1 /*
2 * Copyright (c) 2002, 2017, 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 "classfile/stringTable.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc/parallel/cardTableExtension.hpp"
29 #include "gc/parallel/gcTaskManager.hpp"
30 #include "gc/parallel/parallelScavengeHeap.hpp"
31 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
32 #include "gc/parallel/psMarkSweep.hpp"
33 #include "gc/parallel/psParallelCompact.inline.hpp"
34 #include "gc/parallel/psScavenge.inline.hpp"
35 #include "gc/parallel/psTasks.hpp"
36 #include "gc/shared/collectorPolicy.hpp"
37 #include "gc/shared/gcCause.hpp"
38 #include "gc/shared/gcHeapSummary.hpp"
39 #include "gc/shared/gcId.hpp"
40 #include "gc/shared/gcLocker.inline.hpp"
41 #include "gc/shared/gcTimer.hpp"
42 #include "gc/shared/gcTrace.hpp"
43 #include "gc/shared/gcTraceTime.inline.hpp"
44 #include "gc/shared/isGCActiveMark.hpp"
45 #include "gc/shared/referencePolicy.hpp"
46 #include "gc/shared/referenceProcessor.hpp"
47 #include "gc/shared/spaceDecorator.hpp"
48 #include "memory/resourceArea.hpp"
49 #include "logging/log.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "runtime/biasedLocking.hpp"
52 #include "runtime/handles.inline.hpp"
53 #include "runtime/threadCritical.hpp"
54 #include "runtime/vmThread.hpp"
55 #include "runtime/vm_operations.hpp"
56 #include "services/memoryService.hpp"
57 #include "utilities/stack.inline.hpp"
58
59 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
60 int PSScavenge::_consecutive_skipped_scavenges = 0;
61 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
62 CardTableExtension* PSScavenge::_card_table = NULL;
63 bool PSScavenge::_survivor_overflow = false;
64 uint PSScavenge::_tenuring_threshold = 0;
65 HeapWord* PSScavenge::_young_generation_boundary = NULL;
66 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
67 elapsedTimer PSScavenge::_accumulated_time;
68 STWGCTimer PSScavenge::_gc_timer;
69 ParallelScavengeTracer PSScavenge::_gc_tracer;
70 CollectorCounters* PSScavenge::_counters = NULL;
71
72 // Define before use
73 class PSIsAliveClosure: public BoolObjectClosure {
74 public:
75 bool do_object_b(oop p) {
76 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
77 }
78 };
79
80 PSIsAliveClosure PSScavenge::_is_alive_closure;
81
82 class PSKeepAliveClosure: public OopClosure {
83 protected:
84 MutableSpace* _to_space;
85 PSPromotionManager* _promotion_manager;
86
87 public:
88 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
89 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
90 _to_space = heap->young_gen()->to_space();
91
92 assert(_promotion_manager != NULL, "Sanity");
93 }
94
95 template <class T> void do_oop_work(T* p) {
96 assert (!oopDesc::is_null(*p), "expected non-null ref");
97 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
98 "expected an oop while scanning weak refs");
99
100 // Weak refs may be visited more than once.
101 if (PSScavenge::should_scavenge(p, _to_space)) {
102 _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
103 }
104 }
105 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
106 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
107 };
108
109 class PSEvacuateFollowersClosure: public VoidClosure {
110 private:
111 PSPromotionManager* _promotion_manager;
112 public:
113 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
114
115 virtual void do_void() {
116 assert(_promotion_manager != NULL, "Sanity");
117 _promotion_manager->drain_stacks(true);
118 guarantee(_promotion_manager->stacks_empty(),
119 "stacks should be empty at this point");
120 }
121 };
122
123 class PSRefProcTaskProxy: public GCTask {
124 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
125 ProcessTask & _rp_task;
126 uint _work_id;
127 public:
128 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
129 : _rp_task(rp_task),
130 _work_id(work_id)
131 { }
132
133 private:
134 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
135 virtual void do_it(GCTaskManager* manager, uint which);
136 };
137
138 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
139 {
140 PSPromotionManager* promotion_manager =
141 PSPromotionManager::gc_thread_promotion_manager(which);
142 assert(promotion_manager != NULL, "sanity check");
143 PSKeepAliveClosure keep_alive(promotion_manager);
144 PSEvacuateFollowersClosure evac_followers(promotion_manager);
145 PSIsAliveClosure is_alive;
146 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
147 }
148
149 class PSRefEnqueueTaskProxy: public GCTask {
150 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
151 EnqueueTask& _enq_task;
152 uint _work_id;
153
154 public:
155 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
156 : _enq_task(enq_task),
157 _work_id(work_id)
158 { }
159
160 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
161 virtual void do_it(GCTaskManager* manager, uint which)
162 {
163 _enq_task.work(_work_id);
164 }
165 };
166
167 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
168 virtual void execute(ProcessTask& task);
169 virtual void execute(EnqueueTask& task);
170 };
171
172 void PSRefProcTaskExecutor::execute(ProcessTask& task)
173 {
174 GCTaskQueue* q = GCTaskQueue::create();
175 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
176 for(uint i=0; i < manager->active_workers(); i++) {
177 q->enqueue(new PSRefProcTaskProxy(task, i));
178 }
179 ParallelTaskTerminator terminator(manager->active_workers(),
180 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
181 if (task.marks_oops_alive() && manager->active_workers() > 1) {
182 for (uint j = 0; j < manager->active_workers(); j++) {
183 q->enqueue(new StealTask(&terminator));
184 }
185 }
186 manager->execute_and_wait(q);
187 }
188
189
190 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
191 {
192 GCTaskQueue* q = GCTaskQueue::create();
193 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
194 for(uint i=0; i < manager->active_workers(); i++) {
195 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
196 }
197 manager->execute_and_wait(q);
198 }
199
200 // This method contains all heap specific policy for invoking scavenge.
201 // PSScavenge::invoke_no_policy() will do nothing but attempt to
202 // scavenge. It will not clean up after failed promotions, bail out if
203 // we've exceeded policy time limits, or any other special behavior.
204 // All such policy should be placed here.
205 //
206 // Note that this method should only be called from the vm_thread while
207 // at a safepoint!
208 bool PSScavenge::invoke() {
209 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
210 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
211 assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
212
213 ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
214 PSAdaptiveSizePolicy* policy = heap->size_policy();
215 IsGCActiveMark mark;
216
217 const bool scavenge_done = PSScavenge::invoke_no_policy();
218 const bool need_full_gc = !scavenge_done ||
219 policy->should_full_GC(heap->old_gen()->free_in_bytes());
220 bool full_gc_done = false;
221
222 if (UsePerfData) {
223 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
224 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
225 counters->update_full_follows_scavenge(ffs_val);
226 }
227
228 if (need_full_gc) {
229 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
230 CollectorPolicy* cp = heap->collector_policy();
231 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
232
233 if (UseParallelOldGC) {
234 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
235 } else {
236 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
237 }
238 }
239
240 return full_gc_done;
241 }
242
243 // This method contains no policy. You should probably
244 // be calling invoke() instead.
245 bool PSScavenge::invoke_no_policy() {
246 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
247 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
248
249 _gc_timer.register_gc_start();
250
251 TimeStamp scavenge_entry;
252 TimeStamp scavenge_midpoint;
253 TimeStamp scavenge_exit;
254
255 scavenge_entry.update();
256
257 if (GCLocker::check_active_before_gc()) {
258 return false;
259 }
260
261 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
262 GCCause::Cause gc_cause = heap->gc_cause();
263
264 // Check for potential problems.
265 if (!should_attempt_scavenge()) {
266 return false;
267 }
268
269 GCIdMark gc_id_mark;
270 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
271
272 bool promotion_failure_occurred = false;
273
274 PSYoungGen* young_gen = heap->young_gen();
275 PSOldGen* old_gen = heap->old_gen();
276 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
277
278 heap->increment_total_collections();
279
280 if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
281 // Gather the feedback data for eden occupancy.
282 young_gen->eden_space()->accumulate_statistics();
283 }
284
285 heap->print_heap_before_gc();
286 heap->trace_heap_before_gc(&_gc_tracer);
287
288 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
289 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
290
291 // Fill in TLABs
292 heap->accumulate_statistics_all_tlabs();
293 heap->ensure_parsability(true); // retire TLABs
294
295 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
296 HandleMark hm; // Discard invalid handles created during verification
297 Universe::verify("Before GC");
298 }
299
300 {
301 ResourceMark rm;
302 HandleMark hm;
303
304 GCTraceCPUTime tcpu;
305 GCTraceTime(Info, gc) tm("Pause Young", NULL, gc_cause, true);
306 TraceCollectorStats tcs(counters());
307 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
308
309 if (TraceYoungGenTime) accumulated_time()->start();
310
311 // Let the size policy know we're starting
312 size_policy->minor_collection_begin();
313
314 // Verify the object start arrays.
315 if (VerifyObjectStartArray &&
316 VerifyBeforeGC) {
317 old_gen->verify_object_start_array();
318 }
319
320 // Verify no unmarked old->young roots
321 if (VerifyRememberedSets) {
322 CardTableExtension::verify_all_young_refs_imprecise();
323 }
324
325 assert(young_gen->to_space()->is_empty(),
326 "Attempt to scavenge with live objects in to_space");
327 young_gen->to_space()->clear(SpaceDecorator::Mangle);
328
329 save_to_space_top_before_gc();
330
331 #if defined(COMPILER2) || INCLUDE_JVMCI
332 DerivedPointerTable::clear();
333 #endif
334
335 reference_processor()->enable_discovery();
336 reference_processor()->setup_policy(false);
337
338 PreGCValues pre_gc_values(heap);
339
340 // Reset our survivor overflow.
341 set_survivor_overflow(false);
342
343 // We need to save the old top values before
344 // creating the promotion_manager. We pass the top
345 // values to the card_table, to prevent it from
346 // straying into the promotion labs.
347 HeapWord* old_top = old_gen->object_space()->top();
348
349 // Release all previously held resources
350 gc_task_manager()->release_all_resources();
351
352 // Set the number of GC threads to be used in this collection
353 gc_task_manager()->set_active_gang();
354 gc_task_manager()->task_idle_workers();
355 // Get the active number of workers here and use that value
356 // throughout the methods.
357 uint active_workers = gc_task_manager()->active_workers();
358
359 PSPromotionManager::pre_scavenge();
360
361 // We'll use the promotion manager again later.
362 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
363 {
364 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
365 ParallelScavengeHeap::ParStrongRootsScope psrs;
366
367 GCTaskQueue* q = GCTaskQueue::create();
368
369 if (!old_gen->object_space()->is_empty()) {
370 // There are only old-to-young pointers if there are objects
371 // in the old gen.
372 uint stripe_total = active_workers;
373 for(uint i=0; i < stripe_total; i++) {
374 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
375 }
376 }
377
378 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
379 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
380 // We scan the thread roots in parallel
381 Threads::create_thread_roots_tasks(q);
382 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
383 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
384 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
385 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
386 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
387 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
388
389 ParallelTaskTerminator terminator(
390 active_workers,
391 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
392 // If active_workers can exceed 1, add a StrealTask.
393 // PSPromotionManager::drain_stacks_depth() does not fully drain its
394 // stacks and expects a StealTask to complete the draining if
395 // ParallelGCThreads is > 1.
396 if (gc_task_manager()->workers() > 1) {
397 for (uint j = 0; j < active_workers; j++) {
398 q->enqueue(new StealTask(&terminator));
399 }
400 }
401
402 gc_task_manager()->execute_and_wait(q);
403 }
404
405 scavenge_midpoint.update();
406
407 // Process reference objects discovered during scavenge
408 {
409 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
410
411 reference_processor()->setup_policy(false); // not always_clear
412 reference_processor()->set_active_mt_degree(active_workers);
413 PSKeepAliveClosure keep_alive(promotion_manager);
414 PSEvacuateFollowersClosure evac_followers(promotion_manager);
415 ReferenceProcessorStats stats;
416 if (reference_processor()->processing_is_mt()) {
417 PSRefProcTaskExecutor task_executor;
418 stats = reference_processor()->process_discovered_references(
419 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
420 &_gc_timer);
421 } else {
422 stats = reference_processor()->process_discovered_references(
423 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
424 }
425
426 _gc_tracer.report_gc_reference_stats(stats);
427
428 // Enqueue reference objects discovered during scavenge.
429 if (reference_processor()->processing_is_mt()) {
430 PSRefProcTaskExecutor task_executor;
431 reference_processor()->enqueue_discovered_references(&task_executor);
432 } else {
433 reference_processor()->enqueue_discovered_references(NULL);
434 }
435 }
436
437 {
438 GCTraceTime(Debug, gc, phases) tm("Scrub String Table", &_gc_timer);
439 // Unlink any dead interned Strings and process the remaining live ones.
440 PSScavengeRootsClosure root_closure(promotion_manager);
441 StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
442 }
443
444 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
445 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
446 if (promotion_failure_occurred) {
447 clean_up_failed_promotion();
448 log_info(gc, promotion)("Promotion failed");
449 }
450
451 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
452
453 // Let the size policy know we're done. Note that we count promotion
454 // failure cleanup time as part of the collection (otherwise, we're
455 // implicitly saying it's mutator time).
456 size_policy->minor_collection_end(gc_cause);
457
458 if (!promotion_failure_occurred) {
459 // Swap the survivor spaces.
460 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
461 young_gen->from_space()->clear(SpaceDecorator::Mangle);
462 young_gen->swap_spaces();
463
464 size_t survived = young_gen->from_space()->used_in_bytes();
465 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
466 size_policy->update_averages(_survivor_overflow, survived, promoted);
467
468 // A successful scavenge should restart the GC time limit count which is
469 // for full GC's.
470 size_policy->reset_gc_overhead_limit_count();
471 if (UseAdaptiveSizePolicy) {
472 // Calculate the new survivor size and tenuring threshold
473
474 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
475 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
476 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
477
478 if (UsePerfData) {
479 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
480 counters->update_old_eden_size(
481 size_policy->calculated_eden_size_in_bytes());
482 counters->update_old_promo_size(
483 size_policy->calculated_promo_size_in_bytes());
484 counters->update_old_capacity(old_gen->capacity_in_bytes());
485 counters->update_young_capacity(young_gen->capacity_in_bytes());
486 counters->update_survived(survived);
487 counters->update_promoted(promoted);
488 counters->update_survivor_overflowed(_survivor_overflow);
489 }
490
491 size_t max_young_size = young_gen->max_size();
492
493 // Deciding a free ratio in the young generation is tricky, so if
494 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
495 // that the old generation size may have been limited because of them) we
496 // should then limit our young generation size using NewRatio to have it
497 // follow the old generation size.
498 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
499 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
500 }
501
502 size_t survivor_limit =
503 size_policy->max_survivor_size(max_young_size);
504 _tenuring_threshold =
505 size_policy->compute_survivor_space_size_and_threshold(
506 _survivor_overflow,
507 _tenuring_threshold,
508 survivor_limit);
509
510 log_debug(gc, age)("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max threshold " UINTX_FORMAT ")",
511 size_policy->calculated_survivor_size_in_bytes(),
512 _tenuring_threshold, MaxTenuringThreshold);
513
514 if (UsePerfData) {
515 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
516 counters->update_tenuring_threshold(_tenuring_threshold);
517 counters->update_survivor_size_counters();
518 }
519
520 // Do call at minor collections?
521 // Don't check if the size_policy is ready at this
522 // level. Let the size_policy check that internally.
523 if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
524 (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
525 // Calculate optimal free space amounts
526 assert(young_gen->max_size() >
527 young_gen->from_space()->capacity_in_bytes() +
528 young_gen->to_space()->capacity_in_bytes(),
529 "Sizes of space in young gen are out-of-bounds");
530
531 size_t young_live = young_gen->used_in_bytes();
532 size_t eden_live = young_gen->eden_space()->used_in_bytes();
533 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
534 size_t max_old_gen_size = old_gen->max_gen_size();
535 size_t max_eden_size = max_young_size -
536 young_gen->from_space()->capacity_in_bytes() -
537 young_gen->to_space()->capacity_in_bytes();
538
539 // Used for diagnostics
540 size_policy->clear_generation_free_space_flags();
541
542 size_policy->compute_eden_space_size(young_live,
543 eden_live,
544 cur_eden,
545 max_eden_size,
546 false /* not full gc*/);
547
548 size_policy->check_gc_overhead_limit(young_live,
549 eden_live,
550 max_old_gen_size,
551 max_eden_size,
552 false /* not full gc*/,
553 gc_cause,
554 heap->collector_policy());
555
556 size_policy->decay_supplemental_growth(false /* not full gc*/);
557 }
558 // Resize the young generation at every collection
559 // even if new sizes have not been calculated. This is
560 // to allow resizes that may have been inhibited by the
561 // relative location of the "to" and "from" spaces.
562
563 // Resizing the old gen at young collections can cause increases
564 // that don't feed back to the generation sizing policy until
565 // a full collection. Don't resize the old gen here.
566
567 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
568 size_policy->calculated_survivor_size_in_bytes());
569
570 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
571 }
572
573 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
574 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
575 // Also update() will case adaptive NUMA chunk resizing.
576 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
577 young_gen->eden_space()->update();
578
579 heap->gc_policy_counters()->update_counters();
580
581 heap->resize_all_tlabs();
582
583 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
584 }
585
586 #if defined(COMPILER2) || INCLUDE_JVMCI
587 DerivedPointerTable::update_pointers();
588 #endif
589
590 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
591
592 // Re-verify object start arrays
593 if (VerifyObjectStartArray &&
594 VerifyAfterGC) {
595 old_gen->verify_object_start_array();
596 }
597
598 // Verify all old -> young cards are now precise
599 if (VerifyRememberedSets) {
600 // Precise verification will give false positives. Until this is fixed,
601 // use imprecise verification.
602 // CardTableExtension::verify_all_young_refs_precise();
603 CardTableExtension::verify_all_young_refs_imprecise();
604 }
605
606 if (TraceYoungGenTime) accumulated_time()->stop();
607
608 young_gen->print_used_change(pre_gc_values.young_gen_used());
609 old_gen->print_used_change(pre_gc_values.old_gen_used());
610 MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
611
612 // Track memory usage and detect low memory
613 MemoryService::track_memory_usage();
614 heap->update_counters();
615
616 gc_task_manager()->release_idle_workers();
617 }
618
619 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
620 HandleMark hm; // Discard invalid handles created during verification
621 Universe::verify("After GC");
622 }
623
624 heap->print_heap_after_gc();
625 heap->trace_heap_after_gc(&_gc_tracer);
626
627 scavenge_exit.update();
628
629 log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
630 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
631 scavenge_exit.ticks());
632 gc_task_manager()->print_task_time_stamps();
633
634 #ifdef TRACESPINNING
635 ParallelTaskTerminator::print_termination_counts();
636 #endif
637
638 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
639
640 _gc_timer.register_gc_end();
641
642 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
643
644 return !promotion_failure_occurred;
645 }
646
647 // This method iterates over all objects in the young generation,
648 // removing all forwarding references. It then restores any preserved marks.
649 void PSScavenge::clean_up_failed_promotion() {
650 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
651 PSYoungGen* young_gen = heap->young_gen();
652
653 RemoveForwardedPointerClosure remove_fwd_ptr_closure;
654 young_gen->object_iterate(&remove_fwd_ptr_closure);
655
656 PSPromotionManager::restore_preserved_marks();
657
658 // Reset the PromotionFailureALot counters.
659 NOT_PRODUCT(heap->reset_promotion_should_fail();)
660 }
661
662 bool PSScavenge::should_attempt_scavenge() {
663 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
664 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
665
666 if (UsePerfData) {
667 counters->update_scavenge_skipped(not_skipped);
668 }
669
670 PSYoungGen* young_gen = heap->young_gen();
671 PSOldGen* old_gen = heap->old_gen();
672
673 // Do not attempt to promote unless to_space is empty
674 if (!young_gen->to_space()->is_empty()) {
675 _consecutive_skipped_scavenges++;
676 if (UsePerfData) {
677 counters->update_scavenge_skipped(to_space_not_empty);
678 }
679 return false;
680 }
681
682 // Test to see if the scavenge will likely fail.
683 PSAdaptiveSizePolicy* policy = heap->size_policy();
684
685 // A similar test is done in the policy's should_full_GC(). If this is
686 // changed, decide if that test should also be changed.
687 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
688 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
689 bool result = promotion_estimate < old_gen->free_in_bytes();
690
691 log_trace(ergo)("%s scavenge: average_promoted " SIZE_FORMAT " padded_average_promoted " SIZE_FORMAT " free in old gen " SIZE_FORMAT,
692 result ? "Do" : "Skip", (size_t) policy->average_promoted_in_bytes(),
693 (size_t) policy->padded_average_promoted_in_bytes(),
694 old_gen->free_in_bytes());
695 if (young_gen->used_in_bytes() < (size_t) policy->padded_average_promoted_in_bytes()) {
696 log_trace(ergo)(" padded_promoted_average is greater than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
697 }
698
699 if (result) {
700 _consecutive_skipped_scavenges = 0;
701 } else {
702 _consecutive_skipped_scavenges++;
703 if (UsePerfData) {
704 counters->update_scavenge_skipped(promoted_too_large);
705 }
706 }
707 return result;
708 }
709
710 // Used to add tasks
711 GCTaskManager* const PSScavenge::gc_task_manager() {
712 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
713 "shouldn't return NULL");
714 return ParallelScavengeHeap::gc_task_manager();
715 }
716
717 // Adaptive size policy support. When the young generation/old generation
718 // boundary moves, _young_generation_boundary must be reset
719 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
720 _young_generation_boundary = v;
721 if (UseCompressedOops) {
722 _young_generation_boundary_compressed = (uintptr_t)oopDesc::encode_heap_oop((oop)v);
723 }
724 }
725
726 void PSScavenge::initialize() {
727 // Arguments must have been parsed
728
729 if (AlwaysTenure || NeverTenure) {
730 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
731 "MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold);
732 _tenuring_threshold = MaxTenuringThreshold;
733 } else {
734 // We want to smooth out our startup times for the AdaptiveSizePolicy
735 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
736 MaxTenuringThreshold;
737 }
738
739 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
740 PSYoungGen* young_gen = heap->young_gen();
741 PSOldGen* old_gen = heap->old_gen();
742
743 // Set boundary between young_gen and old_gen
744 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
745 "old above young");
746 set_young_generation_boundary(young_gen->eden_space()->bottom());
747
748 // Initialize ref handling object for scavenging.
749 MemRegion mr = young_gen->reserved();
750
751 _ref_processor =
752 new ReferenceProcessor(mr, // span
753 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
754 ParallelGCThreads, // mt processing degree
755 true, // mt discovery
756 ParallelGCThreads, // mt discovery degree
757 true, // atomic_discovery
758 NULL); // header provides liveness info
759
760 // Cache the cardtable
761 _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set());
762
763 _counters = new CollectorCounters("PSScavenge", 0);
764 }