Thu, 14 Mar 2013 09:37:38 +0100
6733980: par compact - TraceGen1Time always shows 0.0000 seconds
Summary: Use the correct collector to retrieve accumulated gen1 trace time
Reviewed-by: johnc, jmasa
1 /*
2 * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
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23 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
30 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
33 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
34 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
35 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
36 #include "gc_implementation/parallelScavenge/psTasks.hpp"
37 #include "gc_implementation/shared/isGCActiveMark.hpp"
38 #include "gc_implementation/shared/spaceDecorator.hpp"
39 #include "gc_interface/gcCause.hpp"
40 #include "memory/collectorPolicy.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/referencePolicy.hpp"
43 #include "memory/referenceProcessor.hpp"
44 #include "memory/resourceArea.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "oops/oop.psgc.inline.hpp"
47 #include "runtime/biasedLocking.hpp"
48 #include "runtime/fprofiler.hpp"
49 #include "runtime/handles.inline.hpp"
50 #include "runtime/threadCritical.hpp"
51 #include "runtime/vmThread.hpp"
52 #include "runtime/vm_operations.hpp"
53 #include "services/memoryService.hpp"
54 #include "utilities/stack.inline.hpp"
57 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
58 int PSScavenge::_consecutive_skipped_scavenges = 0;
59 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
60 CardTableExtension* PSScavenge::_card_table = NULL;
61 bool PSScavenge::_survivor_overflow = false;
62 uint PSScavenge::_tenuring_threshold = 0;
63 HeapWord* PSScavenge::_young_generation_boundary = NULL;
64 elapsedTimer PSScavenge::_accumulated_time;
65 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack;
66 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack;
67 CollectorCounters* PSScavenge::_counters = NULL;
68 bool PSScavenge::_promotion_failed = false;
70 // Define before use
71 class PSIsAliveClosure: public BoolObjectClosure {
72 public:
73 void do_object(oop p) {
74 assert(false, "Do not call.");
75 }
76 bool do_object_b(oop p) {
77 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
78 }
79 };
81 PSIsAliveClosure PSScavenge::_is_alive_closure;
83 class PSKeepAliveClosure: public OopClosure {
84 protected:
85 MutableSpace* _to_space;
86 PSPromotionManager* _promotion_manager;
88 public:
89 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
90 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
91 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
92 _to_space = heap->young_gen()->to_space();
94 assert(_promotion_manager != NULL, "Sanity");
95 }
97 template <class T> void do_oop_work(T* p) {
98 assert (!oopDesc::is_null(*p), "expected non-null ref");
99 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
100 "expected an oop while scanning weak refs");
102 // Weak refs may be visited more than once.
103 if (PSScavenge::should_scavenge(p, _to_space)) {
104 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);
105 }
106 }
107 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
108 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
109 };
111 class PSEvacuateFollowersClosure: public VoidClosure {
112 private:
113 PSPromotionManager* _promotion_manager;
114 public:
115 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
117 virtual void do_void() {
118 assert(_promotion_manager != NULL, "Sanity");
119 _promotion_manager->drain_stacks(true);
120 guarantee(_promotion_manager->stacks_empty(),
121 "stacks should be empty at this point");
122 }
123 };
125 class PSPromotionFailedClosure : public ObjectClosure {
126 virtual void do_object(oop obj) {
127 if (obj->is_forwarded()) {
128 obj->init_mark();
129 }
130 }
131 };
133 class PSRefProcTaskProxy: public GCTask {
134 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
135 ProcessTask & _rp_task;
136 uint _work_id;
137 public:
138 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
139 : _rp_task(rp_task),
140 _work_id(work_id)
141 { }
143 private:
144 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
145 virtual void do_it(GCTaskManager* manager, uint which);
146 };
148 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
149 {
150 PSPromotionManager* promotion_manager =
151 PSPromotionManager::gc_thread_promotion_manager(which);
152 assert(promotion_manager != NULL, "sanity check");
153 PSKeepAliveClosure keep_alive(promotion_manager);
154 PSEvacuateFollowersClosure evac_followers(promotion_manager);
155 PSIsAliveClosure is_alive;
156 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
157 }
159 class PSRefEnqueueTaskProxy: public GCTask {
160 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
161 EnqueueTask& _enq_task;
162 uint _work_id;
164 public:
165 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
166 : _enq_task(enq_task),
167 _work_id(work_id)
168 { }
170 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
171 virtual void do_it(GCTaskManager* manager, uint which)
172 {
173 _enq_task.work(_work_id);
174 }
175 };
177 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
178 virtual void execute(ProcessTask& task);
179 virtual void execute(EnqueueTask& task);
180 };
182 void PSRefProcTaskExecutor::execute(ProcessTask& task)
183 {
184 GCTaskQueue* q = GCTaskQueue::create();
185 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
186 for(uint i=0; i < manager->active_workers(); i++) {
187 q->enqueue(new PSRefProcTaskProxy(task, i));
188 }
189 ParallelTaskTerminator terminator(manager->active_workers(),
190 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
191 if (task.marks_oops_alive() && manager->active_workers() > 1) {
192 for (uint j = 0; j < manager->active_workers(); j++) {
193 q->enqueue(new StealTask(&terminator));
194 }
195 }
196 manager->execute_and_wait(q);
197 }
200 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
201 {
202 GCTaskQueue* q = GCTaskQueue::create();
203 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
204 for(uint i=0; i < manager->active_workers(); i++) {
205 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
206 }
207 manager->execute_and_wait(q);
208 }
210 // This method contains all heap specific policy for invoking scavenge.
211 // PSScavenge::invoke_no_policy() will do nothing but attempt to
212 // scavenge. It will not clean up after failed promotions, bail out if
213 // we've exceeded policy time limits, or any other special behavior.
214 // All such policy should be placed here.
215 //
216 // Note that this method should only be called from the vm_thread while
217 // at a safepoint!
218 bool PSScavenge::invoke() {
219 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
220 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
221 assert(!Universe::heap()->is_gc_active(), "not reentrant");
223 ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
224 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
226 PSAdaptiveSizePolicy* policy = heap->size_policy();
227 IsGCActiveMark mark;
229 const bool scavenge_done = PSScavenge::invoke_no_policy();
230 const bool need_full_gc = !scavenge_done ||
231 policy->should_full_GC(heap->old_gen()->free_in_bytes());
232 bool full_gc_done = false;
234 if (UsePerfData) {
235 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
236 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
237 counters->update_full_follows_scavenge(ffs_val);
238 }
240 if (need_full_gc) {
241 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
242 CollectorPolicy* cp = heap->collector_policy();
243 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
245 if (UseParallelOldGC) {
246 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
247 } else {
248 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
249 }
250 }
252 return full_gc_done;
253 }
255 // This method contains no policy. You should probably
256 // be calling invoke() instead.
257 bool PSScavenge::invoke_no_policy() {
258 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
259 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
261 assert(_preserved_mark_stack.is_empty(), "should be empty");
262 assert(_preserved_oop_stack.is_empty(), "should be empty");
264 TimeStamp scavenge_entry;
265 TimeStamp scavenge_midpoint;
266 TimeStamp scavenge_exit;
268 scavenge_entry.update();
270 if (GC_locker::check_active_before_gc()) {
271 return false;
272 }
274 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
275 GCCause::Cause gc_cause = heap->gc_cause();
276 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
278 // Check for potential problems.
279 if (!should_attempt_scavenge()) {
280 return false;
281 }
283 bool promotion_failure_occurred = false;
285 PSYoungGen* young_gen = heap->young_gen();
286 PSOldGen* old_gen = heap->old_gen();
287 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
288 heap->increment_total_collections();
290 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
292 if ((gc_cause != GCCause::_java_lang_system_gc) ||
293 UseAdaptiveSizePolicyWithSystemGC) {
294 // Gather the feedback data for eden occupancy.
295 young_gen->eden_space()->accumulate_statistics();
296 }
298 if (ZapUnusedHeapArea) {
299 // Save information needed to minimize mangling
300 heap->record_gen_tops_before_GC();
301 }
303 heap->print_heap_before_gc();
305 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
306 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
308 size_t prev_used = heap->used();
309 assert(promotion_failed() == false, "Sanity");
311 // Fill in TLABs
312 heap->accumulate_statistics_all_tlabs();
313 heap->ensure_parsability(true); // retire TLABs
315 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
316 HandleMark hm; // Discard invalid handles created during verification
317 gclog_or_tty->print(" VerifyBeforeGC:");
318 Universe::verify();
319 }
321 {
322 ResourceMark rm;
323 HandleMark hm;
325 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
326 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
327 TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
328 TraceCollectorStats tcs(counters());
329 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
331 if (TraceGen0Time) accumulated_time()->start();
333 // Let the size policy know we're starting
334 size_policy->minor_collection_begin();
336 // Verify the object start arrays.
337 if (VerifyObjectStartArray &&
338 VerifyBeforeGC) {
339 old_gen->verify_object_start_array();
340 }
342 // Verify no unmarked old->young roots
343 if (VerifyRememberedSets) {
344 CardTableExtension::verify_all_young_refs_imprecise();
345 }
347 if (!ScavengeWithObjectsInToSpace) {
348 assert(young_gen->to_space()->is_empty(),
349 "Attempt to scavenge with live objects in to_space");
350 young_gen->to_space()->clear(SpaceDecorator::Mangle);
351 } else if (ZapUnusedHeapArea) {
352 young_gen->to_space()->mangle_unused_area();
353 }
354 save_to_space_top_before_gc();
356 COMPILER2_PRESENT(DerivedPointerTable::clear());
358 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
359 reference_processor()->setup_policy(false);
361 // We track how much was promoted to the next generation for
362 // the AdaptiveSizePolicy.
363 size_t old_gen_used_before = old_gen->used_in_bytes();
365 // For PrintGCDetails
366 size_t young_gen_used_before = young_gen->used_in_bytes();
368 // Reset our survivor overflow.
369 set_survivor_overflow(false);
371 // We need to save the old top values before
372 // creating the promotion_manager. We pass the top
373 // values to the card_table, to prevent it from
374 // straying into the promotion labs.
375 HeapWord* old_top = old_gen->object_space()->top();
377 // Release all previously held resources
378 gc_task_manager()->release_all_resources();
380 // Set the number of GC threads to be used in this collection
381 gc_task_manager()->set_active_gang();
382 gc_task_manager()->task_idle_workers();
383 // Get the active number of workers here and use that value
384 // throughout the methods.
385 uint active_workers = gc_task_manager()->active_workers();
386 heap->set_par_threads(active_workers);
388 PSPromotionManager::pre_scavenge();
390 // We'll use the promotion manager again later.
391 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
392 {
393 // TraceTime("Roots");
394 ParallelScavengeHeap::ParStrongRootsScope psrs;
396 GCTaskQueue* q = GCTaskQueue::create();
398 if (!old_gen->object_space()->is_empty()) {
399 // There are only old-to-young pointers if there are objects
400 // in the old gen.
401 uint stripe_total = active_workers;
402 for(uint i=0; i < stripe_total; i++) {
403 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
404 }
405 }
407 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
408 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
409 // We scan the thread roots in parallel
410 Threads::create_thread_roots_tasks(q);
411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
415 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
416 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
418 ParallelTaskTerminator terminator(
419 active_workers,
420 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
421 if (active_workers > 1) {
422 for (uint j = 0; j < active_workers; j++) {
423 q->enqueue(new StealTask(&terminator));
424 }
425 }
427 gc_task_manager()->execute_and_wait(q);
428 }
430 scavenge_midpoint.update();
432 // Process reference objects discovered during scavenge
433 {
434 reference_processor()->setup_policy(false); // not always_clear
435 reference_processor()->set_active_mt_degree(active_workers);
436 PSKeepAliveClosure keep_alive(promotion_manager);
437 PSEvacuateFollowersClosure evac_followers(promotion_manager);
438 if (reference_processor()->processing_is_mt()) {
439 PSRefProcTaskExecutor task_executor;
440 reference_processor()->process_discovered_references(
441 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
442 } else {
443 reference_processor()->process_discovered_references(
444 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
445 }
446 }
448 // Enqueue reference objects discovered during scavenge.
449 if (reference_processor()->processing_is_mt()) {
450 PSRefProcTaskExecutor task_executor;
451 reference_processor()->enqueue_discovered_references(&task_executor);
452 } else {
453 reference_processor()->enqueue_discovered_references(NULL);
454 }
456 // Unlink any dead interned Strings
457 StringTable::unlink(&_is_alive_closure);
458 // Process the remaining live ones
459 PSScavengeRootsClosure root_closure(promotion_manager);
460 StringTable::oops_do(&root_closure);
462 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
463 PSPromotionManager::post_scavenge();
465 promotion_failure_occurred = promotion_failed();
466 if (promotion_failure_occurred) {
467 clean_up_failed_promotion();
468 if (PrintGC) {
469 gclog_or_tty->print("--");
470 }
471 }
473 // Let the size policy know we're done. Note that we count promotion
474 // failure cleanup time as part of the collection (otherwise, we're
475 // implicitly saying it's mutator time).
476 size_policy->minor_collection_end(gc_cause);
478 if (!promotion_failure_occurred) {
479 // Swap the survivor spaces.
482 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
483 young_gen->from_space()->clear(SpaceDecorator::Mangle);
484 young_gen->swap_spaces();
486 size_t survived = young_gen->from_space()->used_in_bytes();
487 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
488 size_policy->update_averages(_survivor_overflow, survived, promoted);
490 // A successful scavenge should restart the GC time limit count which is
491 // for full GC's.
492 size_policy->reset_gc_overhead_limit_count();
493 if (UseAdaptiveSizePolicy) {
494 // Calculate the new survivor size and tenuring threshold
496 if (PrintAdaptiveSizePolicy) {
497 gclog_or_tty->print("AdaptiveSizeStart: ");
498 gclog_or_tty->stamp();
499 gclog_or_tty->print_cr(" collection: %d ",
500 heap->total_collections());
502 if (Verbose) {
503 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
504 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
505 }
506 }
509 if (UsePerfData) {
510 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
511 counters->update_old_eden_size(
512 size_policy->calculated_eden_size_in_bytes());
513 counters->update_old_promo_size(
514 size_policy->calculated_promo_size_in_bytes());
515 counters->update_old_capacity(old_gen->capacity_in_bytes());
516 counters->update_young_capacity(young_gen->capacity_in_bytes());
517 counters->update_survived(survived);
518 counters->update_promoted(promoted);
519 counters->update_survivor_overflowed(_survivor_overflow);
520 }
522 size_t survivor_limit =
523 size_policy->max_survivor_size(young_gen->max_size());
524 _tenuring_threshold =
525 size_policy->compute_survivor_space_size_and_threshold(
526 _survivor_overflow,
527 _tenuring_threshold,
528 survivor_limit);
530 if (PrintTenuringDistribution) {
531 gclog_or_tty->cr();
532 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)",
533 size_policy->calculated_survivor_size_in_bytes(),
534 _tenuring_threshold, MaxTenuringThreshold);
535 }
537 if (UsePerfData) {
538 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
539 counters->update_tenuring_threshold(_tenuring_threshold);
540 counters->update_survivor_size_counters();
541 }
543 // Do call at minor collections?
544 // Don't check if the size_policy is ready at this
545 // level. Let the size_policy check that internally.
546 if (UseAdaptiveSizePolicy &&
547 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
548 ((gc_cause != GCCause::_java_lang_system_gc) ||
549 UseAdaptiveSizePolicyWithSystemGC)) {
551 // Calculate optimial free space amounts
552 assert(young_gen->max_size() >
553 young_gen->from_space()->capacity_in_bytes() +
554 young_gen->to_space()->capacity_in_bytes(),
555 "Sizes of space in young gen are out-of-bounds");
556 size_t max_eden_size = young_gen->max_size() -
557 young_gen->from_space()->capacity_in_bytes() -
558 young_gen->to_space()->capacity_in_bytes();
559 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
560 young_gen->eden_space()->used_in_bytes(),
561 old_gen->used_in_bytes(),
562 young_gen->eden_space()->capacity_in_bytes(),
563 old_gen->max_gen_size(),
564 max_eden_size,
565 false /* full gc*/,
566 gc_cause,
567 heap->collector_policy());
569 }
570 // Resize the young generation at every collection
571 // even if new sizes have not been calculated. This is
572 // to allow resizes that may have been inhibited by the
573 // relative location of the "to" and "from" spaces.
575 // Resizing the old gen at minor collects can cause increases
576 // that don't feed back to the generation sizing policy until
577 // a major collection. Don't resize the old gen here.
579 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
580 size_policy->calculated_survivor_size_in_bytes());
582 if (PrintAdaptiveSizePolicy) {
583 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
584 heap->total_collections());
585 }
586 }
588 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
589 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
590 // Also update() will case adaptive NUMA chunk resizing.
591 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
592 young_gen->eden_space()->update();
594 heap->gc_policy_counters()->update_counters();
596 heap->resize_all_tlabs();
598 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
599 }
601 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
603 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
605 CodeCache::prune_scavenge_root_nmethods();
607 // Re-verify object start arrays
608 if (VerifyObjectStartArray &&
609 VerifyAfterGC) {
610 old_gen->verify_object_start_array();
611 }
613 // Verify all old -> young cards are now precise
614 if (VerifyRememberedSets) {
615 // Precise verification will give false positives. Until this is fixed,
616 // use imprecise verification.
617 // CardTableExtension::verify_all_young_refs_precise();
618 CardTableExtension::verify_all_young_refs_imprecise();
619 }
621 if (TraceGen0Time) accumulated_time()->stop();
623 if (PrintGC) {
624 if (PrintGCDetails) {
625 // Don't print a GC timestamp here. This is after the GC so
626 // would be confusing.
627 young_gen->print_used_change(young_gen_used_before);
628 }
629 heap->print_heap_change(prev_used);
630 }
632 // Track memory usage and detect low memory
633 MemoryService::track_memory_usage();
634 heap->update_counters();
636 gc_task_manager()->release_idle_workers();
637 }
639 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
640 HandleMark hm; // Discard invalid handles created during verification
641 gclog_or_tty->print(" VerifyAfterGC:");
642 Universe::verify();
643 }
645 heap->print_heap_after_gc();
647 if (ZapUnusedHeapArea) {
648 young_gen->eden_space()->check_mangled_unused_area_complete();
649 young_gen->from_space()->check_mangled_unused_area_complete();
650 young_gen->to_space()->check_mangled_unused_area_complete();
651 }
653 scavenge_exit.update();
655 if (PrintGCTaskTimeStamps) {
656 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
657 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
658 scavenge_exit.ticks());
659 gc_task_manager()->print_task_time_stamps();
660 }
662 #ifdef TRACESPINNING
663 ParallelTaskTerminator::print_termination_counts();
664 #endif
666 return !promotion_failure_occurred;
667 }
669 // This method iterates over all objects in the young generation,
670 // unforwarding markOops. It then restores any preserved mark oops,
671 // and clears the _preserved_mark_stack.
672 void PSScavenge::clean_up_failed_promotion() {
673 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
674 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
675 assert(promotion_failed(), "Sanity");
677 PSYoungGen* young_gen = heap->young_gen();
679 {
680 ResourceMark rm;
682 // Unforward all pointers in the young gen.
683 PSPromotionFailedClosure unforward_closure;
684 young_gen->object_iterate(&unforward_closure);
686 if (PrintGC && Verbose) {
687 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
688 }
690 // Restore any saved marks.
691 while (!_preserved_oop_stack.is_empty()) {
692 oop obj = _preserved_oop_stack.pop();
693 markOop mark = _preserved_mark_stack.pop();
694 obj->set_mark(mark);
695 }
697 // Clear the preserved mark and oop stack caches.
698 _preserved_mark_stack.clear(true);
699 _preserved_oop_stack.clear(true);
700 _promotion_failed = false;
701 }
703 // Reset the PromotionFailureALot counters.
704 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
705 }
707 // This method is called whenever an attempt to promote an object
708 // fails. Some markOops will need preservation, some will not. Note
709 // that the entire eden is traversed after a failed promotion, with
710 // all forwarded headers replaced by the default markOop. This means
711 // it is not neccessary to preserve most markOops.
712 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
713 _promotion_failed = true;
714 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
715 // Should use per-worker private stakcs hetre rather than
716 // locking a common pair of stacks.
717 ThreadCritical tc;
718 _preserved_oop_stack.push(obj);
719 _preserved_mark_stack.push(obj_mark);
720 }
721 }
723 bool PSScavenge::should_attempt_scavenge() {
724 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
725 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
726 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
728 if (UsePerfData) {
729 counters->update_scavenge_skipped(not_skipped);
730 }
732 PSYoungGen* young_gen = heap->young_gen();
733 PSOldGen* old_gen = heap->old_gen();
735 if (!ScavengeWithObjectsInToSpace) {
736 // Do not attempt to promote unless to_space is empty
737 if (!young_gen->to_space()->is_empty()) {
738 _consecutive_skipped_scavenges++;
739 if (UsePerfData) {
740 counters->update_scavenge_skipped(to_space_not_empty);
741 }
742 return false;
743 }
744 }
746 // Test to see if the scavenge will likely fail.
747 PSAdaptiveSizePolicy* policy = heap->size_policy();
749 // A similar test is done in the policy's should_full_GC(). If this is
750 // changed, decide if that test should also be changed.
751 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
752 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
753 bool result = promotion_estimate < old_gen->free_in_bytes();
755 if (PrintGCDetails && Verbose) {
756 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
757 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
758 " padded_average_promoted " SIZE_FORMAT
759 " free in old gen " SIZE_FORMAT,
760 (size_t) policy->average_promoted_in_bytes(),
761 (size_t) policy->padded_average_promoted_in_bytes(),
762 old_gen->free_in_bytes());
763 if (young_gen->used_in_bytes() <
764 (size_t) policy->padded_average_promoted_in_bytes()) {
765 gclog_or_tty->print_cr(" padded_promoted_average is greater"
766 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
767 }
768 }
770 if (result) {
771 _consecutive_skipped_scavenges = 0;
772 } else {
773 _consecutive_skipped_scavenges++;
774 if (UsePerfData) {
775 counters->update_scavenge_skipped(promoted_too_large);
776 }
777 }
778 return result;
779 }
781 // Used to add tasks
782 GCTaskManager* const PSScavenge::gc_task_manager() {
783 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
784 "shouldn't return NULL");
785 return ParallelScavengeHeap::gc_task_manager();
786 }
788 void PSScavenge::initialize() {
789 // Arguments must have been parsed
791 if (AlwaysTenure) {
792 _tenuring_threshold = 0;
793 } else if (NeverTenure) {
794 _tenuring_threshold = markOopDesc::max_age + 1;
795 } else {
796 // We want to smooth out our startup times for the AdaptiveSizePolicy
797 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
798 MaxTenuringThreshold;
799 }
801 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
802 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
804 PSYoungGen* young_gen = heap->young_gen();
805 PSOldGen* old_gen = heap->old_gen();
807 // Set boundary between young_gen and old_gen
808 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
809 "old above young");
810 _young_generation_boundary = young_gen->eden_space()->bottom();
812 // Initialize ref handling object for scavenging.
813 MemRegion mr = young_gen->reserved();
815 _ref_processor =
816 new ReferenceProcessor(mr, // span
817 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
818 (int) ParallelGCThreads, // mt processing degree
819 true, // mt discovery
820 (int) ParallelGCThreads, // mt discovery degree
821 true, // atomic_discovery
822 NULL, // header provides liveness info
823 false); // next field updates do not need write barrier
825 // Cache the cardtable
826 BarrierSet* bs = Universe::heap()->barrier_set();
827 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
828 _card_table = (CardTableExtension*)bs;
830 _counters = new CollectorCounters("PSScavenge", 0);
831 }