jdk8-mips64-public/hotspot: comparison src/share/vm/gc_implementation/parNew/parNewGeneration.cpp

--1:000000000000
+:f90c822e73f8
+/*
+* Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+*
+* This code is free software; you can redistribute it and/or modify it
+* under the terms of the GNU General Public License version 2 only, as
+* published by the Free Software Foundation.
+*
+* This code is distributed in the hope that it will be useful, but WITHOUT
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+* version 2 for more details (a copy is included in the LICENSE file that
+* accompanied this code).
+*
+* You should have received a copy of the GNU General Public License version
+* 2 along with this work; if not, write to the Free Software Foundation,
+* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*
+* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+* or visit www.oracle.com if you need additional information or have any
+* questions.
+*
+*/
+#include "precompiled.hpp"
+#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp"
+#include "gc_implementation/parNew/parNewGeneration.hpp"
+#include "gc_implementation/parNew/parOopClosures.inline.hpp"
+#include "gc_implementation/shared/adaptiveSizePolicy.hpp"
+#include "gc_implementation/shared/ageTable.hpp"
+#include "gc_implementation/shared/parGCAllocBuffer.hpp"
+#include "gc_implementation/shared/gcHeapSummary.hpp"
+#include "gc_implementation/shared/gcTimer.hpp"
+#include "gc_implementation/shared/gcTrace.hpp"
+#include "gc_implementation/shared/gcTraceTime.hpp"
+#include "gc_implementation/shared/copyFailedInfo.hpp"
+#include "gc_implementation/shared/spaceDecorator.hpp"
+#include "memory/defNewGeneration.inline.hpp"
+#include "memory/genCollectedHeap.hpp"
+#include "memory/genOopClosures.inline.hpp"
+#include "memory/generation.hpp"
+#include "memory/generation.inline.hpp"
+#include "memory/referencePolicy.hpp"
+#include "memory/resourceArea.hpp"
+#include "memory/sharedHeap.hpp"
+#include "memory/space.hpp"
+#include "oops/objArrayOop.hpp"
+#include "oops/oop.inline.hpp"
+#include "oops/oop.pcgc.inline.hpp"
+#include "runtime/handles.hpp"
+#include "runtime/handles.inline.hpp"
+#include "runtime/java.hpp"
+#include "runtime/thread.hpp"
+#include "utilities/copy.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/workgroup.hpp"
+PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
+#endif
+ParScanThreadState::ParScanThreadState(Space* to_space_,
+ParNewGeneration* gen_,
+Generation* old_gen_,
+int thread_num_,
+ObjToScanQueueSet* work_queue_set_,
+Stack<oop, mtGC>* overflow_stacks_,
+size_t desired_plab_sz_,
+ParallelTaskTerminator& term_) :
+_to_space(to_space_), _old_gen(old_gen_), _young_gen(gen_), _thread_num(thread_num_),
+_work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false),
+_overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL),
+_ageTable(false), // false ==> not the global age table, no perf data.
+_to_space_alloc_buffer(desired_plab_sz_),
+_to_space_closure(gen_, this), _old_gen_closure(gen_, this),
+_to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this),
+_older_gen_closure(gen_, this),
+_evacuate_followers(this, &_to_space_closure, &_old_gen_closure,
+&_to_space_root_closure, gen_, &_old_gen_root_closure,
+work_queue_set_, &term_),
+_is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this),
+_keep_alive_closure(&_scan_weak_ref_closure),
+_strong_roots_time(0.0), _term_time(0.0)
+{
+#if TASKQUEUE_STATS
+_term_attempts = 0;
+_overflow_refills = 0;
+_overflow_refill_objs = 0;
+#endif // TASKQUEUE_STATS
+_survivor_chunk_array =
+(ChunkArray*) old_gen()->get_data_recorder(thread_num());
+_hash_seed = 17;  // Might want to take time-based random value.
+_start = os::elapsedTime();
+_old_gen_closure.set_generation(old_gen_);
+_old_gen_root_closure.set_generation(old_gen_);
+}
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+void ParScanThreadState::record_survivor_plab(HeapWord* plab_start,
+size_t plab_word_size) {
+ChunkArray* sca = survivor_chunk_array();
+if (sca != NULL) {
+// A non-null SCA implies that we want the PLAB data recorded.
+sca->record_sample(plab_start, plab_word_size);
+}
+}
+bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const {
+return new_obj->is_objArray() &&
+arrayOop(new_obj)->length() > ParGCArrayScanChunk &&
+new_obj != old_obj;
+}
+void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) {
+assert(old->is_objArray(), "must be obj array");
+assert(old->is_forwarded(), "must be forwarded");
+assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
+assert(!old_gen()->is_in(old), "must be in young generation.");
+objArrayOop obj = objArrayOop(old->forwardee());
+// Process ParGCArrayScanChunk elements now
+// and push the remainder back onto queue
+int start     = arrayOop(old)->length();
+int end       = obj->length();
+int remainder = end - start;
+assert(start <= end, "just checking");
+if (remainder > 2 * ParGCArrayScanChunk) {
+// Test above combines last partial chunk with a full chunk
+end = start + ParGCArrayScanChunk;
+arrayOop(old)->set_length(end);
+// Push remainder.
+bool ok = work_queue()->push(old);
+assert(ok, "just popped, push must be okay");
+} else {
+// Restore length so that it can be used if there
+// is a promotion failure and forwarding pointers
+// must be removed.
+arrayOop(old)->set_length(end);
+}
+// process our set of indices (include header in first chunk)
+// should make sure end is even (aligned to HeapWord in case of compressed oops)
+if ((HeapWord *)obj < young_old_boundary()) {
+// object is in to_space
+obj->oop_iterate_range(&_to_space_closure, start, end);
+} else {
+// object is in old generation
+obj->oop_iterate_range(&_old_gen_closure, start, end);
+}
+}
+void ParScanThreadState::trim_queues(int max_size) {
+ObjToScanQueue* queue = work_queue();
+do {
+while (queue->size() > (juint)max_size) {
+oop obj_to_scan;
+if (queue->pop_local(obj_to_scan)) {
+if ((HeapWord *)obj_to_scan < young_old_boundary()) {
+if (obj_to_scan->is_objArray() &&
+obj_to_scan->is_forwarded() &&
+obj_to_scan->forwardee() != obj_to_scan) {
+scan_partial_array_and_push_remainder(obj_to_scan);
+} else {
+// object is in to_space
+obj_to_scan->oop_iterate(&_to_space_closure);
+}
+} else {
+// object is in old generation
+obj_to_scan->oop_iterate(&_old_gen_closure);
+}
+}
+}
+// For the  case of compressed oops, we have a private, non-shared
+// overflow stack, so we eagerly drain it so as to more evenly
+// distribute load early. Note: this may be good to do in
+// general rather than delay for the final stealing phase.
+// If applicable, we'll transfer a set of objects over to our
+// work queue, allowing them to be stolen and draining our
+// private overflow stack.
+} while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this));
+}
+bool ParScanThreadState::take_from_overflow_stack() {
+assert(ParGCUseLocalOverflow, "Else should not call");
+assert(young_gen()->overflow_list() == NULL, "Error");
+ObjToScanQueue* queue = work_queue();
+Stack<oop, mtGC>* const of_stack = overflow_stack();
+const size_t num_overflow_elems = of_stack->size();
+const size_t space_available = queue->max_elems() - queue->size();
+const size_t num_take_elems = MIN3(space_available / 4,
+ParGCDesiredObjsFromOverflowList,
+num_overflow_elems);
+// Transfer the most recent num_take_elems from the overflow
+// stack to our work queue.
+for (size_t i = 0; i != num_take_elems; i++) {
+oop cur = of_stack->pop();
+oop obj_to_push = cur->forwardee();
+assert(Universe::heap()->is_in_reserved(cur), "Should be in heap");
+assert(!old_gen()->is_in_reserved(cur), "Should be in young gen");
+assert(Universe::heap()->is_in_reserved(obj_to_push), "Should be in heap");
+if (should_be_partially_scanned(obj_to_push, cur)) {
+assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
+obj_to_push = cur;
+}
+bool ok = queue->push(obj_to_push);
+assert(ok, "Should have succeeded");
+}
+assert(young_gen()->overflow_list() == NULL, "Error");
+return num_take_elems > 0;  // was something transferred?
+}
+void ParScanThreadState::push_on_overflow_stack(oop p) {
+assert(ParGCUseLocalOverflow, "Else should not call");
+overflow_stack()->push(p);
+assert(young_gen()->overflow_list() == NULL, "Error");
+}
+HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) {
+// Otherwise, if the object is small enough, try to reallocate the
+// buffer.
+HeapWord* obj = NULL;
+if (!_to_space_full) {
+ParGCAllocBuffer* const plab = to_space_alloc_buffer();
+Space*            const sp   = to_space();
+if (word_sz * 100 <
+ParallelGCBufferWastePct * plab->word_sz()) {
+// Is small enough; abandon this buffer and start a new one.
+plab->retire(false, false);
+size_t buf_size = plab->word_sz();
+HeapWord* buf_space = sp->par_allocate(buf_size);
+if (buf_space == NULL) {
+const size_t min_bytes =
+ParGCAllocBuffer::min_size() << LogHeapWordSize;
+size_t free_bytes = sp->free();
+while(buf_space == NULL && free_bytes >= min_bytes) {
+buf_size = free_bytes >> LogHeapWordSize;
+assert(buf_size == (size_t)align_object_size(buf_size),
+"Invariant");
+buf_space  = sp->par_allocate(buf_size);
+free_bytes = sp->free();
+}
+}
+if (buf_space != NULL) {
+plab->set_word_size(buf_size);
+plab->set_buf(buf_space);
+record_survivor_plab(buf_space, buf_size);
+obj = plab->allocate(word_sz);
+// Note that we cannot compare buf_size < word_sz below
+// because of AlignmentReserve (see ParGCAllocBuffer::allocate()).
+assert(obj != NULL || plab->words_remaining() < word_sz,
+"Else should have been able to allocate");
+// It's conceivable that we may be able to use the
+// buffer we just grabbed for subsequent small requests
+// even if not for this one.
+} else {
+// We're used up.
+_to_space_full = true;
+}
+} else {
+// Too large; allocate the object individually.
+obj = sp->par_allocate(word_sz);
+}
+}
+return obj;
+}
+void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj,
+size_t word_sz) {
+// Is the alloc in the current alloc buffer?
+if (to_space_alloc_buffer()->contains(obj)) {
+assert(to_space_alloc_buffer()->contains(obj + word_sz - 1),
+"Should contain whole object.");
+to_space_alloc_buffer()->undo_allocation(obj, word_sz);
+} else {
+CollectedHeap::fill_with_object(obj, word_sz);
+}
+}
+void ParScanThreadState::print_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<oop, mtGC>*       overflow_stacks_,
+size_t                  desired_plab_sz,
+ParallelTaskTerminator& term);
+~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); }
+inline ParScanThreadState& thread_state(int i);
+void trace_promotion_failed(YoungGCTracer& gc_tracer);
+void reset(int active_workers, bool promotion_failed);
+void flush();
+#if TASKQUEUE_STATS
+static void
+print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
+void print_termination_stats(outputStream* const st = gclog_or_tty);
+static void
+print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
+void print_taskqueue_stats(outputStream* const st = gclog_or_tty);
+void reset_stats();
+#endif // TASKQUEUE_STATS
+private:
+ParallelTaskTerminator& _term;
+ParNewGeneration&       _gen;
+Generation&             _next_gen;
+public:
+bool is_valid(int id) const { return id < length(); }
+ParallelTaskTerminator* terminator() { return &_term; }
+};
+ParScanThreadStateSet::ParScanThreadStateSet(
+int num_threads, Space& to_space, ParNewGeneration& gen,
+Generation& old_gen, ObjToScanQueueSet& queue_set,
+Stack<oop, mtGC>* overflow_stacks,
+size_t desired_plab_sz, ParallelTaskTerminator& term)
+: ResourceArray(sizeof(ParScanThreadState), num_threads),
+_gen(gen), _next_gen(old_gen), _term(term)
+{
+assert(num_threads > 0, "sanity check!");
+assert(ParGCUseLocalOverflow == (overflow_stacks != NULL),
+"overflow_stack allocation mismatch");
+// Initialize states.
+for (int i = 0; i < num_threads; ++i) {
+new ((ParScanThreadState*)_data + i)
+ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set,
+overflow_stacks, desired_plab_sz, term);
+}
+}
+inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i)
+{
+assert(i >= 0 && i < length(), "sanity check!");
+return ((ParScanThreadState*)_data)[i];
+}
+void ParScanThreadStateSet::trace_promotion_failed(YoungGCTracer& gc_tracer) {
+for (int i = 0; i < length(); ++i) {
+if (thread_state(i).promotion_failed()) {
+gc_tracer.report_promotion_failed(thread_state(i).promotion_failed_info());
+thread_state(i).promotion_failed_info().reset();
+}
+}
+}
+void ParScanThreadStateSet::reset(int active_threads, bool promotion_failed)
+{
+_term.reset_for_reuse(active_threads);
+if (promotion_failed) {
+for (int i = 0; i < length(); ++i) {
+thread_state(i).print_promotion_failure_size();
+}
+}
+}
+#if TASKQUEUE_STATS
+void
+ParScanThreadState::reset_stats()
+{
+taskqueue_stats().reset();
+_term_attempts = 0;
+_overflow_refills = 0;
+_overflow_refill_objs = 0;
+}
+void ParScanThreadStateSet::reset_stats()
+{
+for (int i = 0; i < length(); ++i) {
+thread_state(i).reset_stats();
+}
+}
+void
+ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st)
+{
+st->print_raw_cr("GC Termination Stats");
+st->print_raw_cr("     elapsed  --strong roots-- "
+"-------termination-------");
+st->print_raw_cr("thr     ms        ms       %   "
+"    ms       %   attempts");
+st->print_raw_cr("--- --------- --------- ------ "
+"--------- ------ --------");
+}
+void ParScanThreadStateSet::print_termination_stats(outputStream* const st)
+{
+print_termination_stats_hdr(st);
+for (int i = 0; i < length(); ++i) {
+const ParScanThreadState & pss = thread_state(i);
+const double elapsed_ms = pss.elapsed_time() * 1000.0;
+const double s_roots_ms = pss.strong_roots_time() * 1000.0;
+const double term_ms = pss.term_time() * 1000.0;
+st->print_cr("%3d %9.2f %9.2f %6.2f "
+"%9.2f %6.2f " SIZE_FORMAT_W(8),
+i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
+term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts());
+}
+}
+// Print stats related to work queue activity.
+void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st)
+{
+st->print_raw_cr("GC Task Stats");
+st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
+st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
+}
+void ParScanThreadStateSet::print_taskqueue_stats(outputStream* const st)
+{
+print_taskqueue_stats_hdr(st);
+TaskQueueStats totals;
+for (int i = 0; i < length(); ++i) {
+const ParScanThreadState & pss = thread_state(i);
+const TaskQueueStats & stats = pss.taskqueue_stats();
+st->print("%3d ", i); stats.print(st); st->cr();
+totals += stats;
+if (pss.overflow_refills() > 0) {
+st->print_cr("    " SIZE_FORMAT_W(10) " overflow refills    "
+SIZE_FORMAT_W(10) " overflow objects",
+pss.overflow_refills(), pss.overflow_refill_objs());
+}
+}
+st->print("tot "); totals.print(st); st->cr();
+DEBUG_ONLY(totals.verify());
+}
+#endif // TASKQUEUE_STATS
+void ParScanThreadStateSet::flush()
+{
+// Work in this loop should be kept as lightweight as
+// possible since this might otherwise become a bottleneck
+// to scaling. Should we add heavy-weight work into this
+// loop, consider parallelizing the loop into the worker threads.
+for (int i = 0; i < length(); ++i) {
+ParScanThreadState& par_scan_state = thread_state(i);
+// Flush stats related to To-space PLAB activity and
+// retire the last buffer.
+par_scan_state.to_space_alloc_buffer()->
+flush_stats_and_retire(_gen.plab_stats(),
+true /* end_of_gc */,
+false /* retain */);
+// Every thread has its own age table.  We need to merge
+// them all into one.
+ageTable *local_table = par_scan_state.age_table();
+_gen.age_table()->merge(local_table);
+// Inform old gen that we're done.
+_next_gen.par_promote_alloc_done(i);
+_next_gen.par_oop_since_save_marks_iterate_done(i);
+}
+if (UseConcMarkSweepGC && ParallelGCThreads > 0) {
+// We need to call this even when ResizeOldPLAB is disabled
+// so as to avoid breaking some asserts. While we may be able
+// to avoid this by reorganizing the code a bit, I am loathe
+// to do that unless we find cases where ergo leads to bad
+// performance.
+CFLS_LAB::compute_desired_plab_size();
+}
+}
+ParScanClosure::ParScanClosure(ParNewGeneration* g,
+ParScanThreadState* par_scan_state) :
+OopsInKlassOrGenClosure(g), _par_scan_state(par_scan_state), _g(g)
+{
+assert(_g->level() == 0, "Optimized for youngest generation");
+_boundary = _g->reserved().end();
+}
+void ParScanWithBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, false); }
+void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); }
+void ParScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, false); }
+void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); }
+void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, true); }
+void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); }
+void ParRootScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, true); }
+void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); }
+ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g,
+ParScanThreadState* par_scan_state)
+: ScanWeakRefClosure(g), _par_scan_state(par_scan_state)
+{}
+void ParScanWeakRefClosure::do_oop(oop* p)       { ParScanWeakRefClosure::do_oop_work(p); }
+void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); }
+#ifdef WIN32
+#pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */
+#endif
+ParEvacuateFollowersClosure::ParEvacuateFollowersClosure(
+ParScanThreadState* par_scan_state_,
+ParScanWithoutBarrierClosure* to_space_closure_,
+ParScanWithBarrierClosure* old_gen_closure_,
+ParRootScanWithoutBarrierClosure* to_space_root_closure_,
+ParNewGeneration* par_gen_,
+ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_,
+ObjToScanQueueSet* task_queues_,
+ParallelTaskTerminator* terminator_) :
+_par_scan_state(par_scan_state_),
+_to_space_closure(to_space_closure_),
+_old_gen_closure(old_gen_closure_),
+_to_space_root_closure(to_space_root_closure_),
+_old_gen_root_closure(old_gen_root_closure_),
+_par_gen(par_gen_),
+_task_queues(task_queues_),
+_terminator(terminator_)
+{}
+void ParEvacuateFollowersClosure::do_void() {
+ObjToScanQueue* work_q = par_scan_state()->work_queue();
+while (true) {
+// Scan to-space and old-gen objs until we run out of both.
+oop obj_to_scan;
+par_scan_state()->trim_queues(0);
+// We have no local work, attempt to steal from other threads.
+// attempt to steal work from promoted.
+if (task_queues()->steal(par_scan_state()->thread_num(),
+par_scan_state()->hash_seed(),
+obj_to_scan)) {
+bool res = work_q->push(obj_to_scan);
+assert(res, "Empty queue should have room for a push.");
+//   if successful, goto Start.
+continue;
+// try global overflow list.
+} else if (par_gen()->take_from_overflow_list(par_scan_state())) {
+continue;
+}
+// Otherwise, offer termination.
+par_scan_state()->start_term_time();
+if (terminator()->offer_termination()) break;
+par_scan_state()->end_term_time();
+}
+assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0,
+"Broken overflow list?");
+// Finish the last termination pause.
+par_scan_state()->end_term_time();
+}
+ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen,
+HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) :
+AbstractGangTask("ParNewGeneration collection"),
+_gen(gen), _next_gen(next_gen),
+_young_old_boundary(young_old_boundary),
+_state_set(state_set)
+{}
+// Reset the terminator for the given number of
+// active threads.
+void ParNewGenTask::set_for_termination(int active_workers) {
+_state_set->reset(active_workers, _gen->promotion_failed());
+// Should the heap be passed in?  There's only 1 for now so
+// grab it instead.
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+gch->set_n_termination(active_workers);
+}
+void ParNewGenTask::work(uint worker_id) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+// Since this is being done in a separate thread, need new resource
+// and handle marks.
+ResourceMark rm;
+HandleMark hm;
+// We would need multiple old-gen queues otherwise.
+assert(gch->n_gens() == 2, "Par young collection currently only works with one older gen.");
+Generation* old_gen = gch->next_gen(_gen);
+ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id);
+assert(_state_set->is_valid(worker_id), "Should not have been called");
+par_scan_state.set_young_old_boundary(_young_old_boundary);
+KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(),
+gch->rem_set()->klass_rem_set());
+int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
+par_scan_state.start_strong_roots();
+gch->gen_process_strong_roots(_gen->level(),
+true,  // Process younger gens, if any,
+// as strong roots.
+false, // no scope; this is parallel code
+true,  // is scavenging
+SharedHeap::ScanningOption(so),
+&par_scan_state.to_space_root_closure(),
+true,   // walk *all* scavengable nmethods
+&par_scan_state.older_gen_closure(),
+&klass_scan_closure);
+par_scan_state.end_strong_roots();
+// "evacuate followers".
+par_scan_state.evacuate_followers_closure().do_void();
+}
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
+#endif
+ParNewGeneration::
+ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level)
+: DefNewGeneration(rs, initial_byte_size, level, "PCopy"),
+_overflow_list(NULL),
+_is_alive_closure(this),
+_plab_stats(YoungPLABSize, PLABWeight)
+{
+NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;)
+NOT_PRODUCT(_num_par_pushes = 0;)
+_task_queues = new ObjToScanQueueSet(ParallelGCThreads);
+guarantee(_task_queues != NULL, "task_queues allocation failure.");
+for (uint i1 = 0; i1 < ParallelGCThreads; i1++) {
+ObjToScanQueue *q = new ObjToScanQueue();
+guarantee(q != NULL, "work_queue Allocation failure.");
+_task_queues->register_queue(i1, q);
+}
+for (uint i2 = 0; i2 < ParallelGCThreads; i2++)
+_task_queues->queue(i2)->initialize();
+_overflow_stacks = NULL;
+if (ParGCUseLocalOverflow) {
+// typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal
+// with ','
+typedef Stack<oop, mtGC> GCOopStack;
+_overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC);
+for (size_t i = 0; i < ParallelGCThreads; ++i) {
+new (_overflow_stacks + i) Stack<oop, mtGC>();
+}
+}
+if (UsePerfData) {
+EXCEPTION_MARK;
+ResourceMark rm;
+const char* cname =
+PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
+PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
+ParallelGCThreads, CHECK);
+}
+}
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+// ParNewGeneration::
+ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
+DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
+template <class T>
+void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
+#ifdef ASSERT
+{
+assert(!oopDesc::is_null(*p), "expected non-null ref");
+oop obj = oopDesc::load_decode_heap_oop_not_null(p);
+// We never expect to see a null reference being processed
+// as a weak reference.
+assert(obj->is_oop(), "expected an oop while scanning weak refs");
+}
+#endif // ASSERT
+_par_cl->do_oop_nv(p);
+if (Universe::heap()->is_in_reserved(p)) {
+oop obj = oopDesc::load_decode_heap_oop_not_null(p);
+_rs->write_ref_field_gc_par(p, obj);
+}
+}
+void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p)       { ParKeepAliveClosure::do_oop_work(p); }
+void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
+// ParNewGeneration::
+KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
+DefNewGeneration::KeepAliveClosure(cl) {}
+template <class T>
+void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) {
+#ifdef ASSERT
+{
+assert(!oopDesc::is_null(*p), "expected non-null ref");
+oop obj = oopDesc::load_decode_heap_oop_not_null(p);
+// We never expect to see a null reference being processed
+// as a weak reference.
+assert(obj->is_oop(), "expected an oop while scanning weak refs");
+}
+#endif // ASSERT
+_cl->do_oop_nv(p);
+if (Universe::heap()->is_in_reserved(p)) {
+oop obj = oopDesc::load_decode_heap_oop_not_null(p);
+_rs->write_ref_field_gc_par(p, obj);
+}
+}
+void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p)       { KeepAliveClosure::do_oop_work(p); }
+void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
+template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
+T heap_oop = oopDesc::load_heap_oop(p);
+if (!oopDesc::is_null(heap_oop)) {
+oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+if ((HeapWord*)obj < _boundary) {
+assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
+oop new_obj = obj->is_forwarded()
+? obj->forwardee()
+: _g->DefNewGeneration::copy_to_survivor_space(obj);
+oopDesc::encode_store_heap_oop_not_null(p, new_obj);
+}
+if (_gc_barrier) {
+// If p points to a younger generation, mark the card.
+if ((HeapWord*)obj < _gen_boundary) {
+_rs->write_ref_field_gc_par(p, obj);
+}
+}
+}
+}
+void ScanClosureWithParBarrier::do_oop(oop* p)       { ScanClosureWithParBarrier::do_oop_work(p); }
+void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
+class ParNewRefProcTaskProxy: public AbstractGangTask {
+typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
+public:
+ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen,
+Generation& next_gen,
+HeapWord* young_old_boundary,
+ParScanThreadStateSet& state_set);
+private:
+virtual void work(uint worker_id);
+virtual void set_for_termination(int active_workers) {
+_state_set.terminator()->reset_for_reuse(active_workers);
+}
+private:
+ParNewGeneration&      _gen;
+ProcessTask&           _task;
+Generation&            _next_gen;
+HeapWord*              _young_old_boundary;
+ParScanThreadStateSet& _state_set;
+};
+ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(
+ProcessTask& task, ParNewGeneration& gen,
+Generation& next_gen,
+HeapWord* young_old_boundary,
+ParScanThreadStateSet& state_set)
+: AbstractGangTask("ParNewGeneration parallel reference processing"),
+_gen(gen),
+_task(task),
+_next_gen(next_gen),
+_young_old_boundary(young_old_boundary),
+_state_set(state_set)
+{
+}
+void ParNewRefProcTaskProxy::work(uint worker_id)
+{
+ResourceMark rm;
+HandleMark hm;
+ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id);
+par_scan_state.set_young_old_boundary(_young_old_boundary);
+_task.work(worker_id, par_scan_state.is_alive_closure(),
+par_scan_state.keep_alive_closure(),
+par_scan_state.evacuate_followers_closure());
+}
+class ParNewRefEnqueueTaskProxy: public AbstractGangTask {
+typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
+EnqueueTask& _task;
+public:
+ParNewRefEnqueueTaskProxy(EnqueueTask& task)
+: AbstractGangTask("ParNewGeneration parallel reference enqueue"),
+_task(task)
+{ }
+virtual void work(uint worker_id)
+{
+_task.work(worker_id);
+}
+};
+void ParNewRefProcTaskExecutor::execute(ProcessTask& task)
+{
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+assert(gch->kind() == CollectedHeap::GenCollectedHeap,
+"not a generational heap");
+FlexibleWorkGang* workers = gch->workers();
+assert(workers != NULL, "Need parallel worker threads.");
+_state_set.reset(workers->active_workers(), _generation.promotion_failed());
+ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(),
+_generation.reserved().end(), _state_set);
+workers->run_task(&rp_task);
+_state_set.reset(0 /* bad value in debug if not reset */,
+_generation.promotion_failed());
+}
+void ParNewRefProcTaskExecutor::execute(EnqueueTask& task)
+{
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+FlexibleWorkGang* workers = gch->workers();
+assert(workers != NULL, "Need parallel worker threads.");
+ParNewRefEnqueueTaskProxy enq_task(task);
+workers->run_task(&enq_task);
+}
+void ParNewRefProcTaskExecutor::set_single_threaded_mode()
+{
+_state_set.flush();
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+gch->set_par_threads(0);  // 0 ==> non-parallel.
+gch->save_marks();
+}
+ScanClosureWithParBarrier::
+ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
+ScanClosure(g, gc_barrier) {}
+EvacuateFollowersClosureGeneral::
+EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
+OopsInGenClosure* cur,
+OopsInGenClosure* older) :
+_gch(gch), _level(level),
+_scan_cur_or_nonheap(cur), _scan_older(older)
+{}
+void EvacuateFollowersClosureGeneral::do_void() {
+do {
+// Beware: this call will lead to closure applications via virtual
+// calls.
+_gch->oop_since_save_marks_iterate(_level,
+_scan_cur_or_nonheap,
+_scan_older);
+} while (!_gch->no_allocs_since_save_marks(_level));
+}
+// A Generation that does parallel young-gen collection.
+bool ParNewGeneration::_avoid_promotion_undo = false;
+void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set, ParNewTracer& gc_tracer) {
+assert(_promo_failure_scan_stack.is_empty(), "post condition");
+_promo_failure_scan_stack.clear(true); // Clear cached segments.
+remove_forwarding_pointers();
+if (PrintGCDetails) {
+gclog_or_tty->print(" (promotion failed)");
+}
+// All the spaces are in play for mark-sweep.
+swap_spaces();  // Make life simpler for CMS || rescan; see 6483690.
+from()->set_next_compaction_space(to());
+gch->set_incremental_collection_failed();
+// Inform the next generation that a promotion failure occurred.
+_next_gen->promotion_failure_occurred();
+// Trace promotion failure in the parallel GC threads
+thread_state_set.trace_promotion_failed(gc_tracer);
+// Single threaded code may have reported promotion failure to the global state
+if (_promotion_failed_info.has_failed()) {
+gc_tracer.report_promotion_failed(_promotion_failed_info);
+}
+// Reset the PromotionFailureALot counters.
+NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
+}
+void ParNewGeneration::collect(bool   full,
+bool   clear_all_soft_refs,
+size_t size,
+bool   is_tlab) {
+assert(full || size > 0, "otherwise we don't want to collect");
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+_gc_timer->register_gc_start();
+assert(gch->kind() == CollectedHeap::GenCollectedHeap,
+"not a CMS generational heap");
+AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
+FlexibleWorkGang* workers = gch->workers();
+assert(workers != NULL, "Need workgang for parallel work");
+int active_workers =
+AdaptiveSizePolicy::calc_active_workers(workers->total_workers(),
+workers->active_workers(),
+Threads::number_of_non_daemon_threads());
+workers->set_active_workers(active_workers);
+assert(gch->n_gens() == 2,
+"Par collection currently only works with single older gen.");
+_next_gen = gch->next_gen(this);
+// Do we have to avoid promotion_undo?
+if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) {
+set_avoid_promotion_undo(true);
+}
+// If the next generation is too full to accommodate worst-case promotion
+// from this generation, pass on collection; let the next generation
+// do it.
+if (!collection_attempt_is_safe()) {
+gch->set_incremental_collection_failed();  // slight lie, in that we did not even attempt one
+return;
+}
+assert(to()->is_empty(), "Else not collection_attempt_is_safe");
+ParNewTracer gc_tracer;
+gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
+gch->trace_heap_before_gc(&gc_tracer);
+init_assuming_no_promotion_failure();
+if (UseAdaptiveSizePolicy) {
+set_survivor_overflow(false);
+size_policy->minor_collection_begin();
+}
+GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
+// Capture heap used before collection (for printing).
+size_t gch_prev_used = gch->used();
+SpecializationStats::clear();
+age_table()->clear();
+to()->clear(SpaceDecorator::Mangle);
+gch->save_marks();
+assert(workers != NULL, "Need parallel worker threads.");
+int n_workers = active_workers;
+// Set the correct parallelism (number of queues) in the reference processor
+ref_processor()->set_active_mt_degree(n_workers);
+// Always set the terminator for the active number of workers
+// because only those workers go through the termination protocol.
+ParallelTaskTerminator _term(n_workers, task_queues());
+ParScanThreadStateSet thread_state_set(workers->active_workers(),
+*to(), *this, *_next_gen, *task_queues(),
+_overflow_stacks, desired_plab_sz(), _term);
+ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set);
+gch->set_par_threads(n_workers);
+gch->rem_set()->prepare_for_younger_refs_iterate(true);
+// It turns out that even when we're using 1 thread, doing the work in a
+// separate thread causes wide variance in run times.  We can't help this
+// in the multi-threaded case, but we special-case n=1 here to get
+// repeatable measurements of the 1-thread overhead of the parallel code.
+if (n_workers > 1) {
+GenCollectedHeap::StrongRootsScope srs(gch);
+workers->run_task(&tsk);
+} else {
+GenCollectedHeap::StrongRootsScope srs(gch);
+tsk.work(0);
+}
+thread_state_set.reset(0 /* Bad value in debug if not reset */,
+promotion_failed());
+// Process (weak) reference objects found during scavenge.
+ReferenceProcessor* rp = ref_processor();
+IsAliveClosure is_alive(this);
+ScanWeakRefClosure scan_weak_ref(this);
+KeepAliveClosure keep_alive(&scan_weak_ref);
+ScanClosure               scan_without_gc_barrier(this, false);
+ScanClosureWithParBarrier scan_with_gc_barrier(this, true);
+set_promo_failure_scan_stack_closure(&scan_without_gc_barrier);
+EvacuateFollowersClosureGeneral evacuate_followers(gch, _level,
+&scan_without_gc_barrier, &scan_with_gc_barrier);
+rp->setup_policy(clear_all_soft_refs);
+// Can  the mt_degree be set later (at run_task() time would be best)?
+rp->set_active_mt_degree(active_workers);
+ReferenceProcessorStats stats;
+if (rp->processing_is_mt()) {
+ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
+stats = rp->process_discovered_references(&is_alive, &keep_alive,
+&evacuate_followers, &task_executor,
+_gc_timer);
+} else {
+thread_state_set.flush();
+gch->set_par_threads(0);  // 0 ==> non-parallel.
+gch->save_marks();
+stats = rp->process_discovered_references(&is_alive, &keep_alive,
+&evacuate_followers, NULL,
+_gc_timer);
+}
+gc_tracer.report_gc_reference_stats(stats);
+if (!promotion_failed()) {
+// Swap the survivor spaces.
+eden()->clear(SpaceDecorator::Mangle);
+from()->clear(SpaceDecorator::Mangle);
+if (ZapUnusedHeapArea) {
+// This is now done here because of the piece-meal mangling which
+// can check for valid mangling at intermediate points in the
+// collection(s).  When a minor collection fails to collect
+// sufficient space resizing of the young generation can occur
+// an redistribute the spaces in the young generation.  Mangle
+// here so that unzapped regions don't get distributed to
+// other spaces.
+to()->mangle_unused_area();
+}
+swap_spaces();
+// A successful scavenge should restart the GC time limit count which is
+// for full GC's.
+size_policy->reset_gc_overhead_limit_count();
+assert(to()->is_empty(), "to space should be empty now");
+adjust_desired_tenuring_threshold();
+} else {
+handle_promotion_failed(gch, thread_state_set, gc_tracer);
+}
+// set new iteration safe limit for the survivor spaces
+from()->set_concurrent_iteration_safe_limit(from()->top());
+to()->set_concurrent_iteration_safe_limit(to()->top());
+if (ResizePLAB) {
+plab_stats()->adjust_desired_plab_sz(n_workers);
+}
+if (PrintGC && !PrintGCDetails) {
+gch->print_heap_change(gch_prev_used);
+}
+if (PrintGCDetails && ParallelGCVerbose) {
+TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats());
+TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats());
+}
+if (UseAdaptiveSizePolicy) {
+size_policy->minor_collection_end(gch->gc_cause());
+size_policy->avg_survived()->sample(from()->used());
+}
+// We need to use a monotonically non-deccreasing time in ms
+// or we will see time-warp warnings and os::javaTimeMillis()
+// does not guarantee monotonicity.
+jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
+update_time_of_last_gc(now);
+SpecializationStats::print();
+rp->set_enqueuing_is_done(true);
+if (rp->processing_is_mt()) {
+ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
+rp->enqueue_discovered_references(&task_executor);
+} else {
+rp->enqueue_discovered_references(NULL);
+}
+rp->verify_no_references_recorded();
+gch->trace_heap_after_gc(&gc_tracer);
+gc_tracer.report_tenuring_threshold(tenuring_threshold());
+_gc_timer->register_gc_end();
+gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
+}
+static int sum;
+void ParNewGeneration::waste_some_time() {
+for (int i = 0; i < 100; i++) {
+sum += i;
+}
+}
+static const oop ClaimedForwardPtr = cast_to_oop<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;
+}
+#ifdef ASSERT
+bool ParNewGeneration::is_legal_forward_ptr(oop p) {
+return
+(_avoid_promotion_undo && p == ClaimedForwardPtr)
+|| Universe::heap()->is_in_reserved(p);
+}
+#endif
+void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
+if (m->must_be_preserved_for_promotion_failure(obj)) {
+// We should really have separate per-worker stacks, rather
+// than use locking of a common pair of stacks.
+MutexLocker ml(ParGCRareEvent_lock);
+preserve_mark(obj, m);
+}
+}
+// Multiple GC threads may try to promote an object.  If the object
+// is successfully promoted, a forwarding pointer will be installed in
+// the object in the young generation.  This method claims the right
+// to install the forwarding pointer before it copies the object,
+// thus avoiding the need to undo the copy as in
+// copy_to_survivor_space_avoiding_with_undo.
+oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo(
+ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
+// In the sequential version, this assert also says that the object is
+// not forwarded.  That might not be the case here.  It is the case that
+// the caller observed it to be not forwarded at some time in the past.
+assert(is_in_reserved(old), "shouldn't be scavenging this oop");
+// The sequential code read "old->age()" below.  That doesn't work here,
+// since the age is in the mark word, and that might be overwritten with
+// a forwarding pointer by a parallel thread.  So we must save the mark
+// word in a local and then analyze it.
+oopDesc dummyOld;
+dummyOld.set_mark(m);
+assert(!dummyOld.is_forwarded(),
+"should not be called with forwarding pointer mark word.");
+oop new_obj = NULL;
+oop forward_ptr;
+// Try allocating obj in to-space (unless too old)
+if (dummyOld.age() < tenuring_threshold()) {
+new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
+if (new_obj == NULL) {
+set_survivor_overflow(true);
+}
+}
+if (new_obj == NULL) {
+// Either to-space is full or we decided to promote
+// try allocating obj tenured
+// Attempt to install a null forwarding pointer (atomically),
+// to claim the right to install the real forwarding pointer.
+forward_ptr = old->forward_to_atomic(ClaimedForwardPtr);
+if (forward_ptr != NULL) {
+// someone else beat us to it.
+return real_forwardee(old);
+}
+new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
+old, m, sz);
+if (new_obj == NULL) {
+// promotion failed, forward to self
+_promotion_failed = true;
+new_obj = old;
+preserve_mark_if_necessary(old, m);
+par_scan_state->register_promotion_failure(sz);
+}
+old->forward_to(new_obj);
+forward_ptr = NULL;
+} else {
+// Is in to-space; do copying ourselves.
+Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
+forward_ptr = old->forward_to_atomic(new_obj);
+// Restore the mark word copied above.
+new_obj->set_mark(m);
+// Increment age if obj still in new generation
+new_obj->incr_age();
+par_scan_state->age_table()->add(new_obj, sz);
+}
+assert(new_obj != NULL, "just checking");
+#ifndef PRODUCT
+// This code must come after the CAS test, or it will print incorrect
+// information.
+if (TraceScavenge) {
+gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
+is_in_reserved(new_obj) ? "copying" : "tenuring",
+new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
+}
+#endif
+if (forward_ptr == NULL) {
+oop obj_to_push = new_obj;
+if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
+// Length field used as index of next element to be scanned.
+// Real length can be obtained from real_forwardee()
+arrayOop(old)->set_length(0);
+obj_to_push = old;
+assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
+"push forwarded object");
+}
+// Push it on one of the queues of to-be-scanned objects.
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
+// Add stats for overflow pushes.
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print("queue overflow!\n");
+}
+push_on_overflow_list(old, par_scan_state);
+TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
+}
+return new_obj;
+}
+// Oops.  Someone beat us to it.  Undo the allocation.  Where did we
+// allocate it?
+if (is_in_reserved(new_obj)) {
+// Must be in to_space.
+assert(to()->is_in_reserved(new_obj), "Checking");
+if (forward_ptr == ClaimedForwardPtr) {
+// Wait to get the real forwarding pointer value.
+forward_ptr = real_forwardee(old);
+}
+par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
+}
+return forward_ptr;
+}
+// Multiple GC threads may try to promote the same object.  If two
+// or more GC threads copy the object, only one wins the race to install
+// the forwarding pointer.  The other threads have to undo their copy.
+oop ParNewGeneration::copy_to_survivor_space_with_undo(
+ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
+// In the sequential version, this assert also says that the object is
+// not forwarded.  That might not be the case here.  It is the case that
+// the caller observed it to be not forwarded at some time in the past.
+assert(is_in_reserved(old), "shouldn't be scavenging this oop");
+// The sequential code read "old->age()" below.  That doesn't work here,
+// since the age is in the mark word, and that might be overwritten with
+// a forwarding pointer by a parallel thread.  So we must save the mark
+// word here, install it in a local oopDesc, and then analyze it.
+oopDesc dummyOld;
+dummyOld.set_mark(m);
+assert(!dummyOld.is_forwarded(),
+"should not be called with forwarding pointer mark word.");
+bool failed_to_promote = false;
+oop new_obj = NULL;
+oop forward_ptr;
+// Try allocating obj in to-space (unless too old)
+if (dummyOld.age() < tenuring_threshold()) {
+new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
+if (new_obj == NULL) {
+set_survivor_overflow(true);
+}
+}
+if (new_obj == NULL) {
+// Either to-space is full or we decided to promote
+// try allocating obj tenured
+new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
+old, m, sz);
+if (new_obj == NULL) {
+// promotion failed, forward to self
+forward_ptr = old->forward_to_atomic(old);
+new_obj = old;
+if (forward_ptr != NULL) {
+return forward_ptr;   // someone else succeeded
+}
+_promotion_failed = true;
+failed_to_promote = true;
+preserve_mark_if_necessary(old, m);
+par_scan_state->register_promotion_failure(sz);
+}
+} else {
+// Is in to-space; do copying ourselves.
+Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
+// Restore the mark word copied above.
+new_obj->set_mark(m);
+// Increment age if new_obj still in new generation
+new_obj->incr_age();
+par_scan_state->age_table()->add(new_obj, sz);
+}
+assert(new_obj != NULL, "just checking");
+#ifndef PRODUCT
+// This code must come after the CAS test, or it will print incorrect
+// information.
+if (TraceScavenge) {
+gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
+is_in_reserved(new_obj) ? "copying" : "tenuring",
+new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
+}
+#endif
+// Now attempt to install the forwarding pointer (atomically).
+// We have to copy the mark word before overwriting with forwarding
+// ptr, so we can restore it below in the copy.
+if (!failed_to_promote) {
+forward_ptr = old->forward_to_atomic(new_obj);
+}
+if (forward_ptr == NULL) {
+oop obj_to_push = new_obj;
+if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
+// Length field used as index of next element to be scanned.
+// Real length can be obtained from real_forwardee()
+arrayOop(old)->set_length(0);
+obj_to_push = old;
+assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
+"push forwarded object");
+}
+// Push it on one of the queues of to-be-scanned objects.
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
+// Add stats for overflow pushes.
+push_on_overflow_list(old, par_scan_state);
+TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
+}
+return new_obj;
+}
+// Oops.  Someone beat us to it.  Undo the allocation.  Where did we
+// allocate it?
+if (is_in_reserved(new_obj)) {
+// Must be in to_space.
+assert(to()->is_in_reserved(new_obj), "Checking");
+par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
+} else {
+assert(!_avoid_promotion_undo, "Should not be here if avoiding.");
+_next_gen->par_promote_alloc_undo(par_scan_state->thread_num(),
+(HeapWord*)new_obj, sz);
+}
+return forward_ptr;
+}
+#ifndef PRODUCT
+// It's OK to call this multi-threaded;  the worst thing
+// that can happen is that we'll get a bunch of closely
+// spaced simulated oveflows, but that's OK, in fact
+// probably good as it would exercise the overflow code
+// under contention.
+bool ParNewGeneration::should_simulate_overflow() {
+if (_overflow_counter-- <= 0) { // just being defensive
+_overflow_counter = ParGCWorkQueueOverflowInterval;
+return true;
+} else {
+return false;
+}
+}
+#endif
+// In case we are using compressed oops, we need to be careful.
+// If the object being pushed is an object array, then its length
+// field keeps track of the "grey boundary" at which the next
+// incremental scan will be done (see ParGCArrayScanChunk).
+// When using compressed oops, this length field is kept in the
+// lower 32 bits of the erstwhile klass word and cannot be used
+// for the overflow chaining pointer (OCP below). As such the OCP
+// would itself need to be compressed into the top 32-bits in this
+// case. Unfortunately, see below, in the event that we have a
+// promotion failure, the node to be pushed on the list can be
+// outside of the Java heap, so the heap-based pointer compression
+// would not work (we would have potential aliasing between C-heap
+// and Java-heap pointers). For this reason, when using compressed
+// oops, we simply use a worker-thread-local, non-shared overflow
+// list in the form of a growable array, with a slightly different
+// overflow stack draining strategy. If/when we start using fat
+// stacks here, we can go back to using (fat) pointer chains
+// (although some performance comparisons would be useful since
+// single global lists have their own performance disadvantages
+// as we were made painfully aware not long ago, see 6786503).
+#define BUSY (cast_to_oop<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_ptr(&_num_par_pushes);
+assert(_num_par_pushes > 0, "Tautology");
+#endif
+if (from_space_obj->forwardee() == from_space_obj) {
+oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1, mtGC);
+listhead->forward_to(from_space_obj);
+from_space_obj = listhead;
+}
+oop observed_overflow_list = _overflow_list;
+oop cur_overflow_list;
+do {
+cur_overflow_list = observed_overflow_list;
+if (cur_overflow_list != BUSY) {
+from_space_obj->set_klass_to_list_ptr(cur_overflow_list);
+} else {
+from_space_obj->set_klass_to_list_ptr(NULL);
+}
+observed_overflow_list =
+(oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list);
+} while (cur_overflow_list != observed_overflow_list);
+}
+}
+bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) {
+bool res;
+if (ParGCUseLocalOverflow) {
+res = par_scan_state->take_from_overflow_stack();
+} else {
+assert(!UseCompressedOops, "Error");
+res = take_from_overflow_list_work(par_scan_state);
+}
+return res;
+}
+// *NOTE*: The overflow list manipulation code here and
+// in CMSCollector:: are very similar in shape,
+// except that in the CMS case we thread the objects
+// directly into the list via their mark word, and do
+// not need to deal with special cases below related
+// to chunking of object arrays and promotion failure
+// handling.
+// CR 6797058 has been filed to attempt consolidation of
+// the common code.
+// Because of the common code, if you make any changes in
+// the code below, please check the CMS version to see if
+// similar changes might be needed.
+// See CMSCollector::par_take_from_overflow_list() for
+// more extensive documentation comments.
+bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) {
+ObjToScanQueue* work_q = par_scan_state->work_queue();
+// How many to take?
+size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4,
+(size_t)ParGCDesiredObjsFromOverflowList);
+assert(!UseCompressedOops, "Error");
+assert(par_scan_state->overflow_stack() == NULL, "Error");
+if (_overflow_list == NULL) return false;
+// Otherwise, there was something there; try claiming the list.
+oop prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
+// Trim off a prefix of at most objsFromOverflow items
+Thread* tid = Thread::current();
+size_t spin_count = (size_t)ParallelGCThreads;
+size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100);
+for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) {
+// someone grabbed it before we did ...
+// ... we spin for a short while...
+os::sleep(tid, sleep_time_millis, false);
+if (_overflow_list == NULL) {
+// nothing left to take
+return false;
+} else if (_overflow_list != BUSY) {
+// try and grab the prefix
+prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
+}
+}
+if (prefix == NULL || prefix == BUSY) {
+// Nothing to take or waited long enough
+if (prefix == NULL) {
+// Write back the NULL in case we overwrote it with BUSY above
+// and it is still the same value.
+(void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
+}
+return false;
+}
+assert(prefix != NULL && prefix != BUSY, "Error");
+size_t i = 1;
+oop cur = prefix;
+while (i < objsFromOverflow && cur->klass_or_null() != NULL) {
+i++; cur = cur->list_ptr_from_klass();
+}
+// Reattach remaining (suffix) to overflow list
+if (cur->klass_or_null() == NULL) {
+// Write back the NULL in lieu of the BUSY we wrote
+// above and it is still the same value.
+if (_overflow_list == BUSY) {
+(void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
+}
+} else {
+assert(cur->klass_or_null() != (Klass*)(address)BUSY, "Error");
+oop suffix = cur->list_ptr_from_klass();       // suffix will be put back on global list
+cur->set_klass_to_list_ptr(NULL);     // break off suffix
+// It's possible that the list is still in the empty(busy) state
+// we left it in a short while ago; in that case we may be
+// able to place back the suffix.
+oop observed_overflow_list = _overflow_list;
+oop cur_overflow_list = observed_overflow_list;
+bool attached = false;
+while (observed_overflow_list == BUSY || observed_overflow_list == NULL) {
+observed_overflow_list =
+(oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
+if (cur_overflow_list == observed_overflow_list) {
+attached = true;
+break;
+} else cur_overflow_list = observed_overflow_list;
+}
+if (!attached) {
+// Too bad, someone else got in in between; we'll need to do a splice.
+// Find the last item of suffix list
+oop last = suffix;
+while (last->klass_or_null() != NULL) {
+last = last->list_ptr_from_klass();
+}
+// Atomically prepend suffix to current overflow list
+observed_overflow_list = _overflow_list;
+do {
+cur_overflow_list = observed_overflow_list;
+if (cur_overflow_list != BUSY) {
+// Do the splice ...
+last->set_klass_to_list_ptr(cur_overflow_list);
+} else { // cur_overflow_list == BUSY
+last->set_klass_to_list_ptr(NULL);
+}
+observed_overflow_list =
+(oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
+} while (cur_overflow_list != observed_overflow_list);
+}
+}
+// Push objects on prefix list onto this thread's work queue
+assert(prefix != NULL && prefix != BUSY, "program logic");
+cur = prefix;
+ssize_t n = 0;
+while (cur != NULL) {
+oop obj_to_push = cur->forwardee();
+oop next        = cur->list_ptr_from_klass();
+cur->set_klass(obj_to_push->klass());
+// This may be an array object that is self-forwarded. In that case, the list pointer
+// space, cur, is not in the Java heap, but rather in the C-heap and should be freed.
+if (!is_in_reserved(cur)) {
+// This can become a scaling bottleneck when there is work queue overflow coincident
+// with promotion failure.
+oopDesc* f = cur;
+FREE_C_HEAP_ARRAY(oopDesc, f, mtGC);
+} else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) {
+assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
+obj_to_push = cur;
+}
+bool ok = work_q->push(obj_to_push);
+assert(ok, "Should have succeeded");
+cur = next;
+n++;
+}
+TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n));
+#ifndef PRODUCT
+assert(_num_par_pushes >= n, "Too many pops?");
+Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
+#endif
+return true;
+}
+#undef BUSY
+void ParNewGeneration::ref_processor_init() {
+if (_ref_processor == NULL) {
+// Allocate and initialize a reference processor
+_ref_processor =
+new ReferenceProcessor(_reserved,                  // span
+ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
+(int) ParallelGCThreads,    // mt processing degree
+refs_discovery_is_mt(),     // mt discovery
+(int) ParallelGCThreads,    // mt discovery degree
+refs_discovery_is_atomic(), // atomic_discovery
+NULL);                      // is_alive_non_header
+}
+}
+const char* ParNewGeneration::name() const {
+return "par new generation";
+}

Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/gc_implementation/parNew/parNewGeneration.cpp

src/share/vm/gc_implementation/parNew/parNewGeneration.cpp