--- old/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp 2015-05-13 13:54:32.159362890 +0200 +++ /dev/null 2015-03-18 17:10:38.111854831 +0100 @@ -1,1490 +0,0 @@ -/* - * Copyright (c) 2001, 2015, 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/compactibleFreeListSpace.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/copyFailedInfo.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/plab.inline.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/referencePolicy.hpp" -#include "memory/resourceArea.hpp" -#include "memory/strongRootsScope.hpp" -#include "memory/space.hpp" -#include "oops/objArrayOop.hpp" -#include "oops/oop.inline.hpp" -#include "runtime/atomic.inline.hpp" -#include "runtime/handles.hpp" -#include "runtime/handles.inline.hpp" -#include "runtime/java.hpp" -#include "runtime/thread.inline.hpp" -#include "utilities/copy.hpp" -#include "utilities/globalDefinitions.hpp" -#include "utilities/stack.inline.hpp" -#include "utilities/taskqueue.inline.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* 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(GenCollectedHeap::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(GenCollectedHeap::heap()->is_in_reserved(cur), "Should be in heap"); - assert(!old_gen()->is_in_reserved(cur), "Should be in young gen"); - assert(GenCollectedHeap::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) { - PLAB* 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(); - size_t buf_size = plab->word_sz(); - HeapWord* buf_space = sp->par_allocate(buf_size); - if (buf_space == NULL) { - const size_t min_bytes = - PLAB::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_aligned(word_sz, SurvivorAlignmentInBytes); - // Note that we cannot compare buf_size < word_sz below - // because of AlignmentReserve (see PLAB::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) { - to_space_alloc_buffer()->undo_allocation(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(const YoungGCTracer* gc_tracer); - void reset(uint 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& _old_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), _old_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(const 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(uint 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_and_retire_stats(_gen.plab_stats()); - - // 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. - _old_gen.par_promote_alloc_done(i); - _old_gen.par_oop_since_save_marks_iterate_done(i); - } - - if (UseConcMarkSweepGC) { - // 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* old_gen, - HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) : - AbstractGangTask("ParNewGeneration collection"), - _gen(gen), _old_gen(old_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(uint 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; - - 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()); - CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, - &par_scan_state.to_space_root_closure(), - false); - - par_scan_state.start_strong_roots(); - gch->gen_process_roots(_gen->level(), - true, // Process younger gens, if any, - // as strong roots. - false, // no scope; this is parallel code - GenCollectedHeap::SO_ScavengeCodeCache, - GenCollectedHeap::StrongAndWeakRoots, - &par_scan_state.to_space_root_closure(), - &par_scan_state.older_gen_closure(), - &cld_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 (GenCollectedHeap::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 (GenCollectedHeap::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& old_gen, - HeapWord* young_old_boundary, - ParScanThreadStateSet& state_set); - -private: - virtual void work(uint worker_id); - virtual void set_for_termination(uint active_workers) { - _state_set.terminator()->reset_for_reuse(active_workers); - } -private: - ParNewGeneration& _gen; - ProcessTask& _task; - Generation& _old_gen; - HeapWord* _young_old_boundary; - ParScanThreadStateSet& _state_set; -}; - -ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(ProcessTask& task, - ParNewGeneration& gen, - Generation& old_gen, - HeapWord* young_old_boundary, - ParScanThreadStateSet& state_set) - : AbstractGangTask("ParNewGeneration parallel reference processing"), - _gen(gen), - _task(task), - _old_gen(old_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(); - 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. - -void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set) { - 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. - _old_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(gch->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(); - - AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); - FlexibleWorkGang* workers = gch->workers(); - assert(workers != NULL, "Need workgang for parallel work"); - uint active_workers = - AdaptiveSizePolicy::calc_active_workers(workers->total_workers(), - workers->active_workers(), - Threads::number_of_non_daemon_threads()); - workers->set_active_workers(active_workers); - _old_gen = gch->old_gen(); - - // 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"); - - _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, _gc_tracer.gc_id()); - // Capture heap used before collection (for printing). - size_t gch_prev_used = gch->used(); - - age_table()->clear(); - to()->clear(SpaceDecorator::Mangle); - - gch->save_marks(); - assert(workers != NULL, "Need parallel worker threads."); - uint 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, *_old_gen, *task_queues(), - _overflow_stacks, desired_plab_sz(), _term); - - ParNewGenTask tsk(this, _old_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) { - StrongRootsScope srs; - workers->run_task(&tsk); - } else { - StrongRootsScope srs; - tsk.work(0); - } - thread_state_set.reset(0 /* Bad value in debug if not reset */, - promotion_failed()); - - // Trace and reset failed promotion info. - if (promotion_failed()) { - thread_state_set.trace_promotion_failed(gc_tracer()); - } - - // 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, _gc_tracer.gc_id()); - } 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.gc_id()); - } - _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); - } - // 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); - } - - TASKQUEUE_STATS_ONLY(if (PrintTerminationStats) thread_state_set.print_termination_stats()); - TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) 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-decreasing 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); - - 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; -} - -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( - 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); - } - - if (!_promotion_failed) { - new_obj = _old_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); - assert(GenCollectedHeap::heap()->is_in_reserved(new_obj), "illegal forwarding pointer value."); - 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(), p2i(old), p2i(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; -} - -#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 overflows, 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); - } 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"; -} --- /dev/null 2015-03-18 17:10:38.111854831 +0100 +++ new/src/share/vm/gc/cms/parNewGeneration.cpp 2015-05-13 13:54:31.843349777 +0200 @@ -0,0 +1,1490 @@ +/* + * Copyright (c) 2001, 2015, 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/cms/compactibleFreeListSpace.hpp" +#include "gc/cms/concurrentMarkSweepGeneration.hpp" +#include "gc/cms/parNewGeneration.hpp" +#include "gc/cms/parOopClosures.inline.hpp" +#include "gc/serial/defNewGeneration.inline.hpp" +#include "gc/shared/adaptiveSizePolicy.hpp" +#include "gc/shared/ageTable.hpp" +#include "gc/shared/copyFailedInfo.hpp" +#include "gc/shared/gcHeapSummary.hpp" +#include "gc/shared/gcTimer.hpp" +#include "gc/shared/gcTrace.hpp" +#include "gc/shared/gcTraceTime.hpp" +#include "gc/shared/genCollectedHeap.hpp" +#include "gc/shared/genOopClosures.inline.hpp" +#include "gc/shared/generation.hpp" +#include "gc/shared/plab.inline.hpp" +#include "gc/shared/referencePolicy.hpp" +#include "gc/shared/space.hpp" +#include "gc/shared/spaceDecorator.hpp" +#include "gc/shared/strongRootsScope.hpp" +#include "gc/shared/taskqueue.inline.hpp" +#include "gc/shared/workgroup.hpp" +#include "memory/resourceArea.hpp" +#include "oops/objArrayOop.hpp" +#include "oops/oop.inline.hpp" +#include "runtime/atomic.inline.hpp" +#include "runtime/handles.hpp" +#include "runtime/handles.inline.hpp" +#include "runtime/java.hpp" +#include "runtime/thread.inline.hpp" +#include "utilities/copy.hpp" +#include "utilities/globalDefinitions.hpp" +#include "utilities/stack.inline.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* 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(GenCollectedHeap::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(GenCollectedHeap::heap()->is_in_reserved(cur), "Should be in heap"); + assert(!old_gen()->is_in_reserved(cur), "Should be in young gen"); + assert(GenCollectedHeap::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) { + PLAB* 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(); + size_t buf_size = plab->word_sz(); + HeapWord* buf_space = sp->par_allocate(buf_size); + if (buf_space == NULL) { + const size_t min_bytes = + PLAB::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_aligned(word_sz, SurvivorAlignmentInBytes); + // Note that we cannot compare buf_size < word_sz below + // because of AlignmentReserve (see PLAB::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) { + to_space_alloc_buffer()->undo_allocation(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(const YoungGCTracer* gc_tracer); + void reset(uint 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& _old_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), _old_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(const 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(uint 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_and_retire_stats(_gen.plab_stats()); + + // 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. + _old_gen.par_promote_alloc_done(i); + _old_gen.par_oop_since_save_marks_iterate_done(i); + } + + if (UseConcMarkSweepGC) { + // 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* old_gen, + HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) : + AbstractGangTask("ParNewGeneration collection"), + _gen(gen), _old_gen(old_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(uint 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; + + 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()); + CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, + &par_scan_state.to_space_root_closure(), + false); + + par_scan_state.start_strong_roots(); + gch->gen_process_roots(_gen->level(), + true, // Process younger gens, if any, + // as strong roots. + false, // no scope; this is parallel code + GenCollectedHeap::SO_ScavengeCodeCache, + GenCollectedHeap::StrongAndWeakRoots, + &par_scan_state.to_space_root_closure(), + &par_scan_state.older_gen_closure(), + &cld_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 (GenCollectedHeap::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 (GenCollectedHeap::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& old_gen, + HeapWord* young_old_boundary, + ParScanThreadStateSet& state_set); + +private: + virtual void work(uint worker_id); + virtual void set_for_termination(uint active_workers) { + _state_set.terminator()->reset_for_reuse(active_workers); + } +private: + ParNewGeneration& _gen; + ProcessTask& _task; + Generation& _old_gen; + HeapWord* _young_old_boundary; + ParScanThreadStateSet& _state_set; +}; + +ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(ProcessTask& task, + ParNewGeneration& gen, + Generation& old_gen, + HeapWord* young_old_boundary, + ParScanThreadStateSet& state_set) + : AbstractGangTask("ParNewGeneration parallel reference processing"), + _gen(gen), + _task(task), + _old_gen(old_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(); + 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. + +void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set) { + 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. + _old_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(gch->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(); + + AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); + FlexibleWorkGang* workers = gch->workers(); + assert(workers != NULL, "Need workgang for parallel work"); + uint active_workers = + AdaptiveSizePolicy::calc_active_workers(workers->total_workers(), + workers->active_workers(), + Threads::number_of_non_daemon_threads()); + workers->set_active_workers(active_workers); + _old_gen = gch->old_gen(); + + // 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"); + + _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, _gc_tracer.gc_id()); + // Capture heap used before collection (for printing). + size_t gch_prev_used = gch->used(); + + age_table()->clear(); + to()->clear(SpaceDecorator::Mangle); + + gch->save_marks(); + assert(workers != NULL, "Need parallel worker threads."); + uint 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, *_old_gen, *task_queues(), + _overflow_stacks, desired_plab_sz(), _term); + + ParNewGenTask tsk(this, _old_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) { + StrongRootsScope srs; + workers->run_task(&tsk); + } else { + StrongRootsScope srs; + tsk.work(0); + } + thread_state_set.reset(0 /* Bad value in debug if not reset */, + promotion_failed()); + + // Trace and reset failed promotion info. + if (promotion_failed()) { + thread_state_set.trace_promotion_failed(gc_tracer()); + } + + // 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, _gc_tracer.gc_id()); + } 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.gc_id()); + } + _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); + } + // 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); + } + + TASKQUEUE_STATS_ONLY(if (PrintTerminationStats) thread_state_set.print_termination_stats()); + TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) 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-decreasing 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); + + 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; +} + +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( + 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); + } + + if (!_promotion_failed) { + new_obj = _old_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); + assert(GenCollectedHeap::heap()->is_in_reserved(new_obj), "illegal forwarding pointer value."); + 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(), p2i(old), p2i(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; +} + +#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 overflows, 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); + } 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"; +}