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.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "aot/aotLoader.hpp"
27 #include "classfile/classLoaderDataGraph.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "gc/parallel/gcTaskManager.hpp"
31 #include "gc/parallel/parallelScavengeHeap.hpp"
32 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
33 #include "gc/parallel/psClosure.inline.hpp"
34 #include "gc/parallel/psMarkSweepProxy.hpp"
35 #include "gc/parallel/psParallelCompact.inline.hpp"
36 #include "gc/parallel/psPromotionManager.inline.hpp"
37 #include "gc/parallel/psRootType.inline.hpp"
38 #include "gc/parallel/psScavenge.inline.hpp"
39 #include "gc/parallel/psTasks.hpp"
40 #include "gc/shared/gcCause.hpp"
41 #include "gc/shared/gcHeapSummary.hpp"
42 #include "gc/shared/gcId.hpp"
43 #include "gc/shared/gcLocker.hpp"
44 #include "gc/shared/gcTimer.hpp"
45 #include "gc/shared/gcTrace.hpp"
46 #include "gc/shared/gcTraceTime.inline.hpp"
47 #include "gc/shared/isGCActiveMark.hpp"
48 #include "gc/shared/referencePolicy.hpp"
49 #include "gc/shared/referenceProcessor.hpp"
50 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
51 #include "gc/shared/scavengableNMethods.hpp"
52 #include "gc/shared/spaceDecorator.hpp"
53 #include "gc/shared/weakProcessor.hpp"
54 #include "gc/shared/workerPolicy.hpp"
55 #include "gc/shared/workgroup.hpp"
56 #if INCLUDE_JVMCI
57 #include "jvmci/jvmci.hpp"
58 #endif
59 #include "memory/resourceArea.hpp"
60 #include "memory/universe.hpp"
61 #include "logging/log.hpp"
62 #include "oops/access.inline.hpp"
63 #include "oops/compressedOops.inline.hpp"
64 #include "oops/oop.inline.hpp"
65 #include "runtime/biasedLocking.hpp"
66 #include "runtime/handles.inline.hpp"
67 #include "runtime/threadCritical.hpp"
68 #include "runtime/vmThread.hpp"
69 #include "runtime/vmOperations.hpp"
70 #include "services/management.hpp"
71 #include "services/memoryService.hpp"
72 #include "utilities/stack.inline.hpp"
73
74
75 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
76 int PSScavenge::_consecutive_skipped_scavenges = 0;
77 SpanSubjectToDiscoveryClosure PSScavenge::_span_based_discoverer;
78 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
79 PSCardTable* PSScavenge::_card_table = NULL;
80 bool PSScavenge::_survivor_overflow = false;
81 uint PSScavenge::_tenuring_threshold = 0;
82 HeapWord* PSScavenge::_young_generation_boundary = NULL;
83 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
84 elapsedTimer PSScavenge::_accumulated_time;
85 STWGCTimer PSScavenge::_gc_timer;
86 ParallelScavengeTracer PSScavenge::_gc_tracer;
87 CollectorCounters* PSScavenge::_counters = NULL;
88
89 void scavenge_roots_task(Parallel::RootType::Value root_type, uint which) {
90 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
91
92 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(which);
93 PSScavengeRootsClosure roots_closure(pm);
94 PSPromoteRootsClosure roots_to_old_closure(pm);
95
96 switch (root_type) {
97 case Parallel::RootType::universe:
98 Universe::oops_do(&roots_closure);
99 break;
100
101 case Parallel::RootType::jni_handles:
102 JNIHandles::oops_do(&roots_closure);
103 break;
104
105 case Parallel::RootType::object_synchronizer:
106 ObjectSynchronizer::oops_do(&roots_closure);
107 break;
108
109 case Parallel::RootType::system_dictionary:
110 SystemDictionary::oops_do(&roots_closure);
111 break;
112
113 case Parallel::RootType::class_loader_data:
114 {
115 PSScavengeCLDClosure cld_closure(pm);
116 ClassLoaderDataGraph::cld_do(&cld_closure);
117 }
118 break;
119
120 case Parallel::RootType::management:
121 Management::oops_do(&roots_closure);
122 break;
123
124 case Parallel::RootType::jvmti:
125 JvmtiExport::oops_do(&roots_closure);
126 break;
127
128 case Parallel::RootType::code_cache:
129 {
130 MarkingCodeBlobClosure code_closure(&roots_to_old_closure, CodeBlobToOopClosure::FixRelocations);
131 ScavengableNMethods::nmethods_do(&code_closure);
132 AOTLoader::oops_do(&roots_closure);
133 }
134 break;
135
136 #if INCLUDE_JVMCI
137 case Parallel::RootType::jvmci:
138 JVMCI::oops_do(&roots_closure);
139 break;
140 #endif
141
142 case Parallel::RootType::sentinel:
143 DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
144 fatal("Bad enumeration value: %u", root_type);
145 break;
146 }
147
148 // Do the real work
149 pm->drain_stacks(false);
150 }
151
152 void steal_task(ParallelTaskTerminator& terminator, uint worker_id) {
153 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
154
155 PSPromotionManager* pm =
156 PSPromotionManager::gc_thread_promotion_manager(worker_id);
157 pm->drain_stacks(true);
158 guarantee(pm->stacks_empty(),
159 "stacks should be empty at this point");
160
161 while (true) {
162 StarTask p;
163 if (PSPromotionManager::steal_depth(worker_id, p)) {
164 TASKQUEUE_STATS_ONLY(pm->record_steal(p));
165 pm->process_popped_location_depth(p);
166 pm->drain_stacks_depth(true);
167 } else {
168 if (terminator.offer_termination()) {
169 break;
170 }
171 }
172 }
173 guarantee(pm->stacks_empty(), "stacks should be empty at this point");
174 }
175
176 // Define before use
177 class PSIsAliveClosure: public BoolObjectClosure {
178 public:
179 bool do_object_b(oop p) {
180 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
181 }
182 };
183
184 PSIsAliveClosure PSScavenge::_is_alive_closure;
185
186 class PSKeepAliveClosure: public OopClosure {
187 protected:
188 MutableSpace* _to_space;
189 PSPromotionManager* _promotion_manager;
190
191 public:
192 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
193 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
194 _to_space = heap->young_gen()->to_space();
195
196 assert(_promotion_manager != NULL, "Sanity");
197 }
198
199 template <class T> void do_oop_work(T* p) {
200 assert (oopDesc::is_oop(RawAccess<IS_NOT_NULL>::oop_load(p)),
201 "expected an oop while scanning weak refs");
202
203 // Weak refs may be visited more than once.
204 if (PSScavenge::should_scavenge(p, _to_space)) {
205 _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
206 }
207 }
208 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
209 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
210 };
211
212 class PSEvacuateFollowersClosure: public VoidClosure {
213 private:
214 PSPromotionManager* _promotion_manager;
215 public:
216 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
217
218 virtual void do_void() {
219 assert(_promotion_manager != NULL, "Sanity");
220 _promotion_manager->drain_stacks(true);
221 guarantee(_promotion_manager->stacks_empty(),
222 "stacks should be empty at this point");
223 }
224 };
225
226 class PSRefProcTaskProxy: public GCTask {
227 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
228 ProcessTask & _rp_task;
229 uint _work_id;
230 public:
231 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
232 : _rp_task(rp_task),
233 _work_id(work_id)
234 { }
235
236 private:
237 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
238 virtual void do_it(GCTaskManager* manager, uint which);
239 };
240
241 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
242 {
243 PSPromotionManager* promotion_manager =
244 PSPromotionManager::gc_thread_promotion_manager(which);
245 assert(promotion_manager != NULL, "sanity check");
246 PSKeepAliveClosure keep_alive(promotion_manager);
247 PSEvacuateFollowersClosure evac_followers(promotion_manager);
248 PSIsAliveClosure is_alive;
249 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
250 }
251
252 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
253 virtual void execute(ProcessTask& task, uint ergo_workers);
254 };
255
256 void PSRefProcTaskExecutor::execute(ProcessTask& task, uint ergo_workers)
257 {
258 GCTaskQueue* q = GCTaskQueue::create();
259 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
260 uint active_workers = manager->active_workers();
261
262 assert(active_workers == ergo_workers,
263 "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
264 ergo_workers, active_workers);
265
266 for(uint i=0; i < active_workers; i++) {
267 q->enqueue(new PSRefProcTaskProxy(task, i));
268 }
269 TaskTerminator terminator(active_workers,
270 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
271 if (task.marks_oops_alive() && active_workers > 1) {
272 for (uint j = 0; j < active_workers; j++) {
273 q->enqueue(new StealTask(terminator.terminator()));
274 }
275 }
276 manager->execute_and_wait(q);
277 }
278
279 // This method contains all heap specific policy for invoking scavenge.
280 // PSScavenge::invoke_no_policy() will do nothing but attempt to
281 // scavenge. It will not clean up after failed promotions, bail out if
282 // we've exceeded policy time limits, or any other special behavior.
283 // All such policy should be placed here.
284 //
285 // Note that this method should only be called from the vm_thread while
286 // at a safepoint!
287 bool PSScavenge::invoke() {
288 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
289 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
290 assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
291
292 ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
293 PSAdaptiveSizePolicy* policy = heap->size_policy();
294 IsGCActiveMark mark;
295
296 const bool scavenge_done = PSScavenge::invoke_no_policy();
297 const bool need_full_gc = !scavenge_done ||
298 policy->should_full_GC(heap->old_gen()->free_in_bytes());
299 bool full_gc_done = false;
300
301 if (UsePerfData) {
302 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
303 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
304 counters->update_full_follows_scavenge(ffs_val);
305 }
306
307 if (need_full_gc) {
308 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
309 SoftRefPolicy* srp = heap->soft_ref_policy();
310 const bool clear_all_softrefs = srp->should_clear_all_soft_refs();
311
312 if (UseParallelOldGC) {
313 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
314 } else {
315 full_gc_done = PSMarkSweepProxy::invoke_no_policy(clear_all_softrefs);
316 }
317 }
318
319 return full_gc_done;
320 }
321
322 class PSThreadRootsTaskClosure : public ThreadClosure {
323 uint _worker_id;
324 public:
325 PSThreadRootsTaskClosure(uint worker_id) : _worker_id(worker_id) { }
326 virtual void do_thread(Thread* thread) {
327 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
328
329 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(_worker_id);
330 PSScavengeRootsClosure roots_closure(pm);
331 MarkingCodeBlobClosure roots_in_blobs(&roots_closure, CodeBlobToOopClosure::FixRelocations);
332
333 thread->oops_do(&roots_closure, &roots_in_blobs);
334
335 // Do the real work
336 pm->drain_stacks(false);
337 }
338 };
339 //
340 // OldToYoungRootsTask
341 //
342 // This task is used to scan old to young roots in parallel
343 //
344 // A GC thread executing this tasks divides the generation (old gen)
345 // into slices and takes a stripe in the slice as its part of the
346 // work.
347 //
348 // +===============+ slice 0
349 // | stripe 0 |
350 // +---------------+
351 // | stripe 1 |
352 // +---------------+
353 // | stripe 2 |
354 // +---------------+
355 // | stripe 3 |
356 // +===============+ slice 1
357 // | stripe 0 |
358 // +---------------+
359 // | stripe 1 |
360 // +---------------+
361 // | stripe 2 |
362 // +---------------+
363 // | stripe 3 |
364 // +===============+ slice 2
365 // ...
366 //
367 // A task is created for each stripe. In this case there are 4 tasks
368 // created. A GC thread first works on its stripe within slice 0
369 // and then moves to its stripe in the next slice until all stripes
370 // exceed the top of the generation. Note that having fewer GC threads
371 // than stripes works because all the tasks are executed so all stripes
372 // will be covered. In this example if 4 tasks have been created to cover
373 // all the stripes and there are only 3 threads, one of the threads will
374 // get the tasks with the 4th stripe. However, there is a dependence in
375 // PSCardTable::scavenge_contents_parallel() on the number
376 // of tasks created. In scavenge_contents_parallel the distance
377 // to the next stripe is calculated based on the number of tasks.
378 // If the stripe width is ssize, a task's next stripe is at
379 // ssize * number_of_tasks (= slice_stride). In this case after
380 // finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1
381 // by adding slice_stride to the start of stripe 0 in slice 0 to get
382 // to the start of stride 0 in slice 1.
383
384 class ScavengeRootsTask : public AbstractGangTask {
385 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
386 EnumClaimer<Parallel::RootType::Value> _enum_claimer;
387 PSOldGen* _old_gen;
388 HeapWord* _gen_top;
389 uint _active_workers;
390 bool _is_empty;
391 TaskTerminator _terminator;
392
393 public:
394 ScavengeRootsTask(
395 PSOldGen* old_gen,
396 HeapWord* gen_top,
397 uint active_workers,
398 bool is_empty)
399 : AbstractGangTask("ScavengeRootsTask"),
400 _strong_roots_scope(active_workers),
401 _enum_claimer(Parallel::RootType::sentinel),
402 _old_gen(old_gen),
403 _gen_top(gen_top),
404 _active_workers(active_workers),
405 _is_empty(is_empty),
406 _terminator(active_workers, PSPromotionManager::vm_thread_promotion_manager()->stack_array_depth()) {
407 }
408
409 virtual void work(uint worker_id) {
410 ResourceMark rm;
411
412 if (!_is_empty) {
413 // There are only old-to-young pointers if there are objects
414 // in the old gen.
415
416 // There are not old-to-young pointers if the old gen is empty.
417 assert(!_old_gen->object_space()->is_empty(),
418 "Should not be called is there is no work");
419 assert(_old_gen != NULL, "Sanity");
420 assert(_old_gen->object_space()->contains(_gen_top) || _gen_top == _old_gen->object_space()->top(), "Sanity");
421 assert(worker_id < ParallelGCThreads, "Sanity");
422
423 {
424 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
425 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
426
427 card_table->scavenge_contents_parallel(_old_gen->start_array(),
428 _old_gen->object_space(),
429 _gen_top,
430 pm,
431 worker_id,
432 _active_workers);
433
434 // Do the real work
435 pm->drain_stacks(false);
436 }
437 }
438
439 for (Parallel::RootType::Value root_type; _enum_claimer.try_claim(root_type); /* empty */) {
440 scavenge_roots_task(root_type, worker_id);
441 }
442
443 PSThreadRootsTaskClosure closure(worker_id);
444 Threads::possibly_parallel_threads_do(true /*parallel */, &closure);
445
446
447 // If active_workers can exceed 1, add a StrealTask.
448 // PSPromotionManager::drain_stacks_depth() does not fully drain its
449 // stacks and expects a StealTask to complete the draining if
450 // ParallelGCThreads is > 1.
451
452 if (_active_workers > 1) {
453 steal_task(*_terminator.terminator() , worker_id);
454 }
455 }
456 };
457
458 // This method contains no policy. You should probably
459 // be calling invoke() instead.
460 bool PSScavenge::invoke_no_policy() {
461 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
462 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
463
464 _gc_timer.register_gc_start();
465
466 TimeStamp scavenge_entry;
467 TimeStamp scavenge_midpoint;
468 TimeStamp scavenge_exit;
469
470 scavenge_entry.update();
471
472 if (GCLocker::check_active_before_gc()) {
473 return false;
474 }
475
476 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
477 GCCause::Cause gc_cause = heap->gc_cause();
478
479 // Check for potential problems.
480 if (!should_attempt_scavenge()) {
481 return false;
482 }
483
484 GCIdMark gc_id_mark;
485 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
486
487 bool promotion_failure_occurred = false;
488
489 PSYoungGen* young_gen = heap->young_gen();
490 PSOldGen* old_gen = heap->old_gen();
491 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
492
493 heap->increment_total_collections();
494
495 if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
496 // Gather the feedback data for eden occupancy.
497 young_gen->eden_space()->accumulate_statistics();
498 }
499
500 heap->print_heap_before_gc();
501 heap->trace_heap_before_gc(&_gc_tracer);
502
503 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
504 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
505
506 // Fill in TLABs
507 heap->ensure_parsability(true); // retire TLABs
508
509 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
510 HandleMark hm; // Discard invalid handles created during verification
511 Universe::verify("Before GC");
512 }
513
514 {
515 ResourceMark rm;
516 HandleMark hm;
517
518 GCTraceCPUTime tcpu;
519 GCTraceTime(Info, gc) tm("Pause Young", NULL, gc_cause, true);
520 TraceCollectorStats tcs(counters());
521 TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause);
522
523 if (log_is_enabled(Debug, gc, heap, exit)) {
524 accumulated_time()->start();
525 }
526
527 // Let the size policy know we're starting
528 size_policy->minor_collection_begin();
529
530 // Verify the object start arrays.
531 if (VerifyObjectStartArray &&
532 VerifyBeforeGC) {
533 old_gen->verify_object_start_array();
534 }
535
536 // Verify no unmarked old->young roots
537 if (VerifyRememberedSets) {
538 heap->card_table()->verify_all_young_refs_imprecise();
539 }
540
541 assert(young_gen->to_space()->is_empty(),
542 "Attempt to scavenge with live objects in to_space");
543 young_gen->to_space()->clear(SpaceDecorator::Mangle);
544
545 save_to_space_top_before_gc();
546
547 #if COMPILER2_OR_JVMCI
548 DerivedPointerTable::clear();
549 #endif
550
551 reference_processor()->enable_discovery();
552 reference_processor()->setup_policy(false);
553
554 PreGCValues pre_gc_values(heap);
555
556 // Reset our survivor overflow.
557 set_survivor_overflow(false);
558
559 // We need to save the old top values before
560 // creating the promotion_manager. We pass the top
561 // values to the card_table, to prevent it from
562 // straying into the promotion labs.
563 HeapWord* old_top = old_gen->object_space()->top();
564
565 uint active_workers = ParallelScavengeHeap::heap()->workers().update_active_workers(WorkerPolicy::calc_active_workers(
566 ParallelScavengeHeap::heap()->workers().total_workers(),
567 ParallelScavengeHeap::heap()->workers().active_workers(),
568 Threads::number_of_non_daemon_threads()));
569
570 // Release all previously held resources
571 gc_task_manager()->release_all_resources();
572
573 // Set the number of GC threads to be used in this collection
574 gc_task_manager()->set_active_gang();
575 gc_task_manager()->task_idle_workers();
576
577 assert(active_workers == gc_task_manager()->active_workers(), "sanity, taskmanager and workgang ought to agree");
578
579 PSPromotionManager::pre_scavenge();
580
581 // We'll use the promotion manager again later.
582 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
583 {
584 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
585
586 ScavengeRootsTask task(old_gen, old_top, active_workers, old_gen->object_space()->is_empty());
587 ParallelScavengeHeap::heap()->workers().run_task(&task);
588 }
589
590 scavenge_midpoint.update();
591
592 // Process reference objects discovered during scavenge
593 {
594 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
595
596 reference_processor()->setup_policy(false); // not always_clear
597 reference_processor()->set_active_mt_degree(active_workers);
598 PSKeepAliveClosure keep_alive(promotion_manager);
599 PSEvacuateFollowersClosure evac_followers(promotion_manager);
600 ReferenceProcessorStats stats;
601 ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
602 if (reference_processor()->processing_is_mt()) {
603 PSRefProcTaskExecutor task_executor;
604 stats = reference_processor()->process_discovered_references(
605 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
606 &pt);
607 } else {
608 stats = reference_processor()->process_discovered_references(
609 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &pt);
610 }
611
612 _gc_tracer.report_gc_reference_stats(stats);
613 pt.print_all_references();
614 }
615
616 assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
617
618 PSScavengeRootsClosure root_closure(promotion_manager);
619
620 {
621 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
622 WeakProcessor::weak_oops_do(&_is_alive_closure, &root_closure);
623 }
624
625 // Verify that usage of root_closure didn't copy any objects.
626 assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
627
628 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
629 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
630 if (promotion_failure_occurred) {
631 clean_up_failed_promotion();
632 log_info(gc, promotion)("Promotion failed");
633 }
634
635 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
636
637 // Let the size policy know we're done. Note that we count promotion
638 // failure cleanup time as part of the collection (otherwise, we're
639 // implicitly saying it's mutator time).
640 size_policy->minor_collection_end(gc_cause);
641
642 if (!promotion_failure_occurred) {
643 // Swap the survivor spaces.
644 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
645 young_gen->from_space()->clear(SpaceDecorator::Mangle);
646 young_gen->swap_spaces();
647
648 size_t survived = young_gen->from_space()->used_in_bytes();
649 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
650 size_policy->update_averages(_survivor_overflow, survived, promoted);
651
652 // A successful scavenge should restart the GC time limit count which is
653 // for full GC's.
654 size_policy->reset_gc_overhead_limit_count();
655 if (UseAdaptiveSizePolicy) {
656 // Calculate the new survivor size and tenuring threshold
657
658 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
659 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
660 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
661
662 if (UsePerfData) {
663 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
664 counters->update_old_eden_size(
665 size_policy->calculated_eden_size_in_bytes());
666 counters->update_old_promo_size(
667 size_policy->calculated_promo_size_in_bytes());
668 counters->update_old_capacity(old_gen->capacity_in_bytes());
669 counters->update_young_capacity(young_gen->capacity_in_bytes());
670 counters->update_survived(survived);
671 counters->update_promoted(promoted);
672 counters->update_survivor_overflowed(_survivor_overflow);
673 }
674
675 size_t max_young_size = young_gen->max_size();
676
677 // Deciding a free ratio in the young generation is tricky, so if
678 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
679 // that the old generation size may have been limited because of them) we
680 // should then limit our young generation size using NewRatio to have it
681 // follow the old generation size.
682 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
683 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
684 }
685
686 size_t survivor_limit =
687 size_policy->max_survivor_size(max_young_size);
688 _tenuring_threshold =
689 size_policy->compute_survivor_space_size_and_threshold(
690 _survivor_overflow,
691 _tenuring_threshold,
692 survivor_limit);
693
694 log_debug(gc, age)("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max threshold " UINTX_FORMAT ")",
695 size_policy->calculated_survivor_size_in_bytes(),
696 _tenuring_threshold, MaxTenuringThreshold);
697
698 if (UsePerfData) {
699 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
700 counters->update_tenuring_threshold(_tenuring_threshold);
701 counters->update_survivor_size_counters();
702 }
703
704 // Do call at minor collections?
705 // Don't check if the size_policy is ready at this
706 // level. Let the size_policy check that internally.
707 if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
708 (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
709 // Calculate optimal free space amounts
710 assert(young_gen->max_size() >
711 young_gen->from_space()->capacity_in_bytes() +
712 young_gen->to_space()->capacity_in_bytes(),
713 "Sizes of space in young gen are out-of-bounds");
714
715 size_t young_live = young_gen->used_in_bytes();
716 size_t eden_live = young_gen->eden_space()->used_in_bytes();
717 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
718 size_t max_old_gen_size = old_gen->max_gen_size();
719 size_t max_eden_size = max_young_size -
720 young_gen->from_space()->capacity_in_bytes() -
721 young_gen->to_space()->capacity_in_bytes();
722
723 // Used for diagnostics
724 size_policy->clear_generation_free_space_flags();
725
726 size_policy->compute_eden_space_size(young_live,
727 eden_live,
728 cur_eden,
729 max_eden_size,
730 false /* not full gc*/);
731
732 size_policy->check_gc_overhead_limit(eden_live,
733 max_old_gen_size,
734 max_eden_size,
735 false /* not full gc*/,
736 gc_cause,
737 heap->soft_ref_policy());
738
739 size_policy->decay_supplemental_growth(false /* not full gc*/);
740 }
741 // Resize the young generation at every collection
742 // even if new sizes have not been calculated. This is
743 // to allow resizes that may have been inhibited by the
744 // relative location of the "to" and "from" spaces.
745
746 // Resizing the old gen at young collections can cause increases
747 // that don't feed back to the generation sizing policy until
748 // a full collection. Don't resize the old gen here.
749
750 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
751 size_policy->calculated_survivor_size_in_bytes());
752
753 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
754 }
755
756 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
757 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
758 // Also update() will case adaptive NUMA chunk resizing.
759 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
760 young_gen->eden_space()->update();
761
762 heap->gc_policy_counters()->update_counters();
763
764 heap->resize_all_tlabs();
765
766 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
767 }
768
769 #if COMPILER2_OR_JVMCI
770 DerivedPointerTable::update_pointers();
771 #endif
772
773 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
774
775 // Re-verify object start arrays
776 if (VerifyObjectStartArray &&
777 VerifyAfterGC) {
778 old_gen->verify_object_start_array();
779 }
780
781 // Verify all old -> young cards are now precise
782 if (VerifyRememberedSets) {
783 // Precise verification will give false positives. Until this is fixed,
784 // use imprecise verification.
785 // heap->card_table()->verify_all_young_refs_precise();
786 heap->card_table()->verify_all_young_refs_imprecise();
787 }
788
789 if (log_is_enabled(Debug, gc, heap, exit)) {
790 accumulated_time()->stop();
791 }
792
793 young_gen->print_used_change(pre_gc_values.young_gen_used());
794 old_gen->print_used_change(pre_gc_values.old_gen_used());
795 MetaspaceUtils::print_metaspace_change(pre_gc_values.metadata_used());
796
797 // Track memory usage and detect low memory
798 MemoryService::track_memory_usage();
799 heap->update_counters();
800
801 gc_task_manager()->release_idle_workers();
802 }
803
804 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
805 HandleMark hm; // Discard invalid handles created during verification
806 Universe::verify("After GC");
807 }
808
809 heap->print_heap_after_gc();
810 heap->trace_heap_after_gc(&_gc_tracer);
811
812 scavenge_exit.update();
813
814 log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
815 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
816 scavenge_exit.ticks());
817 gc_task_manager()->print_task_time_stamps();
818
819 #ifdef TRACESPINNING
820 ParallelTaskTerminator::print_termination_counts();
821 #endif
822
823 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
824
825 _gc_timer.register_gc_end();
826
827 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
828
829 return !promotion_failure_occurred;
830 }
831
832 // This method iterates over all objects in the young generation,
833 // removing all forwarding references. It then restores any preserved marks.
834 void PSScavenge::clean_up_failed_promotion() {
835 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
836 PSYoungGen* young_gen = heap->young_gen();
837
838 RemoveForwardedPointerClosure remove_fwd_ptr_closure;
839 young_gen->object_iterate(&remove_fwd_ptr_closure);
840
841 PSPromotionManager::restore_preserved_marks();
842
843 // Reset the PromotionFailureALot counters.
844 NOT_PRODUCT(heap->reset_promotion_should_fail();)
845 }
846
847 bool PSScavenge::should_attempt_scavenge() {
848 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
849 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
850
851 if (UsePerfData) {
852 counters->update_scavenge_skipped(not_skipped);
853 }
854
855 PSYoungGen* young_gen = heap->young_gen();
856 PSOldGen* old_gen = heap->old_gen();
857
858 // Do not attempt to promote unless to_space is empty
859 if (!young_gen->to_space()->is_empty()) {
860 _consecutive_skipped_scavenges++;
861 if (UsePerfData) {
862 counters->update_scavenge_skipped(to_space_not_empty);
863 }
864 return false;
865 }
866
867 // Test to see if the scavenge will likely fail.
868 PSAdaptiveSizePolicy* policy = heap->size_policy();
869
870 // A similar test is done in the policy's should_full_GC(). If this is
871 // changed, decide if that test should also be changed.
872 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
873 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
874 bool result = promotion_estimate < old_gen->free_in_bytes();
875
876 log_trace(ergo)("%s scavenge: average_promoted " SIZE_FORMAT " padded_average_promoted " SIZE_FORMAT " free in old gen " SIZE_FORMAT,
877 result ? "Do" : "Skip", (size_t) policy->average_promoted_in_bytes(),
878 (size_t) policy->padded_average_promoted_in_bytes(),
879 old_gen->free_in_bytes());
880 if (young_gen->used_in_bytes() < (size_t) policy->padded_average_promoted_in_bytes()) {
881 log_trace(ergo)(" padded_promoted_average is greater than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
882 }
883
884 if (result) {
885 _consecutive_skipped_scavenges = 0;
886 } else {
887 _consecutive_skipped_scavenges++;
888 if (UsePerfData) {
889 counters->update_scavenge_skipped(promoted_too_large);
890 }
891 }
892 return result;
893 }
894
895 // Used to add tasks
896 GCTaskManager* const PSScavenge::gc_task_manager() {
897 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
898 "shouldn't return NULL");
899 return ParallelScavengeHeap::gc_task_manager();
900 }
901
902 // Adaptive size policy support. When the young generation/old generation
903 // boundary moves, _young_generation_boundary must be reset
904 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
905 _young_generation_boundary = v;
906 if (UseCompressedOops) {
907 _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode((oop)v);
908 }
909 }
910
911 void PSScavenge::initialize() {
912 // Arguments must have been parsed
913
914 if (AlwaysTenure || NeverTenure) {
915 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
916 "MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold);
917 _tenuring_threshold = MaxTenuringThreshold;
918 } else {
919 // We want to smooth out our startup times for the AdaptiveSizePolicy
920 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
921 MaxTenuringThreshold;
922 }
923
924 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
925 PSYoungGen* young_gen = heap->young_gen();
926 PSOldGen* old_gen = heap->old_gen();
927
928 // Set boundary between young_gen and old_gen
929 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
930 "old above young");
931 set_young_generation_boundary(young_gen->eden_space()->bottom());
932
933 // Initialize ref handling object for scavenging.
934 _span_based_discoverer.set_span(young_gen->reserved());
935 _ref_processor =
936 new ReferenceProcessor(&_span_based_discoverer,
937 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
938 ParallelGCThreads, // mt processing degree
939 true, // mt discovery
940 ParallelGCThreads, // mt discovery degree
941 true, // atomic_discovery
942 NULL, // header provides liveness info
943 false);
944
945 // Cache the cardtable
946 _card_table = heap->card_table();
947
948 _counters = new CollectorCounters("Parallel young collection pauses", 0);
949 }