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