1/*
2 * Copyright (c) 2002, 2019, 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 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25#include "precompiled.hpp"
26#include "classfile/stringTable.hpp"
27#include "code/codeCache.hpp"
28#include "gc/parallel/gcTaskManager.hpp"
29#include "gc/parallel/parallelScavengeHeap.hpp"
30#include "gc/parallel/psAdaptiveSizePolicy.hpp"
31#include "gc/parallel/psClosure.inline.hpp"
32#include "gc/parallel/psMarkSweepProxy.hpp"
33#include "gc/parallel/psParallelCompact.inline.hpp"
34#include "gc/parallel/psPromotionManager.inline.hpp"
35#include "gc/parallel/psScavenge.inline.hpp"
36#include "gc/parallel/psTasks.hpp"
37#include "gc/shared/gcCause.hpp"
38#include "gc/shared/gcHeapSummary.hpp"
39#include "gc/shared/gcId.hpp"
40#include "gc/shared/gcLocker.hpp"
41#include "gc/shared/gcTimer.hpp"
42#include "gc/shared/gcTrace.hpp"
43#include "gc/shared/gcTraceTime.inline.hpp"
44#include "gc/shared/isGCActiveMark.hpp"
45#include "gc/shared/referencePolicy.hpp"
46#include "gc/shared/referenceProcessor.hpp"
47#include "gc/shared/referenceProcessorPhaseTimes.hpp"
48#include "gc/shared/spaceDecorator.hpp"
49#include "gc/shared/weakProcessor.hpp"
50#include "memory/resourceArea.hpp"
51#include "memory/universe.hpp"
52#include "logging/log.hpp"
53#include "oops/access.inline.hpp"
54#include "oops/compressedOops.inline.hpp"
55#include "oops/oop.inline.hpp"
56#include "runtime/biasedLocking.hpp"
57#include "runtime/handles.inline.hpp"
58#include "runtime/threadCritical.hpp"
59#include "runtime/vmThread.hpp"
60#include "runtime/vmOperations.hpp"
61#include "services/memoryService.hpp"
62#include "utilities/stack.inline.hpp"
63
64HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
65int PSScavenge::_consecutive_skipped_scavenges = 0;
66SpanSubjectToDiscoveryClosure PSScavenge::_span_based_discoverer;
67ReferenceProcessor* PSScavenge::_ref_processor = NULL;
68PSCardTable* PSScavenge::_card_table = NULL;
69bool PSScavenge::_survivor_overflow = false;
70uint PSScavenge::_tenuring_threshold = 0;
71HeapWord* PSScavenge::_young_generation_boundary = NULL;
72uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
73elapsedTimer PSScavenge::_accumulated_time;
74STWGCTimer PSScavenge::_gc_timer;
75ParallelScavengeTracer PSScavenge::_gc_tracer;
76CollectorCounters* PSScavenge::_counters = NULL;
77
78// Define before use
79class PSIsAliveClosure: public BoolObjectClosure {
80public:
81 bool do_object_b(oop p) {
82 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
83 }
84};
85
86PSIsAliveClosure PSScavenge::_is_alive_closure;
87
88class PSKeepAliveClosure: public OopClosure {
89protected:
90 MutableSpace* _to_space;
91 PSPromotionManager* _promotion_manager;
92
93public:
94 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
95 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
96 _to_space = heap->young_gen()->to_space();
97
98 assert(_promotion_manager != NULL, "Sanity");
99 }
100
101 template <class T> void do_oop_work(T* p) {
102 assert (oopDesc::is_oop(RawAccess<IS_NOT_NULL>::oop_load(p)),
103 "expected an oop while scanning weak refs");
104
105 // Weak refs may be visited more than once.
106 if (PSScavenge::should_scavenge(p, _to_space)) {
107 _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
108 }
109 }
110 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
111 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
112};
113
114class PSEvacuateFollowersClosure: public VoidClosure {
115 private:
116 PSPromotionManager* _promotion_manager;
117 public:
118 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
119
120 virtual void do_void() {
121 assert(_promotion_manager != NULL, "Sanity");
122 _promotion_manager->drain_stacks(true);
123 guarantee(_promotion_manager->stacks_empty(),
124 "stacks should be empty at this point");
125 }
126};
127
128class PSRefProcTaskProxy: public GCTask {
129 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
130 ProcessTask & _rp_task;
131 uint _work_id;
132public:
133 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
134 : _rp_task(rp_task),
135 _work_id(work_id)
136 { }
137
138private:
139 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
140 virtual void do_it(GCTaskManager* manager, uint which);
141};
142
143void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
144{
145 PSPromotionManager* promotion_manager =
146 PSPromotionManager::gc_thread_promotion_manager(which);
147 assert(promotion_manager != NULL, "sanity check");
148 PSKeepAliveClosure keep_alive(promotion_manager);
149 PSEvacuateFollowersClosure evac_followers(promotion_manager);
150 PSIsAliveClosure is_alive;
151 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
152}
153
154class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
155 virtual void execute(ProcessTask& task, uint ergo_workers);
156};
157
158void PSRefProcTaskExecutor::execute(ProcessTask& task, uint ergo_workers)
159{
160 GCTaskQueue* q = GCTaskQueue::create();
161 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
162 uint active_workers = manager->active_workers();
163
164 assert(active_workers == ergo_workers,
165 "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
166 ergo_workers, active_workers);
167
168 for(uint i=0; i < active_workers; i++) {
169 q->enqueue(new PSRefProcTaskProxy(task, i));
170 }
171 TaskTerminator terminator(active_workers,
172 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
173 if (task.marks_oops_alive() && active_workers > 1) {
174 for (uint j = 0; j < active_workers; j++) {
175 q->enqueue(new StealTask(terminator.terminator()));
176 }
177 }
178 manager->execute_and_wait(q);
179}
180
181// This method contains all heap specific policy for invoking scavenge.
182// PSScavenge::invoke_no_policy() will do nothing but attempt to
183// scavenge. It will not clean up after failed promotions, bail out if
184// we've exceeded policy time limits, or any other special behavior.
185// All such policy should be placed here.
186//
187// Note that this method should only be called from the vm_thread while
188// at a safepoint!
189bool PSScavenge::invoke() {
190 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
191 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
192 assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
193
194 ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
195 PSAdaptiveSizePolicy* policy = heap->size_policy();
196 IsGCActiveMark mark;
197
198 const bool scavenge_done = PSScavenge::invoke_no_policy();
199 const bool need_full_gc = !scavenge_done ||
200 policy->should_full_GC(heap->old_gen()->free_in_bytes());
201 bool full_gc_done = false;
202
203 if (UsePerfData) {
204 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
205 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
206 counters->update_full_follows_scavenge(ffs_val);
207 }
208
209 if (need_full_gc) {
210 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
211 SoftRefPolicy* srp = heap->soft_ref_policy();
212 const bool clear_all_softrefs = srp->should_clear_all_soft_refs();
213
214 if (UseParallelOldGC) {
215 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
216 } else {
217 full_gc_done = PSMarkSweepProxy::invoke_no_policy(clear_all_softrefs);
218 }
219 }
220
221 return full_gc_done;
222}
223
224class PSAddThreadRootsTaskClosure : public ThreadClosure {
225private:
226 GCTaskQueue* _q;
227
228public:
229 PSAddThreadRootsTaskClosure(GCTaskQueue* q) : _q(q) { }
230 void do_thread(Thread* t) {
231 _q->enqueue(new ThreadRootsTask(t));
232 }
233};
234
235// This method contains no policy. You should probably
236// be calling invoke() instead.
237bool PSScavenge::invoke_no_policy() {
238 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
239 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
240
241 _gc_timer.register_gc_start();
242
243 TimeStamp scavenge_entry;
244 TimeStamp scavenge_midpoint;
245 TimeStamp scavenge_exit;
246
247 scavenge_entry.update();
248
249 if (GCLocker::check_active_before_gc()) {
250 return false;
251 }
252
253 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
254 GCCause::Cause gc_cause = heap->gc_cause();
255
256 // Check for potential problems.
257 if (!should_attempt_scavenge()) {
258 return false;
259 }
260
261 GCIdMark gc_id_mark;
262 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
263
264 bool promotion_failure_occurred = false;
265
266 PSYoungGen* young_gen = heap->young_gen();
267 PSOldGen* old_gen = heap->old_gen();
268 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
269
270 heap->increment_total_collections();
271
272 if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
273 // Gather the feedback data for eden occupancy.
274 young_gen->eden_space()->accumulate_statistics();
275 }
276
277 heap->print_heap_before_gc();
278 heap->trace_heap_before_gc(&_gc_tracer);
279
280 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
281 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
282
283 // Fill in TLABs
284 heap->ensure_parsability(true); // retire TLABs
285
286 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
287 HandleMark hm; // Discard invalid handles created during verification
288 Universe::verify("Before GC");
289 }
290
291 {
292 ResourceMark rm;
293 HandleMark hm;
294
295 GCTraceCPUTime tcpu;
296 GCTraceTime(Info, gc) tm("Pause Young", NULL, gc_cause, true);
297 TraceCollectorStats tcs(counters());
298 TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause);
299
300 if (log_is_enabled(Debug, gc, heap, exit)) {
301 accumulated_time()->start();
302 }
303
304 // Let the size policy know we're starting
305 size_policy->minor_collection_begin();
306
307 // Verify the object start arrays.
308 if (VerifyObjectStartArray &&
309 VerifyBeforeGC) {
310 old_gen->verify_object_start_array();
311 }
312
313 // Verify no unmarked old->young roots
314 if (VerifyRememberedSets) {
315 heap->card_table()->verify_all_young_refs_imprecise();
316 }
317
318 assert(young_gen->to_space()->is_empty(),
319 "Attempt to scavenge with live objects in to_space");
320 young_gen->to_space()->clear(SpaceDecorator::Mangle);
321
322 save_to_space_top_before_gc();
323
324#if COMPILER2_OR_JVMCI
325 DerivedPointerTable::clear();
326#endif
327
328 reference_processor()->enable_discovery();
329 reference_processor()->setup_policy(false);
330
331 PreGCValues pre_gc_values(heap);
332
333 // Reset our survivor overflow.
334 set_survivor_overflow(false);
335
336 // We need to save the old top values before
337 // creating the promotion_manager. We pass the top
338 // values to the card_table, to prevent it from
339 // straying into the promotion labs.
340 HeapWord* old_top = old_gen->object_space()->top();
341
342 // Release all previously held resources
343 gc_task_manager()->release_all_resources();
344
345 // Set the number of GC threads to be used in this collection
346 gc_task_manager()->set_active_gang();
347 gc_task_manager()->task_idle_workers();
348 // Get the active number of workers here and use that value
349 // throughout the methods.
350 uint active_workers = gc_task_manager()->active_workers();
351
352 PSPromotionManager::pre_scavenge();
353
354 // We'll use the promotion manager again later.
355 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
356 {
357 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
358 ParallelScavengeHeap::ParStrongRootsScope psrs;
359
360 GCTaskQueue* q = GCTaskQueue::create();
361
362 if (!old_gen->object_space()->is_empty()) {
363 // There are only old-to-young pointers if there are objects
364 // in the old gen.
365 uint stripe_total = active_workers;
366 for(uint i=0; i < stripe_total; i++) {
367 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
368 }
369 }
370
371 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
372 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
373 // We scan the thread roots in parallel
374 PSAddThreadRootsTaskClosure cl(q);
375 Threads::java_threads_and_vm_thread_do(&cl);
376 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
377 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
378 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
379 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
380 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
381 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
382 JVMCI_ONLY(q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmci));)
383
384 TaskTerminator terminator(active_workers,
385 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
386 // If active_workers can exceed 1, add a StrealTask.
387 // PSPromotionManager::drain_stacks_depth() does not fully drain its
388 // stacks and expects a StealTask to complete the draining if
389 // ParallelGCThreads is > 1.
390 if (gc_task_manager()->workers() > 1) {
391 for (uint j = 0; j < active_workers; j++) {
392 q->enqueue(new StealTask(terminator.terminator()));
393 }
394 }
395
396 gc_task_manager()->execute_and_wait(q);
397 }
398
399 scavenge_midpoint.update();
400
401 // Process reference objects discovered during scavenge
402 {
403 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
404
405 reference_processor()->setup_policy(false); // not always_clear
406 reference_processor()->set_active_mt_degree(active_workers);
407 PSKeepAliveClosure keep_alive(promotion_manager);
408 PSEvacuateFollowersClosure evac_followers(promotion_manager);
409 ReferenceProcessorStats stats;
410 ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
411 if (reference_processor()->processing_is_mt()) {
412 PSRefProcTaskExecutor task_executor;
413 stats = reference_processor()->process_discovered_references(
414 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
415 &pt);
416 } else {
417 stats = reference_processor()->process_discovered_references(
418 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &pt);
419 }
420
421 _gc_tracer.report_gc_reference_stats(stats);
422 pt.print_all_references();
423 }
424
425 assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
426
427 PSScavengeRootsClosure root_closure(promotion_manager);
428
429 {
430 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
431 WeakProcessor::weak_oops_do(&_is_alive_closure, &root_closure);
432 }
433
434 // Verify that usage of root_closure didn't copy any objects.
435 assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
436
437 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
438 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
439 if (promotion_failure_occurred) {
440 clean_up_failed_promotion();
441 log_info(gc, promotion)("Promotion failed");
442 }
443
444 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
445
446 // Let the size policy know we're done. Note that we count promotion
447 // failure cleanup time as part of the collection (otherwise, we're
448 // implicitly saying it's mutator time).
449 size_policy->minor_collection_end(gc_cause);
450
451 if (!promotion_failure_occurred) {
452 // Swap the survivor spaces.
453 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
454 young_gen->from_space()->clear(SpaceDecorator::Mangle);
455 young_gen->swap_spaces();
456
457 size_t survived = young_gen->from_space()->used_in_bytes();
458 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
459 size_policy->update_averages(_survivor_overflow, survived, promoted);
460
461 // A successful scavenge should restart the GC time limit count which is
462 // for full GC's.
463 size_policy->reset_gc_overhead_limit_count();
464 if (UseAdaptiveSizePolicy) {
465 // Calculate the new survivor size and tenuring threshold
466
467 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
468 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
469 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
470
471 if (UsePerfData) {
472 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
473 counters->update_old_eden_size(
474 size_policy->calculated_eden_size_in_bytes());
475 counters->update_old_promo_size(
476 size_policy->calculated_promo_size_in_bytes());
477 counters->update_old_capacity(old_gen->capacity_in_bytes());
478 counters->update_young_capacity(young_gen->capacity_in_bytes());
479 counters->update_survived(survived);
480 counters->update_promoted(promoted);
481 counters->update_survivor_overflowed(_survivor_overflow);
482 }
483
484 size_t max_young_size = young_gen->max_size();
485
486 // Deciding a free ratio in the young generation is tricky, so if
487 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
488 // that the old generation size may have been limited because of them) we
489 // should then limit our young generation size using NewRatio to have it
490 // follow the old generation size.
491 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
492 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
493 }
494
495 size_t survivor_limit =
496 size_policy->max_survivor_size(max_young_size);
497 _tenuring_threshold =
498 size_policy->compute_survivor_space_size_and_threshold(
499 _survivor_overflow,
500 _tenuring_threshold,
501 survivor_limit);
502
503 log_debug(gc, age)("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max threshold " UINTX_FORMAT ")",
504 size_policy->calculated_survivor_size_in_bytes(),
505 _tenuring_threshold, MaxTenuringThreshold);
506
507 if (UsePerfData) {
508 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
509 counters->update_tenuring_threshold(_tenuring_threshold);
510 counters->update_survivor_size_counters();
511 }
512
513 // Do call at minor collections?
514 // Don't check if the size_policy is ready at this
515 // level. Let the size_policy check that internally.
516 if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
517 (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
518 // Calculate optimal free space amounts
519 assert(young_gen->max_size() >
520 young_gen->from_space()->capacity_in_bytes() +
521 young_gen->to_space()->capacity_in_bytes(),
522 "Sizes of space in young gen are out-of-bounds");
523
524 size_t young_live = young_gen->used_in_bytes();
525 size_t eden_live = young_gen->eden_space()->used_in_bytes();
526 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
527 size_t max_old_gen_size = old_gen->max_gen_size();
528 size_t max_eden_size = max_young_size -
529 young_gen->from_space()->capacity_in_bytes() -
530 young_gen->to_space()->capacity_in_bytes();
531
532 // Used for diagnostics
533 size_policy->clear_generation_free_space_flags();
534
535 size_policy->compute_eden_space_size(young_live,
536 eden_live,
537 cur_eden,
538 max_eden_size,
539 false /* not full gc*/);
540
541 size_policy->check_gc_overhead_limit(eden_live,
542 max_old_gen_size,
543 max_eden_size,
544 false /* not full gc*/,
545 gc_cause,
546 heap->soft_ref_policy());
547
548 size_policy->decay_supplemental_growth(false /* not full gc*/);
549 }
550 // Resize the young generation at every collection
551 // even if new sizes have not been calculated. This is
552 // to allow resizes that may have been inhibited by the
553 // relative location of the "to" and "from" spaces.
554
555 // Resizing the old gen at young collections can cause increases
556 // that don't feed back to the generation sizing policy until
557 // a full collection. Don't resize the old gen here.
558
559 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
560 size_policy->calculated_survivor_size_in_bytes());
561
562 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
563 }
564
565 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
566 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
567 // Also update() will case adaptive NUMA chunk resizing.
568 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
569 young_gen->eden_space()->update();
570
571 heap->gc_policy_counters()->update_counters();
572
573 heap->resize_all_tlabs();
574
575 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
576 }
577
578#if COMPILER2_OR_JVMCI
579 DerivedPointerTable::update_pointers();
580#endif
581
582 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
583
584 // Re-verify object start arrays
585 if (VerifyObjectStartArray &&
586 VerifyAfterGC) {
587 old_gen->verify_object_start_array();
588 }
589
590 // Verify all old -> young cards are now precise
591 if (VerifyRememberedSets) {
592 // Precise verification will give false positives. Until this is fixed,
593 // use imprecise verification.
594 // heap->card_table()->verify_all_young_refs_precise();
595 heap->card_table()->verify_all_young_refs_imprecise();
596 }
597
598 if (log_is_enabled(Debug, gc, heap, exit)) {
599 accumulated_time()->stop();
600 }
601
602 young_gen->print_used_change(pre_gc_values.young_gen_used());
603 old_gen->print_used_change(pre_gc_values.old_gen_used());
604 MetaspaceUtils::print_metaspace_change(pre_gc_values.metadata_used());
605
606 // Track memory usage and detect low memory
607 MemoryService::track_memory_usage();
608 heap->update_counters();
609
610 gc_task_manager()->release_idle_workers();
611 }
612
613 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
614 HandleMark hm; // Discard invalid handles created during verification
615 Universe::verify("After GC");
616 }
617
618 heap->print_heap_after_gc();
619 heap->trace_heap_after_gc(&_gc_tracer);
620
621 scavenge_exit.update();
622
623 log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
624 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
625 scavenge_exit.ticks());
626 gc_task_manager()->print_task_time_stamps();
627
628#ifdef TRACESPINNING
629 ParallelTaskTerminator::print_termination_counts();
630#endif
631
632 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
633
634 _gc_timer.register_gc_end();
635
636 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
637
638 return !promotion_failure_occurred;
639}
640
641// This method iterates over all objects in the young generation,
642// removing all forwarding references. It then restores any preserved marks.
643void PSScavenge::clean_up_failed_promotion() {
644 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
645 PSYoungGen* young_gen = heap->young_gen();
646
647 RemoveForwardedPointerClosure remove_fwd_ptr_closure;
648 young_gen->object_iterate(&remove_fwd_ptr_closure);
649
650 PSPromotionManager::restore_preserved_marks();
651
652 // Reset the PromotionFailureALot counters.
653 NOT_PRODUCT(heap->reset_promotion_should_fail();)
654}
655
656bool PSScavenge::should_attempt_scavenge() {
657 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
658 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
659
660 if (UsePerfData) {
661 counters->update_scavenge_skipped(not_skipped);
662 }
663
664 PSYoungGen* young_gen = heap->young_gen();
665 PSOldGen* old_gen = heap->old_gen();
666
667 // Do not attempt to promote unless to_space is empty
668 if (!young_gen->to_space()->is_empty()) {
669 _consecutive_skipped_scavenges++;
670 if (UsePerfData) {
671 counters->update_scavenge_skipped(to_space_not_empty);
672 }
673 return false;
674 }
675
676 // Test to see if the scavenge will likely fail.
677 PSAdaptiveSizePolicy* policy = heap->size_policy();
678
679 // A similar test is done in the policy's should_full_GC(). If this is
680 // changed, decide if that test should also be changed.
681 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
682 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
683 bool result = promotion_estimate < old_gen->free_in_bytes();
684
685 log_trace(ergo)("%s scavenge: average_promoted " SIZE_FORMAT " padded_average_promoted " SIZE_FORMAT " free in old gen " SIZE_FORMAT,
686 result ? "Do" : "Skip", (size_t) policy->average_promoted_in_bytes(),
687 (size_t) policy->padded_average_promoted_in_bytes(),
688 old_gen->free_in_bytes());
689 if (young_gen->used_in_bytes() < (size_t) policy->padded_average_promoted_in_bytes()) {
690 log_trace(ergo)(" padded_promoted_average is greater than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
691 }
692
693 if (result) {
694 _consecutive_skipped_scavenges = 0;
695 } else {
696 _consecutive_skipped_scavenges++;
697 if (UsePerfData) {
698 counters->update_scavenge_skipped(promoted_too_large);
699 }
700 }
701 return result;
702}
703
704 // Used to add tasks
705GCTaskManager* const PSScavenge::gc_task_manager() {
706 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
707 "shouldn't return NULL");
708 return ParallelScavengeHeap::gc_task_manager();
709}
710
711// Adaptive size policy support. When the young generation/old generation
712// boundary moves, _young_generation_boundary must be reset
713void PSScavenge::set_young_generation_boundary(HeapWord* v) {
714 _young_generation_boundary = v;
715 if (UseCompressedOops) {
716 _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode((oop)v);
717 }
718}
719
720void PSScavenge::initialize() {
721 // Arguments must have been parsed
722
723 if (AlwaysTenure || NeverTenure) {
724 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
725 "MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold);
726 _tenuring_threshold = MaxTenuringThreshold;
727 } else {
728 // We want to smooth out our startup times for the AdaptiveSizePolicy
729 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
730 MaxTenuringThreshold;
731 }
732
733 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
734 PSYoungGen* young_gen = heap->young_gen();
735 PSOldGen* old_gen = heap->old_gen();
736
737 // Set boundary between young_gen and old_gen
738 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
739 "old above young");
740 set_young_generation_boundary(young_gen->eden_space()->bottom());
741
742 // Initialize ref handling object for scavenging.
743 _span_based_discoverer.set_span(young_gen->reserved());
744 _ref_processor =
745 new ReferenceProcessor(&_span_based_discoverer,
746 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
747 ParallelGCThreads, // mt processing degree
748 true, // mt discovery
749 ParallelGCThreads, // mt discovery degree
750 true, // atomic_discovery
751 NULL, // header provides liveness info
752 false);
753
754 // Cache the cardtable
755 _card_table = heap->card_table();
756
757 _counters = new CollectorCounters("Parallel young collection pauses", 0);
758}
759