diff -r 000000000000 -r f90c822e73f8 src/share/vm/gc_implementation/parNew/parNewGeneration.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp Wed Apr 27 01:25:04 2016 +0800 @@ -0,0 +1,1647 @@ +/* + * Copyright (c) 2001, 2014, 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/gcHeapSummary.hpp" +#include "gc_implementation/shared/gcTimer.hpp" +#include "gc_implementation/shared/gcTrace.hpp" +#include "gc_implementation/shared/gcTraceTime.hpp" +#include "gc_implementation/shared/copyFailedInfo.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" + +PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC + +#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* 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), + _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* 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_promotion_failure_size() { + if (_promotion_failed_info.has_failed() && PrintPromotionFailure) { + gclog_or_tty->print(" (%d: promotion failure size = " SIZE_FORMAT ") ", + _thread_num, _promotion_failed_info.first_size()); + } +} + +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* overflow_stacks_, + size_t desired_plab_sz, + ParallelTaskTerminator& term); + + ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); } + + inline ParScanThreadState& thread_state(int i); + + void trace_promotion_failed(YoungGCTracer& gc_tracer); + 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* 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::trace_promotion_failed(YoungGCTracer& gc_tracer) { + for (int i = 0; i < length(); ++i) { + if (thread_state(i).promotion_failed()) { + gc_tracer.report_promotion_failed(thread_state(i).promotion_failed_info()); + thread_state(i).promotion_failed_info().reset(); + } + } +} + +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_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); +} + +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 GCOopStack; + + _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC); + for (size_t i = 0; i < ParallelGCThreads; ++i) { + new (_overflow_stacks + i) Stack(); + } + } + + 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 +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 +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 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)); +} + + +// A Generation that does parallel young-gen collection. + +bool ParNewGeneration::_avoid_promotion_undo = false; + +void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set, ParNewTracer& gc_tracer) { + 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(); + + // Trace promotion failure in the parallel GC threads + thread_state_set.trace_promotion_failed(gc_tracer); + // Single threaded code may have reported promotion failure to the global state + if (_promotion_failed_info.has_failed()) { + gc_tracer.report_promotion_failed(_promotion_failed_info); + } + // Reset the PromotionFailureALot counters. + NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) +} + +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(); + + _gc_timer->register_gc_start(); + + 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); + assert(gch->n_gens() == 2, + "Par collection currently only works with single older gen."); + _next_gen = gch->next_gen(this); + // 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 accommodate 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"); + + ParNewTracer gc_tracer; + gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); + gch->trace_heap_before_gc(&gc_tracer); + + init_assuming_no_promotion_failure(); + + if (UseAdaptiveSizePolicy) { + set_survivor_overflow(false); + size_policy->minor_collection_begin(); + } + + GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL); + // 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); + ReferenceProcessorStats stats; + if (rp->processing_is_mt()) { + ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); + stats = rp->process_discovered_references(&is_alive, &keep_alive, + &evacuate_followers, &task_executor, + _gc_timer); + } else { + thread_state_set.flush(); + gch->set_par_threads(0); // 0 ==> non-parallel. + gch->save_marks(); + stats = rp->process_discovered_references(&is_alive, &keep_alive, + &evacuate_followers, NULL, + _gc_timer); + } + gc_tracer.report_gc_reference_stats(stats); + 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 { + handle_promotion_failed(gch, thread_state_set, gc_tracer); + } + // 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(); + + gch->trace_heap_after_gc(&gc_tracer); + gc_tracer.report_tenuring_threshold(tenuring_threshold()); + + _gc_timer->register_gc_end(); + + gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); +} + +static int sum; +void ParNewGeneration::waste_some_time() { + for (int i = 0; i < 100; i++) { + sum += i; + } +} + +static const oop ClaimedForwardPtr = cast_to_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); + par_scan_state->register_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(), (void *)old, (void *)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); + par_scan_state->register_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(), (void *)old, (void *)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 (cast_to_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 = cast_to_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 = cast_to_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 + } +} + +const char* ParNewGeneration::name() const { + return "par new generation"; +}