--- a/src/hotspot/share/gc/cms/parNewGeneration.cpp Fri Nov 08 14:54:17 2019 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,1446 +0,0 @@
-/*
- * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- *
- */
-
-#include "precompiled.hpp"
-#include "classfile/stringTable.hpp"
-#include "gc/cms/cmsHeap.inline.hpp"
-#include "gc/cms/compactibleFreeListSpace.hpp"
-#include "gc/cms/concurrentMarkSweepGeneration.hpp"
-#include "gc/cms/parNewGeneration.inline.hpp"
-#include "gc/cms/parOopClosures.inline.hpp"
-#include "gc/serial/defNewGeneration.inline.hpp"
-#include "gc/shared/adaptiveSizePolicy.hpp"
-#include "gc/shared/ageTable.inline.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.inline.hpp"
-#include "gc/shared/genOopClosures.inline.hpp"
-#include "gc/shared/generation.hpp"
-#include "gc/shared/plab.inline.hpp"
-#include "gc/shared/preservedMarks.inline.hpp"
-#include "gc/shared/referencePolicy.hpp"
-#include "gc/shared/referenceProcessorPhaseTimes.hpp"
-#include "gc/shared/space.hpp"
-#include "gc/shared/spaceDecorator.inline.hpp"
-#include "gc/shared/strongRootsScope.hpp"
-#include "gc/shared/taskqueue.inline.hpp"
-#include "gc/shared/weakProcessor.hpp"
-#include "gc/shared/workgroup.hpp"
-#include "gc/shared/workerPolicy.hpp"
-#include "logging/log.hpp"
-#include "logging/logStream.hpp"
-#include "memory/iterator.inline.hpp"
-#include "memory/resourceArea.hpp"
-#include "oops/access.inline.hpp"
-#include "oops/compressedOops.inline.hpp"
-#include "oops/objArrayOop.hpp"
-#include "oops/oop.inline.hpp"
-#include "runtime/atomic.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"
-
-ParScanThreadState::ParScanThreadState(Space* to_space_,
- ParNewGeneration* young_gen_,
- Generation* old_gen_,
- int thread_num_,
- ObjToScanQueueSet* work_queue_set_,
- Stack<oop, mtGC>* overflow_stacks_,
- PreservedMarks* preserved_marks_,
- size_t desired_plab_sz_,
- TaskTerminator& term_) :
- _work_queue(work_queue_set_->queue(thread_num_)),
- _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL),
- _preserved_marks(preserved_marks_),
- _to_space_alloc_buffer(desired_plab_sz_),
- _to_space_closure(young_gen_, this),
- _old_gen_closure(young_gen_, this),
- _to_space_root_closure(young_gen_, this),
- _older_gen_closure(young_gen_, this),
- _old_gen_root_closure(young_gen_, this),
- _evacuate_followers(this, &_to_space_closure, &_old_gen_closure,
- &_to_space_root_closure, young_gen_, &_old_gen_root_closure,
- work_queue_set_, term_.terminator()),
- _is_alive_closure(young_gen_),
- _scan_weak_ref_closure(young_gen_, this),
- _keep_alive_closure(&_scan_weak_ref_closure),
- _to_space(to_space_),
- _young_gen(young_gen_),
- _old_gen(old_gen_),
- _young_old_boundary(NULL),
- _thread_num(thread_num_),
- _ageTable(false), // false ==> not the global age table, no perf data.
- _to_space_full(false),
- _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());
- _start = os::elapsedTime();
- _old_gen_closure.set_generation(old_gen_);
- _old_gen_root_closure.set_generation(old_gen_);
-}
-
-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(CMSHeap::heap()->is_in_reserved(old), "must be in heap.");
- assert(!old_gen()->is_in(old), "must be in young generation.");
-
- objArrayOop obj = objArrayOop(old->forwardee());
- // Process ParGCArrayScanChunk elements now
- // and push the remainder back onto queue
- int start = arrayOop(old)->length();
- int end = obj->length();
- int remainder = end - start;
- assert(start <= end, "just checking");
- if (remainder > 2 * ParGCArrayScanChunk) {
- // Test above combines last partial chunk with a full chunk
- end = start + ParGCArrayScanChunk;
- arrayOop(old)->set_length(end);
- // Push remainder.
- bool ok = work_queue()->push(old);
- assert(ok, "just popped, push must be okay");
- } else {
- // Restore length so that it can be used if there
- // is a promotion failure and forwarding pointers
- // must be removed.
- arrayOop(old)->set_length(end);
- }
-
- // process our set of indices (include header in first chunk)
- // should make sure end is even (aligned to HeapWord in case of compressed oops)
- if ((HeapWord *)obj < young_old_boundary()) {
- // object is in to_space
- obj->oop_iterate_range(&_to_space_closure, start, end);
- } else {
- // object is in old generation
- obj->oop_iterate_range(&_old_gen_closure, start, end);
- }
-}
-
-void ParScanThreadState::trim_queues(int max_size) {
- ObjToScanQueue* queue = work_queue();
- do {
- while (queue->size() > (juint)max_size) {
- oop obj_to_scan;
- if (queue->pop_local(obj_to_scan)) {
- if ((HeapWord *)obj_to_scan < young_old_boundary()) {
- if (obj_to_scan->is_objArray() &&
- obj_to_scan->is_forwarded() &&
- obj_to_scan->forwardee() != obj_to_scan) {
- scan_partial_array_and_push_remainder(obj_to_scan);
- } else {
- // object is in to_space
- obj_to_scan->oop_iterate(&_to_space_closure);
- }
- } else {
- // object is in old generation
- obj_to_scan->oop_iterate(&_old_gen_closure);
- }
- }
- }
- // For the case of compressed oops, we have a private, non-shared
- // overflow stack, so we eagerly drain it so as to more evenly
- // distribute load early. Note: this may be good to do in
- // general rather than delay for the final stealing phase.
- // If applicable, we'll transfer a set of objects over to our
- // work queue, allowing them to be stolen and draining our
- // private overflow stack.
- } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this));
-}
-
-bool ParScanThreadState::take_from_overflow_stack() {
- assert(ParGCUseLocalOverflow, "Else should not call");
- assert(young_gen()->overflow_list() == NULL, "Error");
- ObjToScanQueue* queue = work_queue();
- Stack<oop, mtGC>* const of_stack = overflow_stack();
- const size_t num_overflow_elems = of_stack->size();
- const size_t space_available = queue->max_elems() - queue->size();
- const size_t num_take_elems = MIN3(space_available / 4,
- (size_t)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(CMSHeap::heap()->is_in_reserved(cur), "Should be in heap");
- assert(!old_gen()->is_in_reserved(cur), "Should be in young gen");
- assert(CMSHeap::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) {
- // 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();
- // The minimum size has to be twice SurvivorAlignmentInBytes to
- // allow for padding used in the alignment of 1 word. A padding
- // of 1 is too small for a filler word so the padding size will
- // be increased by SurvivorAlignmentInBytes.
- size_t min_usable_size = 2 * static_cast<size_t>(SurvivorAlignmentInBytes >> LogHeapWordSize);
- size_t buf_size = MAX2(plab->word_sz(), min_usable_size);
- HeapWord* buf_space = sp->par_allocate(buf_size);
- if (buf_space == NULL) {
- const size_t min_bytes = MAX2(PLAB::min_size(), min_usable_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_buf(buf_space, buf_size);
- 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 requested object size "
- SIZE_FORMAT ", PLAB size " SIZE_FORMAT ", SurvivorAlignmentInBytes "
- SIZE_FORMAT ", words_remaining " SIZE_FORMAT,
- word_sz, buf_size, SurvivorAlignmentInBytes, plab->words_remaining());
- // 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()) {
- log_trace(gc, promotion)(" (%d: promotion failure size = " SIZE_FORMAT ") ",
- _thread_num, _promotion_failed_info.first_size());
- }
-}
-
-class ParScanThreadStateSet: StackObj {
-public:
- // Initializes states for the specified number of threads;
- ParScanThreadStateSet(int num_threads,
- Space& to_space,
- ParNewGeneration& young_gen,
- Generation& old_gen,
- ObjToScanQueueSet& queue_set,
- Stack<oop, mtGC>* overflow_stacks_,
- PreservedMarksSet& preserved_marks_set,
- size_t desired_plab_sz,
- TaskTerminator& 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);
- void print_termination_stats();
- static void
- print_taskqueue_stats_hdr(outputStream* const st);
- void print_taskqueue_stats();
- void reset_stats();
- #endif // TASKQUEUE_STATS
-
-private:
- TaskTerminator& _term;
- ParNewGeneration& _young_gen;
- Generation& _old_gen;
- ParScanThreadState* _per_thread_states;
- const int _num_threads;
- public:
- bool is_valid(int id) const { return id < _num_threads; }
- ParallelTaskTerminator* terminator() { return _term.terminator(); }
-};
-
-ParScanThreadStateSet::ParScanThreadStateSet(int num_threads,
- Space& to_space,
- ParNewGeneration& young_gen,
- Generation& old_gen,
- ObjToScanQueueSet& queue_set,
- Stack<oop, mtGC>* overflow_stacks,
- PreservedMarksSet& preserved_marks_set,
- size_t desired_plab_sz,
- TaskTerminator& term)
- : _term(term),
- _young_gen(young_gen),
- _old_gen(old_gen),
- _per_thread_states(NEW_RESOURCE_ARRAY(ParScanThreadState, num_threads)),
- _num_threads(num_threads)
-{
- 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(_per_thread_states + i)
- ParScanThreadState(&to_space, &young_gen, &old_gen, i, &queue_set,
- overflow_stacks, preserved_marks_set.get(i),
- desired_plab_sz, term);
- }
-}
-
-inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i) {
- assert(i >= 0 && i < _num_threads, "sanity check!");
- return _per_thread_states[i];
-}
-
-void ParScanThreadStateSet::trace_promotion_failed(const YoungGCTracer* gc_tracer) {
- for (int i = 0; i < _num_threads; ++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.terminator()->reset_for_reuse(active_threads);
- if (promotion_failed) {
- for (int i = 0; i < _num_threads; ++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 < _num_threads; ++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() {
- Log(gc, task, stats) log;
- if (!log.is_debug()) {
- return;
- }
-
- ResourceMark rm;
- LogStream ls(log.debug());
- outputStream* st = &ls;
-
- print_termination_stats_hdr(st);
-
- for (int i = 0; i < _num_threads; ++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() {
- if (!log_is_enabled(Trace, gc, task, stats)) {
- return;
- }
- Log(gc, task, stats) log;
- ResourceMark rm;
- LogStream ls(log.trace());
- outputStream* st = &ls;
- print_taskqueue_stats_hdr(st);
-
- TaskQueueStats totals;
- for (int i = 0; i < _num_threads; ++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 < _num_threads; ++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(_young_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();
- _young_gen.age_table()->merge(local_table);
-
- // Inform old gen that we're done.
- _old_gen.par_promote_alloc_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.
- CompactibleFreeListSpaceLAB::compute_desired_plab_size();
- }
-}
-
-ParScanClosure::ParScanClosure(ParNewGeneration* g,
- ParScanThreadState* par_scan_state) :
- OopsInClassLoaderDataOrGenClosure(g), _par_scan_state(par_scan_state), _g(g) {
- _boundary = _g->reserved().end();
-}
-
-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)
-{}
-
-#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_),
- _to_space_root_closure(to_space_root_closure_),
- _old_gen_closure(old_gen_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(),
- 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* young_gen,
- Generation* old_gen,
- HeapWord* young_old_boundary,
- ParScanThreadStateSet* state_set,
- StrongRootsScope* strong_roots_scope) :
- AbstractGangTask("ParNewGeneration collection"),
- _young_gen(young_gen), _old_gen(old_gen),
- _young_old_boundary(young_old_boundary),
- _state_set(state_set),
- _strong_roots_scope(strong_roots_scope)
-{}
-
-void ParNewGenTask::work(uint worker_id) {
- CMSHeap* heap = CMSHeap::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);
-
- CLDScanClosure cld_scan_closure(&par_scan_state.to_space_root_closure(),
- heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
-
- par_scan_state.start_strong_roots();
- heap->young_process_roots(_strong_roots_scope,
- &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();
-
- // This will collapse this worker's promoted object list that's
- // created during the main ParNew parallel phase of ParNew. This has
- // to be called after all workers have finished promoting objects
- // and scanning promoted objects. It should be safe calling it from
- // here, given that we can only reach here after all thread have
- // offered termination, i.e., after there is no more work to be
- // done. It will also disable promotion tracking for the rest of
- // this GC as it's not necessary to be on during reference processing.
- _old_gen->par_oop_since_save_marks_iterate_done((int) worker_id);
-}
-
-ParNewGeneration::ParNewGeneration(ReservedSpace rs,
- size_t initial_byte_size,
- size_t min_byte_size,
- size_t max_byte_size)
- : DefNewGeneration(rs, initial_byte_size, min_byte_size, max_byte_size, "CMS young collection pauses"),
- _plab_stats("Young", YoungPLABSize, PLABWeight),
- _overflow_list(NULL),
- _is_alive_closure(this)
-{
- 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 i = 0; i < ParallelGCThreads; i++) {
- ObjToScanQueue *q = new ObjToScanQueue();
- guarantee(q != NULL, "work_queue Allocation failure.");
- _task_queues->register_queue(i, q);
- }
-
- for (uint i = 0; i < ParallelGCThreads; i++) {
- _task_queues->queue(i)->initialize();
- }
-
- _overflow_stacks = NULL;
- if (ParGCUseLocalOverflow) {
- // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal with ','
- typedef Stack<oop, mtGC> GCOopStack;
-
- _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC);
- for (size_t i = 0; i < ParallelGCThreads; ++i) {
- new (_overflow_stacks + i) Stack<oop, mtGC>();
- }
- }
-
- if (UsePerfData) {
- EXCEPTION_MARK;
- ResourceMark rm;
-
- const char* cname =
- PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
- PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
- ParallelGCThreads, CHECK);
- }
-}
-
-// ParNewGeneration::
-ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
- DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
-
-template <class T>
-void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
-#ifdef ASSERT
- {
- oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
- // We never expect to see a null reference being processed
- // as a weak reference.
- assert(oopDesc::is_oop(obj), "expected an oop while scanning weak refs");
- }
-#endif // ASSERT
-
- Devirtualizer::do_oop_no_verify(_par_cl, p);
-
- if (CMSHeap::heap()->is_in_reserved(p)) {
- oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);;
- _rs->write_ref_field_gc_par(p, obj);
- }
-}
-
-void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p) { ParKeepAliveClosure::do_oop_work(p); }
-void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
-
-// ParNewGeneration::
-KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
- DefNewGeneration::KeepAliveClosure(cl) {}
-
-template <class T>
-void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) {
-#ifdef ASSERT
- {
- oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
- // We never expect to see a null reference being processed
- // as a weak reference.
- assert(oopDesc::is_oop(obj), "expected an oop while scanning weak refs");
- }
-#endif // ASSERT
-
- Devirtualizer::do_oop_no_verify(_cl, p);
-
- if (CMSHeap::heap()->is_in_reserved(p)) {
- oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
- _rs->write_ref_field_gc_par(p, obj);
- }
-}
-
-void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p) { KeepAliveClosure::do_oop_work(p); }
-void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
-
-template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
- T heap_oop = RawAccess<>::oop_load(p);
- if (!CompressedOops::is_null(heap_oop)) {
- oop obj = CompressedOops::decode_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);
- RawAccess<IS_NOT_NULL>::oop_store(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& young_gen,
- Generation& old_gen,
- HeapWord* young_old_boundary,
- ParScanThreadStateSet& state_set);
-
-private:
- virtual void work(uint worker_id);
-private:
- ParNewGeneration& _young_gen;
- ProcessTask& _task;
- Generation& _old_gen;
- HeapWord* _young_old_boundary;
- ParScanThreadStateSet& _state_set;
-};
-
-ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(ProcessTask& task,
- ParNewGeneration& young_gen,
- Generation& old_gen,
- HeapWord* young_old_boundary,
- ParScanThreadStateSet& state_set)
- : AbstractGangTask("ParNewGeneration parallel reference processing"),
- _young_gen(young_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());
-}
-
-void ParNewRefProcTaskExecutor::execute(ProcessTask& task, uint ergo_workers) {
- CMSHeap* gch = CMSHeap::heap();
- WorkGang* workers = gch->workers();
- assert(workers != NULL, "Need parallel worker threads.");
- assert(workers->active_workers() == ergo_workers,
- "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
- ergo_workers, workers->active_workers());
- _state_set.reset(workers->active_workers(), _young_gen.promotion_failed());
- ParNewRefProcTaskProxy rp_task(task, _young_gen, _old_gen,
- _young_gen.reserved().end(), _state_set);
- workers->run_task(&rp_task, workers->active_workers());
- _state_set.reset(0 /* bad value in debug if not reset */,
- _young_gen.promotion_failed());
-}
-
-void ParNewRefProcTaskExecutor::set_single_threaded_mode() {
- _state_set.flush();
- CMSHeap* heap = CMSHeap::heap();
- heap->save_marks();
-}
-
-ScanClosureWithParBarrier::
-ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
- OopsInClassLoaderDataOrGenClosure(g), _g(g), _boundary(g->reserved().end()), _gc_barrier(gc_barrier)
-{ }
-
-template <typename OopClosureType1, typename OopClosureType2>
-EvacuateFollowersClosureGeneral<OopClosureType1, OopClosureType2>::
-EvacuateFollowersClosureGeneral(CMSHeap* heap,
- OopClosureType1* cur,
- OopClosureType2* older) :
- _heap(heap),
- _scan_cur_or_nonheap(cur), _scan_older(older)
-{ }
-
-template <typename OopClosureType1, typename OopClosureType2>
-void EvacuateFollowersClosureGeneral<OopClosureType1, OopClosureType2>::do_void() {
- do {
- _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap,
- _scan_older);
- } while (!_heap->no_allocs_since_save_marks());
-}
-
-// A Generation that does parallel young-gen collection.
-
-void ParNewGeneration::handle_promotion_failed(CMSHeap* 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();
- log_info(gc, promotion)("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");
-
- CMSHeap* gch = CMSHeap::heap();
-
- _gc_timer->register_gc_start();
-
- AdaptiveSizePolicy* size_policy = gch->size_policy();
- WorkGang* workers = gch->workers();
- assert(workers != NULL, "Need workgang for parallel work");
- uint active_workers =
- WorkerPolicy::calc_active_workers(workers->total_workers(),
- workers->active_workers(),
- Threads::number_of_non_daemon_threads());
- active_workers = workers->update_active_workers(active_workers);
- log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers->total_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();
-
- GCTraceTime(Trace, gc, phases) t1("ParNew", NULL, gch->gc_cause());
-
- age_table()->clear();
- to()->clear(SpaceDecorator::Mangle);
-
- gch->save_marks();
-
- // Set the correct parallelism (number of queues) in the reference processor
- ref_processor()->set_active_mt_degree(active_workers);
-
- // Need to initialize the preserved marks before the ThreadStateSet c'tor.
- _preserved_marks_set.init(active_workers);
-
- // Always set the terminator for the active number of workers
- // because only those workers go through the termination protocol.
- TaskTerminator _term(active_workers, task_queues());
- ParScanThreadStateSet thread_state_set(active_workers,
- *to(), *this, *_old_gen, *task_queues(),
- _overflow_stacks, _preserved_marks_set,
- desired_plab_sz(), _term);
-
- thread_state_set.reset(active_workers, promotion_failed());
-
- {
- StrongRootsScope srs(active_workers);
-
- ParNewGenTask tsk(this, _old_gen, reserved().end(), &thread_state_set, &srs);
- 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.
- // Might multiple workers ever be used? If yes, initialization
- // has been done such that the single threaded path should not be used.
- if (workers->total_workers() > 1) {
- workers->run_task(&tsk);
- } else {
- 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<ScanClosure, ScanClosureWithParBarrier> evacuate_followers(
- gch, &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;
- ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
- if (rp->processing_is_mt()) {
- ParNewRefProcTaskExecutor task_executor(*this, *_old_gen, thread_state_set);
- stats = rp->process_discovered_references(&is_alive, &keep_alive,
- &evacuate_followers, &task_executor,
- &pt);
- } else {
- thread_state_set.flush();
- gch->save_marks();
- stats = rp->process_discovered_references(&is_alive, &keep_alive,
- &evacuate_followers, NULL,
- &pt);
- }
- _gc_tracer.report_gc_reference_stats(stats);
- _gc_tracer.report_tenuring_threshold(tenuring_threshold());
- pt.print_all_references();
-
- assert(gch->no_allocs_since_save_marks(), "evacuation should be done at this point");
-
- WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
-
- // Verify that the usage of keep_alive only forwarded
- // the oops and did not find anything new to copy.
- assert(gch->no_allocs_since_save_marks(), "unexpectedly copied objects");
-
- 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 young collection fails to collect
- // sufficient space resizing of the young generation can occur
- // and 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);
- }
- _preserved_marks_set.reclaim();
- // 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());
-
- plab_stats()->adjust_desired_plab_sz();
-
- TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats());
- TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats());
-
- // 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);
- rp->verify_no_references_recorded();
-
- gch->trace_heap_after_gc(gc_tracer());
-
- _gc_timer->register_gc_end();
-
- _gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
-}
-
-size_t ParNewGeneration::desired_plab_sz() {
- return _plab_stats.desired_plab_sz(CMSHeap::heap()->workers()->active_workers());
-}
-
-static int sum;
-void ParNewGeneration::waste_some_time() {
- for (int i = 0; i < 100; i++) {
- sum += i;
- }
-}
-
-static const oop ClaimedForwardPtr = cast_to_oop<intptr_t>(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;
-}
-
-// 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,
- markWord 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_raw(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) {
- // 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, m);
- 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;
-
- par_scan_state->preserved_marks()->push_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(CMSHeap::heap()->is_in_reserved(new_obj), "illegal forwarding pointer value.");
- forward_ptr = old->forward_to_atomic(new_obj, m);
- // Restore the mark word copied above.
- new_obj->set_mark_raw(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");
-
- // This code must come after the CAS test, or it will print incorrect
- // information.
- log_develop_trace(gc, scavenge)("{%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());
-
- 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.
- log_develop_trace(gc)("Queue Overflow");
- 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<intptr_t>(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(&_num_par_pushes);
- assert(_num_par_pushes > 0, "Tautology");
-#endif
- if (from_space_obj->forwardee() == from_space_obj) {
- oopDesc* listhead = NEW_C_HEAP_OBJ(oopDesc, 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 =
- Atomic::cmpxchg((oopDesc*)from_space_obj, &_overflow_list, (oopDesc*)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((oopDesc*)BUSY, &_overflow_list));
- // Trim off a prefix of at most objsFromOverflow items
- size_t spin_count = 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/block for a short while...
- os::naked_sleep(sleep_time_millis);
- 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((oopDesc*)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((oopDesc*)NULL, &_overflow_list, (oopDesc*)BUSY);
- }
- return false;
- }
- assert(prefix != NULL && prefix != BUSY, "Error");
- oop cur = prefix;
- for (size_t i = 1; i < objsFromOverflow; ++i) {
- oop next = cur->list_ptr_from_klass();
- if (next == NULL) break;
- cur = next;
- }
- assert(cur != NULL, "Loop postcondition");
-
- // Reattach remaining (suffix) to overflow list
- oop suffix = cur->list_ptr_from_klass();
- if (suffix == 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((oopDesc*)NULL, &_overflow_list, (oopDesc*)BUSY);
- }
- } else {
- assert(suffix != BUSY, "Error");
- // 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 =
- Atomic::cmpxchg((oopDesc*)suffix, &_overflow_list, (oopDesc*)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 (true) {
- oop next = last->list_ptr_from_klass();
- if (next == NULL) break;
- last = next;
- }
- // 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 =
- Atomic::cmpxchg((oopDesc*)suffix, &_overflow_list, (oopDesc*)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_OBJ(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::sub(n, &_num_par_pushes);
-#endif
- return true;
-}
-#undef BUSY
-
-void ParNewGeneration::ref_processor_init() {
- if (_ref_processor == NULL) {
- // Allocate and initialize a reference processor
- _span_based_discoverer.set_span(_reserved);
- _ref_processor =
- new ReferenceProcessor(&_span_based_discoverer, // span
- ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
- ParallelGCThreads, // mt processing degree
- refs_discovery_is_mt(), // mt discovery
- ParallelGCThreads, // mt discovery degree
- refs_discovery_is_atomic(), // atomic_discovery
- NULL, // is_alive_non_header
- false); // disable adjusting number of processing threads
- }
-}
-
-const char* ParNewGeneration::name() const {
- return "par new generation";
-}
-
-void ParNewGeneration::restore_preserved_marks() {
- SharedRestorePreservedMarksTaskExecutor task_executor(CMSHeap::heap()->workers());
- _preserved_marks_set.restore(&task_executor);
-}