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android / platform / libcore / 8153779ad32 / . / hotspot / src / share / vm / gc_implementation / concurrentMarkSweep / compactibleFreeListSpace.cpp
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/*
* Copyright 2001-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
# include "incls/_precompiled.incl"
# include "incls/_compactibleFreeListSpace.cpp.incl"
/////////////////////////////////////////////////////////////////////////
//// CompactibleFreeListSpace
/////////////////////////////////////////////////////////////////////////
// highest ranked free list lock rank
int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
// Constructor
CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs,
MemRegion mr, bool use_adaptive_freelists,
FreeBlockDictionary::DictionaryChoice dictionaryChoice) :
_dictionaryChoice(dictionaryChoice),
_adaptive_freelists(use_adaptive_freelists),
_bt(bs, mr),
// free list locks are in the range of values taken by _lockRank
// This range currently is [_leaf+2, _leaf+3]
// Note: this requires that CFLspace c'tors
// are called serially in the order in which the locks are
// are acquired in the program text. This is true today.
_freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true),
_parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
"CompactibleFreeListSpace._dict_par_lock", true),
_rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
CMSRescanMultiple),
_marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
CMSConcMarkMultiple),
_collector(NULL)
{
_bt.set_space(this);
initialize(mr, true);
// We have all of "mr", all of which we place in the dictionary
// as one big chunk. We'll need to decide here which of several
// possible alternative dictionary implementations to use. For
// now the choice is easy, since we have only one working
// implementation, namely, the simple binary tree (splaying
// temporarily disabled).
switch (dictionaryChoice) {
case FreeBlockDictionary::dictionaryBinaryTree:
_dictionary = new BinaryTreeDictionary(mr);
break;
case FreeBlockDictionary::dictionarySplayTree:
case FreeBlockDictionary::dictionarySkipList:
default:
warning("dictionaryChoice: selected option not understood; using"
" default BinaryTreeDictionary implementation instead.");
_dictionary = new BinaryTreeDictionary(mr);
break;
}
splitBirth(mr.word_size());
assert(_dictionary != NULL, "CMS dictionary initialization");
// The indexed free lists are initially all empty and are lazily
// filled in on demand. Initialize the array elements to NULL.
initializeIndexedFreeListArray();
// Not using adaptive free lists assumes that allocation is first
// from the linAB's. Also a cms perm gen which can be compacted
// has to have the klass's klassKlass allocated at a lower
// address in the heap than the klass so that the klassKlass is
// moved to its new location before the klass is moved.
// Set the _refillSize for the linear allocation blocks
if (!use_adaptive_freelists) {
FreeChunk* fc = _dictionary->getChunk(mr.word_size());
// The small linAB initially has all the space and will allocate
// a chunk of any size.
HeapWord* addr = (HeapWord*) fc;
_smallLinearAllocBlock.set(addr, fc->size() ,
1024*SmallForLinearAlloc, fc->size());
// Note that _unallocated_block is not updated here.
// Allocations from the linear allocation block should
// update it.
} else {
_smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
SmallForLinearAlloc);
}
// CMSIndexedFreeListReplenish should be at least 1
CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
_promoInfo.setSpace(this);
if (UseCMSBestFit) {
_fitStrategy = FreeBlockBestFitFirst;
} else {
_fitStrategy = FreeBlockStrategyNone;
}
checkFreeListConsistency();
// Initialize locks for parallel case.
if (ParallelGCThreads > 0) {
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
_indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
"a freelist par lock",
true);
if (_indexedFreeListParLocks[i] == NULL)
vm_exit_during_initialization("Could not allocate a par lock");
DEBUG_ONLY(
_indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
)
}
_dictionary->set_par_lock(&_parDictionaryAllocLock);
}
}
// Like CompactibleSpace forward() but always calls cross_threshold() to
// update the block offset table. Removed initialize_threshold call because
// CFLS does not use a block offset array for contiguous spaces.
HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
CompactPoint* cp, HeapWord* compact_top) {
// q is alive
// First check if we should switch compaction space
assert(this == cp->space, "'this' should be current compaction space.");
size_t compaction_max_size = pointer_delta(end(), compact_top);
assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
"virtual adjustObjectSize_v() method is not correct");
size_t adjusted_size = adjustObjectSize(size);
assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
"no small fragments allowed");
assert(minimum_free_block_size() == MinChunkSize,
"for de-virtualized reference below");
// Can't leave a nonzero size, residual fragment smaller than MinChunkSize
if (adjusted_size + MinChunkSize > compaction_max_size &&
adjusted_size != compaction_max_size) {
do {
// switch to next compaction space
cp->space->set_compaction_top(compact_top);
cp->space = cp->space->next_compaction_space();
if (cp->space == NULL) {
cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen);
assert(cp->gen != NULL, "compaction must succeed");
cp->space = cp->gen->first_compaction_space();
assert(cp->space != NULL, "generation must have a first compaction space");
}
compact_top = cp->space->bottom();
cp->space->set_compaction_top(compact_top);
// The correct adjusted_size may not be the same as that for this method
// (i.e., cp->space may no longer be "this" so adjust the size again.
// Use the virtual method which is not used above to save the virtual
// dispatch.
adjusted_size = cp->space->adjust_object_size_v(size);
compaction_max_size = pointer_delta(cp->space->end(), compact_top);
assert(cp->space->minimum_free_block_size() == 0, "just checking");
} while (adjusted_size > compaction_max_size);
}
// store the forwarding pointer into the mark word
if ((HeapWord*)q != compact_top) {
q->forward_to(oop(compact_top));
assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
} else {
// if the object isn't moving we can just set the mark to the default
// mark and handle it specially later on.
q->init_mark();
assert(q->forwardee() == NULL, "should be forwarded to NULL");
}
debug_only(MarkSweep::register_live_oop(q, adjusted_size));
compact_top += adjusted_size;
// we need to update the offset table so that the beginnings of objects can be
// found during scavenge. Note that we are updating the offset table based on
// where the object will be once the compaction phase finishes.
// Always call cross_threshold(). A contiguous space can only call it when
// the compaction_top exceeds the current threshold but not for an
// non-contiguous space.
cp->threshold =
cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
return compact_top;
}
// A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
// and use of single_block instead of alloc_block. The name here is not really
// appropriate - maybe a more general name could be invented for both the
// contiguous and noncontiguous spaces.
HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
_bt.single_block(start, the_end);
return end();
}
// Initialize them to NULL.
void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
for (size_t i = 0; i < IndexSetSize; i++) {
// Note that on platforms where objects are double word aligned,
// the odd array elements are not used. It is convenient, however,
// to map directly from the object size to the array element.
_indexedFreeList[i].reset(IndexSetSize);
_indexedFreeList[i].set_size(i);
assert(_indexedFreeList[i].count() == 0, "reset check failed");
assert(_indexedFreeList[i].head() == NULL, "reset check failed");
assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
}
}
void CompactibleFreeListSpace::resetIndexedFreeListArray() {
for (int i = 1; i < IndexSetSize; i++) {
assert(_indexedFreeList[i].size() == (size_t) i,
"Indexed free list sizes are incorrect");
_indexedFreeList[i].reset(IndexSetSize);
assert(_indexedFreeList[i].count() == 0, "reset check failed");
assert(_indexedFreeList[i].head() == NULL, "reset check failed");
assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
}
}
void CompactibleFreeListSpace::reset(MemRegion mr) {
resetIndexedFreeListArray();
dictionary()->reset();
if (BlockOffsetArrayUseUnallocatedBlock) {
assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
// Everything's allocated until proven otherwise.
_bt.set_unallocated_block(end());
}
if (!mr.is_empty()) {
assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
_bt.single_block(mr.start(), mr.word_size());
FreeChunk* fc = (FreeChunk*) mr.start();
fc->setSize(mr.word_size());
if (mr.word_size() >= IndexSetSize ) {
returnChunkToDictionary(fc);
} else {
_bt.verify_not_unallocated((HeapWord*)fc, fc->size());
_indexedFreeList[mr.word_size()].returnChunkAtHead(fc);
}
}
_promoInfo.reset();
_smallLinearAllocBlock._ptr = NULL;
_smallLinearAllocBlock._word_size = 0;
}
void CompactibleFreeListSpace::reset_after_compaction() {
// Reset the space to the new reality - one free chunk.
MemRegion mr(compaction_top(), end());
reset(mr);
// Now refill the linear allocation block(s) if possible.
if (_adaptive_freelists) {
refillLinearAllocBlocksIfNeeded();
} else {
// Place as much of mr in the linAB as we can get,
// provided it was big enough to go into the dictionary.
FreeChunk* fc = dictionary()->findLargestDict();
if (fc != NULL) {
assert(fc->size() == mr.word_size(),
"Why was the chunk broken up?");
removeChunkFromDictionary(fc);
HeapWord* addr = (HeapWord*) fc;
_smallLinearAllocBlock.set(addr, fc->size() ,
1024*SmallForLinearAlloc, fc->size());
// Note that _unallocated_block is not updated here.
}
}
}
// Walks the entire dictionary, returning a coterminal
// chunk, if it exists. Use with caution since it involves
// a potentially complete walk of a potentially large tree.
FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
assert_lock_strong(&_freelistLock);
return dictionary()->find_chunk_ends_at(end());
}
#ifndef PRODUCT
void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
_indexedFreeList[i].allocation_stats()->set_returnedBytes(0);
}
}
size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
size_t sum = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
sum += _indexedFreeList[i].allocation_stats()->returnedBytes();
}
return sum;
}
size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
size_t count = 0;
for (int i = MinChunkSize; i < IndexSetSize; i++) {
debug_only(
ssize_t total_list_count = 0;
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
fc = fc->next()) {
total_list_count++;
}
assert(total_list_count == _indexedFreeList[i].count(),
"Count in list is incorrect");
)
count += _indexedFreeList[i].count();
}
return count;
}
size_t CompactibleFreeListSpace::totalCount() {
size_t num = totalCountInIndexedFreeLists();
num += dictionary()->totalCount();
if (_smallLinearAllocBlock._word_size != 0) {
num++;
}
return num;
}
#endif
bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
FreeChunk* fc = (FreeChunk*) p;
return fc->isFree();
}
size_t CompactibleFreeListSpace::used() const {
return capacity() - free();
}
size_t CompactibleFreeListSpace::free() const {
// "MT-safe, but not MT-precise"(TM), if you will: i.e.
// if you do this while the structures are in flux you
// may get an approximate answer only; for instance
// because there is concurrent allocation either
// directly by mutators or for promotion during a GC.
// It's "MT-safe", however, in the sense that you are guaranteed
// not to crash and burn, for instance, because of walking
// pointers that could disappear as you were walking them.
// The approximation is because the various components
// that are read below are not read atomically (and
// further the computation of totalSizeInIndexedFreeLists()
// is itself a non-atomic computation. The normal use of
// this is during a resize operation at the end of GC
// and at that time you are guaranteed to get the
// correct actual value. However, for instance, this is
// also read completely asynchronously by the "perf-sampler"
// that supports jvmstat, and you are apt to see the values
// flicker in such cases.
assert(_dictionary != NULL, "No _dictionary?");
return (_dictionary->totalChunkSize(DEBUG_ONLY(freelistLock())) +
totalSizeInIndexedFreeLists() +
_smallLinearAllocBlock._word_size) * HeapWordSize;
}
size_t CompactibleFreeListSpace::max_alloc_in_words() const {
assert(_dictionary != NULL, "No _dictionary?");
assert_locked();
size_t res = _dictionary->maxChunkSize();
res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
(size_t) SmallForLinearAlloc - 1));
// XXX the following could potentially be pretty slow;
// should one, pesimally for the rare cases when res
// caclulated above is less than IndexSetSize,
// just return res calculated above? My reasoning was that
// those cases will be so rare that the extra time spent doesn't
// really matter....
// Note: do not change the loop test i >= res + IndexSetStride
// to i > res below, because i is unsigned and res may be zero.
for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
i -= IndexSetStride) {
if (_indexedFreeList[i].head() != NULL) {
assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
return i;
}
}
return res;
}
void CompactibleFreeListSpace::reportFreeListStatistics() const {
assert_lock_strong(&_freelistLock);
assert(PrintFLSStatistics != 0, "Reporting error");
_dictionary->reportStatistics();
if (PrintFLSStatistics > 1) {
reportIndexedFreeListStatistics();
size_t totalSize = totalSizeInIndexedFreeLists() +
_dictionary->totalChunkSize(DEBUG_ONLY(freelistLock()));
gclog_or_tty->print(" free=%ld frag=%1.4f\n", totalSize, flsFrag());
}
}
void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const {
assert_lock_strong(&_freelistLock);
gclog_or_tty->print("Statistics for IndexedFreeLists:\n"
"--------------------------------\n");
size_t totalSize = totalSizeInIndexedFreeLists();
size_t freeBlocks = numFreeBlocksInIndexedFreeLists();
gclog_or_tty->print("Total Free Space: %d\n", totalSize);
gclog_or_tty->print("Max Chunk Size: %d\n", maxChunkSizeInIndexedFreeLists());
gclog_or_tty->print("Number of Blocks: %d\n", freeBlocks);
if (freeBlocks != 0) {
gclog_or_tty->print("Av. Block Size: %d\n", totalSize/freeBlocks);
}
}
size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
size_t res = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
debug_only(
ssize_t recount = 0;
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
fc = fc->next()) {
recount += 1;
}
assert(recount == _indexedFreeList[i].count(),
"Incorrect count in list");
)
res += _indexedFreeList[i].count();
}
return res;
}
size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
if (_indexedFreeList[i].head() != NULL) {
assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
return (size_t)i;
}
}
return 0;
}
void CompactibleFreeListSpace::set_end(HeapWord* value) {
HeapWord* prevEnd = end();
assert(prevEnd != value, "unnecessary set_end call");
assert(prevEnd == NULL || value >= unallocated_block(), "New end is below unallocated block");
_end = value;
if (prevEnd != NULL) {
// Resize the underlying block offset table.
_bt.resize(pointer_delta(value, bottom()));
if (value <= prevEnd) {
assert(value >= unallocated_block(), "New end is below unallocated block");
} else {
// Now, take this new chunk and add it to the free blocks.
// Note that the BOT has not yet been updated for this block.
size_t newFcSize = pointer_delta(value, prevEnd);
// XXX This is REALLY UGLY and should be fixed up. XXX
if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) {
// Mark the boundary of the new block in BOT
_bt.mark_block(prevEnd, value);
// put it all in the linAB
if (ParallelGCThreads == 0) {
_smallLinearAllocBlock._ptr = prevEnd;
_smallLinearAllocBlock._word_size = newFcSize;
repairLinearAllocBlock(&_smallLinearAllocBlock);
} else { // ParallelGCThreads > 0
MutexLockerEx x(parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
_smallLinearAllocBlock._ptr = prevEnd;
_smallLinearAllocBlock._word_size = newFcSize;
repairLinearAllocBlock(&_smallLinearAllocBlock);
}
// Births of chunks put into a LinAB are not recorded. Births
// of chunks as they are allocated out of a LinAB are.
} else {
// Add the block to the free lists, if possible coalescing it
// with the last free block, and update the BOT and census data.
addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
}
}
}
}
class FreeListSpace_DCTOC : public Filtering_DCTOC {
CompactibleFreeListSpace* _cfls;
CMSCollector* _collector;
protected:
// Override.
#define walk_mem_region_with_cl_DECL(ClosureType) \
virtual void walk_mem_region_with_cl(MemRegion mr, \
HeapWord* bottom, HeapWord* top, \
ClosureType* cl); \
void walk_mem_region_with_cl_par(MemRegion mr, \
HeapWord* bottom, HeapWord* top, \
ClosureType* cl); \
void walk_mem_region_with_cl_nopar(MemRegion mr, \
HeapWord* bottom, HeapWord* top, \
ClosureType* cl)
walk_mem_region_with_cl_DECL(OopClosure);
walk_mem_region_with_cl_DECL(FilteringClosure);
public:
FreeListSpace_DCTOC(CompactibleFreeListSpace* sp,
CMSCollector* collector,
OopClosure* cl,
CardTableModRefBS::PrecisionStyle precision,
HeapWord* boundary) :
Filtering_DCTOC(sp, cl, precision, boundary),
_cfls(sp), _collector(collector) {}
};
// We de-virtualize the block-related calls below, since we know that our
// space is a CompactibleFreeListSpace.
#define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \
HeapWord* bottom, \
HeapWord* top, \
ClosureType* cl) { \
if (SharedHeap::heap()->n_par_threads() > 0) { \
walk_mem_region_with_cl_par(mr, bottom, top, cl); \
} else { \
walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
} \
} \
void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
HeapWord* bottom, \
HeapWord* top, \
ClosureType* cl) { \
/* Skip parts that are before "mr", in case "block_start" sent us \
back too far. */ \
HeapWord* mr_start = mr.start(); \
size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
HeapWord* next = bottom + bot_size; \
while (next < mr_start) { \
bottom = next; \
bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
next = bottom + bot_size; \
} \
\
while (bottom < top) { \
if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
!_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
oop(bottom)) && \
!_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
bottom += _cfls->adjustObjectSize(word_sz); \
} else { \
bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
} \
} \
} \
void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
HeapWord* bottom, \
HeapWord* top, \
ClosureType* cl) { \
/* Skip parts that are before "mr", in case "block_start" sent us \
back too far. */ \
HeapWord* mr_start = mr.start(); \
size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
HeapWord* next = bottom + bot_size; \
while (next < mr_start) { \
bottom = next; \
bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
next = bottom + bot_size; \
} \
\
while (bottom < top) { \
if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
!_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
oop(bottom)) && \
!_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
bottom += _cfls->adjustObjectSize(word_sz); \
} else { \
bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
} \
} \
}
// (There are only two of these, rather than N, because the split is due
// only to the introduction of the FilteringClosure, a local part of the
// impl of this abstraction.)
FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(OopClosure)
FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
DirtyCardToOopClosure*
CompactibleFreeListSpace::new_dcto_cl(OopClosure* cl,
CardTableModRefBS::PrecisionStyle precision,
HeapWord* boundary) {
return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary);
}
// Note on locking for the space iteration functions:
// since the collector's iteration activities are concurrent with
// allocation activities by mutators, absent a suitable mutual exclusion
// mechanism the iterators may go awry. For instace a block being iterated
// may suddenly be allocated or divided up and part of it allocated and
// so on.
// Apply the given closure to each block in the space.
void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
assert_lock_strong(freelistLock());
HeapWord *cur, *limit;
for (cur = bottom(), limit = end(); cur < limit;
cur += cl->do_blk_careful(cur));
}
// Apply the given closure to each block in the space.
void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
assert_lock_strong(freelistLock());
HeapWord *cur, *limit;
for (cur = bottom(), limit = end(); cur < limit;
cur += cl->do_blk(cur));
}
// Apply the given closure to each oop in the space.
void CompactibleFreeListSpace::oop_iterate(OopClosure* cl) {
assert_lock_strong(freelistLock());
HeapWord *cur, *limit;
size_t curSize;
for (cur = bottom(), limit = end(); cur < limit;
cur += curSize) {
curSize = block_size(cur);
if (block_is_obj(cur)) {
oop(cur)->oop_iterate(cl);
}
}
}
// Apply the given closure to each oop in the space \intersect memory region.
void CompactibleFreeListSpace::oop_iterate(MemRegion mr, OopClosure* cl) {
assert_lock_strong(freelistLock());
if (is_empty()) {
return;
}
MemRegion cur = MemRegion(bottom(), end());
mr = mr.intersection(cur);
if (mr.is_empty()) {
return;
}
if (mr.equals(cur)) {
oop_iterate(cl);
return;
}
assert(mr.end() <= end(), "just took an intersection above");
HeapWord* obj_addr = block_start(mr.start());
HeapWord* t = mr.end();
SpaceMemRegionOopsIterClosure smr_blk(cl, mr);
if (block_is_obj(obj_addr)) {
// Handle first object specially.
oop obj = oop(obj_addr);
obj_addr += adjustObjectSize(obj->oop_iterate(&smr_blk));
} else {
FreeChunk* fc = (FreeChunk*)obj_addr;
obj_addr += fc->size();
}
while (obj_addr < t) {
HeapWord* obj = obj_addr;
obj_addr += block_size(obj_addr);
// If "obj_addr" is not greater than top, then the
// entire object "obj" is within the region.
if (obj_addr <= t) {
if (block_is_obj(obj)) {
oop(obj)->oop_iterate(cl);
}
} else {
// "obj" extends beyond end of region
if (block_is_obj(obj)) {
oop(obj)->oop_iterate(&smr_blk);
}
break;
}
}
}
// NOTE: In the following methods, in order to safely be able to
// apply the closure to an object, we need to be sure that the
// object has been initialized. We are guaranteed that an object
// is initialized if we are holding the Heap_lock with the
// world stopped.
void CompactibleFreeListSpace::verify_objects_initialized() const {
if (is_init_completed()) {
assert_locked_or_safepoint(Heap_lock);
if (Universe::is_fully_initialized()) {
guarantee(SafepointSynchronize::is_at_safepoint(),
"Required for objects to be initialized");
}
} // else make a concession at vm start-up
}
// Apply the given closure to each object in the space
void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
assert_lock_strong(freelistLock());
NOT_PRODUCT(verify_objects_initialized());
HeapWord *cur, *limit;
size_t curSize;
for (cur = bottom(), limit = end(); cur < limit;
cur += curSize) {
curSize = block_size(cur);
if (block_is_obj(cur)) {
blk->do_object(oop(cur));
}
}
}
void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
UpwardsObjectClosure* cl) {
assert_locked();
NOT_PRODUCT(verify_objects_initialized());
Space::object_iterate_mem(mr, cl);
}
// Callers of this iterator beware: The closure application should
// be robust in the face of uninitialized objects and should (always)
// return a correct size so that the next addr + size below gives us a
// valid block boundary. [See for instance,
// ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
// in ConcurrentMarkSweepGeneration.cpp.]
HeapWord*
CompactibleFreeListSpace::object_iterate_careful(ObjectClosureCareful* cl) {
assert_lock_strong(freelistLock());
HeapWord *addr, *last;
size_t size;
for (addr = bottom(), last = end();
addr < last; addr += size) {
FreeChunk* fc = (FreeChunk*)addr;
if (fc->isFree()) {
// Since we hold the free list lock, which protects direct
// allocation in this generation by mutators, a free object
// will remain free throughout this iteration code.
size = fc->size();
} else {
// Note that the object need not necessarily be initialized,
// because (for instance) the free list lock does NOT protect
// object initialization. The closure application below must
// therefore be correct in the face of uninitialized objects.
size = cl->do_object_careful(oop(addr));
if (size == 0) {
// An unparsable object found. Signal early termination.
return addr;
}
}
}
return NULL;
}
// Callers of this iterator beware: The closure application should
// be robust in the face of uninitialized objects and should (always)
// return a correct size so that the next addr + size below gives us a
// valid block boundary. [See for instance,
// ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
// in ConcurrentMarkSweepGeneration.cpp.]
HeapWord*
CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
ObjectClosureCareful* cl) {
assert_lock_strong(freelistLock());
// Can't use used_region() below because it may not necessarily
// be the same as [bottom(),end()); although we could
// use [used_region().start(),round_to(used_region().end(),CardSize)),
// that appears too cumbersome, so we just do the simpler check
// in the assertion below.
assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
"mr should be non-empty and within used space");
HeapWord *addr, *end;
size_t size;
for (addr = block_start_careful(mr.start()), end = mr.end();
addr < end; addr += size) {
FreeChunk* fc = (FreeChunk*)addr;
if (fc->isFree()) {
// Since we hold the free list lock, which protects direct
// allocation in this generation by mutators, a free object
// will remain free throughout this iteration code.
size = fc->size();
} else {
// Note that the object need not necessarily be initialized,
// because (for instance) the free list lock does NOT protect
// object initialization. The closure application below must
// therefore be correct in the face of uninitialized objects.
size = cl->do_object_careful_m(oop(addr), mr);
if (size == 0) {
// An unparsable object found. Signal early termination.
return addr;
}
}
}
return NULL;
}
HeapWord* CompactibleFreeListSpace::block_start(const void* p) const {
NOT_PRODUCT(verify_objects_initialized());
return _bt.block_start(p);
}
HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
return _bt.block_start_careful(p);
}
size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
NOT_PRODUCT(verify_objects_initialized());
assert(MemRegion(bottom(), end()).contains(p), "p not in space");
// This must be volatile, or else there is a danger that the compiler
// will compile the code below into a sometimes-infinite loop, by keeping
// the value read the first time in a register.
oop o = (oop)p;
volatile oop* second_word_addr = o->klass_addr();
while (true) {
klassOop k = (klassOop)(*second_word_addr);
// We must do this until we get a consistent view of the object.
if (FreeChunk::secondWordIndicatesFreeChunk((intptr_t)k)) {
FreeChunk* fc = (FreeChunk*)p;
volatile size_t* sz_addr = (volatile size_t*)(fc->size_addr());
size_t res = (*sz_addr);
klassOop k2 = (klassOop)(*second_word_addr); // Read to confirm.
if (k == k2) {
assert(res != 0, "Block size should not be 0");
return res;
}
} else if (k != NULL) {
assert(k->is_oop(true /* ignore mark word */), "Should really be klass oop.");
assert(o->is_parsable(), "Should be parsable");
assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
size_t res = o->size_given_klass(k->klass_part());
res = adjustObjectSize(res);
assert(res != 0, "Block size should not be 0");
return res;
}
}
}
// A variant of the above that uses the Printezis bits for
// unparsable but allocated objects. This avoids any possible
// stalls waiting for mutators to initialize objects, and is
// thus potentially faster than the variant above. However,
// this variant may return a zero size for a block that is
// under mutation and for which a consistent size cannot be
// inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
const CMSCollector* c)
const {
assert(MemRegion(bottom(), end()).contains(p), "p not in space");
// This must be volatile, or else there is a danger that the compiler
// will compile the code below into a sometimes-infinite loop, by keeping
// the value read the first time in a register.
oop o = (oop)p;
volatile oop* second_word_addr = o->klass_addr();
DEBUG_ONLY(uint loops = 0;)
while (true) {
klassOop k = (klassOop)(*second_word_addr);
// We must do this until we get a consistent view of the object.
if (FreeChunk::secondWordIndicatesFreeChunk((intptr_t)k)) {
FreeChunk* fc = (FreeChunk*)p;
volatile size_t* sz_addr = (volatile size_t*)(fc->size_addr());
size_t res = (*sz_addr);
klassOop k2 = (klassOop)(*second_word_addr); // Read to confirm.
if (k == k2) {
assert(res != 0, "Block size should not be 0");
assert(loops == 0, "Should be 0");
return res;
}
} else if (k != NULL && o->is_parsable()) {
assert(k->is_oop(), "Should really be klass oop.");
assert(o->is_oop(), "Should be an oop");
size_t res = o->size_given_klass(k->klass_part());
res = adjustObjectSize(res);
assert(res != 0, "Block size should not be 0");
return res;
} else {
return c->block_size_if_printezis_bits(p);
}
assert(loops == 0, "Can loop at most once");
DEBUG_ONLY(loops++;)
}
}
size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
NOT_PRODUCT(verify_objects_initialized());
assert(MemRegion(bottom(), end()).contains(p), "p not in space");
FreeChunk* fc = (FreeChunk*)p;
if (fc->isFree()) {
return fc->size();
} else {
// Ignore mark word because this may be a recently promoted
// object whose mark word is used to chain together grey
// objects (the last one would have a null value).
assert(oop(p)->is_oop(true), "Should be an oop");
return adjustObjectSize(oop(p)->size());
}
}
// This implementation assumes that the property of "being an object" is
// stable. But being a free chunk may not be (because of parallel
// promotion.)
bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
FreeChunk* fc = (FreeChunk*)p;
assert(is_in_reserved(p), "Should be in space");
// When doing a mark-sweep-compact of the CMS generation, this
// assertion may fail because prepare_for_compaction() uses
// space that is garbage to maintain information on ranges of
// live objects so that these live ranges can be moved as a whole.
// Comment out this assertion until that problem can be solved
// (i.e., that the block start calculation may look at objects
// at address below "p" in finding the object that contains "p"
// and those objects (if garbage) may have been modified to hold
// live range information.
// assert(ParallelGCThreads > 0 || _bt.block_start(p) == p, "Should be a block boundary");
klassOop k = oop(p)->klass();
intptr_t ki = (intptr_t)k;
if (FreeChunk::secondWordIndicatesFreeChunk(ki)) return false;
if (k != NULL) {
// Ignore mark word because it may have been used to
// chain together promoted objects (the last one
// would have a null value).
assert(oop(p)->is_oop(true), "Should be an oop");
return true;
} else {
return false; // Was not an object at the start of collection.
}
}
// Check if the object is alive. This fact is checked either by consulting
// the main marking bitmap in the sweeping phase or, if it's a permanent
// generation and we're not in the sweeping phase, by checking the
// perm_gen_verify_bit_map where we store the "deadness" information if
// we did not sweep the perm gen in the most recent previous GC cycle.
bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
assert (block_is_obj(p), "The address should point to an object");
// If we're sweeping, we use object liveness information from the main bit map
// for both perm gen and old gen.
// We don't need to lock the bitmap (live_map or dead_map below), because
// EITHER we are in the middle of the sweeping phase, and the
// main marking bit map (live_map below) is locked,
// OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
// is stable, because it's mutated only in the sweeping phase.
if (_collector->abstract_state() == CMSCollector::Sweeping) {
CMSBitMap* live_map = _collector->markBitMap();
return live_map->isMarked((HeapWord*) p);
} else {
// If we're not currently sweeping and we haven't swept the perm gen in
// the previous concurrent cycle then we may have dead but unswept objects
// in the perm gen. In this case, we use the "deadness" information
// that we had saved in perm_gen_verify_bit_map at the last sweep.
if (!CMSClassUnloadingEnabled && _collector->_permGen->reserved().contains(p)) {
if (_collector->verifying()) {
CMSBitMap* dead_map = _collector->perm_gen_verify_bit_map();
// Object is marked in the dead_map bitmap at the previous sweep
// when we know that it's dead; if the bitmap is not allocated then
// the object is alive.
return (dead_map->sizeInBits() == 0) // bit_map has been allocated
|| !dead_map->par_isMarked((HeapWord*) p);
} else {
return false; // We can't say for sure if it's live, so we say that it's dead.
}
}
}
return true;
}
bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
FreeChunk* fc = (FreeChunk*)p;
assert(is_in_reserved(p), "Should be in space");
assert(_bt.block_start(p) == p, "Should be a block boundary");
if (!fc->isFree()) {
// Ignore mark word because it may have been used to
// chain together promoted objects (the last one
// would have a null value).
assert(oop(p)->is_oop(true), "Should be an oop");
return true;
}
return false;
}
// "MT-safe but not guaranteed MT-precise" (TM); you may get an
// approximate answer if you don't hold the freelistlock when you call this.
size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
size_t size = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
debug_only(
// We may be calling here without the lock in which case we
// won't do this modest sanity check.
if (freelistLock()->owned_by_self()) {
size_t total_list_size = 0;
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
fc = fc->next()) {
total_list_size += i;
}
assert(total_list_size == i * _indexedFreeList[i].count(),
"Count in list is incorrect");
}
)
size += i * _indexedFreeList[i].count();
}
return size;
}
HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
return allocate(size);
}
HeapWord*
CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
}
HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
assert_lock_strong(freelistLock());
HeapWord* res = NULL;
assert(size == adjustObjectSize(size),
"use adjustObjectSize() before calling into allocate()");
if (_adaptive_freelists) {
res = allocate_adaptive_freelists(size);
} else { // non-adaptive free lists
res = allocate_non_adaptive_freelists(size);
}
if (res != NULL) {
// check that res does lie in this space!
assert(is_in_reserved(res), "Not in this space!");
assert(is_aligned((void*)res), "alignment check");
FreeChunk* fc = (FreeChunk*)res;
fc->markNotFree();
assert(!fc->isFree(), "shouldn't be marked free");
assert(oop(fc)->klass() == NULL, "should look uninitialized");
// Verify that the block offset table shows this to
// be a single block, but not one which is unallocated.
_bt.verify_single_block(res, size);
_bt.verify_not_unallocated(res, size);
// mangle a just allocated object with a distinct pattern.
debug_only(fc->mangleAllocated(size));
}
return res;
}
HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) {
HeapWord* res = NULL;
// try and use linear allocation for smaller blocks
if (size < _smallLinearAllocBlock._allocation_size_limit) {
// if successful, the following also adjusts block offset table
res = getChunkFromSmallLinearAllocBlock(size);
}
// Else triage to indexed lists for smaller sizes
if (res == NULL) {
if (size < SmallForDictionary) {
res = (HeapWord*) getChunkFromIndexedFreeList(size);
} else {
// else get it from the big dictionary; if even this doesn't
// work we are out of luck.
res = (HeapWord*)getChunkFromDictionaryExact(size);
}
}
return res;
}
HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
assert_lock_strong(freelistLock());
HeapWord* res = NULL;
assert(size == adjustObjectSize(size),
"use adjustObjectSize() before calling into allocate()");
// Strategy
// if small
// exact size from small object indexed list if small
// small or large linear allocation block (linAB) as appropriate
// take from lists of greater sized chunks
// else
// dictionary
// small or large linear allocation block if it has the space
// Try allocating exact size from indexTable first
if (size < IndexSetSize) {
res = (HeapWord*) getChunkFromIndexedFreeList(size);
if(res != NULL) {
assert(res != (HeapWord*)_indexedFreeList[size].head(),
"Not removed from free list");
// no block offset table adjustment is necessary on blocks in
// the indexed lists.
// Try allocating from the small LinAB
} else if (size < _smallLinearAllocBlock._allocation_size_limit &&
(res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
// if successful, the above also adjusts block offset table
// Note that this call will refill the LinAB to
// satisfy the request. This is different that
// evm.
// Don't record chunk off a LinAB? smallSplitBirth(size);
} else {
// Raid the exact free lists larger than size, even if they are not
// overpopulated.
res = (HeapWord*) getChunkFromGreater(size);
}
} else {
// Big objects get allocated directly from the dictionary.
res = (HeapWord*) getChunkFromDictionaryExact(size);
if (res == NULL) {
// Try hard not to fail since an allocation failure will likely
// trigger a synchronous GC. Try to get the space from the
// allocation blocks.
res = getChunkFromSmallLinearAllocBlockRemainder(size);
}
}
return res;
}
// A worst-case estimate of the space required (in HeapWords) to expand the heap
// when promoting obj.
size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
// Depending on the object size, expansion may require refilling either a
// bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
// is added because the dictionary may over-allocate to avoid fragmentation.
size_t space = obj_size;
if (!_adaptive_freelists) {
space = MAX2(space, _smallLinearAllocBlock._refillSize);
}
space += _promoInfo.refillSize() + 2 * MinChunkSize;
return space;
}
FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
FreeChunk* ret;
assert(numWords >= MinChunkSize, "Size is less than minimum");
assert(linearAllocationWouldFail() || bestFitFirst(),
"Should not be here");
size_t i;
size_t currSize = numWords + MinChunkSize;
assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
FreeList* fl = &_indexedFreeList[i];
if (fl->head()) {
ret = getFromListGreater(fl, numWords);
assert(ret == NULL || ret->isFree(), "Should be returning a free chunk");
return ret;
}
}
currSize = MAX2((size_t)SmallForDictionary,
(size_t)(numWords + MinChunkSize));
/* Try to get a chunk that satisfies request, while avoiding
fragmentation that can't be handled. */
{
ret = dictionary()->getChunk(currSize);
if (ret != NULL) {
assert(ret->size() - numWords >= MinChunkSize,
"Chunk is too small");
_bt.allocated((HeapWord*)ret, ret->size());
/* Carve returned chunk. */
(void) splitChunkAndReturnRemainder(ret, numWords);
/* Label this as no longer a free chunk. */
assert(ret->isFree(), "This chunk should be free");
ret->linkPrev(NULL);
}
assert(ret == NULL || ret->isFree(), "Should be returning a free chunk");
return ret;
}
ShouldNotReachHere();
}
bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc)
const {
assert(fc->size() < IndexSetSize, "Size of chunk is too large");
return _indexedFreeList[fc->size()].verifyChunkInFreeLists(fc);
}
bool CompactibleFreeListSpace::verifyChunkInFreeLists(FreeChunk* fc) const {
if (fc->size() >= IndexSetSize) {
return dictionary()->verifyChunkInFreeLists(fc);
} else {
return verifyChunkInIndexedFreeLists(fc);
}
}
#ifndef PRODUCT
void CompactibleFreeListSpace::assert_locked() const {
CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
}
#endif
FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
// In the parallel case, the main thread holds the free list lock
// on behalf the parallel threads.
assert_locked();
FreeChunk* fc;
{
// If GC is parallel, this might be called by several threads.
// This should be rare enough that the locking overhead won't affect
// the sequential code.
MutexLockerEx x(parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
fc = getChunkFromDictionary(size);
}
if (fc != NULL) {
fc->dontCoalesce();
assert(fc->isFree(), "Should be free, but not coalescable");
// Verify that the block offset table shows this to
// be a single block, but not one which is unallocated.
_bt.verify_single_block((HeapWord*)fc, fc->size());
_bt.verify_not_unallocated((HeapWord*)fc, fc->size());
}
return fc;
}
oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size, oop* ref) {
assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
assert_locked();
// if we are tracking promotions, then first ensure space for
// promotion (including spooling space for saving header if necessary).
// then allocate and copy, then track promoted info if needed.
// When tracking (see PromotionInfo::track()), the mark word may
// be displaced and in this case restoration of the mark word
// occurs in the (oop_since_save_marks_)iterate phase.
if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
return NULL;
}
// Call the allocate(size_t, bool) form directly to avoid the
// additional call through the allocate(size_t) form. Having
// the compile inline the call is problematic because allocate(size_t)
// is a virtual method.
HeapWord* res = allocate(adjustObjectSize(obj_size));
if (res != NULL) {
Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
// if we should be tracking promotions, do so.
if (_promoInfo.tracking()) {
_promoInfo.track((PromotedObject*)res);
}
}
return oop(res);
}
HeapWord*
CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
assert_locked();
assert(size >= MinChunkSize, "minimum chunk size");
assert(size < _smallLinearAllocBlock._allocation_size_limit,
"maximum from smallLinearAllocBlock");
return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
}
HeapWord*
CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
size_t size) {
assert_locked();
assert(size >= MinChunkSize, "too small");
HeapWord* res = NULL;
// Try to do linear allocation from blk, making sure that
if (blk->_word_size == 0) {
// We have probably been unable to fill this either in the prologue or
// when it was exhausted at the last linear allocation. Bail out until
// next time.
assert(blk->_ptr == NULL, "consistency check");
return NULL;
}
assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
res = getChunkFromLinearAllocBlockRemainder(blk, size);
if (res != NULL) return res;
// about to exhaust this linear allocation block
if (blk->_word_size == size) { // exactly satisfied
res = blk->_ptr;
_bt.allocated(res, blk->_word_size);
} else if (size + MinChunkSize <= blk->_refillSize) {
// Update _unallocated_block if the size is such that chunk would be
// returned to the indexed free list. All other chunks in the indexed
// free lists are allocated from the dictionary so that _unallocated_block
// has already been adjusted for them. Do it here so that the cost
// for all chunks added back to the indexed free lists.
if (blk->_word_size < SmallForDictionary) {
_bt.allocated(blk->_ptr, blk->_word_size);
}
// Return the chunk that isn't big enough, and then refill below.
addChunkToFreeLists(blk->_ptr, blk->_word_size);
_bt.verify_single_block(blk->_ptr, (blk->_ptr + blk->_word_size));
// Don't keep statistics on adding back chunk from a LinAB.
} else {
// A refilled block would not satisfy the request.
return NULL;
}
blk->_ptr = NULL; blk->_word_size = 0;
refillLinearAllocBlock(blk);
assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
"block was replenished");
if (res != NULL) {
splitBirth(size);
repairLinearAllocBlock(blk);
} else if (blk->_ptr != NULL) {
res = blk->_ptr;
size_t blk_size = blk->_word_size;
blk->_word_size -= size;
blk->_ptr += size;
splitBirth(size);
repairLinearAllocBlock(blk);
// Update BOT last so that other (parallel) GC threads see a consistent
// view of the BOT and free blocks.
// Above must occur before BOT is updated below.
_bt.split_block(res, blk_size, size); // adjust block offset table
}
return res;
}
HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
LinearAllocBlock* blk,
size_t size) {
assert_locked();
assert(size >= MinChunkSize, "too small");
HeapWord* res = NULL;
// This is the common case. Keep it simple.
if (blk->_word_size >= size + MinChunkSize) {
assert(blk->_ptr != NULL, "consistency check");
res = blk->_ptr;
// Note that the BOT is up-to-date for the linAB before allocation. It
// indicates the start of the linAB. The split_block() updates the
// BOT for the linAB after the allocation (indicates the start of the
// next chunk to be allocated).
size_t blk_size = blk->_word_size;
blk->_word_size -= size;
blk->_ptr += size;
splitBirth(size);
repairLinearAllocBlock(blk);
// Update BOT last so that other (parallel) GC threads see a consistent
// view of the BOT and free blocks.
// Above must occur before BOT is updated below.
_bt.split_block(res, blk_size, size); // adjust block offset table
_bt.allocated(res, size);
}
return res;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
assert_locked();
assert(size < SmallForDictionary, "just checking");
FreeChunk* res;
res = _indexedFreeList[size].getChunkAtHead();
if (res == NULL) {
res = getChunkFromIndexedFreeListHelper(size);
}
_bt.verify_not_unallocated((HeapWord*) res, size);
return res;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size) {
assert_locked();
FreeChunk* fc = NULL;
if (size < SmallForDictionary) {
assert(_indexedFreeList[size].head() == NULL ||
_indexedFreeList[size].surplus() <= 0,
"List for this size should be empty or under populated");
// Try best fit in exact lists before replenishing the list
if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
// Replenish list.
//
// Things tried that failed.
// Tried allocating out of the two LinAB's first before
// replenishing lists.
// Tried small linAB of size 256 (size in indexed list)
// and replenishing indexed lists from the small linAB.
//
FreeChunk* newFc = NULL;
size_t replenish_size = CMSIndexedFreeListReplenish * size;
if (replenish_size < SmallForDictionary) {
// Do not replenish from an underpopulated size.
if (_indexedFreeList[replenish_size].surplus() > 0 &&
_indexedFreeList[replenish_size].head() != NULL) {
newFc =
_indexedFreeList[replenish_size].getChunkAtHead();
} else {
newFc = bestFitSmall(replenish_size);
}
}
if (newFc != NULL) {
splitDeath(replenish_size);
} else if (replenish_size > size) {
assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
newFc =
getChunkFromIndexedFreeListHelper(replenish_size);
}
if (newFc != NULL) {
assert(newFc->size() == replenish_size, "Got wrong size");
size_t i;
FreeChunk *curFc, *nextFc;
// carve up and link blocks 0, ..., CMSIndexedFreeListReplenish - 2
// The last chunk is not added to the lists but is returned as the
// free chunk.
for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
i = 0;
i < (CMSIndexedFreeListReplenish - 1);
curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
i++) {
curFc->setSize(size);
// Don't record this as a return in order to try and
// determine the "returns" from a GC.
_bt.verify_not_unallocated((HeapWord*) fc, size);
_indexedFreeList[size].returnChunkAtTail(curFc, false);
_bt.mark_block((HeapWord*)curFc, size);
splitBirth(size);
// Don't record the initial population of the indexed list
// as a split birth.
}
// check that the arithmetic was OK above
assert((HeapWord*)nextFc == (HeapWord*)newFc + replenish_size,
"inconsistency in carving newFc");
curFc->setSize(size);
_bt.mark_block((HeapWord*)curFc, size);
splitBirth(size);
return curFc;
}
}
} else {
// Get a free chunk from the free chunk dictionary to be returned to
// replenish the indexed free list.
fc = getChunkFromDictionaryExact(size);
}
assert(fc == NULL || fc->isFree(), "Should be returning a free chunk");
return fc;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
assert_locked();
FreeChunk* fc = _dictionary->getChunk(size);
if (fc == NULL) {
return NULL;
}
_bt.allocated((HeapWord*)fc, fc->size());
if (fc->size() >= size + MinChunkSize) {
fc = splitChunkAndReturnRemainder(fc, size);
}
assert(fc->size() >= size, "chunk too small");
assert(fc->size() < size + MinChunkSize, "chunk too big");
_bt.verify_single_block((HeapWord*)fc, fc->size());
return fc;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
assert_locked();
FreeChunk* fc = _dictionary->getChunk(size);
if (fc == NULL) {
return fc;
}
_bt.allocated((HeapWord*)fc, fc->size());
if (fc->size() == size) {
_bt.verify_single_block((HeapWord*)fc, size);
return fc;
}
assert(fc->size() > size, "getChunk() guarantee");
if (fc->size() < size + MinChunkSize) {
// Return the chunk to the dictionary and go get a bigger one.
returnChunkToDictionary(fc);
fc = _dictionary->getChunk(size + MinChunkSize);
if (fc == NULL) {
return NULL;
}
_bt.allocated((HeapWord*)fc, fc->size());
}
assert(fc->size() >= size + MinChunkSize, "tautology");
fc = splitChunkAndReturnRemainder(fc, size);
assert(fc->size() == size, "chunk is wrong size");
_bt.verify_single_block((HeapWord*)fc, size);
return fc;
}
void
CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
assert_locked();
size_t size = chunk->size();
_bt.verify_single_block((HeapWord*)chunk, size);
// adjust _unallocated_block downward, as necessary
_bt.freed((HeapWord*)chunk, size);
_dictionary->returnChunk(chunk);
}
void
CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
assert_locked();
size_t size = fc->size();
_bt.verify_single_block((HeapWord*) fc, size);
_bt.verify_not_unallocated((HeapWord*) fc, size);
if (_adaptive_freelists) {
_indexedFreeList[size].returnChunkAtTail(fc);
} else {
_indexedFreeList[size].returnChunkAtHead(fc);
}
}
// Add chunk to end of last block -- if it's the largest
// block -- and update BOT and census data. We would
// of course have preferred to coalesce it with the
// last block, but it's currently less expensive to find the
// largest block than it is to find the last.
void
CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
HeapWord* chunk, size_t size) {
// check that the chunk does lie in this space!
assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
assert_locked();
// One of the parallel gc task threads may be here
// whilst others are allocating.
Mutex* lock = NULL;
if (ParallelGCThreads != 0) {
lock = &_parDictionaryAllocLock;
}
FreeChunk* ec;
{
MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
ec = dictionary()->findLargestDict(); // get largest block
if (ec != NULL && ec->end() == chunk) {
// It's a coterminal block - we can coalesce.
size_t old_size = ec->size();
coalDeath(old_size);
removeChunkFromDictionary(ec);
size += old_size;
} else {
ec = (FreeChunk*)chunk;
}
}
ec->setSize(size);
debug_only(ec->mangleFreed(size));
if (size < SmallForDictionary) {
lock = _indexedFreeListParLocks[size];
}
MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
// record the birth under the lock since the recording involves
// manipulation of the list on which the chunk lives and
// if the chunk is allocated and is the last on the list,
// the list can go away.
coalBirth(size);
}
void
CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
size_t size) {
// check that the chunk does lie in this space!
assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
assert_locked();
_bt.verify_single_block(chunk, size);
FreeChunk* fc = (FreeChunk*) chunk;
fc->setSize(size);
debug_only(fc->mangleFreed(size));
if (size < SmallForDictionary) {
returnChunkToFreeList(fc);
} else {
returnChunkToDictionary(fc);
}
}
void
CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
size_t size, bool coalesced) {
assert_locked();
assert(chunk != NULL, "null chunk");
if (coalesced) {
// repair BOT
_bt.single_block(chunk, size);
}
addChunkToFreeLists(chunk, size);
}
// We _must_ find the purported chunk on our free lists;
// we assert if we don't.
void
CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
size_t size = fc->size();
assert_locked();
debug_only(verifyFreeLists());
if (size < SmallForDictionary) {
removeChunkFromIndexedFreeList(fc);
} else {
removeChunkFromDictionary(fc);
}
_bt.verify_single_block((HeapWord*)fc, size);
debug_only(verifyFreeLists());
}
void
CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
size_t size = fc->size();
assert_locked();
assert(fc != NULL, "null chunk");
_bt.verify_single_block((HeapWord*)fc, size);
_dictionary->removeChunk(fc);
// adjust _unallocated_block upward, as necessary
_bt.allocated((HeapWord*)fc, size);
}
void
CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
assert_locked();
size_t size = fc->size();
_bt.verify_single_block((HeapWord*)fc, size);
NOT_PRODUCT(
if (FLSVerifyIndexTable) {
verifyIndexedFreeList(size);
}
)
_indexedFreeList[size].removeChunk(fc);
debug_only(fc->clearNext());
debug_only(fc->clearPrev());
NOT_PRODUCT(
if (FLSVerifyIndexTable) {
verifyIndexedFreeList(size);
}
)
}
FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
/* A hint is the next larger size that has a surplus.
Start search at a size large enough to guarantee that
the excess is >= MIN_CHUNK. */
size_t start = align_object_size(numWords + MinChunkSize);
if (start < IndexSetSize) {
FreeList* it = _indexedFreeList;
size_t hint = _indexedFreeList[start].hint();
while (hint < IndexSetSize) {
assert(hint % MinObjAlignment == 0, "hint should be aligned");
FreeList *fl = &_indexedFreeList[hint];
if (fl->surplus() > 0 && fl->head() != NULL) {
// Found a list with surplus, reset original hint
// and split out a free chunk which is returned.
_indexedFreeList[start].set_hint(hint);
FreeChunk* res = getFromListGreater(fl, numWords);
assert(res == NULL || res->isFree(),
"Should be returning a free chunk");
return res;
}
hint = fl->hint(); /* keep looking */
}
/* None found. */
it[start].set_hint(IndexSetSize);
}
return NULL;
}
/* Requires fl->size >= numWords + MinChunkSize */
FreeChunk* CompactibleFreeListSpace::getFromListGreater(FreeList* fl,
size_t numWords) {
FreeChunk *curr = fl->head();
size_t oldNumWords = curr->size();
assert(numWords >= MinChunkSize, "Word size is too small");
assert(curr != NULL, "List is empty");
assert(oldNumWords >= numWords + MinChunkSize,
"Size of chunks in the list is too small");
fl->removeChunk(curr);
// recorded indirectly by splitChunkAndReturnRemainder -
// smallSplit(oldNumWords, numWords);
FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
// Does anything have to be done for the remainder in terms of
// fixing the card table?
assert(new_chunk == NULL || new_chunk->isFree(),
"Should be returning a free chunk");
return new_chunk;
}
FreeChunk*
CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
size_t new_size) {
assert_locked();
size_t size = chunk->size();
assert(size > new_size, "Split from a smaller block?");
assert(is_aligned(chunk), "alignment problem");
assert(size == adjustObjectSize(size), "alignment problem");
size_t rem_size = size - new_size;
assert(rem_size == adjustObjectSize(rem_size), "alignment problem");
assert(rem_size >= MinChunkSize, "Free chunk smaller than minimum");
FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
assert(is_aligned(ffc), "alignment problem");
ffc->setSize(rem_size);
ffc->linkNext(NULL);
ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
// Above must occur before BOT is updated below.
// adjust block offset table
_bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
if (rem_size < SmallForDictionary) {
bool is_par = (SharedHeap::heap()->n_par_threads() > 0);
if (is_par) _indexedFreeListParLocks[rem_size]->lock();
returnChunkToFreeList(ffc);
split(size, rem_size);
if (is_par) _indexedFreeListParLocks[rem_size]->unlock();
} else {
returnChunkToDictionary(ffc);
split(size ,rem_size);
}
chunk->setSize(new_size);
return chunk;
}
void
CompactibleFreeListSpace::sweep_completed() {
// Now that space is probably plentiful, refill linear
// allocation blocks as needed.
refillLinearAllocBlocksIfNeeded();
}
void
CompactibleFreeListSpace::gc_prologue() {
assert_locked();
if (PrintFLSStatistics != 0) {
gclog_or_tty->print("Before GC:\n");
reportFreeListStatistics();
}
refillLinearAllocBlocksIfNeeded();
}
void
CompactibleFreeListSpace::gc_epilogue() {
assert_locked();
if (PrintGCDetails && Verbose && !_adaptive_freelists) {
if (_smallLinearAllocBlock._word_size == 0)
warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure");
}
assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
_promoInfo.stopTrackingPromotions();
repairLinearAllocationBlocks();
// Print Space's stats
if (PrintFLSStatistics != 0) {
gclog_or_tty->print("After GC:\n");
reportFreeListStatistics();
}
}
// Iteration support, mostly delegated from a CMS generation
void CompactibleFreeListSpace::save_marks() {
// mark the "end" of the used space at the time of this call;
// note, however, that promoted objects from this point
// on are tracked in the _promoInfo below.
set_saved_mark_word(BlockOffsetArrayUseUnallocatedBlock ?
unallocated_block() : end());
// inform allocator that promotions should be tracked.
assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
_promoInfo.startTrackingPromotions();
}
bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
assert(_promoInfo.tracking(), "No preceding save_marks?");
guarantee(SharedHeap::heap()->n_par_threads() == 0,
"Shouldn't be called (yet) during parallel part of gc.");
return _promoInfo.noPromotions();
}
#define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
\
void CompactibleFreeListSpace:: \
oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
assert(SharedHeap::heap()->n_par_threads() == 0, \
"Shouldn't be called (yet) during parallel part of gc."); \
_promoInfo.promoted_oops_iterate##nv_suffix(blk); \
/* \
* This also restores any displaced headers and removes the elements from \
* the iteration set as they are processed, so that we have a clean slate \
* at the end of the iteration. Note, thus, that if new objects are \
* promoted as a result of the iteration they are iterated over as well. \
*/ \
assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
}
ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
//////////////////////////////////////////////////////////////////////////////
// We go over the list of promoted objects, removing each from the list,
// and applying the closure (this may, in turn, add more elements to
// the tail of the promoted list, and these newly added objects will
// also be processed) until the list is empty.
// To aid verification and debugging, in the non-product builds
// we actually forward _promoHead each time we process a promoted oop.
// Note that this is not necessary in general (i.e. when we don't need to
// call PromotionInfo::verify()) because oop_iterate can only add to the
// end of _promoTail, and never needs to look at _promoHead.
#define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \
\
void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \
NOT_PRODUCT(verify()); \
PromotedObject *curObj, *nextObj; \
for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \
if ((nextObj = curObj->next()) == NULL) { \
/* protect ourselves against additions due to closure application \
below by resetting the list. */ \
assert(_promoTail == curObj, "Should have been the tail"); \
_promoHead = _promoTail = NULL; \
} \
if (curObj->hasDisplacedMark()) { \
/* restore displaced header */ \
oop(curObj)->set_mark(nextDisplacedHeader()); \
} else { \
/* restore prototypical header */ \
oop(curObj)->init_mark(); \
} \
/* The "promoted_mark" should now not be set */ \
assert(!curObj->hasPromotedMark(), \
"Should have been cleared by restoring displaced mark-word"); \
NOT_PRODUCT(_promoHead = nextObj); \
if (cl != NULL) oop(curObj)->oop_iterate(cl); \
if (nextObj == NULL) { /* start at head of list reset above */ \
nextObj = _promoHead; \
} \
} \
assert(noPromotions(), "post-condition violation"); \
assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\
assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \
assert(_firstIndex == _nextIndex, "empty buffer"); \
}
// This should have been ALL_SINCE_...() just like the others,
// but, because the body of the method above is somehwat longer,
// the MSVC compiler cannot cope; as a workaround, we split the
// macro into its 3 constituent parts below (see original macro
// definition in specializedOopClosures.hpp).
SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)
PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)
void CompactibleFreeListSpace::object_iterate_since_last_GC(ObjectClosure* cl) {
// ugghh... how would one do this efficiently for a non-contiguous space?
guarantee(false, "NYI");
}
bool CompactibleFreeListSpace::linearAllocationWouldFail() {
return _smallLinearAllocBlock._word_size == 0;
}
void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
// Fix up linear allocation blocks to look like free blocks
repairLinearAllocBlock(&_smallLinearAllocBlock);
}
void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
assert_locked();
if (blk->_ptr != NULL) {
assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
"Minimum block size requirement");
FreeChunk* fc = (FreeChunk*)(blk->_ptr);
fc->setSize(blk->_word_size);
fc->linkPrev(NULL); // mark as free
fc->dontCoalesce();
assert(fc->isFree(), "just marked it free");
assert(fc->cantCoalesce(), "just marked it uncoalescable");
}
}
void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
assert_locked();
if (_smallLinearAllocBlock._ptr == NULL) {
assert(_smallLinearAllocBlock._word_size == 0,
"Size of linAB should be zero if the ptr is NULL");
// Reset the linAB refill and allocation size limit.
_smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
}
refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
}
void
CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
assert_locked();
assert((blk->_ptr == NULL && blk->_word_size == 0) ||
(blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
"blk invariant");
if (blk->_ptr == NULL) {
refillLinearAllocBlock(blk);
}
if (PrintMiscellaneous && Verbose) {
if (blk->_word_size == 0) {
warning("CompactibleFreeListSpace(prologue):: Linear allocation failure");
}
}
}
void
CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
assert_locked();
assert(blk->_word_size == 0 && blk->_ptr == NULL,
"linear allocation block should be empty");
FreeChunk* fc;
if (blk->_refillSize < SmallForDictionary &&
(fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
// A linAB's strategy might be to use small sizes to reduce
// fragmentation but still get the benefits of allocation from a
// linAB.
} else {
fc = getChunkFromDictionary(blk->_refillSize);
}
if (fc != NULL) {
blk->_ptr = (HeapWord*)fc;
blk->_word_size = fc->size();
fc->dontCoalesce(); // to prevent sweeper from sweeping us up
}
}
// Support for compaction
void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
SCAN_AND_FORWARD(cp,end,block_is_obj,block_size);
// prepare_for_compaction() uses the space between live objects
// so that later phase can skip dead space quickly. So verification
// of the free lists doesn't work after.
}
#define obj_size(q) adjustObjectSize(oop(q)->size())
#define adjust_obj_size(s) adjustObjectSize(s)
void CompactibleFreeListSpace::adjust_pointers() {
// In other versions of adjust_pointers(), a bail out
// based on the amount of live data in the generation
// (i.e., if 0, bail out) may be used.
// Cannot test used() == 0 here because the free lists have already
// been mangled by the compaction.
SCAN_AND_ADJUST_POINTERS(adjust_obj_size);
// See note about verification in prepare_for_compaction().
}
void CompactibleFreeListSpace::compact() {
SCAN_AND_COMPACT(obj_size);
}
// fragmentation_metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
// where fbs is free block sizes
double CompactibleFreeListSpace::flsFrag() const {
size_t itabFree = totalSizeInIndexedFreeLists();
double frag = 0.0;
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
double sz = i;
frag += _indexedFreeList[i].count() * (sz * sz);
}
double totFree = itabFree +
_dictionary->totalChunkSize(DEBUG_ONLY(freelistLock()));
if (totFree > 0) {
frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
(totFree * totFree));
frag = (double)1.0 - frag;
} else {
assert(frag == 0.0, "Follows from totFree == 0");
}
return frag;
}
#define CoalSurplusPercent 1.05
#define SplitSurplusPercent 1.10
void CompactibleFreeListSpace::beginSweepFLCensus(
float inter_sweep_current,
float inter_sweep_estimate) {
assert_locked();
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
FreeList* fl = &_indexedFreeList[i];
fl->compute_desired(inter_sweep_current, inter_sweep_estimate);
fl->set_coalDesired((ssize_t)((double)fl->desired() * CoalSurplusPercent));
fl->set_beforeSweep(fl->count());
fl->set_bfrSurp(fl->surplus());
}
_dictionary->beginSweepDictCensus(CoalSurplusPercent,
inter_sweep_current,
inter_sweep_estimate);
}
void CompactibleFreeListSpace::setFLSurplus() {
assert_locked();
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
FreeList *fl = &_indexedFreeList[i];
fl->set_surplus(fl->count() -
(ssize_t)((double)fl->desired() * SplitSurplusPercent));
}
}
void CompactibleFreeListSpace::setFLHints() {
assert_locked();
size_t i;
size_t h = IndexSetSize;
for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
FreeList *fl = &_indexedFreeList[i];
fl->set_hint(h);
if (fl->surplus() > 0) {
h = i;
}
}
}
void CompactibleFreeListSpace::clearFLCensus() {
assert_locked();
int i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
FreeList *fl = &_indexedFreeList[i];
fl->set_prevSweep(fl->count());
fl->set_coalBirths(0);
fl->set_coalDeaths(0);
fl->set_splitBirths(0);
fl->set_splitDeaths(0);
}
}
void CompactibleFreeListSpace::endSweepFLCensus(int sweepCt) {
setFLSurplus();
setFLHints();
if (PrintGC && PrintFLSCensus > 0) {
printFLCensus(sweepCt);
}
clearFLCensus();
assert_locked();
_dictionary->endSweepDictCensus(SplitSurplusPercent);
}
bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
if (size < SmallForDictionary) {
FreeList *fl = &_indexedFreeList[size];
return (fl->coalDesired() < 0) ||
((int)fl->count() > fl->coalDesired());
} else {
return dictionary()->coalDictOverPopulated(size);
}
}
void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
FreeList *fl = &_indexedFreeList[size];
fl->increment_coalBirths();
fl->increment_surplus();
}
void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
FreeList *fl = &_indexedFreeList[size];
fl->increment_coalDeaths();
fl->decrement_surplus();
}
void CompactibleFreeListSpace::coalBirth(size_t size) {
if (size < SmallForDictionary) {
smallCoalBirth(size);
} else {
dictionary()->dictCensusUpdate(size,
false /* split */,
true /* birth */);
}
}
void CompactibleFreeListSpace::coalDeath(size_t size) {
if(size < SmallForDictionary) {
smallCoalDeath(size);
} else {
dictionary()->dictCensusUpdate(size,
false /* split */,
false /* birth */);
}
}
void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
FreeList *fl = &_indexedFreeList[size];
fl->increment_splitBirths();
fl->increment_surplus();
}
void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
FreeList *fl = &_indexedFreeList[size];
fl->increment_splitDeaths();
fl->decrement_surplus();
}
void CompactibleFreeListSpace::splitBirth(size_t size) {
if (size < SmallForDictionary) {
smallSplitBirth(size);
} else {
dictionary()->dictCensusUpdate(size,
true /* split */,
true /* birth */);
}
}
void CompactibleFreeListSpace::splitDeath(size_t size) {
if (size < SmallForDictionary) {
smallSplitDeath(size);
} else {
dictionary()->dictCensusUpdate(size,
true /* split */,
false /* birth */);
}
}
void CompactibleFreeListSpace::split(size_t from, size_t to1) {
size_t to2 = from - to1;
splitDeath(from);
splitBirth(to1);
splitBirth(to2);
}
void CompactibleFreeListSpace::print() const {
tty->print(" CompactibleFreeListSpace");
Space::print();
}
void CompactibleFreeListSpace::prepare_for_verify() {
assert_locked();
repairLinearAllocationBlocks();
// Verify that the SpoolBlocks look like free blocks of
// appropriate sizes... To be done ...
}
class VerifyAllBlksClosure: public BlkClosure {
const CompactibleFreeListSpace* _sp;
const MemRegion _span;
public:
VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
MemRegion span) : _sp(sp), _span(span) { }
size_t do_blk(HeapWord* addr) {
size_t res;
if (_sp->block_is_obj(addr)) {
oop p = oop(addr);
guarantee(p->is_oop(), "Should be an oop");
res = _sp->adjustObjectSize(p->size());
if (_sp->obj_is_alive(addr)) {
p->verify();
}
} else {
FreeChunk* fc = (FreeChunk*)addr;
res = fc->size();
if (FLSVerifyLists && !fc->cantCoalesce()) {
guarantee(_sp->verifyChunkInFreeLists(fc),
"Chunk should be on a free list");
}
}
guarantee(res != 0, "Livelock: no rank reduction!");
return res;
}
};
class VerifyAllOopsClosure: public OopClosure {
const CMSCollector* _collector;
const CompactibleFreeListSpace* _sp;
const MemRegion _span;
const bool _past_remark;
const CMSBitMap* _bit_map;
public:
VerifyAllOopsClosure(const CMSCollector* collector,
const CompactibleFreeListSpace* sp, MemRegion span,
bool past_remark, CMSBitMap* bit_map) :
OopClosure(), _collector(collector), _sp(sp), _span(span),
_past_remark(past_remark), _bit_map(bit_map) { }
void do_oop(oop* ptr) {
oop p = *ptr;
if (p != NULL) {
if (_span.contains(p)) { // the interior oop points into CMS heap
if (!_span.contains(ptr)) { // reference from outside CMS heap
// Should be a valid object; the first disjunct below allows
// us to sidestep an assertion in block_is_obj() that insists
// that p be in _sp. Note that several generations (and spaces)
// are spanned by _span (CMS heap) above.
guarantee(!_sp->is_in_reserved(p) || _sp->block_is_obj((HeapWord*)p),
"Should be an object");
guarantee(p->is_oop(), "Should be an oop");
p->verify();
if (_past_remark) {
// Remark has been completed, the object should be marked
_bit_map->isMarked((HeapWord*)p);
}
}
else { // reference within CMS heap
if (_past_remark) {
// Remark has been completed -- so the referent should have
// been marked, if referring object is.
if (_bit_map->isMarked(_collector->block_start(ptr))) {
guarantee(_bit_map->isMarked((HeapWord*)p), "Marking error?");
}
}
}
} else if (_sp->is_in_reserved(ptr)) {
// the reference is from FLS, and points out of FLS
guarantee(p->is_oop(), "Should be an oop");
p->verify();
}
}
}
};
void CompactibleFreeListSpace::verify(bool ignored) const {
assert_lock_strong(&_freelistLock);
verify_objects_initialized();
MemRegion span = _collector->_span;
bool past_remark = (_collector->abstract_state() ==
CMSCollector::Sweeping);
ResourceMark rm;
HandleMark hm;
// Check integrity of CFL data structures
_promoInfo.verify();
_dictionary->verify();
if (FLSVerifyIndexTable) {
verifyIndexedFreeLists();
}
// Check integrity of all objects and free blocks in space
{
VerifyAllBlksClosure cl(this, span);
((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
}
// Check that all references in the heap to FLS
// are to valid objects in FLS or that references in
// FLS are to valid objects elsewhere in the heap
if (FLSVerifyAllHeapReferences)
{
VerifyAllOopsClosure cl(_collector, this, span, past_remark,
_collector->markBitMap());
CollectedHeap* ch = Universe::heap();
ch->oop_iterate(&cl); // all oops in generations
ch->permanent_oop_iterate(&cl); // all oops in perm gen
}
if (VerifyObjectStartArray) {
// Verify the block offset table
_bt.verify();
}
}
#ifndef PRODUCT
void CompactibleFreeListSpace::verifyFreeLists() const {
if (FLSVerifyLists) {
_dictionary->verify();
verifyIndexedFreeLists();
} else {
if (FLSVerifyDictionary) {
_dictionary->verify();
}
if (FLSVerifyIndexTable) {
verifyIndexedFreeLists();
}
}
}
#endif
void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
size_t i = 0;
for (; i < MinChunkSize; i++) {
guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
}
for (; i < IndexSetSize; i++) {
verifyIndexedFreeList(i);
}
}
void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
guarantee(size % 2 == 0, "Odd slots should be empty");
for (FreeChunk* fc = _indexedFreeList[size].head(); fc != NULL;
fc = fc->next()) {
guarantee(fc->size() == size, "Size inconsistency");
guarantee(fc->isFree(), "!free?");
guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
}
}
#ifndef PRODUCT
void CompactibleFreeListSpace::checkFreeListConsistency() const {
assert(_dictionary->minSize() <= IndexSetSize,
"Some sizes can't be allocated without recourse to"
" linear allocation buffers");
assert(MIN_TREE_CHUNK_SIZE*HeapWordSize == sizeof(TreeChunk),
"else MIN_TREE_CHUNK_SIZE is wrong");
assert((IndexSetStride == 2 && IndexSetStart == 2) ||
(IndexSetStride == 1 && IndexSetStart == 1), "just checking");
assert((IndexSetStride != 2) || (MinChunkSize % 2 == 0),
"Some for-loops may be incorrectly initialized");
assert((IndexSetStride != 2) || (IndexSetSize % 2 == 1),
"For-loops that iterate over IndexSet with stride 2 may be wrong");
}
#endif
void CompactibleFreeListSpace::printFLCensus(int sweepCt) const {
assert_lock_strong(&_freelistLock);
ssize_t bfrSurp = 0;
ssize_t surplus = 0;
ssize_t desired = 0;
ssize_t prevSweep = 0;
ssize_t beforeSweep = 0;
ssize_t count = 0;
ssize_t coalBirths = 0;
ssize_t coalDeaths = 0;
ssize_t splitBirths = 0;
ssize_t splitDeaths = 0;
gclog_or_tty->print("end sweep# %d\n", sweepCt);
gclog_or_tty->print("%4s\t" "%7s\t" "%7s\t" "%7s\t" "%7s\t"
"%7s\t" "%7s\t" "%7s\t" "%7s\t" "%7s\t"
"%7s\t" "\n",
"size", "bfrsurp", "surplus", "desired", "prvSwep",
"bfrSwep", "count", "cBirths", "cDeaths", "sBirths",
"sDeaths");
size_t totalFree = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
const FreeList *fl = &_indexedFreeList[i];
totalFree += fl->count() * fl->size();
gclog_or_tty->print("%4d\t" "%7d\t" "%7d\t" "%7d\t"
"%7d\t" "%7d\t" "%7d\t" "%7d\t"
"%7d\t" "%7d\t" "%7d\t" "\n",
fl->size(), fl->bfrSurp(), fl->surplus(), fl->desired(),
fl->prevSweep(), fl->beforeSweep(), fl->count(), fl->coalBirths(),
fl->coalDeaths(), fl->splitBirths(), fl->splitDeaths());
bfrSurp += fl->bfrSurp();
surplus += fl->surplus();
desired += fl->desired();
prevSweep += fl->prevSweep();
beforeSweep += fl->beforeSweep();
count += fl->count();
coalBirths += fl->coalBirths();
coalDeaths += fl->coalDeaths();
splitBirths += fl->splitBirths();
splitDeaths += fl->splitDeaths();
}
gclog_or_tty->print("%4s\t"
"%7d\t" "%7d\t" "%7d\t" "%7d\t" "%7d\t"
"%7d\t" "%7d\t" "%7d\t" "%7d\t" "%7d\t" "\n",
"totl",
bfrSurp, surplus, desired, prevSweep, beforeSweep,
count, coalBirths, coalDeaths, splitBirths, splitDeaths);
gclog_or_tty->print_cr("Total free in indexed lists %d words", totalFree);
gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n",
(double)(splitBirths+coalBirths-splitDeaths-coalDeaths)/
(prevSweep != 0 ? (double)prevSweep : 1.0),
(double)(desired - count)/(desired != 0 ? (double)desired : 1.0));
_dictionary->printDictCensus();
}
// Return the next displaced header, incrementing the pointer and
// recycling spool area as necessary.
markOop PromotionInfo::nextDisplacedHeader() {
assert(_spoolHead != NULL, "promotionInfo inconsistency");
assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
"Empty spool space: no displaced header can be fetched");
assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
markOop hdr = _spoolHead->displacedHdr[_firstIndex];
// Spool forward
if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
// forward to next block, recycling this block into spare spool buffer
SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
_spoolHead->nextSpoolBlock = _spareSpool;
_spareSpool = _spoolHead;
_spoolHead = tmp;
_firstIndex = 1;
NOT_PRODUCT(
if (_spoolHead == NULL) { // all buffers fully consumed
assert(_spoolTail == NULL && _nextIndex == 1,
"spool buffers processing inconsistency");
}
)
}
return hdr;
}
void PromotionInfo::track(PromotedObject* trackOop) {
track(trackOop, oop(trackOop)->klass());
}
void PromotionInfo::track(PromotedObject* trackOop, klassOop klassOfOop) {
// make a copy of header as it may need to be spooled
markOop mark = oop(trackOop)->mark();
trackOop->clearNext();
if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {
// save non-prototypical header, and mark oop
saveDisplacedHeader(mark);
trackOop->setDisplacedMark();
} else {
// we'd like to assert something like the following:
// assert(mark == markOopDesc::prototype(), "consistency check");
// ... but the above won't work because the age bits have not (yet) been
// cleared. The remainder of the check would be identical to the
// condition checked in must_be_preserved() above, so we don't really
// have anything useful to check here!
}
if (_promoTail != NULL) {
assert(_promoHead != NULL, "List consistency");
_promoTail->setNext(trackOop);
_promoTail = trackOop;
} else {
assert(_promoHead == NULL, "List consistency");
_promoHead = _promoTail = trackOop;
}
// Mask as newly promoted, so we can skip over such objects
// when scanning dirty cards
assert(!trackOop->hasPromotedMark(), "Should not have been marked");
trackOop->setPromotedMark();
}
// Save the given displaced header, incrementing the pointer and
// obtaining more spool area as necessary.
void PromotionInfo::saveDisplacedHeader(markOop hdr) {
assert(_spoolHead != NULL && _spoolTail != NULL,
"promotionInfo inconsistency");
assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
_spoolTail->displacedHdr[_nextIndex] = hdr;
// Spool forward
if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
// get a new spooling block
assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
_splice_point = _spoolTail; // save for splicing
_spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
_spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
// ... but will attempt filling before next promotion attempt
_nextIndex = 1;
}
}
// Ensure that spooling space exists. Return false if spooling space
// could not be obtained.
bool PromotionInfo::ensure_spooling_space_work() {
assert(!has_spooling_space(), "Only call when there is no spooling space");
// Try and obtain more spooling space
SpoolBlock* newSpool = getSpoolBlock();
assert(newSpool == NULL ||
(newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
"getSpoolBlock() sanity check");
if (newSpool == NULL) {
return false;
}
_nextIndex = 1;
if (_spoolTail == NULL) {
_spoolTail = newSpool;
if (_spoolHead == NULL) {
_spoolHead = newSpool;
_firstIndex = 1;
} else {
assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
"Splice point invariant");
// Extra check that _splice_point is connected to list
#ifdef ASSERT
{
SpoolBlock* blk = _spoolHead;
for (; blk->nextSpoolBlock != NULL;
blk = blk->nextSpoolBlock);
assert(blk != NULL && blk == _splice_point,
"Splice point incorrect");
}
#endif // ASSERT
_splice_point->nextSpoolBlock = newSpool;
}
} else {
assert(_spoolHead != NULL, "spool list consistency");
_spoolTail->nextSpoolBlock = newSpool;
_spoolTail = newSpool;
}
return true;
}
// Get a free spool buffer from the free pool, getting a new block
// from the heap if necessary.
SpoolBlock* PromotionInfo::getSpoolBlock() {
SpoolBlock* res;
if ((res = _spareSpool) != NULL) {
_spareSpool = _spareSpool->nextSpoolBlock;
res->nextSpoolBlock = NULL;
} else { // spare spool exhausted, get some from heap
res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
if (res != NULL) {
res->init();
}
}
assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
return res;
}
void PromotionInfo::startTrackingPromotions() {
assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
"spooling inconsistency?");
_firstIndex = _nextIndex = 1;
_tracking = true;
}
void PromotionInfo::stopTrackingPromotions() {
assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
"spooling inconsistency?");
_firstIndex = _nextIndex = 1;
_tracking = false;
}
// When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
// points to the next slot available for filling.
// The set of slots holding displaced headers are then all those in the
// right-open interval denoted by:
//
// [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
//
// When _spoolTail is NULL, then the set of slots with displaced headers
// is all those starting at the slot <_spoolHead, _firstIndex> and
// going up to the last slot of last block in the linked list.
// In this lartter case, _splice_point points to the tail block of
// this linked list of blocks holding displaced headers.
void PromotionInfo::verify() const {
// Verify the following:
// 1. the number of displaced headers matches the number of promoted
// objects that have displaced headers
// 2. each promoted object lies in this space
debug_only(
PromotedObject* junk = NULL;
assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),
"Offset of PromotedObject::_next is expected to align with "
" the OopDesc::_mark within OopDesc");
)
// FIXME: guarantee????
guarantee(_spoolHead == NULL || _spoolTail != NULL ||
_splice_point != NULL, "list consistency");
guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
// count the number of objects with displaced headers
size_t numObjsWithDisplacedHdrs = 0;
for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
// the last promoted object may fail the mark() != NULL test of is_oop().
guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop");
if (curObj->hasDisplacedMark()) {
numObjsWithDisplacedHdrs++;
}
}
// Count the number of displaced headers
size_t numDisplacedHdrs = 0;
for (SpoolBlock* curSpool = _spoolHead;
curSpool != _spoolTail && curSpool != NULL;
curSpool = curSpool->nextSpoolBlock) {
// the first entry is just a self-pointer; indices 1 through
// bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
"first entry of displacedHdr should be self-referential");
numDisplacedHdrs += curSpool->bufferSize - 1;
}
guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
"internal consistency");
guarantee(_spoolTail != NULL || _nextIndex == 1,
"Inconsistency between _spoolTail and _nextIndex");
// We overcounted (_firstIndex-1) worth of slots in block
// _spoolHead and we undercounted (_nextIndex-1) worth of
// slots in block _spoolTail. We make an appropriate
// adjustment by subtracting the first and adding the
// second: - (_firstIndex - 1) + (_nextIndex - 1)
numDisplacedHdrs += (_nextIndex - _firstIndex);
guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
}
CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) :
_cfls(cfls)
{
_blocks_to_claim = CMSParPromoteBlocksToClaim;
for (size_t i = CompactibleFreeListSpace::IndexSetStart;
i < CompactibleFreeListSpace::IndexSetSize;
i += CompactibleFreeListSpace::IndexSetStride) {
_indexedFreeList[i].set_size(i);
}
}
HeapWord* CFLS_LAB::alloc(size_t word_sz) {
FreeChunk* res;
word_sz = _cfls->adjustObjectSize(word_sz);
if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
// This locking manages sync with other large object allocations.
MutexLockerEx x(_cfls->parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
res = _cfls->getChunkFromDictionaryExact(word_sz);
if (res == NULL) return NULL;
} else {
FreeList* fl = &_indexedFreeList[word_sz];
bool filled = false; //TRAP
if (fl->count() == 0) {
bool filled = true; //TRAP
// Attempt to refill this local free list.
_cfls->par_get_chunk_of_blocks(word_sz, _blocks_to_claim, fl);
// If it didn't work, give up.
if (fl->count() == 0) return NULL;
}
res = fl->getChunkAtHead();
assert(res != NULL, "Why was count non-zero?");
}
res->markNotFree();
assert(!res->isFree(), "shouldn't be marked free");
assert(oop(res)->klass() == NULL, "should look uninitialized");
// mangle a just allocated object with a distinct pattern.
debug_only(res->mangleAllocated(word_sz));
return (HeapWord*)res;
}
void CFLS_LAB::retire() {
for (size_t i = CompactibleFreeListSpace::IndexSetStart;
i < CompactibleFreeListSpace::IndexSetSize;
i += CompactibleFreeListSpace::IndexSetStride) {
if (_indexedFreeList[i].count() > 0) {
MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
Mutex::_no_safepoint_check_flag);
_cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
// Reset this list.
_indexedFreeList[i] = FreeList();
_indexedFreeList[i].set_size(i);
}
}
}
void
CompactibleFreeListSpace::
par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl) {
assert(fl->count() == 0, "Precondition.");
assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
"Precondition");
// We'll try all multiples of word_sz in the indexed set (starting with
// word_sz itself), then try getting a big chunk and splitting it.
int k = 1;
size_t cur_sz = k * word_sz;
bool found = false;
while (cur_sz < CompactibleFreeListSpace::IndexSetSize && k == 1) {
FreeList* gfl = &_indexedFreeList[cur_sz];
FreeList fl_for_cur_sz; // Empty.
fl_for_cur_sz.set_size(cur_sz);
{
MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
Mutex::_no_safepoint_check_flag);
if (gfl->count() != 0) {
size_t nn = MAX2(n/k, (size_t)1);
gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
found = true;
}
}
// Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
if (found) {
if (k == 1) {
fl->prepend(&fl_for_cur_sz);
} else {
// Divide each block on fl_for_cur_sz up k ways.
FreeChunk* fc;
while ((fc = fl_for_cur_sz.getChunkAtHead()) != NULL) {
// Must do this in reverse order, so that anybody attempting to
// access the main chunk sees it as a single free block until we
// change it.
size_t fc_size = fc->size();
for (int i = k-1; i >= 0; i--) {
FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
ffc->setSize(word_sz);
ffc->linkNext(NULL);
ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
// Above must occur before BOT is updated below.
// splitting from the right, fc_size == (k - i + 1) * wordsize
_bt.mark_block((HeapWord*)ffc, word_sz);
fc_size -= word_sz;
_bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
_bt.verify_single_block((HeapWord*)fc, fc_size);
_bt.verify_single_block((HeapWord*)ffc, ffc->size());
// Push this on "fl".
fl->returnChunkAtHead(ffc);
}
// TRAP
assert(fl->tail()->next() == NULL, "List invariant.");
}
}
return;
}
k++; cur_sz = k * word_sz;
}
// Otherwise, we'll split a block from the dictionary.
FreeChunk* fc = NULL;
FreeChunk* rem_fc = NULL;
size_t rem;
{
MutexLockerEx x(parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
while (n > 0) {
fc = dictionary()->getChunk(MAX2(n * word_sz,
_dictionary->minSize()),
FreeBlockDictionary::atLeast);
if (fc != NULL) {
_bt.allocated((HeapWord*)fc, fc->size()); // update _unallocated_blk
dictionary()->dictCensusUpdate(fc->size(),
true /*split*/,
false /*birth*/);
break;
} else {
n--;
}
}
if (fc == NULL) return;
// Otherwise, split up that block.
size_t nn = fc->size() / word_sz;
n = MIN2(nn, n);
rem = fc->size() - n * word_sz;
// If there is a remainder, and it's too small, allocate one fewer.
if (rem > 0 && rem < MinChunkSize) {
n--; rem += word_sz;
}
// First return the remainder, if any.
// Note that we hold the lock until we decide if we're going to give
// back the remainder to the dictionary, since a contending allocator
// may otherwise see the heap as empty. (We're willing to take that
// hit if the block is a small block.)
if (rem > 0) {
size_t prefix_size = n * word_sz;
rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
rem_fc->setSize(rem);
rem_fc->linkNext(NULL);
rem_fc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
// Above must occur before BOT is updated below.
_bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
if (rem >= IndexSetSize) {
returnChunkToDictionary(rem_fc);
dictionary()->dictCensusUpdate(fc->size(),
true /*split*/,
true /*birth*/);
rem_fc = NULL;
}
// Otherwise, return it to the small list below.
}
}
//
if (rem_fc != NULL) {
MutexLockerEx x(_indexedFreeListParLocks[rem],
Mutex::_no_safepoint_check_flag);
_bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
_indexedFreeList[rem].returnChunkAtHead(rem_fc);
smallSplitBirth(rem);
}
// Now do the splitting up.
// Must do this in reverse order, so that anybody attempting to
// access the main chunk sees it as a single free block until we
// change it.
size_t fc_size = n * word_sz;
// All but first chunk in this loop
for (ssize_t i = n-1; i > 0; i--) {
FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
ffc->setSize(word_sz);
ffc->linkNext(NULL);
ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
// Above must occur before BOT is updated below.
// splitting from the right, fc_size == (n - i + 1) * wordsize
_bt.mark_block((HeapWord*)ffc, word_sz);
fc_size -= word_sz;
_bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
_bt.verify_single_block((HeapWord*)ffc, ffc->size());
_bt.verify_single_block((HeapWord*)fc, fc_size);
// Push this on "fl".
fl->returnChunkAtHead(ffc);
}
// First chunk
fc->setSize(word_sz);
fc->linkNext(NULL);
fc->linkPrev(NULL);
_bt.verify_not_unallocated((HeapWord*)fc, fc->size());
_bt.verify_single_block((HeapWord*)fc, fc->size());
fl->returnChunkAtHead(fc);
{
MutexLockerEx x(_indexedFreeListParLocks[word_sz],
Mutex::_no_safepoint_check_flag);
ssize_t new_births = _indexedFreeList[word_sz].splitBirths() + n;
_indexedFreeList[word_sz].set_splitBirths(new_births);
ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
_indexedFreeList[word_sz].set_surplus(new_surplus);
}
// TRAP
assert(fl->tail()->next() == NULL, "List invariant.");
}
// Set up the space's par_seq_tasks structure for work claiming
// for parallel rescan. See CMSParRemarkTask where this is currently used.
// XXX Need to suitably abstract and generalize this and the next
// method into one.
void
CompactibleFreeListSpace::
initialize_sequential_subtasks_for_rescan(int n_threads) {
// The "size" of each task is fixed according to rescan_task_size.
assert(n_threads > 0, "Unexpected n_threads argument");
const size_t task_size = rescan_task_size();
size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
assert((used_region().start() + (n_tasks - 1)*task_size <
used_region().end()) &&
(used_region().start() + n_tasks*task_size >=
used_region().end()), "n_task calculation incorrect");
SequentialSubTasksDone* pst = conc_par_seq_tasks();
assert(!pst->valid(), "Clobbering existing data?");
pst->set_par_threads(n_threads);
pst->set_n_tasks((int)n_tasks);
}
// Set up the space's par_seq_tasks structure for work claiming
// for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
void
CompactibleFreeListSpace::
initialize_sequential_subtasks_for_marking(int n_threads,
HeapWord* low) {
// The "size" of each task is fixed according to rescan_task_size.
assert(n_threads > 0, "Unexpected n_threads argument");
const size_t task_size = marking_task_size();
assert(task_size > CardTableModRefBS::card_size_in_words &&
(task_size % CardTableModRefBS::card_size_in_words == 0),
"Otherwise arithmetic below would be incorrect");
MemRegion span = _gen->reserved();
if (low != NULL) {
if (span.contains(low)) {
// Align low down to a card boundary so that
// we can use block_offset_careful() on span boundaries.
HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
CardTableModRefBS::card_size);
// Clip span prefix at aligned_low
span = span.intersection(MemRegion(aligned_low, span.end()));
} else if (low > span.end()) {
span = MemRegion(low, low); // Null region
} // else use entire span
}
assert(span.is_empty() ||
((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
"span should start at a card boundary");
size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
assert(n_tasks == 0 ||
((span.start() + (n_tasks - 1)*task_size < span.end()) &&
(span.start() + n_tasks*task_size >= span.end())),
"n_task calculation incorrect");
SequentialSubTasksDone* pst = conc_par_seq_tasks();
assert(!pst->valid(), "Clobbering existing data?");
pst->set_par_threads(n_threads);
pst->set_n_tasks((int)n_tasks);
}