| /* |
| * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp" |
| #include "gc_implementation/parNew/parNewGeneration.hpp" |
| #include "gc_implementation/parNew/parOopClosures.inline.hpp" |
| #include "gc_implementation/shared/adaptiveSizePolicy.hpp" |
| #include "gc_implementation/shared/ageTable.hpp" |
| #include "gc_implementation/shared/parGCAllocBuffer.hpp" |
| #include "gc_implementation/shared/spaceDecorator.hpp" |
| #include "memory/defNewGeneration.inline.hpp" |
| #include "memory/genCollectedHeap.hpp" |
| #include "memory/genOopClosures.inline.hpp" |
| #include "memory/generation.hpp" |
| #include "memory/generation.inline.hpp" |
| #include "memory/referencePolicy.hpp" |
| #include "memory/resourceArea.hpp" |
| #include "memory/sharedHeap.hpp" |
| #include "memory/space.hpp" |
| #include "oops/objArrayOop.hpp" |
| #include "oops/oop.inline.hpp" |
| #include "oops/oop.pcgc.inline.hpp" |
| #include "runtime/handles.hpp" |
| #include "runtime/handles.inline.hpp" |
| #include "runtime/java.hpp" |
| #include "runtime/thread.hpp" |
| #include "utilities/copy.hpp" |
| #include "utilities/globalDefinitions.hpp" |
| #include "utilities/workgroup.hpp" |
| |
| #ifdef _MSC_VER |
| #pragma warning( push ) |
| #pragma warning( disable:4355 ) // 'this' : used in base member initializer list |
| #endif |
| ParScanThreadState::ParScanThreadState(Space* to_space_, |
| ParNewGeneration* gen_, |
| Generation* old_gen_, |
| int thread_num_, |
| ObjToScanQueueSet* work_queue_set_, |
| Stack<oop, mtGC>* overflow_stacks_, |
| size_t desired_plab_sz_, |
| ParallelTaskTerminator& term_) : |
| _to_space(to_space_), _old_gen(old_gen_), _young_gen(gen_), _thread_num(thread_num_), |
| _work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false), |
| _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL), |
| _ageTable(false), // false ==> not the global age table, no perf data. |
| _to_space_alloc_buffer(desired_plab_sz_), |
| _to_space_closure(gen_, this), _old_gen_closure(gen_, this), |
| _to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this), |
| _older_gen_closure(gen_, this), |
| _evacuate_followers(this, &_to_space_closure, &_old_gen_closure, |
| &_to_space_root_closure, gen_, &_old_gen_root_closure, |
| work_queue_set_, &term_), |
| _is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this), |
| _keep_alive_closure(&_scan_weak_ref_closure), |
| _promotion_failure_size(0), |
| _strong_roots_time(0.0), _term_time(0.0) |
| { |
| #if TASKQUEUE_STATS |
| _term_attempts = 0; |
| _overflow_refills = 0; |
| _overflow_refill_objs = 0; |
| #endif // TASKQUEUE_STATS |
| |
| _survivor_chunk_array = |
| (ChunkArray*) old_gen()->get_data_recorder(thread_num()); |
| _hash_seed = 17; // Might want to take time-based random value. |
| _start = os::elapsedTime(); |
| _old_gen_closure.set_generation(old_gen_); |
| _old_gen_root_closure.set_generation(old_gen_); |
| } |
| #ifdef _MSC_VER |
| #pragma warning( pop ) |
| #endif |
| |
| void ParScanThreadState::record_survivor_plab(HeapWord* plab_start, |
| size_t plab_word_size) { |
| ChunkArray* sca = survivor_chunk_array(); |
| if (sca != NULL) { |
| // A non-null SCA implies that we want the PLAB data recorded. |
| sca->record_sample(plab_start, plab_word_size); |
| } |
| } |
| |
| bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const { |
| return new_obj->is_objArray() && |
| arrayOop(new_obj)->length() > ParGCArrayScanChunk && |
| new_obj != old_obj; |
| } |
| |
| void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) { |
| assert(old->is_objArray(), "must be obj array"); |
| assert(old->is_forwarded(), "must be forwarded"); |
| assert(Universe::heap()->is_in_reserved(old), "must be in heap."); |
| assert(!old_gen()->is_in(old), "must be in young generation."); |
| |
| objArrayOop obj = objArrayOop(old->forwardee()); |
| // Process ParGCArrayScanChunk elements now |
| // and push the remainder back onto queue |
| int start = arrayOop(old)->length(); |
| int end = obj->length(); |
| int remainder = end - start; |
| assert(start <= end, "just checking"); |
| if (remainder > 2 * ParGCArrayScanChunk) { |
| // Test above combines last partial chunk with a full chunk |
| end = start + ParGCArrayScanChunk; |
| arrayOop(old)->set_length(end); |
| // Push remainder. |
| bool ok = work_queue()->push(old); |
| assert(ok, "just popped, push must be okay"); |
| } else { |
| // Restore length so that it can be used if there |
| // is a promotion failure and forwarding pointers |
| // must be removed. |
| arrayOop(old)->set_length(end); |
| } |
| |
| // process our set of indices (include header in first chunk) |
| // should make sure end is even (aligned to HeapWord in case of compressed oops) |
| if ((HeapWord *)obj < young_old_boundary()) { |
| // object is in to_space |
| obj->oop_iterate_range(&_to_space_closure, start, end); |
| } else { |
| // object is in old generation |
| obj->oop_iterate_range(&_old_gen_closure, start, end); |
| } |
| } |
| |
| |
| void ParScanThreadState::trim_queues(int max_size) { |
| ObjToScanQueue* queue = work_queue(); |
| do { |
| while (queue->size() > (juint)max_size) { |
| oop obj_to_scan; |
| if (queue->pop_local(obj_to_scan)) { |
| if ((HeapWord *)obj_to_scan < young_old_boundary()) { |
| if (obj_to_scan->is_objArray() && |
| obj_to_scan->is_forwarded() && |
| obj_to_scan->forwardee() != obj_to_scan) { |
| scan_partial_array_and_push_remainder(obj_to_scan); |
| } else { |
| // object is in to_space |
| obj_to_scan->oop_iterate(&_to_space_closure); |
| } |
| } else { |
| // object is in old generation |
| obj_to_scan->oop_iterate(&_old_gen_closure); |
| } |
| } |
| } |
| // For the case of compressed oops, we have a private, non-shared |
| // overflow stack, so we eagerly drain it so as to more evenly |
| // distribute load early. Note: this may be good to do in |
| // general rather than delay for the final stealing phase. |
| // If applicable, we'll transfer a set of objects over to our |
| // work queue, allowing them to be stolen and draining our |
| // private overflow stack. |
| } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this)); |
| } |
| |
| bool ParScanThreadState::take_from_overflow_stack() { |
| assert(ParGCUseLocalOverflow, "Else should not call"); |
| assert(young_gen()->overflow_list() == NULL, "Error"); |
| ObjToScanQueue* queue = work_queue(); |
| Stack<oop, mtGC>* const of_stack = overflow_stack(); |
| const size_t num_overflow_elems = of_stack->size(); |
| const size_t space_available = queue->max_elems() - queue->size(); |
| const size_t num_take_elems = MIN3(space_available / 4, |
| ParGCDesiredObjsFromOverflowList, |
| num_overflow_elems); |
| // Transfer the most recent num_take_elems from the overflow |
| // stack to our work queue. |
| for (size_t i = 0; i != num_take_elems; i++) { |
| oop cur = of_stack->pop(); |
| oop obj_to_push = cur->forwardee(); |
| assert(Universe::heap()->is_in_reserved(cur), "Should be in heap"); |
| assert(!old_gen()->is_in_reserved(cur), "Should be in young gen"); |
| assert(Universe::heap()->is_in_reserved(obj_to_push), "Should be in heap"); |
| if (should_be_partially_scanned(obj_to_push, cur)) { |
| assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
| obj_to_push = cur; |
| } |
| bool ok = queue->push(obj_to_push); |
| assert(ok, "Should have succeeded"); |
| } |
| assert(young_gen()->overflow_list() == NULL, "Error"); |
| return num_take_elems > 0; // was something transferred? |
| } |
| |
| void ParScanThreadState::push_on_overflow_stack(oop p) { |
| assert(ParGCUseLocalOverflow, "Else should not call"); |
| overflow_stack()->push(p); |
| assert(young_gen()->overflow_list() == NULL, "Error"); |
| } |
| |
| HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) { |
| |
| // Otherwise, if the object is small enough, try to reallocate the |
| // buffer. |
| HeapWord* obj = NULL; |
| if (!_to_space_full) { |
| ParGCAllocBuffer* const plab = to_space_alloc_buffer(); |
| Space* const sp = to_space(); |
| if (word_sz * 100 < |
| ParallelGCBufferWastePct * plab->word_sz()) { |
| // Is small enough; abandon this buffer and start a new one. |
| plab->retire(false, false); |
| size_t buf_size = plab->word_sz(); |
| HeapWord* buf_space = sp->par_allocate(buf_size); |
| if (buf_space == NULL) { |
| const size_t min_bytes = |
| ParGCAllocBuffer::min_size() << LogHeapWordSize; |
| size_t free_bytes = sp->free(); |
| while(buf_space == NULL && free_bytes >= min_bytes) { |
| buf_size = free_bytes >> LogHeapWordSize; |
| assert(buf_size == (size_t)align_object_size(buf_size), |
| "Invariant"); |
| buf_space = sp->par_allocate(buf_size); |
| free_bytes = sp->free(); |
| } |
| } |
| if (buf_space != NULL) { |
| plab->set_word_size(buf_size); |
| plab->set_buf(buf_space); |
| record_survivor_plab(buf_space, buf_size); |
| obj = plab->allocate(word_sz); |
| // Note that we cannot compare buf_size < word_sz below |
| // because of AlignmentReserve (see ParGCAllocBuffer::allocate()). |
| assert(obj != NULL || plab->words_remaining() < word_sz, |
| "Else should have been able to allocate"); |
| // It's conceivable that we may be able to use the |
| // buffer we just grabbed for subsequent small requests |
| // even if not for this one. |
| } else { |
| // We're used up. |
| _to_space_full = true; |
| } |
| |
| } else { |
| // Too large; allocate the object individually. |
| obj = sp->par_allocate(word_sz); |
| } |
| } |
| return obj; |
| } |
| |
| |
| void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj, |
| size_t word_sz) { |
| // Is the alloc in the current alloc buffer? |
| if (to_space_alloc_buffer()->contains(obj)) { |
| assert(to_space_alloc_buffer()->contains(obj + word_sz - 1), |
| "Should contain whole object."); |
| to_space_alloc_buffer()->undo_allocation(obj, word_sz); |
| } else { |
| CollectedHeap::fill_with_object(obj, word_sz); |
| } |
| } |
| |
| void ParScanThreadState::print_and_clear_promotion_failure_size() { |
| if (_promotion_failure_size != 0) { |
| if (PrintPromotionFailure) { |
| gclog_or_tty->print(" (%d: promotion failure size = " SIZE_FORMAT ") ", |
| _thread_num, _promotion_failure_size); |
| } |
| _promotion_failure_size = 0; |
| } |
| } |
| |
| class ParScanThreadStateSet: private ResourceArray { |
| public: |
| // Initializes states for the specified number of threads; |
| ParScanThreadStateSet(int num_threads, |
| Space& to_space, |
| ParNewGeneration& gen, |
| Generation& old_gen, |
| ObjToScanQueueSet& queue_set, |
| Stack<oop, mtGC>* overflow_stacks_, |
| size_t desired_plab_sz, |
| ParallelTaskTerminator& term); |
| |
| ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); } |
| |
| inline ParScanThreadState& thread_state(int i); |
| |
| void reset(int active_workers, bool promotion_failed); |
| void flush(); |
| |
| #if TASKQUEUE_STATS |
| static void |
| print_termination_stats_hdr(outputStream* const st = gclog_or_tty); |
| void print_termination_stats(outputStream* const st = gclog_or_tty); |
| static void |
| print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); |
| void print_taskqueue_stats(outputStream* const st = gclog_or_tty); |
| void reset_stats(); |
| #endif // TASKQUEUE_STATS |
| |
| private: |
| ParallelTaskTerminator& _term; |
| ParNewGeneration& _gen; |
| Generation& _next_gen; |
| public: |
| bool is_valid(int id) const { return id < length(); } |
| ParallelTaskTerminator* terminator() { return &_term; } |
| }; |
| |
| |
| ParScanThreadStateSet::ParScanThreadStateSet( |
| int num_threads, Space& to_space, ParNewGeneration& gen, |
| Generation& old_gen, ObjToScanQueueSet& queue_set, |
| Stack<oop, mtGC>* overflow_stacks, |
| size_t desired_plab_sz, ParallelTaskTerminator& term) |
| : ResourceArray(sizeof(ParScanThreadState), num_threads), |
| _gen(gen), _next_gen(old_gen), _term(term) |
| { |
| assert(num_threads > 0, "sanity check!"); |
| assert(ParGCUseLocalOverflow == (overflow_stacks != NULL), |
| "overflow_stack allocation mismatch"); |
| // Initialize states. |
| for (int i = 0; i < num_threads; ++i) { |
| new ((ParScanThreadState*)_data + i) |
| ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set, |
| overflow_stacks, desired_plab_sz, term); |
| } |
| } |
| |
| inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i) |
| { |
| assert(i >= 0 && i < length(), "sanity check!"); |
| return ((ParScanThreadState*)_data)[i]; |
| } |
| |
| |
| void ParScanThreadStateSet::reset(int active_threads, bool promotion_failed) |
| { |
| _term.reset_for_reuse(active_threads); |
| if (promotion_failed) { |
| for (int i = 0; i < length(); ++i) { |
| thread_state(i).print_and_clear_promotion_failure_size(); |
| } |
| } |
| } |
| |
| #if TASKQUEUE_STATS |
| void |
| ParScanThreadState::reset_stats() |
| { |
| taskqueue_stats().reset(); |
| _term_attempts = 0; |
| _overflow_refills = 0; |
| _overflow_refill_objs = 0; |
| } |
| |
| void ParScanThreadStateSet::reset_stats() |
| { |
| for (int i = 0; i < length(); ++i) { |
| thread_state(i).reset_stats(); |
| } |
| } |
| |
| void |
| ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st) |
| { |
| st->print_raw_cr("GC Termination Stats"); |
| st->print_raw_cr(" elapsed --strong roots-- " |
| "-------termination-------"); |
| st->print_raw_cr("thr ms ms % " |
| " ms % attempts"); |
| st->print_raw_cr("--- --------- --------- ------ " |
| "--------- ------ --------"); |
| } |
| |
| void ParScanThreadStateSet::print_termination_stats(outputStream* const st) |
| { |
| print_termination_stats_hdr(st); |
| |
| for (int i = 0; i < length(); ++i) { |
| const ParScanThreadState & pss = thread_state(i); |
| const double elapsed_ms = pss.elapsed_time() * 1000.0; |
| const double s_roots_ms = pss.strong_roots_time() * 1000.0; |
| const double term_ms = pss.term_time() * 1000.0; |
| st->print_cr("%3d %9.2f %9.2f %6.2f " |
| "%9.2f %6.2f " SIZE_FORMAT_W(8), |
| i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, |
| term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts()); |
| } |
| } |
| |
| // Print stats related to work queue activity. |
| void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st) |
| { |
| st->print_raw_cr("GC Task Stats"); |
| st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); |
| st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); |
| } |
| |
| void ParScanThreadStateSet::print_taskqueue_stats(outputStream* const st) |
| { |
| print_taskqueue_stats_hdr(st); |
| |
| TaskQueueStats totals; |
| for (int i = 0; i < length(); ++i) { |
| const ParScanThreadState & pss = thread_state(i); |
| const TaskQueueStats & stats = pss.taskqueue_stats(); |
| st->print("%3d ", i); stats.print(st); st->cr(); |
| totals += stats; |
| |
| if (pss.overflow_refills() > 0) { |
| st->print_cr(" " SIZE_FORMAT_W(10) " overflow refills " |
| SIZE_FORMAT_W(10) " overflow objects", |
| pss.overflow_refills(), pss.overflow_refill_objs()); |
| } |
| } |
| st->print("tot "); totals.print(st); st->cr(); |
| |
| DEBUG_ONLY(totals.verify()); |
| } |
| #endif // TASKQUEUE_STATS |
| |
| void ParScanThreadStateSet::flush() |
| { |
| // Work in this loop should be kept as lightweight as |
| // possible since this might otherwise become a bottleneck |
| // to scaling. Should we add heavy-weight work into this |
| // loop, consider parallelizing the loop into the worker threads. |
| for (int i = 0; i < length(); ++i) { |
| ParScanThreadState& par_scan_state = thread_state(i); |
| |
| // Flush stats related to To-space PLAB activity and |
| // retire the last buffer. |
| par_scan_state.to_space_alloc_buffer()-> |
| flush_stats_and_retire(_gen.plab_stats(), |
| true /* end_of_gc */, |
| false /* retain */); |
| |
| // Every thread has its own age table. We need to merge |
| // them all into one. |
| ageTable *local_table = par_scan_state.age_table(); |
| _gen.age_table()->merge(local_table); |
| |
| // Inform old gen that we're done. |
| _next_gen.par_promote_alloc_done(i); |
| _next_gen.par_oop_since_save_marks_iterate_done(i); |
| } |
| |
| if (UseConcMarkSweepGC && ParallelGCThreads > 0) { |
| // We need to call this even when ResizeOldPLAB is disabled |
| // so as to avoid breaking some asserts. While we may be able |
| // to avoid this by reorganizing the code a bit, I am loathe |
| // to do that unless we find cases where ergo leads to bad |
| // performance. |
| CFLS_LAB::compute_desired_plab_size(); |
| } |
| } |
| |
| ParScanClosure::ParScanClosure(ParNewGeneration* g, |
| ParScanThreadState* par_scan_state) : |
| OopsInKlassOrGenClosure(g), _par_scan_state(par_scan_state), _g(g) |
| { |
| assert(_g->level() == 0, "Optimized for youngest generation"); |
| _boundary = _g->reserved().end(); |
| } |
| |
| void ParScanWithBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, false); } |
| void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); } |
| |
| void ParScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, false); } |
| void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); } |
| |
| void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, true); } |
| void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); } |
| |
| void ParRootScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, true); } |
| void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); } |
| |
| ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g, |
| ParScanThreadState* par_scan_state) |
| : ScanWeakRefClosure(g), _par_scan_state(par_scan_state) |
| {} |
| |
| void ParScanWeakRefClosure::do_oop(oop* p) { ParScanWeakRefClosure::do_oop_work(p); } |
| void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); } |
| |
| #ifdef WIN32 |
| #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */ |
| #endif |
| |
| ParEvacuateFollowersClosure::ParEvacuateFollowersClosure( |
| ParScanThreadState* par_scan_state_, |
| ParScanWithoutBarrierClosure* to_space_closure_, |
| ParScanWithBarrierClosure* old_gen_closure_, |
| ParRootScanWithoutBarrierClosure* to_space_root_closure_, |
| ParNewGeneration* par_gen_, |
| ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_, |
| ObjToScanQueueSet* task_queues_, |
| ParallelTaskTerminator* terminator_) : |
| |
| _par_scan_state(par_scan_state_), |
| _to_space_closure(to_space_closure_), |
| _old_gen_closure(old_gen_closure_), |
| _to_space_root_closure(to_space_root_closure_), |
| _old_gen_root_closure(old_gen_root_closure_), |
| _par_gen(par_gen_), |
| _task_queues(task_queues_), |
| _terminator(terminator_) |
| {} |
| |
| void ParEvacuateFollowersClosure::do_void() { |
| ObjToScanQueue* work_q = par_scan_state()->work_queue(); |
| |
| while (true) { |
| |
| // Scan to-space and old-gen objs until we run out of both. |
| oop obj_to_scan; |
| par_scan_state()->trim_queues(0); |
| |
| // We have no local work, attempt to steal from other threads. |
| |
| // attempt to steal work from promoted. |
| if (task_queues()->steal(par_scan_state()->thread_num(), |
| par_scan_state()->hash_seed(), |
| obj_to_scan)) { |
| bool res = work_q->push(obj_to_scan); |
| assert(res, "Empty queue should have room for a push."); |
| |
| // if successful, goto Start. |
| continue; |
| |
| // try global overflow list. |
| } else if (par_gen()->take_from_overflow_list(par_scan_state())) { |
| continue; |
| } |
| |
| // Otherwise, offer termination. |
| par_scan_state()->start_term_time(); |
| if (terminator()->offer_termination()) break; |
| par_scan_state()->end_term_time(); |
| } |
| assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0, |
| "Broken overflow list?"); |
| // Finish the last termination pause. |
| par_scan_state()->end_term_time(); |
| } |
| |
| ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen, |
| HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) : |
| AbstractGangTask("ParNewGeneration collection"), |
| _gen(gen), _next_gen(next_gen), |
| _young_old_boundary(young_old_boundary), |
| _state_set(state_set) |
| {} |
| |
| // Reset the terminator for the given number of |
| // active threads. |
| void ParNewGenTask::set_for_termination(int active_workers) { |
| _state_set->reset(active_workers, _gen->promotion_failed()); |
| // Should the heap be passed in? There's only 1 for now so |
| // grab it instead. |
| GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| gch->set_n_termination(active_workers); |
| } |
| |
| // The "i" passed to this method is the part of the work for |
| // this thread. It is not the worker ID. The "i" is derived |
| // from _started_workers which is incremented in internal_note_start() |
| // called in GangWorker loop() and which is called under the |
| // which is called under the protection of the gang monitor and is |
| // called after a task is started. So "i" is based on |
| // first-come-first-served. |
| |
| void ParNewGenTask::work(uint worker_id) { |
| GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| // Since this is being done in a separate thread, need new resource |
| // and handle marks. |
| ResourceMark rm; |
| HandleMark hm; |
| // We would need multiple old-gen queues otherwise. |
| assert(gch->n_gens() == 2, "Par young collection currently only works with one older gen."); |
| |
| Generation* old_gen = gch->next_gen(_gen); |
| |
| ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id); |
| assert(_state_set->is_valid(worker_id), "Should not have been called"); |
| |
| par_scan_state.set_young_old_boundary(_young_old_boundary); |
| |
| KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(), |
| gch->rem_set()->klass_rem_set()); |
| |
| int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; |
| |
| par_scan_state.start_strong_roots(); |
| gch->gen_process_strong_roots(_gen->level(), |
| true, // Process younger gens, if any, |
| // as strong roots. |
| false, // no scope; this is parallel code |
| true, // is scavenging |
| SharedHeap::ScanningOption(so), |
| &par_scan_state.to_space_root_closure(), |
| true, // walk *all* scavengable nmethods |
| &par_scan_state.older_gen_closure(), |
| &klass_scan_closure); |
| par_scan_state.end_strong_roots(); |
| |
| // "evacuate followers". |
| par_scan_state.evacuate_followers_closure().do_void(); |
| } |
| |
| #ifdef _MSC_VER |
| #pragma warning( push ) |
| #pragma warning( disable:4355 ) // 'this' : used in base member initializer list |
| #endif |
| ParNewGeneration:: |
| ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level) |
| : DefNewGeneration(rs, initial_byte_size, level, "PCopy"), |
| _overflow_list(NULL), |
| _is_alive_closure(this), |
| _plab_stats(YoungPLABSize, PLABWeight) |
| { |
| NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;) |
| NOT_PRODUCT(_num_par_pushes = 0;) |
| _task_queues = new ObjToScanQueueSet(ParallelGCThreads); |
| guarantee(_task_queues != NULL, "task_queues allocation failure."); |
| |
| for (uint i1 = 0; i1 < ParallelGCThreads; i1++) { |
| ObjToScanQueue *q = new ObjToScanQueue(); |
| guarantee(q != NULL, "work_queue Allocation failure."); |
| _task_queues->register_queue(i1, q); |
| } |
| |
| for (uint i2 = 0; i2 < ParallelGCThreads; i2++) |
| _task_queues->queue(i2)->initialize(); |
| |
| _overflow_stacks = NULL; |
| if (ParGCUseLocalOverflow) { |
| |
| // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal |
| // with ',' |
| typedef Stack<oop, mtGC> GCOopStack; |
| |
| _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC); |
| for (size_t i = 0; i < ParallelGCThreads; ++i) { |
| new (_overflow_stacks + i) Stack<oop, mtGC>(); |
| } |
| } |
| |
| if (UsePerfData) { |
| EXCEPTION_MARK; |
| ResourceMark rm; |
| |
| const char* cname = |
| PerfDataManager::counter_name(_gen_counters->name_space(), "threads"); |
| PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None, |
| ParallelGCThreads, CHECK); |
| } |
| } |
| #ifdef _MSC_VER |
| #pragma warning( pop ) |
| #endif |
| |
| // ParNewGeneration:: |
| ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) : |
| DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {} |
| |
| template <class T> |
| void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) { |
| #ifdef ASSERT |
| { |
| assert(!oopDesc::is_null(*p), "expected non-null ref"); |
| oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
| // We never expect to see a null reference being processed |
| // as a weak reference. |
| assert(obj->is_oop(), "expected an oop while scanning weak refs"); |
| } |
| #endif // ASSERT |
| |
| _par_cl->do_oop_nv(p); |
| |
| if (Universe::heap()->is_in_reserved(p)) { |
| oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
| _rs->write_ref_field_gc_par(p, obj); |
| } |
| } |
| |
| void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p) { ParKeepAliveClosure::do_oop_work(p); } |
| void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); } |
| |
| // ParNewGeneration:: |
| KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) : |
| DefNewGeneration::KeepAliveClosure(cl) {} |
| |
| template <class T> |
| void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) { |
| #ifdef ASSERT |
| { |
| assert(!oopDesc::is_null(*p), "expected non-null ref"); |
| oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
| // We never expect to see a null reference being processed |
| // as a weak reference. |
| assert(obj->is_oop(), "expected an oop while scanning weak refs"); |
| } |
| #endif // ASSERT |
| |
| _cl->do_oop_nv(p); |
| |
| if (Universe::heap()->is_in_reserved(p)) { |
| oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
| _rs->write_ref_field_gc_par(p, obj); |
| } |
| } |
| |
| void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p) { KeepAliveClosure::do_oop_work(p); } |
| void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); } |
| |
| template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) { |
| T heap_oop = oopDesc::load_heap_oop(p); |
| if (!oopDesc::is_null(heap_oop)) { |
| oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); |
| if ((HeapWord*)obj < _boundary) { |
| assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?"); |
| oop new_obj = obj->is_forwarded() |
| ? obj->forwardee() |
| : _g->DefNewGeneration::copy_to_survivor_space(obj); |
| oopDesc::encode_store_heap_oop_not_null(p, new_obj); |
| } |
| if (_gc_barrier) { |
| // If p points to a younger generation, mark the card. |
| if ((HeapWord*)obj < _gen_boundary) { |
| _rs->write_ref_field_gc_par(p, obj); |
| } |
| } |
| } |
| } |
| |
| void ScanClosureWithParBarrier::do_oop(oop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
| void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
| |
| class ParNewRefProcTaskProxy: public AbstractGangTask { |
| typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
| public: |
| ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen, |
| Generation& next_gen, |
| HeapWord* young_old_boundary, |
| ParScanThreadStateSet& state_set); |
| |
| private: |
| virtual void work(uint worker_id); |
| virtual void set_for_termination(int active_workers) { |
| _state_set.terminator()->reset_for_reuse(active_workers); |
| } |
| private: |
| ParNewGeneration& _gen; |
| ProcessTask& _task; |
| Generation& _next_gen; |
| HeapWord* _young_old_boundary; |
| ParScanThreadStateSet& _state_set; |
| }; |
| |
| ParNewRefProcTaskProxy::ParNewRefProcTaskProxy( |
| ProcessTask& task, ParNewGeneration& gen, |
| Generation& next_gen, |
| HeapWord* young_old_boundary, |
| ParScanThreadStateSet& state_set) |
| : AbstractGangTask("ParNewGeneration parallel reference processing"), |
| _gen(gen), |
| _task(task), |
| _next_gen(next_gen), |
| _young_old_boundary(young_old_boundary), |
| _state_set(state_set) |
| { |
| } |
| |
| void ParNewRefProcTaskProxy::work(uint worker_id) |
| { |
| ResourceMark rm; |
| HandleMark hm; |
| ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id); |
| par_scan_state.set_young_old_boundary(_young_old_boundary); |
| _task.work(worker_id, par_scan_state.is_alive_closure(), |
| par_scan_state.keep_alive_closure(), |
| par_scan_state.evacuate_followers_closure()); |
| } |
| |
| class ParNewRefEnqueueTaskProxy: public AbstractGangTask { |
| typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; |
| EnqueueTask& _task; |
| |
| public: |
| ParNewRefEnqueueTaskProxy(EnqueueTask& task) |
| : AbstractGangTask("ParNewGeneration parallel reference enqueue"), |
| _task(task) |
| { } |
| |
| virtual void work(uint worker_id) |
| { |
| _task.work(worker_id); |
| } |
| }; |
| |
| |
| void ParNewRefProcTaskExecutor::execute(ProcessTask& task) |
| { |
| GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| assert(gch->kind() == CollectedHeap::GenCollectedHeap, |
| "not a generational heap"); |
| FlexibleWorkGang* workers = gch->workers(); |
| assert(workers != NULL, "Need parallel worker threads."); |
| _state_set.reset(workers->active_workers(), _generation.promotion_failed()); |
| ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(), |
| _generation.reserved().end(), _state_set); |
| workers->run_task(&rp_task); |
| _state_set.reset(0 /* bad value in debug if not reset */, |
| _generation.promotion_failed()); |
| } |
| |
| void ParNewRefProcTaskExecutor::execute(EnqueueTask& task) |
| { |
| GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| FlexibleWorkGang* workers = gch->workers(); |
| assert(workers != NULL, "Need parallel worker threads."); |
| ParNewRefEnqueueTaskProxy enq_task(task); |
| workers->run_task(&enq_task); |
| } |
| |
| void ParNewRefProcTaskExecutor::set_single_threaded_mode() |
| { |
| _state_set.flush(); |
| GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| gch->set_par_threads(0); // 0 ==> non-parallel. |
| gch->save_marks(); |
| } |
| |
| ScanClosureWithParBarrier:: |
| ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) : |
| ScanClosure(g, gc_barrier) {} |
| |
| EvacuateFollowersClosureGeneral:: |
| EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level, |
| OopsInGenClosure* cur, |
| OopsInGenClosure* older) : |
| _gch(gch), _level(level), |
| _scan_cur_or_nonheap(cur), _scan_older(older) |
| {} |
| |
| void EvacuateFollowersClosureGeneral::do_void() { |
| do { |
| // Beware: this call will lead to closure applications via virtual |
| // calls. |
| _gch->oop_since_save_marks_iterate(_level, |
| _scan_cur_or_nonheap, |
| _scan_older); |
| } while (!_gch->no_allocs_since_save_marks(_level)); |
| } |
| |
| |
| bool ParNewGeneration::_avoid_promotion_undo = false; |
| |
| // A Generation that does parallel young-gen collection. |
| |
| void ParNewGeneration::collect(bool full, |
| bool clear_all_soft_refs, |
| size_t size, |
| bool is_tlab) { |
| assert(full || size > 0, "otherwise we don't want to collect"); |
| GenCollectedHeap* gch = GenCollectedHeap::heap(); |
| assert(gch->kind() == CollectedHeap::GenCollectedHeap, |
| "not a CMS generational heap"); |
| AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); |
| FlexibleWorkGang* workers = gch->workers(); |
| assert(workers != NULL, "Need workgang for parallel work"); |
| int active_workers = |
| AdaptiveSizePolicy::calc_active_workers(workers->total_workers(), |
| workers->active_workers(), |
| Threads::number_of_non_daemon_threads()); |
| workers->set_active_workers(active_workers); |
| _next_gen = gch->next_gen(this); |
| assert(_next_gen != NULL, |
| "This must be the youngest gen, and not the only gen"); |
| assert(gch->n_gens() == 2, |
| "Par collection currently only works with single older gen."); |
| // Do we have to avoid promotion_undo? |
| if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) { |
| set_avoid_promotion_undo(true); |
| } |
| |
| // If the next generation is too full to accomodate worst-case promotion |
| // from this generation, pass on collection; let the next generation |
| // do it. |
| if (!collection_attempt_is_safe()) { |
| gch->set_incremental_collection_failed(); // slight lie, in that we did not even attempt one |
| return; |
| } |
| assert(to()->is_empty(), "Else not collection_attempt_is_safe"); |
| |
| init_assuming_no_promotion_failure(); |
| |
| if (UseAdaptiveSizePolicy) { |
| set_survivor_overflow(false); |
| size_policy->minor_collection_begin(); |
| } |
| |
| TraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty); |
| // Capture heap used before collection (for printing). |
| size_t gch_prev_used = gch->used(); |
| |
| SpecializationStats::clear(); |
| |
| age_table()->clear(); |
| to()->clear(SpaceDecorator::Mangle); |
| |
| gch->save_marks(); |
| assert(workers != NULL, "Need parallel worker threads."); |
| int n_workers = active_workers; |
| |
| // Set the correct parallelism (number of queues) in the reference processor |
| ref_processor()->set_active_mt_degree(n_workers); |
| |
| // Always set the terminator for the active number of workers |
| // because only those workers go through the termination protocol. |
| ParallelTaskTerminator _term(n_workers, task_queues()); |
| ParScanThreadStateSet thread_state_set(workers->active_workers(), |
| *to(), *this, *_next_gen, *task_queues(), |
| _overflow_stacks, desired_plab_sz(), _term); |
| |
| ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set); |
| gch->set_par_threads(n_workers); |
| gch->rem_set()->prepare_for_younger_refs_iterate(true); |
| // It turns out that even when we're using 1 thread, doing the work in a |
| // separate thread causes wide variance in run times. We can't help this |
| // in the multi-threaded case, but we special-case n=1 here to get |
| // repeatable measurements of the 1-thread overhead of the parallel code. |
| if (n_workers > 1) { |
| GenCollectedHeap::StrongRootsScope srs(gch); |
| workers->run_task(&tsk); |
| } else { |
| GenCollectedHeap::StrongRootsScope srs(gch); |
| tsk.work(0); |
| } |
| thread_state_set.reset(0 /* Bad value in debug if not reset */, |
| promotion_failed()); |
| |
| // Process (weak) reference objects found during scavenge. |
| ReferenceProcessor* rp = ref_processor(); |
| IsAliveClosure is_alive(this); |
| ScanWeakRefClosure scan_weak_ref(this); |
| KeepAliveClosure keep_alive(&scan_weak_ref); |
| ScanClosure scan_without_gc_barrier(this, false); |
| ScanClosureWithParBarrier scan_with_gc_barrier(this, true); |
| set_promo_failure_scan_stack_closure(&scan_without_gc_barrier); |
| EvacuateFollowersClosureGeneral evacuate_followers(gch, _level, |
| &scan_without_gc_barrier, &scan_with_gc_barrier); |
| rp->setup_policy(clear_all_soft_refs); |
| // Can the mt_degree be set later (at run_task() time would be best)? |
| rp->set_active_mt_degree(active_workers); |
| if (rp->processing_is_mt()) { |
| ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); |
| rp->process_discovered_references(&is_alive, &keep_alive, |
| &evacuate_followers, &task_executor); |
| } else { |
| thread_state_set.flush(); |
| gch->set_par_threads(0); // 0 ==> non-parallel. |
| gch->save_marks(); |
| rp->process_discovered_references(&is_alive, &keep_alive, |
| &evacuate_followers, NULL); |
| } |
| if (!promotion_failed()) { |
| // Swap the survivor spaces. |
| eden()->clear(SpaceDecorator::Mangle); |
| from()->clear(SpaceDecorator::Mangle); |
| if (ZapUnusedHeapArea) { |
| // This is now done here because of the piece-meal mangling which |
| // can check for valid mangling at intermediate points in the |
| // collection(s). When a minor collection fails to collect |
| // sufficient space resizing of the young generation can occur |
| // an redistribute the spaces in the young generation. Mangle |
| // here so that unzapped regions don't get distributed to |
| // other spaces. |
| to()->mangle_unused_area(); |
| } |
| swap_spaces(); |
| |
| // A successful scavenge should restart the GC time limit count which is |
| // for full GC's. |
| size_policy->reset_gc_overhead_limit_count(); |
| |
| assert(to()->is_empty(), "to space should be empty now"); |
| |
| adjust_desired_tenuring_threshold(); |
| } else { |
| assert(_promo_failure_scan_stack.is_empty(), "post condition"); |
| _promo_failure_scan_stack.clear(true); // Clear cached segments. |
| |
| remove_forwarding_pointers(); |
| if (PrintGCDetails) { |
| gclog_or_tty->print(" (promotion failed)"); |
| } |
| // All the spaces are in play for mark-sweep. |
| swap_spaces(); // Make life simpler for CMS || rescan; see 6483690. |
| from()->set_next_compaction_space(to()); |
| gch->set_incremental_collection_failed(); |
| // Inform the next generation that a promotion failure occurred. |
| _next_gen->promotion_failure_occurred(); |
| |
| // Reset the PromotionFailureALot counters. |
| NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) |
| } |
| // set new iteration safe limit for the survivor spaces |
| from()->set_concurrent_iteration_safe_limit(from()->top()); |
| to()->set_concurrent_iteration_safe_limit(to()->top()); |
| |
| if (ResizePLAB) { |
| plab_stats()->adjust_desired_plab_sz(n_workers); |
| } |
| |
| if (PrintGC && !PrintGCDetails) { |
| gch->print_heap_change(gch_prev_used); |
| } |
| |
| if (PrintGCDetails && ParallelGCVerbose) { |
| TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats()); |
| TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats()); |
| } |
| |
| if (UseAdaptiveSizePolicy) { |
| size_policy->minor_collection_end(gch->gc_cause()); |
| size_policy->avg_survived()->sample(from()->used()); |
| } |
| |
| // We need to use a monotonically non-deccreasing time in ms |
| // or we will see time-warp warnings and os::javaTimeMillis() |
| // does not guarantee monotonicity. |
| jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; |
| update_time_of_last_gc(now); |
| |
| SpecializationStats::print(); |
| |
| rp->set_enqueuing_is_done(true); |
| if (rp->processing_is_mt()) { |
| ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); |
| rp->enqueue_discovered_references(&task_executor); |
| } else { |
| rp->enqueue_discovered_references(NULL); |
| } |
| rp->verify_no_references_recorded(); |
| } |
| |
| static int sum; |
| void ParNewGeneration::waste_some_time() { |
| for (int i = 0; i < 100; i++) { |
| sum += i; |
| } |
| } |
| |
| static const oop ClaimedForwardPtr = oop(0x4); |
| |
| // Because of concurrency, there are times where an object for which |
| // "is_forwarded()" is true contains an "interim" forwarding pointer |
| // value. Such a value will soon be overwritten with a real value. |
| // This method requires "obj" to have a forwarding pointer, and waits, if |
| // necessary for a real one to be inserted, and returns it. |
| |
| oop ParNewGeneration::real_forwardee(oop obj) { |
| oop forward_ptr = obj->forwardee(); |
| if (forward_ptr != ClaimedForwardPtr) { |
| return forward_ptr; |
| } else { |
| return real_forwardee_slow(obj); |
| } |
| } |
| |
| oop ParNewGeneration::real_forwardee_slow(oop obj) { |
| // Spin-read if it is claimed but not yet written by another thread. |
| oop forward_ptr = obj->forwardee(); |
| while (forward_ptr == ClaimedForwardPtr) { |
| waste_some_time(); |
| assert(obj->is_forwarded(), "precondition"); |
| forward_ptr = obj->forwardee(); |
| } |
| return forward_ptr; |
| } |
| |
| #ifdef ASSERT |
| bool ParNewGeneration::is_legal_forward_ptr(oop p) { |
| return |
| (_avoid_promotion_undo && p == ClaimedForwardPtr) |
| || Universe::heap()->is_in_reserved(p); |
| } |
| #endif |
| |
| void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { |
| if (m->must_be_preserved_for_promotion_failure(obj)) { |
| // We should really have separate per-worker stacks, rather |
| // than use locking of a common pair of stacks. |
| MutexLocker ml(ParGCRareEvent_lock); |
| preserve_mark(obj, m); |
| } |
| } |
| |
| // Multiple GC threads may try to promote an object. If the object |
| // is successfully promoted, a forwarding pointer will be installed in |
| // the object in the young generation. This method claims the right |
| // to install the forwarding pointer before it copies the object, |
| // thus avoiding the need to undo the copy as in |
| // copy_to_survivor_space_avoiding_with_undo. |
| |
| oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo( |
| ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { |
| // In the sequential version, this assert also says that the object is |
| // not forwarded. That might not be the case here. It is the case that |
| // the caller observed it to be not forwarded at some time in the past. |
| assert(is_in_reserved(old), "shouldn't be scavenging this oop"); |
| |
| // The sequential code read "old->age()" below. That doesn't work here, |
| // since the age is in the mark word, and that might be overwritten with |
| // a forwarding pointer by a parallel thread. So we must save the mark |
| // word in a local and then analyze it. |
| oopDesc dummyOld; |
| dummyOld.set_mark(m); |
| assert(!dummyOld.is_forwarded(), |
| "should not be called with forwarding pointer mark word."); |
| |
| oop new_obj = NULL; |
| oop forward_ptr; |
| |
| // Try allocating obj in to-space (unless too old) |
| if (dummyOld.age() < tenuring_threshold()) { |
| new_obj = (oop)par_scan_state->alloc_in_to_space(sz); |
| if (new_obj == NULL) { |
| set_survivor_overflow(true); |
| } |
| } |
| |
| if (new_obj == NULL) { |
| // Either to-space is full or we decided to promote |
| // try allocating obj tenured |
| |
| // Attempt to install a null forwarding pointer (atomically), |
| // to claim the right to install the real forwarding pointer. |
| forward_ptr = old->forward_to_atomic(ClaimedForwardPtr); |
| if (forward_ptr != NULL) { |
| // someone else beat us to it. |
| return real_forwardee(old); |
| } |
| |
| new_obj = _next_gen->par_promote(par_scan_state->thread_num(), |
| old, m, sz); |
| |
| if (new_obj == NULL) { |
| // promotion failed, forward to self |
| _promotion_failed = true; |
| new_obj = old; |
| |
| preserve_mark_if_necessary(old, m); |
| // Log the size of the maiden promotion failure |
| par_scan_state->log_promotion_failure(sz); |
| } |
| |
| old->forward_to(new_obj); |
| forward_ptr = NULL; |
| } else { |
| // Is in to-space; do copying ourselves. |
| Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); |
| forward_ptr = old->forward_to_atomic(new_obj); |
| // Restore the mark word copied above. |
| new_obj->set_mark(m); |
| // Increment age if obj still in new generation |
| new_obj->incr_age(); |
| par_scan_state->age_table()->add(new_obj, sz); |
| } |
| assert(new_obj != NULL, "just checking"); |
| |
| #ifndef PRODUCT |
| // This code must come after the CAS test, or it will print incorrect |
| // information. |
| if (TraceScavenge) { |
| gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}", |
| is_in_reserved(new_obj) ? "copying" : "tenuring", |
| new_obj->klass()->internal_name(), old, new_obj, new_obj->size()); |
| } |
| #endif |
| |
| if (forward_ptr == NULL) { |
| oop obj_to_push = new_obj; |
| if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { |
| // Length field used as index of next element to be scanned. |
| // Real length can be obtained from real_forwardee() |
| arrayOop(old)->set_length(0); |
| obj_to_push = old; |
| assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, |
| "push forwarded object"); |
| } |
| // Push it on one of the queues of to-be-scanned objects. |
| bool simulate_overflow = false; |
| NOT_PRODUCT( |
| if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { |
| // simulate a stack overflow |
| simulate_overflow = true; |
| } |
| ) |
| if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { |
| // Add stats for overflow pushes. |
| if (Verbose && PrintGCDetails) { |
| gclog_or_tty->print("queue overflow!\n"); |
| } |
| push_on_overflow_list(old, par_scan_state); |
| TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0)); |
| } |
| |
| return new_obj; |
| } |
| |
| // Oops. Someone beat us to it. Undo the allocation. Where did we |
| // allocate it? |
| if (is_in_reserved(new_obj)) { |
| // Must be in to_space. |
| assert(to()->is_in_reserved(new_obj), "Checking"); |
| if (forward_ptr == ClaimedForwardPtr) { |
| // Wait to get the real forwarding pointer value. |
| forward_ptr = real_forwardee(old); |
| } |
| par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); |
| } |
| |
| return forward_ptr; |
| } |
| |
| |
| // Multiple GC threads may try to promote the same object. If two |
| // or more GC threads copy the object, only one wins the race to install |
| // the forwarding pointer. The other threads have to undo their copy. |
| |
| oop ParNewGeneration::copy_to_survivor_space_with_undo( |
| ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { |
| |
| // In the sequential version, this assert also says that the object is |
| // not forwarded. That might not be the case here. It is the case that |
| // the caller observed it to be not forwarded at some time in the past. |
| assert(is_in_reserved(old), "shouldn't be scavenging this oop"); |
| |
| // The sequential code read "old->age()" below. That doesn't work here, |
| // since the age is in the mark word, and that might be overwritten with |
| // a forwarding pointer by a parallel thread. So we must save the mark |
| // word here, install it in a local oopDesc, and then analyze it. |
| oopDesc dummyOld; |
| dummyOld.set_mark(m); |
| assert(!dummyOld.is_forwarded(), |
| "should not be called with forwarding pointer mark word."); |
| |
| bool failed_to_promote = false; |
| oop new_obj = NULL; |
| oop forward_ptr; |
| |
| // Try allocating obj in to-space (unless too old) |
| if (dummyOld.age() < tenuring_threshold()) { |
| new_obj = (oop)par_scan_state->alloc_in_to_space(sz); |
| if (new_obj == NULL) { |
| set_survivor_overflow(true); |
| } |
| } |
| |
| if (new_obj == NULL) { |
| // Either to-space is full or we decided to promote |
| // try allocating obj tenured |
| new_obj = _next_gen->par_promote(par_scan_state->thread_num(), |
| old, m, sz); |
| |
| if (new_obj == NULL) { |
| // promotion failed, forward to self |
| forward_ptr = old->forward_to_atomic(old); |
| new_obj = old; |
| |
| if (forward_ptr != NULL) { |
| return forward_ptr; // someone else succeeded |
| } |
| |
| _promotion_failed = true; |
| failed_to_promote = true; |
| |
| preserve_mark_if_necessary(old, m); |
| // Log the size of the maiden promotion failure |
| par_scan_state->log_promotion_failure(sz); |
| } |
| } else { |
| // Is in to-space; do copying ourselves. |
| Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); |
| // Restore the mark word copied above. |
| new_obj->set_mark(m); |
| // Increment age if new_obj still in new generation |
| new_obj->incr_age(); |
| par_scan_state->age_table()->add(new_obj, sz); |
| } |
| assert(new_obj != NULL, "just checking"); |
| |
| #ifndef PRODUCT |
| // This code must come after the CAS test, or it will print incorrect |
| // information. |
| if (TraceScavenge) { |
| gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}", |
| is_in_reserved(new_obj) ? "copying" : "tenuring", |
| new_obj->klass()->internal_name(), old, new_obj, new_obj->size()); |
| } |
| #endif |
| |
| // Now attempt to install the forwarding pointer (atomically). |
| // We have to copy the mark word before overwriting with forwarding |
| // ptr, so we can restore it below in the copy. |
| if (!failed_to_promote) { |
| forward_ptr = old->forward_to_atomic(new_obj); |
| } |
| |
| if (forward_ptr == NULL) { |
| oop obj_to_push = new_obj; |
| if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { |
| // Length field used as index of next element to be scanned. |
| // Real length can be obtained from real_forwardee() |
| arrayOop(old)->set_length(0); |
| obj_to_push = old; |
| assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, |
| "push forwarded object"); |
| } |
| // Push it on one of the queues of to-be-scanned objects. |
| bool simulate_overflow = false; |
| NOT_PRODUCT( |
| if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { |
| // simulate a stack overflow |
| simulate_overflow = true; |
| } |
| ) |
| if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { |
| // Add stats for overflow pushes. |
| push_on_overflow_list(old, par_scan_state); |
| TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0)); |
| } |
| |
| return new_obj; |
| } |
| |
| // Oops. Someone beat us to it. Undo the allocation. Where did we |
| // allocate it? |
| if (is_in_reserved(new_obj)) { |
| // Must be in to_space. |
| assert(to()->is_in_reserved(new_obj), "Checking"); |
| par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); |
| } else { |
| assert(!_avoid_promotion_undo, "Should not be here if avoiding."); |
| _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(), |
| (HeapWord*)new_obj, sz); |
| } |
| |
| return forward_ptr; |
| } |
| |
| #ifndef PRODUCT |
| // It's OK to call this multi-threaded; the worst thing |
| // that can happen is that we'll get a bunch of closely |
| // spaced simulated oveflows, but that's OK, in fact |
| // probably good as it would exercise the overflow code |
| // under contention. |
| bool ParNewGeneration::should_simulate_overflow() { |
| if (_overflow_counter-- <= 0) { // just being defensive |
| _overflow_counter = ParGCWorkQueueOverflowInterval; |
| return true; |
| } else { |
| return false; |
| } |
| } |
| #endif |
| |
| // In case we are using compressed oops, we need to be careful. |
| // If the object being pushed is an object array, then its length |
| // field keeps track of the "grey boundary" at which the next |
| // incremental scan will be done (see ParGCArrayScanChunk). |
| // When using compressed oops, this length field is kept in the |
| // lower 32 bits of the erstwhile klass word and cannot be used |
| // for the overflow chaining pointer (OCP below). As such the OCP |
| // would itself need to be compressed into the top 32-bits in this |
| // case. Unfortunately, see below, in the event that we have a |
| // promotion failure, the node to be pushed on the list can be |
| // outside of the Java heap, so the heap-based pointer compression |
| // would not work (we would have potential aliasing between C-heap |
| // and Java-heap pointers). For this reason, when using compressed |
| // oops, we simply use a worker-thread-local, non-shared overflow |
| // list in the form of a growable array, with a slightly different |
| // overflow stack draining strategy. If/when we start using fat |
| // stacks here, we can go back to using (fat) pointer chains |
| // (although some performance comparisons would be useful since |
| // single global lists have their own performance disadvantages |
| // as we were made painfully aware not long ago, see 6786503). |
| #define BUSY (oop(0x1aff1aff)) |
| void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) { |
| assert(is_in_reserved(from_space_obj), "Should be from this generation"); |
| if (ParGCUseLocalOverflow) { |
| // In the case of compressed oops, we use a private, not-shared |
| // overflow stack. |
| par_scan_state->push_on_overflow_stack(from_space_obj); |
| } else { |
| assert(!UseCompressedOops, "Error"); |
| // if the object has been forwarded to itself, then we cannot |
| // use the klass pointer for the linked list. Instead we have |
| // to allocate an oopDesc in the C-Heap and use that for the linked list. |
| // XXX This is horribly inefficient when a promotion failure occurs |
| // and should be fixed. XXX FIX ME !!! |
| #ifndef PRODUCT |
| Atomic::inc_ptr(&_num_par_pushes); |
| assert(_num_par_pushes > 0, "Tautology"); |
| #endif |
| if (from_space_obj->forwardee() == from_space_obj) { |
| oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1, mtGC); |
| listhead->forward_to(from_space_obj); |
| from_space_obj = listhead; |
| } |
| oop observed_overflow_list = _overflow_list; |
| oop cur_overflow_list; |
| do { |
| cur_overflow_list = observed_overflow_list; |
| if (cur_overflow_list != BUSY) { |
| from_space_obj->set_klass_to_list_ptr(cur_overflow_list); |
| } else { |
| from_space_obj->set_klass_to_list_ptr(NULL); |
| } |
| observed_overflow_list = |
| (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list); |
| } while (cur_overflow_list != observed_overflow_list); |
| } |
| } |
| |
| bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) { |
| bool res; |
| |
| if (ParGCUseLocalOverflow) { |
| res = par_scan_state->take_from_overflow_stack(); |
| } else { |
| assert(!UseCompressedOops, "Error"); |
| res = take_from_overflow_list_work(par_scan_state); |
| } |
| return res; |
| } |
| |
| |
| // *NOTE*: The overflow list manipulation code here and |
| // in CMSCollector:: are very similar in shape, |
| // except that in the CMS case we thread the objects |
| // directly into the list via their mark word, and do |
| // not need to deal with special cases below related |
| // to chunking of object arrays and promotion failure |
| // handling. |
| // CR 6797058 has been filed to attempt consolidation of |
| // the common code. |
| // Because of the common code, if you make any changes in |
| // the code below, please check the CMS version to see if |
| // similar changes might be needed. |
| // See CMSCollector::par_take_from_overflow_list() for |
| // more extensive documentation comments. |
| bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) { |
| ObjToScanQueue* work_q = par_scan_state->work_queue(); |
| // How many to take? |
| size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
| (size_t)ParGCDesiredObjsFromOverflowList); |
| |
| assert(!UseCompressedOops, "Error"); |
| assert(par_scan_state->overflow_stack() == NULL, "Error"); |
| if (_overflow_list == NULL) return false; |
| |
| // Otherwise, there was something there; try claiming the list. |
| oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
| // Trim off a prefix of at most objsFromOverflow items |
| Thread* tid = Thread::current(); |
| size_t spin_count = (size_t)ParallelGCThreads; |
| size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100); |
| for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) { |
| // someone grabbed it before we did ... |
| // ... we spin for a short while... |
| os::sleep(tid, sleep_time_millis, false); |
| if (_overflow_list == NULL) { |
| // nothing left to take |
| return false; |
| } else if (_overflow_list != BUSY) { |
| // try and grab the prefix |
| prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
| } |
| } |
| if (prefix == NULL || prefix == BUSY) { |
| // Nothing to take or waited long enough |
| if (prefix == NULL) { |
| // Write back the NULL in case we overwrote it with BUSY above |
| // and it is still the same value. |
| (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); |
| } |
| return false; |
| } |
| assert(prefix != NULL && prefix != BUSY, "Error"); |
| size_t i = 1; |
| oop cur = prefix; |
| while (i < objsFromOverflow && cur->klass_or_null() != NULL) { |
| i++; cur = cur->list_ptr_from_klass(); |
| } |
| |
| // Reattach remaining (suffix) to overflow list |
| if (cur->klass_or_null() == NULL) { |
| // Write back the NULL in lieu of the BUSY we wrote |
| // above and it is still the same value. |
| if (_overflow_list == BUSY) { |
| (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); |
| } |
| } else { |
| assert(cur->klass_or_null() != (Klass*)(address)BUSY, "Error"); |
| oop suffix = cur->list_ptr_from_klass(); // suffix will be put back on global list |
| cur->set_klass_to_list_ptr(NULL); // break off suffix |
| // It's possible that the list is still in the empty(busy) state |
| // we left it in a short while ago; in that case we may be |
| // able to place back the suffix. |
| oop observed_overflow_list = _overflow_list; |
| oop cur_overflow_list = observed_overflow_list; |
| bool attached = false; |
| while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { |
| observed_overflow_list = |
| (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); |
| if (cur_overflow_list == observed_overflow_list) { |
| attached = true; |
| break; |
| } else cur_overflow_list = observed_overflow_list; |
| } |
| if (!attached) { |
| // Too bad, someone else got in in between; we'll need to do a splice. |
| // Find the last item of suffix list |
| oop last = suffix; |
| while (last->klass_or_null() != NULL) { |
| last = last->list_ptr_from_klass(); |
| } |
| // Atomically prepend suffix to current overflow list |
| observed_overflow_list = _overflow_list; |
| do { |
| cur_overflow_list = observed_overflow_list; |
| if (cur_overflow_list != BUSY) { |
| // Do the splice ... |
| last->set_klass_to_list_ptr(cur_overflow_list); |
| } else { // cur_overflow_list == BUSY |
| last->set_klass_to_list_ptr(NULL); |
| } |
| observed_overflow_list = |
| (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); |
| } while (cur_overflow_list != observed_overflow_list); |
| } |
| } |
| |
| // Push objects on prefix list onto this thread's work queue |
| assert(prefix != NULL && prefix != BUSY, "program logic"); |
| cur = prefix; |
| ssize_t n = 0; |
| while (cur != NULL) { |
| oop obj_to_push = cur->forwardee(); |
| oop next = cur->list_ptr_from_klass(); |
| cur->set_klass(obj_to_push->klass()); |
| // This may be an array object that is self-forwarded. In that case, the list pointer |
| // space, cur, is not in the Java heap, but rather in the C-heap and should be freed. |
| if (!is_in_reserved(cur)) { |
| // This can become a scaling bottleneck when there is work queue overflow coincident |
| // with promotion failure. |
| oopDesc* f = cur; |
| FREE_C_HEAP_ARRAY(oopDesc, f, mtGC); |
| } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) { |
| assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
| obj_to_push = cur; |
| } |
| bool ok = work_q->push(obj_to_push); |
| assert(ok, "Should have succeeded"); |
| cur = next; |
| n++; |
| } |
| TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n)); |
| #ifndef PRODUCT |
| assert(_num_par_pushes >= n, "Too many pops?"); |
| Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); |
| #endif |
| return true; |
| } |
| #undef BUSY |
| |
| void ParNewGeneration::ref_processor_init() |
| { |
| if (_ref_processor == NULL) { |
| // Allocate and initialize a reference processor |
| _ref_processor = |
| new ReferenceProcessor(_reserved, // span |
| ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing |
| (int) ParallelGCThreads, // mt processing degree |
| refs_discovery_is_mt(), // mt discovery |
| (int) ParallelGCThreads, // mt discovery degree |
| refs_discovery_is_atomic(), // atomic_discovery |
| NULL, // is_alive_non_header |
| false); // write barrier for next field updates |
| } |
| } |
| |
| const char* ParNewGeneration::name() const { |
| return "par new generation"; |
| } |