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