1 /*
2 * Copyright (c) 2002, 2015, 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.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.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 "oops/oop.inline.hpp"
50 #include "runtime/biasedLocking.hpp"
51 #include "runtime/fprofiler.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 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack;
71 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack;
72 CollectorCounters* PSScavenge::_counters = NULL;
73
74 // Define before use
75 class PSIsAliveClosure: public BoolObjectClosure {
76 public:
77 bool do_object_b(oop p) {
78 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
79 }
80 };
81
82 PSIsAliveClosure PSScavenge::_is_alive_closure;
83
84 class PSKeepAliveClosure: public OopClosure {
85 protected:
86 MutableSpace* _to_space;
87 PSPromotionManager* _promotion_manager;
88
89 public:
90 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
91 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
92 _to_space = heap->young_gen()->to_space();
93
94 assert(_promotion_manager != NULL, "Sanity");
95 }
96
97 template <class T> void do_oop_work(T* p) {
98 assert (!oopDesc::is_null(*p), "expected non-null ref");
99 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
100 "expected an oop while scanning weak refs");
101
102 // Weak refs may be visited more than once.
103 if (PSScavenge::should_scavenge(p, _to_space)) {
104 _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
105 }
106 }
107 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
108 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
109 };
110
111 class PSEvacuateFollowersClosure: public VoidClosure {
112 private:
113 PSPromotionManager* _promotion_manager;
114 public:
115 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
116
117 virtual void do_void() {
118 assert(_promotion_manager != NULL, "Sanity");
119 _promotion_manager->drain_stacks(true);
120 guarantee(_promotion_manager->stacks_empty(),
121 "stacks should be empty at this point");
122 }
123 };
124
125 class PSPromotionFailedClosure : public ObjectClosure {
126 virtual void do_object(oop obj) {
127 if (obj->is_forwarded()) {
128 obj->init_mark();
129 }
130 }
131 };
132
133 class PSRefProcTaskProxy: public GCTask {
134 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
135 ProcessTask & _rp_task;
136 uint _work_id;
137 public:
138 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
139 : _rp_task(rp_task),
140 _work_id(work_id)
141 { }
142
143 private:
144 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
145 virtual void do_it(GCTaskManager* manager, uint which);
146 };
147
148 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
149 {
150 PSPromotionManager* promotion_manager =
151 PSPromotionManager::gc_thread_promotion_manager(which);
152 assert(promotion_manager != NULL, "sanity check");
153 PSKeepAliveClosure keep_alive(promotion_manager);
154 PSEvacuateFollowersClosure evac_followers(promotion_manager);
155 PSIsAliveClosure is_alive;
156 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
157 }
158
159 class PSRefEnqueueTaskProxy: public GCTask {
160 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
161 EnqueueTask& _enq_task;
162 uint _work_id;
163
164 public:
165 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
166 : _enq_task(enq_task),
167 _work_id(work_id)
168 { }
169
170 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
171 virtual void do_it(GCTaskManager* manager, uint which)
172 {
173 _enq_task.work(_work_id);
174 }
175 };
176
177 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
178 virtual void execute(ProcessTask& task);
179 virtual void execute(EnqueueTask& task);
180 };
181
182 void PSRefProcTaskExecutor::execute(ProcessTask& task)
183 {
184 GCTaskQueue* q = GCTaskQueue::create();
185 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
186 for(uint i=0; i < manager->active_workers(); i++) {
187 q->enqueue(new PSRefProcTaskProxy(task, i));
188 }
189 ParallelTaskTerminator terminator(manager->active_workers(),
190 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
191 if (task.marks_oops_alive() && manager->active_workers() > 1) {
192 for (uint j = 0; j < manager->active_workers(); j++) {
193 q->enqueue(new StealTask(&terminator));
194 }
195 }
196 manager->execute_and_wait(q);
197 }
198
199
200 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
201 {
202 GCTaskQueue* q = GCTaskQueue::create();
203 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
204 for(uint i=0; i < manager->active_workers(); i++) {
205 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
206 }
207 manager->execute_and_wait(q);
208 }
209
210 // This method contains all heap specific policy for invoking scavenge.
211 // PSScavenge::invoke_no_policy() will do nothing but attempt to
212 // scavenge. It will not clean up after failed promotions, bail out if
213 // we've exceeded policy time limits, or any other special behavior.
214 // All such policy should be placed here.
215 //
216 // Note that this method should only be called from the vm_thread while
217 // at a safepoint!
218 bool PSScavenge::invoke() {
219 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
220 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
221 assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
222
223 ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
224 PSAdaptiveSizePolicy* policy = heap->size_policy();
225 IsGCActiveMark mark;
226
227 const bool scavenge_done = PSScavenge::invoke_no_policy();
228 const bool need_full_gc = !scavenge_done ||
229 policy->should_full_GC(heap->old_gen()->free_in_bytes());
230 bool full_gc_done = false;
231
232 if (UsePerfData) {
233 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
234 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
235 counters->update_full_follows_scavenge(ffs_val);
236 }
237
238 if (need_full_gc) {
239 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
240 CollectorPolicy* cp = heap->collector_policy();
241 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
242
243 if (UseParallelOldGC) {
244 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
245 } else {
246 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
247 }
248 }
249
250 return full_gc_done;
251 }
252
253 // This method contains no policy. You should probably
254 // be calling invoke() instead.
255 bool PSScavenge::invoke_no_policy() {
256 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
257 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
258
259 assert(_preserved_mark_stack.is_empty(), "should be empty");
260 assert(_preserved_oop_stack.is_empty(), "should be empty");
261
262 _gc_timer.register_gc_start();
263
264 TimeStamp scavenge_entry;
265 TimeStamp scavenge_midpoint;
266 TimeStamp scavenge_exit;
267
268 scavenge_entry.update();
269
270 if (GC_locker::check_active_before_gc()) {
271 return false;
272 }
273
274 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
275 GCCause::Cause gc_cause = heap->gc_cause();
276
277 // Check for potential problems.
278 if (!should_attempt_scavenge()) {
279 return false;
280 }
281
282 GCIdMark gc_id_mark;
283 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
284
285 bool promotion_failure_occurred = false;
286
287 PSYoungGen* young_gen = heap->young_gen();
288 PSOldGen* old_gen = heap->old_gen();
289 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
290
291 heap->increment_total_collections();
292
293 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
294
295 if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
296 // Gather the feedback data for eden occupancy.
297 young_gen->eden_space()->accumulate_statistics();
298 }
299
300 if (ZapUnusedHeapArea) {
301 // Save information needed to minimize mangling
302 heap->record_gen_tops_before_GC();
303 }
304
305 heap->print_heap_before_gc();
306 heap->trace_heap_before_gc(&_gc_tracer);
307
308 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
309 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
310
311 size_t prev_used = heap->used();
312
313 // Fill in TLABs
314 heap->accumulate_statistics_all_tlabs();
315 heap->ensure_parsability(true); // retire TLABs
316
317 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
318 HandleMark hm; // Discard invalid handles created during verification
319 Universe::verify(" VerifyBeforeGC:");
320 }
321
322 {
323 ResourceMark rm;
324 HandleMark hm;
325
326 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
327 GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
328 TraceCollectorStats tcs(counters());
329 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
330
331 if (TraceYoungGenTime) accumulated_time()->start();
332
333 // Let the size policy know we're starting
334 size_policy->minor_collection_begin();
335
336 // Verify the object start arrays.
337 if (VerifyObjectStartArray &&
338 VerifyBeforeGC) {
339 old_gen->verify_object_start_array();
340 }
341
342 // Verify no unmarked old->young roots
343 if (VerifyRememberedSets) {
344 CardTableExtension::verify_all_young_refs_imprecise();
345 }
346
347 if (!ScavengeWithObjectsInToSpace) {
348 assert(young_gen->to_space()->is_empty(),
349 "Attempt to scavenge with live objects in to_space");
350 young_gen->to_space()->clear(SpaceDecorator::Mangle);
351 } else if (ZapUnusedHeapArea) {
352 young_gen->to_space()->mangle_unused_area();
353 }
354 save_to_space_top_before_gc();
355
356 COMPILER2_PRESENT(DerivedPointerTable::clear());
357
358 reference_processor()->enable_discovery();
359 reference_processor()->setup_policy(false);
360
361 // We track how much was promoted to the next generation for
362 // the AdaptiveSizePolicy.
363 size_t old_gen_used_before = old_gen->used_in_bytes();
364
365 // For PrintGCDetails
366 size_t young_gen_used_before = young_gen->used_in_bytes();
367
368 // Reset our survivor overflow.
369 set_survivor_overflow(false);
370
371 // We need to save the old top values before
372 // creating the promotion_manager. We pass the top
373 // values to the card_table, to prevent it from
374 // straying into the promotion labs.
375 HeapWord* old_top = old_gen->object_space()->top();
376
377 // Release all previously held resources
378 gc_task_manager()->release_all_resources();
379
380 // Set the number of GC threads to be used in this collection
381 gc_task_manager()->set_active_gang();
382 gc_task_manager()->task_idle_workers();
383 // Get the active number of workers here and use that value
384 // throughout the methods.
385 uint active_workers = gc_task_manager()->active_workers();
386
387 PSPromotionManager::pre_scavenge();
388
389 // We'll use the promotion manager again later.
390 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
391 {
392 GCTraceTime tm("Scavenge", false, false, &_gc_timer);
393 ParallelScavengeHeap::ParStrongRootsScope psrs;
394
395 GCTaskQueue* q = GCTaskQueue::create();
396
397 if (!old_gen->object_space()->is_empty()) {
398 // There are only old-to-young pointers if there are objects
399 // in the old gen.
400 uint stripe_total = active_workers;
401 for(uint i=0; i < stripe_total; i++) {
402 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
403 }
404 }
405
406 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
407 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
408 // We scan the thread roots in parallel
409 Threads::create_thread_roots_tasks(q);
410 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
415 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
416 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
417
418 ParallelTaskTerminator terminator(
419 active_workers,
420 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
421 if (active_workers > 1) {
422 for (uint j = 0; j < active_workers; j++) {
423 q->enqueue(new StealTask(&terminator));
424 }
425 }
426
427 gc_task_manager()->execute_and_wait(q);
428 }
429
430 scavenge_midpoint.update();
431
432 // Process reference objects discovered during scavenge
433 {
434 GCTraceTime tm("References", false, false, &_gc_timer);
435
436 reference_processor()->setup_policy(false); // not always_clear
437 reference_processor()->set_active_mt_degree(active_workers);
438 PSKeepAliveClosure keep_alive(promotion_manager);
439 PSEvacuateFollowersClosure evac_followers(promotion_manager);
440 ReferenceProcessorStats stats;
441 if (reference_processor()->processing_is_mt()) {
442 PSRefProcTaskExecutor task_executor;
443 stats = reference_processor()->process_discovered_references(
444 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
445 &_gc_timer);
446 } else {
447 stats = reference_processor()->process_discovered_references(
448 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
449 }
450
451 _gc_tracer.report_gc_reference_stats(stats);
452
453 // Enqueue reference objects discovered during scavenge.
454 if (reference_processor()->processing_is_mt()) {
455 PSRefProcTaskExecutor task_executor;
456 reference_processor()->enqueue_discovered_references(&task_executor);
457 } else {
458 reference_processor()->enqueue_discovered_references(NULL);
459 }
460 }
461
462 {
463 GCTraceTime tm("StringTable", false, false, &_gc_timer);
464 // Unlink any dead interned Strings and process the remaining live ones.
465 PSScavengeRootsClosure root_closure(promotion_manager);
466 StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
467 }
468
469 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
470 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
471 if (promotion_failure_occurred) {
472 clean_up_failed_promotion();
473 if (PrintGC) {
474 gclog_or_tty->print("--");
475 }
476 }
477
478 // Let the size policy know we're done. Note that we count promotion
479 // failure cleanup time as part of the collection (otherwise, we're
480 // implicitly saying it's mutator time).
481 size_policy->minor_collection_end(gc_cause);
482
483 if (!promotion_failure_occurred) {
484 // Swap the survivor spaces.
485 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
486 young_gen->from_space()->clear(SpaceDecorator::Mangle);
487 young_gen->swap_spaces();
488
489 size_t survived = young_gen->from_space()->used_in_bytes();
490 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
491 size_policy->update_averages(_survivor_overflow, survived, promoted);
492
493 // A successful scavenge should restart the GC time limit count which is
494 // for full GC's.
495 size_policy->reset_gc_overhead_limit_count();
496 if (UseAdaptiveSizePolicy) {
497 // Calculate the new survivor size and tenuring threshold
498
499 if (PrintAdaptiveSizePolicy) {
500 gclog_or_tty->print("AdaptiveSizeStart: ");
501 gclog_or_tty->stamp();
502 gclog_or_tty->print_cr(" collection: %d ",
503 heap->total_collections());
504
505 if (Verbose) {
506 gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
507 " young_gen_capacity: " SIZE_FORMAT,
508 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
509 }
510 }
511
512
513 if (UsePerfData) {
514 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
515 counters->update_old_eden_size(
516 size_policy->calculated_eden_size_in_bytes());
517 counters->update_old_promo_size(
518 size_policy->calculated_promo_size_in_bytes());
519 counters->update_old_capacity(old_gen->capacity_in_bytes());
520 counters->update_young_capacity(young_gen->capacity_in_bytes());
521 counters->update_survived(survived);
522 counters->update_promoted(promoted);
523 counters->update_survivor_overflowed(_survivor_overflow);
524 }
525
526 size_t max_young_size = young_gen->max_size();
527
528 // Deciding a free ratio in the young generation is tricky, so if
529 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
530 // that the old generation size may have been limited because of them) we
531 // should then limit our young generation size using NewRatio to have it
532 // follow the old generation size.
533 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
534 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
535 }
536
537 size_t survivor_limit =
538 size_policy->max_survivor_size(max_young_size);
539 _tenuring_threshold =
540 size_policy->compute_survivor_space_size_and_threshold(
541 _survivor_overflow,
542 _tenuring_threshold,
543 survivor_limit);
544
545 if (PrintTenuringDistribution) {
546 gclog_or_tty->cr();
547 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u"
548 " (max threshold " UINTX_FORMAT ")",
549 size_policy->calculated_survivor_size_in_bytes(),
550 _tenuring_threshold, MaxTenuringThreshold);
551 }
552
553 if (UsePerfData) {
554 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
555 counters->update_tenuring_threshold(_tenuring_threshold);
556 counters->update_survivor_size_counters();
557 }
558
559 // Do call at minor collections?
560 // Don't check if the size_policy is ready at this
561 // level. Let the size_policy check that internally.
562 if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
563 (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
564 // Calculate optimal free space amounts
565 assert(young_gen->max_size() >
566 young_gen->from_space()->capacity_in_bytes() +
567 young_gen->to_space()->capacity_in_bytes(),
568 "Sizes of space in young gen are out-of-bounds");
569
570 size_t young_live = young_gen->used_in_bytes();
571 size_t eden_live = young_gen->eden_space()->used_in_bytes();
572 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
573 size_t max_old_gen_size = old_gen->max_gen_size();
574 size_t max_eden_size = max_young_size -
575 young_gen->from_space()->capacity_in_bytes() -
576 young_gen->to_space()->capacity_in_bytes();
577
578 // Used for diagnostics
579 size_policy->clear_generation_free_space_flags();
580
581 size_policy->compute_eden_space_size(young_live,
582 eden_live,
583 cur_eden,
584 max_eden_size,
585 false /* not full gc*/);
586
587 size_policy->check_gc_overhead_limit(young_live,
588 eden_live,
589 max_old_gen_size,
590 max_eden_size,
591 false /* not full gc*/,
592 gc_cause,
593 heap->collector_policy());
594
595 size_policy->decay_supplemental_growth(false /* not full gc*/);
596 }
597 // Resize the young generation at every collection
598 // even if new sizes have not been calculated. This is
599 // to allow resizes that may have been inhibited by the
600 // relative location of the "to" and "from" spaces.
601
602 // Resizing the old gen at young collections can cause increases
603 // that don't feed back to the generation sizing policy until
604 // a full collection. Don't resize the old gen here.
605
606 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
607 size_policy->calculated_survivor_size_in_bytes());
608
609 if (PrintAdaptiveSizePolicy) {
610 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
611 heap->total_collections());
612 }
613 }
614
615 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
616 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
617 // Also update() will case adaptive NUMA chunk resizing.
618 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
619 young_gen->eden_space()->update();
620
621 heap->gc_policy_counters()->update_counters();
622
623 heap->resize_all_tlabs();
624
625 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
626 }
627
628 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
629
630 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
631
632 {
633 GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);
634
635 CodeCache::prune_scavenge_root_nmethods();
636 }
637
638 // Re-verify object start arrays
639 if (VerifyObjectStartArray &&
640 VerifyAfterGC) {
641 old_gen->verify_object_start_array();
642 }
643
644 // Verify all old -> young cards are now precise
645 if (VerifyRememberedSets) {
646 // Precise verification will give false positives. Until this is fixed,
647 // use imprecise verification.
648 // CardTableExtension::verify_all_young_refs_precise();
649 CardTableExtension::verify_all_young_refs_imprecise();
650 }
651
652 if (TraceYoungGenTime) accumulated_time()->stop();
653
654 if (PrintGC) {
655 if (PrintGCDetails) {
656 // Don't print a GC timestamp here. This is after the GC so
657 // would be confusing.
658 young_gen->print_used_change(young_gen_used_before);
659 }
660 heap->print_heap_change(prev_used);
661 }
662
663 // Track memory usage and detect low memory
664 MemoryService::track_memory_usage();
665 heap->update_counters();
666
667 gc_task_manager()->release_idle_workers();
668 }
669
670 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
671 HandleMark hm; // Discard invalid handles created during verification
672 Universe::verify(" VerifyAfterGC:");
673 }
674
675 heap->print_heap_after_gc();
676 heap->trace_heap_after_gc(&_gc_tracer);
677 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
678
679 if (ZapUnusedHeapArea) {
680 young_gen->eden_space()->check_mangled_unused_area_complete();
681 young_gen->from_space()->check_mangled_unused_area_complete();
682 young_gen->to_space()->check_mangled_unused_area_complete();
683 }
684
685 scavenge_exit.update();
686
687 if (PrintGCTaskTimeStamps) {
688 tty->print_cr("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
689 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
690 scavenge_exit.ticks());
691 gc_task_manager()->print_task_time_stamps();
692 }
693
694 #ifdef TRACESPINNING
695 ParallelTaskTerminator::print_termination_counts();
696 #endif
697
698
699 _gc_timer.register_gc_end();
700
701 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
702
703 return !promotion_failure_occurred;
704 }
705
706 // This method iterates over all objects in the young generation,
707 // unforwarding markOops. It then restores any preserved mark oops,
708 // and clears the _preserved_mark_stack.
709 void PSScavenge::clean_up_failed_promotion() {
710 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
711 PSYoungGen* young_gen = heap->young_gen();
712
713 {
714 ResourceMark rm;
715
716 // Unforward all pointers in the young gen.
717 PSPromotionFailedClosure unforward_closure;
718 young_gen->object_iterate(&unforward_closure);
719
720 if (PrintGC && Verbose) {
721 gclog_or_tty->print_cr("Restoring " SIZE_FORMAT " marks", _preserved_oop_stack.size());
722 }
723
724 // Restore any saved marks.
725 while (!_preserved_oop_stack.is_empty()) {
726 oop obj = _preserved_oop_stack.pop();
727 markOop mark = _preserved_mark_stack.pop();
728 obj->set_mark(mark);
729 }
730
731 // Clear the preserved mark and oop stack caches.
732 _preserved_mark_stack.clear(true);
733 _preserved_oop_stack.clear(true);
734 }
735
736 // Reset the PromotionFailureALot counters.
737 NOT_PRODUCT(heap->reset_promotion_should_fail();)
738 }
739
740 // This method is called whenever an attempt to promote an object
741 // fails. Some markOops will need preservation, some will not. Note
742 // that the entire eden is traversed after a failed promotion, with
743 // all forwarded headers replaced by the default markOop. This means
744 // it is not necessary to preserve most markOops.
745 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
746 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
747 // Should use per-worker private stacks here rather than
748 // locking a common pair of stacks.
749 ThreadCritical tc;
750 _preserved_oop_stack.push(obj);
751 _preserved_mark_stack.push(obj_mark);
752 }
753 }
754
755 bool PSScavenge::should_attempt_scavenge() {
756 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
757 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
758
759 if (UsePerfData) {
760 counters->update_scavenge_skipped(not_skipped);
761 }
762
763 PSYoungGen* young_gen = heap->young_gen();
764 PSOldGen* old_gen = heap->old_gen();
765
766 if (!ScavengeWithObjectsInToSpace) {
767 // Do not attempt to promote unless to_space is empty
768 if (!young_gen->to_space()->is_empty()) {
769 _consecutive_skipped_scavenges++;
770 if (UsePerfData) {
771 counters->update_scavenge_skipped(to_space_not_empty);
772 }
773 return false;
774 }
775 }
776
777 // Test to see if the scavenge will likely fail.
778 PSAdaptiveSizePolicy* policy = heap->size_policy();
779
780 // A similar test is done in the policy's should_full_GC(). If this is
781 // changed, decide if that test should also be changed.
782 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
783 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
784 bool result = promotion_estimate < old_gen->free_in_bytes();
785
786 if (PrintGCDetails && Verbose) {
787 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
788 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
789 " padded_average_promoted " SIZE_FORMAT
790 " free in old gen " SIZE_FORMAT,
791 (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() <
795 (size_t) policy->padded_average_promoted_in_bytes()) {
796 gclog_or_tty->print_cr(" padded_promoted_average is greater"
797 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
798 }
799 }
800
801 if (result) {
802 _consecutive_skipped_scavenges = 0;
803 } else {
804 _consecutive_skipped_scavenges++;
805 if (UsePerfData) {
806 counters->update_scavenge_skipped(promoted_too_large);
807 }
808 }
809 return result;
810 }
811
812 // Used to add tasks
813 GCTaskManager* const PSScavenge::gc_task_manager() {
814 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
815 "shouldn't return NULL");
816 return ParallelScavengeHeap::gc_task_manager();
817 }
818
819 void PSScavenge::initialize() {
820 // Arguments must have been parsed
821
822 if (AlwaysTenure || NeverTenure) {
823 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
824 err_msg("MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold));
825 _tenuring_threshold = MaxTenuringThreshold;
826 } else {
827 // We want to smooth out our startup times for the AdaptiveSizePolicy
828 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
829 MaxTenuringThreshold;
830 }
831
832 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
833 PSYoungGen* young_gen = heap->young_gen();
834 PSOldGen* old_gen = heap->old_gen();
835
836 // Set boundary between young_gen and old_gen
837 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
838 "old above young");
839 set_young_generation_boundary(young_gen->eden_space()->bottom());
840
841 // Initialize ref handling object for scavenging.
842 MemRegion mr = young_gen->reserved();
843
844 _ref_processor =
845 new ReferenceProcessor(mr, // span
846 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
847 ParallelGCThreads, // mt processing degree
848 true, // mt discovery
849 ParallelGCThreads, // mt discovery degree
850 true, // atomic_discovery
851 NULL); // header provides liveness info
852
853 // Cache the cardtable
854 _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set());
855
856 _counters = new CollectorCounters("PSScavenge", 0);
857 }