) {
size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
size_t cur = end - chunk_size();
if (cur >= _num_work_items) {
break;
}
double start_time = os::elapsedTime();
end = MIN2(end, _num_work_items);
for (; cur < end; cur++) {
bool is_young = _work_items[cur].is_young;
do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
double end_time = os::elapsedTime();
double time_taken = end_time - start_time;
if (is_young) {
young_time += time_taken;
has_young_time = true;
} else {
non_young_time += time_taken;
has_non_young_time = true;
}
start_time = end_time;
}
}
if (has_young_time) {
timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
}
if (has_non_young_time) {
timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
}
}
};
void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
_eden.clear();
double free_cset_start_time = os::elapsedTime();
{
uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
cl.name(),
num_workers,
_collection_set.region_length());
workers()->run_task(&cl, num_workers);
}
g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
collection_set->clear();
}
class G1FreeHumongousRegionClosure : public HeapRegionClosure {
private:
FreeRegionList* _free_region_list;
HeapRegionSet* _proxy_set;
uint _humongous_regions_removed;
size_t _freed_bytes;
public:
G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
_free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
}
virtual bool doHeapRegion(HeapRegion* r) {
if (!r->is_starts_humongous()) {
return false;
}
G1CollectedHeap* g1h = G1CollectedHeap::heap();
oop obj = (oop)r->bottom();
G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
// The following checks whether the humongous object is live are sufficient.
// The main additional check (in addition to having a reference from the roots
// or the young gen) is whether the humongous object has a remembered set entry.
//
// A humongous object cannot be live if there is no remembered set for it
// because:
// - there can be no references from within humongous starts regions referencing
// the object because we never allocate other objects into them.
// (I.e. there are no intra-region references that may be missed by the
// remembered set)
// - as soon there is a remembered set entry to the humongous starts region
// (i.e. it has "escaped" to an old object) this remembered set entry will stay
// until the end of a concurrent mark.
//
// It is not required to check whether the object has been found dead by marking
// or not, in fact it would prevent reclamation within a concurrent cycle, as
// all objects allocated during that time are considered live.
// SATB marking is even more conservative than the remembered set.
// So if at this point in the collection there is no remembered set entry,
// nobody has a reference to it.
// At the start of collection we flush all refinement logs, and remembered sets
// are completely up-to-date wrt to references to the humongous object.
//
// Other implementation considerations:
// - never consider object arrays at this time because they would pose
// considerable effort for cleaning up the the remembered sets. This is
// required because stale remembered sets might reference locations that
// are currently allocated into.
uint region_idx = r->hrm_index();
if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
!r->rem_set()->is_empty()) {
log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
region_idx,
(size_t)obj->size() * HeapWordSize,
p2i(r->bottom()),
r->rem_set()->occupied(),
r->rem_set()->strong_code_roots_list_length(),
next_bitmap->isMarked(r->bottom()),
g1h->is_humongous_reclaim_candidate(region_idx),
obj->is_typeArray()
);
return false;
}
guarantee(obj->is_typeArray(),
"Only eagerly reclaiming type arrays is supported, but the object "
PTR_FORMAT " is not.", p2i(r->bottom()));
log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
region_idx,
(size_t)obj->size() * HeapWordSize,
p2i(r->bottom()),
r->rem_set()->occupied(),
r->rem_set()->strong_code_roots_list_length(),
next_bitmap->isMarked(r->bottom()),
g1h->is_humongous_reclaim_candidate(region_idx),
obj->is_typeArray()
);
// Need to clear mark bit of the humongous object if already set.
if (next_bitmap->isMarked(r->bottom())) {
next_bitmap->clear(r->bottom());
}
do {
HeapRegion* next = g1h->next_region_in_humongous(r);
_freed_bytes += r->used();
r->set_containing_set(NULL);
_humongous_regions_removed++;
g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
r = next;
} while (r != NULL);
return false;
}
uint humongous_free_count() {
return _humongous_regions_removed;
}
size_t bytes_freed() const {
return _freed_bytes;
}
};
void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
assert_at_safepoint(true);
if (!G1EagerReclaimHumongousObjects ||
(!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
return;
}
double start_time = os::elapsedTime();
FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
G1FreeHumongousRegionClosure cl(&local_cleanup_list);
heap_region_iterate(&cl);
remove_from_old_sets(0, cl.humongous_free_count());
G1HRPrinter* hrp = hr_printer();
if (hrp->is_active()) {
FreeRegionListIterator iter(&local_cleanup_list);
while (iter.more_available()) {
HeapRegion* hr = iter.get_next();
hrp->cleanup(hr);
}
}
prepend_to_freelist(&local_cleanup_list);
decrement_summary_bytes(cl.bytes_freed());
g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
cl.humongous_free_count());
}
class G1AbandonCollectionSetClosure : public HeapRegionClosure {
public:
virtual bool doHeapRegion(HeapRegion* r) {
assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
G1CollectedHeap::heap()->clear_in_cset(r);
r->set_young_index_in_cset(-1);
return false;
}
};
void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
G1AbandonCollectionSetClosure cl;
collection_set->iterate(&cl);
collection_set->clear();
collection_set->stop_incremental_building();
}
void G1CollectedHeap::set_free_regions_coming() {
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
assert(!free_regions_coming(), "pre-condition");
_free_regions_coming = true;
}
void G1CollectedHeap::reset_free_regions_coming() {
assert(free_regions_coming(), "pre-condition");
{
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
_free_regions_coming = false;
SecondaryFreeList_lock->notify_all();
}
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
}
void G1CollectedHeap::wait_while_free_regions_coming() {
// Most of the time we won't have to wait, so let's do a quick test
// first before we take the lock.
if (!free_regions_coming()) {
return;
}
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
{
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
while (free_regions_coming()) {
SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
}
}
log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
}
bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
return _allocator->is_retained_old_region(hr);
}
void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
_eden.add(hr);
_g1_policy->set_region_eden(hr);
}
#ifdef ASSERT
class NoYoungRegionsClosure: public HeapRegionClosure {
private:
bool _success;
public:
NoYoungRegionsClosure() : _success(true) { }
bool doHeapRegion(HeapRegion* r) {
if (r->is_young()) {
log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
p2i(r->bottom()), p2i(r->end()));
_success = false;
}
return false;
}
bool success() { return _success; }
};
bool G1CollectedHeap::check_young_list_empty() {
bool ret = (young_regions_count() == 0);
NoYoungRegionsClosure closure;
heap_region_iterate(&closure);
ret = ret && closure.success();
return ret;
}
#endif // ASSERT
class TearDownRegionSetsClosure : public HeapRegionClosure {
private:
HeapRegionSet *_old_set;
public:
TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
bool doHeapRegion(HeapRegion* r) {
if (r->is_old()) {
_old_set->remove(r);
} else if(r->is_young()) {
r->uninstall_surv_rate_group();
} else {
// We ignore free regions, we'll empty the free list afterwards.
// We ignore humongous regions, we're not tearing down the
// humongous regions set.
assert(r->is_free() || r->is_humongous(),
"it cannot be another type");
}
return false;
}
~TearDownRegionSetsClosure() {
assert(_old_set->is_empty(), "post-condition");
}
};
void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
assert_at_safepoint(true /* should_be_vm_thread */);
if (!free_list_only) {
TearDownRegionSetsClosure cl(&_old_set);
heap_region_iterate(&cl);
// Note that emptying the _young_list is postponed and instead done as
// the first step when rebuilding the regions sets again. The reason for
// this is that during a full GC string deduplication needs to know if
// a collected region was young or old when the full GC was initiated.
}
_hrm.remove_all_free_regions();
}
void G1CollectedHeap::increase_used(size_t bytes) {
_summary_bytes_used += bytes;
}
void G1CollectedHeap::decrease_used(size_t bytes) {
assert(_summary_bytes_used >= bytes,
"invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
_summary_bytes_used, bytes);
_summary_bytes_used -= bytes;
}
void G1CollectedHeap::set_used(size_t bytes) {
_summary_bytes_used = bytes;
}
class RebuildRegionSetsClosure : public HeapRegionClosure {
private:
bool _free_list_only;
HeapRegionSet* _old_set;
HeapRegionManager* _hrm;
size_t _total_used;
public:
RebuildRegionSetsClosure(bool free_list_only,
HeapRegionSet* old_set, HeapRegionManager* hrm) :
_free_list_only(free_list_only),
_old_set(old_set), _hrm(hrm), _total_used(0) {
assert(_hrm->num_free_regions() == 0, "pre-condition");
if (!free_list_only) {
assert(_old_set->is_empty(), "pre-condition");
}
}
bool doHeapRegion(HeapRegion* r) {
if (r->is_empty()) {
// Add free regions to the free list
r->set_free();
r->set_allocation_context(AllocationContext::system());
_hrm->insert_into_free_list(r);
} else if (!_free_list_only) {
if (r->is_humongous()) {
// We ignore humongous regions. We left the humongous set unchanged.
} else {
assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
// We now consider all regions old, so register as such. Leave
// archive regions set that way, however, while still adding
// them to the old set.
if (!r->is_archive()) {
r->set_old();
}
_old_set->add(r);
}
_total_used += r->used();
}
return false;
}
size_t total_used() {
return _total_used;
}
};
void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
assert_at_safepoint(true /* should_be_vm_thread */);
if (!free_list_only) {
_eden.clear();
_survivor.clear();
}
RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
heap_region_iterate(&cl);
if (!free_list_only) {
set_used(cl.total_used());
if (_archive_allocator != NULL) {
_archive_allocator->clear_used();
}
}
assert(used_unlocked() == recalculate_used(),
"inconsistent used_unlocked(), "
"value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
used_unlocked(), recalculate_used());
}
void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
_refine_cte_cl->set_concurrent(concurrent);
}
bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
HeapRegion* hr = heap_region_containing(p);
return hr->is_in(p);
}
// Methods for the mutator alloc region
HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
bool force) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
assert(!force || g1_policy()->can_expand_young_list(),
"if force is true we should be able to expand the young list");
bool should_allocate = g1_policy()->should_allocate_mutator_region();
if (force || should_allocate) {
HeapRegion* new_alloc_region = new_region(word_size,
false /* is_old */,
false /* do_expand */);
if (new_alloc_region != NULL) {
set_region_short_lived_locked(new_alloc_region);
_hr_printer.alloc(new_alloc_region, !should_allocate);
_verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
return new_alloc_region;
}
}
return NULL;
}
void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
collection_set()->add_eden_region(alloc_region);
increase_used(allocated_bytes);
_hr_printer.retire(alloc_region);
// We update the eden sizes here, when the region is retired,
// instead of when it's allocated, since this is the point that its
// used space has been recored in _summary_bytes_used.
g1mm()->update_eden_size();
}
// Methods for the GC alloc regions
bool G1CollectedHeap::has_more_regions(InCSetState dest) {
if (dest.is_old()) {
return true;
} else {
return survivor_regions_count() < g1_policy()->max_survivor_regions();
}
}
HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
assert(FreeList_lock->owned_by_self(), "pre-condition");
if (!has_more_regions(dest)) {
return NULL;
}
const bool is_survivor = dest.is_young();
HeapRegion* new_alloc_region = new_region(word_size,
!is_survivor,
true /* do_expand */);
if (new_alloc_region != NULL) {
// We really only need to do this for old regions given that we
// should never scan survivors. But it doesn't hurt to do it
// for survivors too.
new_alloc_region->record_timestamp();
if (is_survivor) {
new_alloc_region->set_survivor();
_survivor.add(new_alloc_region);
_verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
} else {
new_alloc_region->set_old();
_verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
}
_hr_printer.alloc(new_alloc_region);
bool during_im = collector_state()->during_initial_mark_pause();
new_alloc_region->note_start_of_copying(during_im);
return new_alloc_region;
}
return NULL;
}
void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes,
InCSetState dest) {
bool during_im = collector_state()->during_initial_mark_pause();
alloc_region->note_end_of_copying(during_im);
g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
if (dest.is_old()) {
_old_set.add(alloc_region);
}
_hr_printer.retire(alloc_region);
}
HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
bool expanded = false;
uint index = _hrm.find_highest_free(&expanded);
if (index != G1_NO_HRM_INDEX) {
if (expanded) {
log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
HeapRegion::GrainWords * HeapWordSize);
}
_hrm.allocate_free_regions_starting_at(index, 1);
return region_at(index);
}
return NULL;
}
// Optimized nmethod scanning
class RegisterNMethodOopClosure: public OopClosure {
G1CollectedHeap* _g1h;
nmethod* _nm;
template <class T> void do_oop_work(T* p) {
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
HeapRegion* hr = _g1h->heap_region_containing(obj);
assert(!hr->is_continues_humongous(),
"trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
" starting at " HR_FORMAT,
p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
// HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
hr->add_strong_code_root_locked(_nm);
}
}
public:
RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
_g1h(g1h), _nm(nm) {}
void do_oop(oop* p) { do_oop_work(p); }
void do_oop(narrowOop* p) { do_oop_work(p); }
};
class UnregisterNMethodOopClosure: public OopClosure {
G1CollectedHeap* _g1h;
nmethod* _nm;
template <class T> void do_oop_work(T* p) {
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
HeapRegion* hr = _g1h->heap_region_containing(obj);
assert(!hr->is_continues_humongous(),
"trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
" starting at " HR_FORMAT,
p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
hr->remove_strong_code_root(_nm);
}
}
public:
UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
_g1h(g1h), _nm(nm) {}
void do_oop(oop* p) { do_oop_work(p); }
void do_oop(narrowOop* p) { do_oop_work(p); }
};
void G1CollectedHeap::register_nmethod(nmethod* nm) {
CollectedHeap::register_nmethod(nm);
guarantee(nm != NULL, "sanity");
RegisterNMethodOopClosure reg_cl(this, nm);
nm->oops_do(&reg_cl);
}
void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
CollectedHeap::unregister_nmethod(nm);
guarantee(nm != NULL, "sanity");
UnregisterNMethodOopClosure reg_cl(this, nm);
nm->oops_do(&reg_cl, true);
}
void G1CollectedHeap::purge_code_root_memory() {
double purge_start = os::elapsedTime();
G1CodeRootSet::purge();
double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
}
class RebuildStrongCodeRootClosure: public CodeBlobClosure {
G1CollectedHeap* _g1h;
public:
RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
_g1h(g1h) {}
void do_code_blob(CodeBlob* cb) {
nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
if (nm == NULL) {
return;
}
if (ScavengeRootsInCode) {
_g1h->register_nmethod(nm);
}
}
};
void G1CollectedHeap::rebuild_strong_code_roots() {
RebuildStrongCodeRootClosure blob_cl(this);
CodeCache::blobs_do(&blob_cl);
}