1 /*
2 * Copyright (c) 2002, 2020, 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/parallelScavengeHeap.hpp"
31 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
32 #include "gc/parallel/psClosure.inline.hpp"
33 #include "gc/parallel/psCompactionManager.hpp"
34 #include "gc/parallel/psParallelCompact.inline.hpp"
35 #include "gc/parallel/psPromotionManager.inline.hpp"
36 #include "gc/parallel/psRootType.hpp"
37 #include "gc/parallel/psScavenge.inline.hpp"
38 #include "gc/shared/gcCause.hpp"
39 #include "gc/shared/gcHeapSummary.hpp"
40 #include "gc/shared/gcId.hpp"
41 #include "gc/shared/gcLocker.hpp"
42 #include "gc/shared/gcTimer.hpp"
43 #include "gc/shared/gcTrace.hpp"
44 #include "gc/shared/gcTraceTime.inline.hpp"
45 #include "gc/shared/isGCActiveMark.hpp"
46 #include "gc/shared/oopStorage.inline.hpp"
47 #include "gc/shared/oopStorageSet.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.inline.hpp"
53 #include "gc/shared/taskTerminator.hpp"
54 #include "gc/shared/weakProcessor.hpp"
55 #include "gc/shared/workerPolicy.hpp"
56 #include "gc/shared/workgroup.hpp"
57 #include "memory/iterator.hpp"
58 #include "memory/resourceArea.hpp"
59 #include "memory/universe.hpp"
60 #include "logging/log.hpp"
61 #include "oops/access.inline.hpp"
62 #include "oops/compressedOops.inline.hpp"
63 #include "oops/oop.inline.hpp"
64 #include "runtime/biasedLocking.hpp"
65 #include "runtime/handles.inline.hpp"
66 #include "runtime/threadCritical.hpp"
67 #include "runtime/vmThread.hpp"
68 #include "runtime/vmOperations.hpp"
69 #include "services/management.hpp"
70 #include "services/memoryService.hpp"
71 #include "utilities/stack.inline.hpp"
72
73 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
74 int PSScavenge::_consecutive_skipped_scavenges = 0;
75 SpanSubjectToDiscoveryClosure PSScavenge::_span_based_discoverer;
76 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
77 PSCardTable* PSScavenge::_card_table = NULL;
78 bool PSScavenge::_survivor_overflow = false;
79 uint PSScavenge::_tenuring_threshold = 0;
80 HeapWord* PSScavenge::_young_generation_boundary = NULL;
81 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
82 elapsedTimer PSScavenge::_accumulated_time;
83 STWGCTimer PSScavenge::_gc_timer;
84 ParallelScavengeTracer PSScavenge::_gc_tracer;
85 CollectorCounters* PSScavenge::_counters = NULL;
86
87 static void scavenge_roots_work(ParallelRootType::Value root_type, uint worker_id) {
88 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
89
90 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
91 PSScavengeRootsClosure roots_closure(pm);
92 PSPromoteRootsClosure roots_to_old_closure(pm);
93
94 switch (root_type) {
95 case ParallelRootType::universe:
96 Universe::oops_do(&roots_closure);
97 break;
98
99 case ParallelRootType::jni_handles:
100 JNIHandles::oops_do(&roots_closure);
101 break;
102
103 case ParallelRootType::object_synchronizer:
104 ObjectSynchronizer::oops_do(&roots_closure);
105 break;
106
107 case ParallelRootType::vm_global:
108 OopStorageSet::vm_global()->oops_do(&roots_closure);
109 break;
110
111 case ParallelRootType::class_loader_data:
112 {
113 PSScavengeCLDClosure cld_closure(pm);
114 ClassLoaderDataGraph::cld_do(&cld_closure);
115 }
116 break;
117
118 case ParallelRootType::management:
119 Management::oops_do(&roots_closure);
120 break;
121
122 case ParallelRootType::jvmti:
123 JvmtiExport::oops_do(&roots_closure);
124 break;
125
126 case ParallelRootType::code_cache:
127 {
128 MarkingCodeBlobClosure code_closure(&roots_to_old_closure, CodeBlobToOopClosure::FixRelocations);
129 ScavengableNMethods::nmethods_do(&code_closure);
130 AOTLoader::oops_do(&roots_closure);
131 }
132 break;
133
134 case ParallelRootType::sentinel:
135 DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
136 fatal("Bad enumeration value: %u", root_type);
137 break;
138 }
139
140 // Do the real work
141 pm->drain_stacks(false);
142 }
143
144 static void steal_work(TaskTerminator& terminator, uint worker_id) {
145 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
146
147 PSPromotionManager* pm =
148 PSPromotionManager::gc_thread_promotion_manager(worker_id);
149 pm->drain_stacks(true);
150 guarantee(pm->stacks_empty(),
151 "stacks should be empty at this point");
152
153 while (true) {
154 ScannerTask task;
155 if (PSPromotionManager::steal_depth(worker_id, task)) {
156 TASKQUEUE_STATS_ONLY(pm->record_steal(task));
157 pm->process_popped_location_depth(task);
158 pm->drain_stacks_depth(true);
159 } else {
160 if (terminator.offer_termination()) {
161 break;
162 }
163 }
164 }
165 guarantee(pm->stacks_empty(), "stacks should be empty at this point");
166 }
167
168 // Define before use
169 class PSIsAliveClosure: public BoolObjectClosure {
170 public:
171 bool do_object_b(oop p) {
172 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
173 }
174 };
175
176 PSIsAliveClosure PSScavenge::_is_alive_closure;
177
178 class PSKeepAliveClosure: public OopClosure {
179 protected:
180 MutableSpace* _to_space;
181 PSPromotionManager* _promotion_manager;
182
183 public:
184 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
185 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
186 _to_space = heap->young_gen()->to_space();
187
188 assert(_promotion_manager != NULL, "Sanity");
189 }
190
191 template <class T> void do_oop_work(T* p) {
192 assert (oopDesc::is_oop(RawAccess<IS_NOT_NULL>::oop_load(p)),
193 "expected an oop while scanning weak refs");
194
195 // Weak refs may be visited more than once.
196 if (PSScavenge::should_scavenge(p, _to_space)) {
197 _promotion_manager->copy_and_push_safe_barrier</*promote_immediately=*/false>(p);
198 }
199 }
200 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
201 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
202 };
203
204 class PSEvacuateFollowersClosure: public VoidClosure {
205 private:
206 PSPromotionManager* _promotion_manager;
207 public:
208 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
209
210 virtual void do_void() {
211 assert(_promotion_manager != NULL, "Sanity");
212 _promotion_manager->drain_stacks(true);
213 guarantee(_promotion_manager->stacks_empty(),
214 "stacks should be empty at this point");
215 }
216 };
217
218 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
219 virtual void execute(ProcessTask& process_task, uint ergo_workers);
220 };
221
222 class PSRefProcTask : public AbstractGangTask {
223 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
224 TaskTerminator _terminator;
225 ProcessTask& _task;
226 uint _active_workers;
227
228 public:
229 PSRefProcTask(ProcessTask& task, uint active_workers)
230 : AbstractGangTask("PSRefProcTask"),
231 _terminator(active_workers, PSPromotionManager::stack_array_depth()),
232 _task(task),
233 _active_workers(active_workers) {
234 }
235
236 virtual void work(uint worker_id) {
237 PSPromotionManager* promotion_manager =
238 PSPromotionManager::gc_thread_promotion_manager(worker_id);
239 assert(promotion_manager != NULL, "sanity check");
240 PSKeepAliveClosure keep_alive(promotion_manager);
241 PSEvacuateFollowersClosure evac_followers(promotion_manager);
242 PSIsAliveClosure is_alive;
243 _task.work(worker_id, is_alive, keep_alive, evac_followers);
244
245 if (_task.marks_oops_alive() && _active_workers > 1) {
246 steal_work(_terminator, worker_id);
247 }
248 }
249 };
250
251 void PSRefProcTaskExecutor::execute(ProcessTask& process_task, uint ergo_workers) {
252 PSRefProcTask task(process_task, ergo_workers);
253 ParallelScavengeHeap::heap()->workers().run_task(&task);
254 }
255
256 // This method contains all heap specific policy for invoking scavenge.
257 // PSScavenge::invoke_no_policy() will do nothing but attempt to
258 // scavenge. It will not clean up after failed promotions, bail out if
259 // we've exceeded policy time limits, or any other special behavior.
260 // All such policy should be placed here.
261 //
262 // Note that this method should only be called from the vm_thread while
263 // at a safepoint!
264 bool PSScavenge::invoke() {
265 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
266 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
267 assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
268
269 ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
270 PSAdaptiveSizePolicy* policy = heap->size_policy();
271 IsGCActiveMark mark;
272
273 const bool scavenge_done = PSScavenge::invoke_no_policy();
274 const bool need_full_gc = !scavenge_done ||
275 policy->should_full_GC(heap->old_gen()->free_in_bytes());
276 bool full_gc_done = false;
277
278 if (UsePerfData) {
279 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
280 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
281 counters->update_full_follows_scavenge(ffs_val);
282 }
283
284 if (need_full_gc) {
285 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
286 SoftRefPolicy* srp = heap->soft_ref_policy();
287 const bool clear_all_softrefs = srp->should_clear_all_soft_refs();
288
289 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
290 }
291
292 return full_gc_done;
293 }
294
295 class PSThreadRootsTaskClosure : public ThreadClosure {
296 uint _worker_id;
297 public:
298 PSThreadRootsTaskClosure(uint worker_id) : _worker_id(worker_id) { }
299 virtual void do_thread(Thread* thread) {
300 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
301
302 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(_worker_id);
303 PSScavengeRootsClosure roots_closure(pm);
304 MarkingCodeBlobClosure roots_in_blobs(&roots_closure, CodeBlobToOopClosure::FixRelocations);
305
306 thread->oops_do(&roots_closure, &roots_in_blobs);
307
308 // Do the real work
309 pm->drain_stacks(false);
310 }
311 };
312
313 class ScavengeRootsTask : public AbstractGangTask {
314 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
315 SequentialSubTasksDone _subtasks;
316 PSOldGen* _old_gen;
317 HeapWord* _gen_top;
318 uint _active_workers;
319 bool _is_empty;
320 TaskTerminator _terminator;
321
322 public:
323 ScavengeRootsTask(PSOldGen* old_gen,
324 HeapWord* gen_top,
325 uint active_workers,
326 bool is_empty) :
327 AbstractGangTask("ScavengeRootsTask"),
328 _strong_roots_scope(active_workers),
329 _subtasks(),
330 _old_gen(old_gen),
331 _gen_top(gen_top),
332 _active_workers(active_workers),
333 _is_empty(is_empty),
334 _terminator(active_workers, PSPromotionManager::vm_thread_promotion_manager()->stack_array_depth()) {
335 _subtasks.set_n_threads(active_workers);
336 _subtasks.set_n_tasks(ParallelRootType::sentinel);
337 }
338
339 virtual void work(uint worker_id) {
340 ResourceMark rm;
341
342 if (!_is_empty) {
343 // There are only old-to-young pointers if there are objects
344 // in the old gen.
345
346 assert(_old_gen != NULL, "Sanity");
347 // There are no old-to-young pointers if the old gen is empty.
348 assert(!_old_gen->object_space()->is_empty(), "Should not be called is there is no work");
349 assert(_old_gen->object_space()->contains(_gen_top) || _gen_top == _old_gen->object_space()->top(), "Sanity");
350 assert(worker_id < ParallelGCThreads, "Sanity");
351
352 {
353 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
354 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
355
356 card_table->scavenge_contents_parallel(_old_gen->start_array(),
357 _old_gen->object_space(),
358 _gen_top,
359 pm,
360 worker_id,
361 _active_workers);
362
363 // Do the real work
364 pm->drain_stacks(false);
365 }
366 }
367
368 for (uint root_type = 0; _subtasks.try_claim_task(root_type); /* empty */ ) {
369 scavenge_roots_work(static_cast<ParallelRootType::Value>(root_type), worker_id);
370 }
371 _subtasks.all_tasks_completed();
372
373 PSThreadRootsTaskClosure closure(worker_id);
374 Threads::possibly_parallel_threads_do(true /*parallel */, &closure);
375
376
377 // If active_workers can exceed 1, add a steal_work().
378 // PSPromotionManager::drain_stacks_depth() does not fully drain its
379 // stacks and expects a steal_work() to complete the draining if
380 // ParallelGCThreads is > 1.
381
382 if (_active_workers > 1) {
383 steal_work(_terminator, worker_id);
384 }
385 }
386 };
387
388 // This method contains no policy. You should probably
389 // be calling invoke() instead.
390 bool PSScavenge::invoke_no_policy() {
391 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
392 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
393
394 _gc_timer.register_gc_start();
395
396 TimeStamp scavenge_entry;
397 TimeStamp scavenge_midpoint;
398 TimeStamp scavenge_exit;
399
400 scavenge_entry.update();
401
402 if (GCLocker::check_active_before_gc()) {
403 return false;
404 }
405
406 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
407 GCCause::Cause gc_cause = heap->gc_cause();
408
409 // Check for potential problems.
410 if (!should_attempt_scavenge()) {
411 return false;
412 }
413
414 GCIdMark gc_id_mark;
415 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
416
417 bool promotion_failure_occurred = false;
418
419 PSYoungGen* young_gen = heap->young_gen();
420 PSOldGen* old_gen = heap->old_gen();
421 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
422
423 heap->increment_total_collections();
424
425 if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
426 // Gather the feedback data for eden occupancy.
427 young_gen->eden_space()->accumulate_statistics();
428 }
429
430 heap->print_heap_before_gc();
431 heap->trace_heap_before_gc(&_gc_tracer);
432
433 assert(!NeverTenure || _tenuring_threshold == markWord::max_age + 1, "Sanity");
434 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
435
436 // Fill in TLABs
437 heap->ensure_parsability(true); // retire TLABs
438
439 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
440 HandleMark hm; // Discard invalid handles created during verification
441 Universe::verify("Before GC");
442 }
443
444 {
445 ResourceMark rm;
446 HandleMark hm;
447
448 GCTraceCPUTime tcpu;
449 GCTraceTime(Info, gc) tm("Pause Young", NULL, gc_cause, true);
450 TraceCollectorStats tcs(counters());
451 TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause);
452
453 if (log_is_enabled(Debug, gc, heap, exit)) {
454 accumulated_time()->start();
455 }
456
457 // Let the size policy know we're starting
458 size_policy->minor_collection_begin();
459
460 // Verify the object start arrays.
461 if (VerifyObjectStartArray &&
462 VerifyBeforeGC) {
463 old_gen->verify_object_start_array();
464 }
465
466 // Verify no unmarked old->young roots
467 if (VerifyRememberedSets) {
468 heap->card_table()->verify_all_young_refs_imprecise();
469 }
470
471 assert(young_gen->to_space()->is_empty(),
472 "Attempt to scavenge with live objects in to_space");
473 young_gen->to_space()->clear(SpaceDecorator::Mangle);
474
475 save_to_space_top_before_gc();
476
477 #if COMPILER2_OR_JVMCI
478 DerivedPointerTable::clear();
479 #endif
480
481 reference_processor()->enable_discovery();
482 reference_processor()->setup_policy(false);
483
484 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
485
486 // Reset our survivor overflow.
487 set_survivor_overflow(false);
488
489 // We need to save the old top values before
490 // creating the promotion_manager. We pass the top
491 // values to the card_table, to prevent it from
492 // straying into the promotion labs.
493 HeapWord* old_top = old_gen->object_space()->top();
494
495 const uint active_workers =
496 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().total_workers(),
497 ParallelScavengeHeap::heap()->workers().active_workers(),
498 Threads::number_of_non_daemon_threads());
499 ParallelScavengeHeap::heap()->workers().update_active_workers(active_workers);
500
501 PSPromotionManager::pre_scavenge();
502
503 // We'll use the promotion manager again later.
504 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
505 {
506 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
507
508 ScavengeRootsTask task(old_gen, old_top, active_workers, old_gen->object_space()->is_empty());
509 ParallelScavengeHeap::heap()->workers().run_task(&task);
510 }
511
512 scavenge_midpoint.update();
513
514 // Process reference objects discovered during scavenge
515 {
516 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
517
518 reference_processor()->setup_policy(false); // not always_clear
519 reference_processor()->set_active_mt_degree(active_workers);
520 PSKeepAliveClosure keep_alive(promotion_manager);
521 PSEvacuateFollowersClosure evac_followers(promotion_manager);
522 ReferenceProcessorStats stats;
523 ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
524 if (reference_processor()->processing_is_mt()) {
525 PSRefProcTaskExecutor task_executor;
526 stats = reference_processor()->process_discovered_references(
527 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
528 &pt);
529 } else {
530 stats = reference_processor()->process_discovered_references(
531 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &pt);
532 }
533
534 _gc_tracer.report_gc_reference_stats(stats);
535 pt.print_all_references();
536 }
537
538 assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
539
540 PSScavengeRootsClosure root_closure(promotion_manager);
541
542 {
543 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
544 WeakProcessor::weak_oops_do(&_is_alive_closure, &root_closure);
545 }
546
547 // Verify that usage of root_closure didn't copy any objects.
548 assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
549
550 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
551 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
552 if (promotion_failure_occurred) {
553 clean_up_failed_promotion();
554 log_info(gc, promotion)("Promotion failed");
555 }
556
557 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
558
559 // Let the size policy know we're done. Note that we count promotion
560 // failure cleanup time as part of the collection (otherwise, we're
561 // implicitly saying it's mutator time).
562 size_policy->minor_collection_end(gc_cause);
563
564 if (!promotion_failure_occurred) {
565 // Swap the survivor spaces.
566 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
567 young_gen->from_space()->clear(SpaceDecorator::Mangle);
568 young_gen->swap_spaces();
569
570 size_t survived = young_gen->from_space()->used_in_bytes();
571 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
572 size_policy->update_averages(_survivor_overflow, survived, promoted);
573
574 // A successful scavenge should restart the GC time limit count which is
575 // for full GC's.
576 size_policy->reset_gc_overhead_limit_count();
577 if (UseAdaptiveSizePolicy) {
578 // Calculate the new survivor size and tenuring threshold
579
580 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
581 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
582 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
583
584 if (UsePerfData) {
585 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
586 counters->update_old_eden_size(
587 size_policy->calculated_eden_size_in_bytes());
588 counters->update_old_promo_size(
589 size_policy->calculated_promo_size_in_bytes());
590 counters->update_old_capacity(old_gen->capacity_in_bytes());
591 counters->update_young_capacity(young_gen->capacity_in_bytes());
592 counters->update_survived(survived);
593 counters->update_promoted(promoted);
594 counters->update_survivor_overflowed(_survivor_overflow);
595 }
596
597 size_t max_young_size = young_gen->max_gen_size();
598
599 // Deciding a free ratio in the young generation is tricky, so if
600 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
601 // that the old generation size may have been limited because of them) we
602 // should then limit our young generation size using NewRatio to have it
603 // follow the old generation size.
604 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
605 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio,
606 young_gen->max_gen_size());
607 }
608
609 size_t survivor_limit =
610 size_policy->max_survivor_size(max_young_size);
611 _tenuring_threshold =
612 size_policy->compute_survivor_space_size_and_threshold(
613 _survivor_overflow,
614 _tenuring_threshold,
615 survivor_limit);
616
617 log_debug(gc, age)("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max threshold " UINTX_FORMAT ")",
618 size_policy->calculated_survivor_size_in_bytes(),
619 _tenuring_threshold, MaxTenuringThreshold);
620
621 if (UsePerfData) {
622 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
623 counters->update_tenuring_threshold(_tenuring_threshold);
624 counters->update_survivor_size_counters();
625 }
626
627 // Do call at minor collections?
628 // Don't check if the size_policy is ready at this
629 // level. Let the size_policy check that internally.
630 if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
631 AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
632 // Calculate optimal free space amounts
633 assert(young_gen->max_gen_size() >
634 young_gen->from_space()->capacity_in_bytes() +
635 young_gen->to_space()->capacity_in_bytes(),
636 "Sizes of space in young gen are out-of-bounds");
637
638 size_t young_live = young_gen->used_in_bytes();
639 size_t eden_live = young_gen->eden_space()->used_in_bytes();
640 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
641 size_t max_old_gen_size = old_gen->max_gen_size();
642 size_t max_eden_size = max_young_size -
643 young_gen->from_space()->capacity_in_bytes() -
644 young_gen->to_space()->capacity_in_bytes();
645
646 // Used for diagnostics
647 size_policy->clear_generation_free_space_flags();
648
649 size_policy->compute_eden_space_size(young_live,
650 eden_live,
651 cur_eden,
652 max_eden_size,
653 false /* not full gc*/);
654
655 size_policy->check_gc_overhead_limit(eden_live,
656 max_old_gen_size,
657 max_eden_size,
658 false /* not full gc*/,
659 gc_cause,
660 heap->soft_ref_policy());
661
662 size_policy->decay_supplemental_growth(false /* not full gc*/);
663 }
664 // Resize the young generation at every collection
665 // even if new sizes have not been calculated. This is
666 // to allow resizes that may have been inhibited by the
667 // relative location of the "to" and "from" spaces.
668
669 // Resizing the old gen at young collections can cause increases
670 // that don't feed back to the generation sizing policy until
671 // a full collection. Don't resize the old gen here.
672
673 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
674 size_policy->calculated_survivor_size_in_bytes());
675
676 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
677 }
678
679 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
680 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
681 // Also update() will case adaptive NUMA chunk resizing.
682 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
683 young_gen->eden_space()->update();
684
685 heap->gc_policy_counters()->update_counters();
686
687 heap->resize_all_tlabs();
688
689 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
690 }
691
692 #if COMPILER2_OR_JVMCI
693 DerivedPointerTable::update_pointers();
694 #endif
695
696 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
697
698 // Re-verify object start arrays
699 if (VerifyObjectStartArray &&
700 VerifyAfterGC) {
701 old_gen->verify_object_start_array();
702 }
703
704 // Verify all old -> young cards are now precise
705 if (VerifyRememberedSets) {
706 // Precise verification will give false positives. Until this is fixed,
707 // use imprecise verification.
708 // heap->card_table()->verify_all_young_refs_precise();
709 heap->card_table()->verify_all_young_refs_imprecise();
710 }
711
712 if (log_is_enabled(Debug, gc, heap, exit)) {
713 accumulated_time()->stop();
714 }
715
716 heap->print_heap_change(pre_gc_values);
717
718 // Track memory usage and detect low memory
719 MemoryService::track_memory_usage();
720 heap->update_counters();
721 }
722
723 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
724 HandleMark hm; // Discard invalid handles created during verification
725 Universe::verify("After GC");
726 }
727
728 heap->print_heap_after_gc();
729 heap->trace_heap_after_gc(&_gc_tracer);
730
731 scavenge_exit.update();
732
733 log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
734 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
735 scavenge_exit.ticks());
736
737 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
738
739 _gc_timer.register_gc_end();
740
741 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
742
743 return !promotion_failure_occurred;
744 }
745
746 // This method iterates over all objects in the young generation,
747 // removing all forwarding references. It then restores any preserved marks.
748 void PSScavenge::clean_up_failed_promotion() {
749 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
750 PSYoungGen* young_gen = heap->young_gen();
751
752 RemoveForwardedPointerClosure remove_fwd_ptr_closure;
753 young_gen->object_iterate(&remove_fwd_ptr_closure);
754
755 PSPromotionManager::restore_preserved_marks();
756
757 // Reset the PromotionFailureALot counters.
758 NOT_PRODUCT(heap->reset_promotion_should_fail();)
759 }
760
761 bool PSScavenge::should_attempt_scavenge() {
762 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
763 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
764
765 if (UsePerfData) {
766 counters->update_scavenge_skipped(not_skipped);
767 }
768
769 PSYoungGen* young_gen = heap->young_gen();
770 PSOldGen* old_gen = heap->old_gen();
771
772 // Do not attempt to promote unless to_space is empty
773 if (!young_gen->to_space()->is_empty()) {
774 _consecutive_skipped_scavenges++;
775 if (UsePerfData) {
776 counters->update_scavenge_skipped(to_space_not_empty);
777 }
778 return false;
779 }
780
781 // Test to see if the scavenge will likely fail.
782 PSAdaptiveSizePolicy* policy = heap->size_policy();
783
784 // A similar test is done in the policy's should_full_GC(). If this is
785 // changed, decide if that test should also be changed.
786 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
787 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
788 bool result = promotion_estimate < old_gen->free_in_bytes();
789
790 log_trace(ergo)("%s scavenge: average_promoted " SIZE_FORMAT " padded_average_promoted " SIZE_FORMAT " free in old gen " SIZE_FORMAT,
791 result ? "Do" : "Skip", (size_t) policy->average_promoted_in_bytes(),
792 (size_t) policy->padded_average_promoted_in_bytes(),
793 old_gen->free_in_bytes());
794 if (young_gen->used_in_bytes() < (size_t) policy->padded_average_promoted_in_bytes()) {
795 log_trace(ergo)(" padded_promoted_average is greater than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
796 }
797
798 if (result) {
799 _consecutive_skipped_scavenges = 0;
800 } else {
801 _consecutive_skipped_scavenges++;
802 if (UsePerfData) {
803 counters->update_scavenge_skipped(promoted_too_large);
804 }
805 }
806 return result;
807 }
808
809 // Adaptive size policy support.
810 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
811 _young_generation_boundary = v;
812 if (UseCompressedOops) {
813 _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode((oop)v);
814 }
815 }
816
817 void PSScavenge::initialize() {
818 // Arguments must have been parsed
819
820 if (AlwaysTenure || NeverTenure) {
821 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markWord::max_age + 1,
822 "MaxTenuringThreshold should be 0 or markWord::max_age + 1, but is %d", (int) MaxTenuringThreshold);
823 _tenuring_threshold = MaxTenuringThreshold;
824 } else {
825 // We want to smooth out our startup times for the AdaptiveSizePolicy
826 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
827 MaxTenuringThreshold;
828 }
829
830 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
831 PSYoungGen* young_gen = heap->young_gen();
832 PSOldGen* old_gen = heap->old_gen();
833
834 // Set boundary between young_gen and old_gen
835 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
836 "old above young");
837 set_young_generation_boundary(young_gen->eden_space()->bottom());
838
839 // Initialize ref handling object for scavenging.
840 _span_based_discoverer.set_span(young_gen->reserved());
841 _ref_processor =
842 new ReferenceProcessor(&_span_based_discoverer,
843 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
844 ParallelGCThreads, // mt processing degree
845 true, // mt discovery
846 ParallelGCThreads, // mt discovery degree
847 true, // atomic_discovery
848 NULL, // header provides liveness info
849 false);
850
851 // Cache the cardtable
852 _card_table = heap->card_table();
853
854 _counters = new CollectorCounters("Parallel young collection pauses", 0);
855 }