1
2 /*
3 * Copyright (c) 2002, 2014, Oracle and/or its affiliates. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
30 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
33 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
34 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
35 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
36 #include "gc_implementation/parallelScavenge/psTasks.hpp"
37 #include "gc_implementation/shared/gcHeapSummary.hpp"
38 #include "gc_implementation/shared/gcTimer.hpp"
39 #include "gc_implementation/shared/gcTrace.hpp"
40 #include "gc_implementation/shared/gcTraceTime.hpp"
41 #include "gc_implementation/shared/isGCActiveMark.hpp"
42 #include "gc_implementation/shared/spaceDecorator.hpp"
43 #include "gc_interface/gcCause.hpp"
44 #include "memory/collectorPolicy.hpp"
45 #include "memory/gcLocker.inline.hpp"
46 #include "memory/referencePolicy.hpp"
47 #include "memory/referenceProcessor.hpp"
48 #include "memory/resourceArea.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "oops/oop.psgc.inline.hpp"
51 #include "runtime/biasedLocking.hpp"
52 #include "runtime/fprofiler.hpp"
53 #include "runtime/handles.inline.hpp"
54 #include "runtime/threadCritical.hpp"
55 #include "runtime/vmThread.hpp"
56 #include "runtime/vm_operations.hpp"
57 #include "services/memoryService.hpp"
58 #include "utilities/stack.inline.hpp"
59
60
61 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
62 int PSScavenge::_consecutive_skipped_scavenges = 0;
63 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
64 CardTableExtension* PSScavenge::_card_table = NULL;
65 bool PSScavenge::_survivor_overflow = false;
66 uint PSScavenge::_tenuring_threshold = 0;
67 HeapWord* PSScavenge::_young_generation_boundary = NULL;
68 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
69 elapsedTimer PSScavenge::_accumulated_time;
70 STWGCTimer PSScavenge::_gc_timer;
71 ParallelScavengeTracer PSScavenge::_gc_tracer;
72 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack;
73 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack;
74 CollectorCounters* PSScavenge::_counters = NULL;
75
76 // Define before use
77 class PSIsAliveClosure: public BoolObjectClosure {
78 public:
79 bool do_object_b(oop p) {
80 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
81 }
82 };
83
84 PSIsAliveClosure PSScavenge::_is_alive_closure;
85
86 class PSKeepAliveClosure: public OopClosure {
87 protected:
88 MutableSpace* _to_space;
89 PSPromotionManager* _promotion_manager;
90
91 public:
92 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
93 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
94 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
95 _to_space = heap->young_gen()->to_space();
96
97 assert(_promotion_manager != NULL, "Sanity");
98 }
99
100 template <class T> void do_oop_work(T* p) {
101 assert (!oopDesc::is_null(*p), "expected non-null ref");
102 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
103 "expected an oop while scanning weak refs");
104
105 // Weak refs may be visited more than once.
106 if (PSScavenge::should_scavenge(p, _to_space)) {
107 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);
108 }
109 }
110 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
111 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
112 };
113
114 class PSEvacuateFollowersClosure: public VoidClosure {
115 private:
116 PSPromotionManager* _promotion_manager;
117 public:
118 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
119
120 virtual void do_void() {
121 assert(_promotion_manager != NULL, "Sanity");
122 _promotion_manager->drain_stacks(true);
123 guarantee(_promotion_manager->stacks_empty(),
124 "stacks should be empty at this point");
125 }
126 };
127
128 class PSPromotionFailedClosure : public ObjectClosure {
129 virtual void do_object(oop obj) {
130 if (obj->is_forwarded()) {
131 obj->init_mark();
132 }
133 }
134 };
135
136 class PSRefProcTaskProxy: public GCTask {
137 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
138 ProcessTask & _rp_task;
139 uint _work_id;
140 public:
141 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
142 : _rp_task(rp_task),
143 _work_id(work_id)
144 { }
145
146 private:
147 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
148 virtual void do_it(GCTaskManager* manager, uint which);
149 };
150
151 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
152 {
153 PSPromotionManager* promotion_manager =
154 PSPromotionManager::gc_thread_promotion_manager(which);
155 assert(promotion_manager != NULL, "sanity check");
156 PSKeepAliveClosure keep_alive(promotion_manager);
157 PSEvacuateFollowersClosure evac_followers(promotion_manager);
158 PSIsAliveClosure is_alive;
159 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
160 }
161
162 class PSRefEnqueueTaskProxy: public GCTask {
163 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
164 EnqueueTask& _enq_task;
165 uint _work_id;
166
167 public:
168 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
169 : _enq_task(enq_task),
170 _work_id(work_id)
171 { }
172
173 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
174 virtual void do_it(GCTaskManager* manager, uint which)
175 {
176 _enq_task.work(_work_id);
177 }
178 };
179
180 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
181 virtual void execute(ProcessTask& task);
182 virtual void execute(EnqueueTask& task);
183 };
184
185 void PSRefProcTaskExecutor::execute(ProcessTask& task)
186 {
187 GCTaskQueue* q = GCTaskQueue::create();
188 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
189 for(uint i=0; i < manager->active_workers(); i++) {
190 q->enqueue(new PSRefProcTaskProxy(task, i));
191 }
192 ParallelTaskTerminator terminator(manager->active_workers(),
193 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
194 if (task.marks_oops_alive() && manager->active_workers() > 1) {
195 for (uint j = 0; j < manager->active_workers(); j++) {
196 q->enqueue(new StealTask(&terminator));
197 }
198 }
199 manager->execute_and_wait(q);
200 }
201
202
203 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
204 {
205 GCTaskQueue* q = GCTaskQueue::create();
206 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
207 for(uint i=0; i < manager->active_workers(); i++) {
208 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
209 }
210 manager->execute_and_wait(q);
211 }
212
213 // This method contains all heap specific policy for invoking scavenge.
214 // PSScavenge::invoke_no_policy() will do nothing but attempt to
215 // scavenge. It will not clean up after failed promotions, bail out if
216 // we've exceeded policy time limits, or any other special behavior.
217 // All such policy should be placed here.
218 //
219 // Note that this method should only be called from the vm_thread while
220 // at a safepoint!
221 bool PSScavenge::invoke() {
222 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
223 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
224 assert(!Universe::heap()->is_gc_active(), "not reentrant");
225
226 ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
227 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
228
229 PSAdaptiveSizePolicy* policy = heap->size_policy();
230 IsGCActiveMark mark;
231
232 const bool scavenge_done = PSScavenge::invoke_no_policy();
233 const bool need_full_gc = !scavenge_done ||
234 policy->should_full_GC(heap->old_gen()->free_in_bytes());
235 bool full_gc_done = false;
236
237 if (UsePerfData) {
238 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
239 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
240 counters->update_full_follows_scavenge(ffs_val);
241 }
242
243 if (need_full_gc) {
244 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
245 CollectorPolicy* cp = heap->collector_policy();
246 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
247
248 if (UseParallelOldGC) {
249 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
250 } else {
251 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
252 }
253 }
254
255 return full_gc_done;
256 }
257
258 // This method contains no policy. You should probably
259 // be calling invoke() instead.
260 bool PSScavenge::invoke_no_policy() {
261 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
262 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
263
264 assert(_preserved_mark_stack.is_empty(), "should be empty");
265 assert(_preserved_oop_stack.is_empty(), "should be empty");
266
267 _gc_timer.register_gc_start();
268
269 TimeStamp scavenge_entry;
270 TimeStamp scavenge_midpoint;
271 TimeStamp scavenge_exit;
272
273 scavenge_entry.update();
274
275 if (GC_locker::check_active_before_gc()) {
276 return false;
277 }
278
279 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
280 GCCause::Cause gc_cause = heap->gc_cause();
281 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
282
283 // Check for potential problems.
284 if (!should_attempt_scavenge()) {
285 return false;
286 }
287
288 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
289
290 bool promotion_failure_occurred = false;
291
292 PSYoungGen* young_gen = heap->young_gen();
293 PSOldGen* old_gen = heap->old_gen();
294 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
295
296 heap->increment_total_collections();
297
298 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
299
300 if ((gc_cause != GCCause::_java_lang_system_gc) ||
301 UseAdaptiveSizePolicyWithSystemGC) {
302 // Gather the feedback data for eden occupancy.
303 young_gen->eden_space()->accumulate_statistics();
304 }
305
306 if (ZapUnusedHeapArea) {
307 // Save information needed to minimize mangling
308 heap->record_gen_tops_before_GC();
309 }
310
311 heap->print_heap_before_gc();
312 heap->trace_heap_before_gc(&_gc_tracer);
313
314 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
315 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
316
317 size_t prev_used = heap->used();
318
319 // Fill in TLABs
320 heap->accumulate_statistics_all_tlabs();
321 heap->ensure_parsability(true); // retire TLABs
322
323 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
324 HandleMark hm; // Discard invalid handles created during verification
325 Universe::verify(" VerifyBeforeGC:");
326 }
327
328 {
329 ResourceMark rm;
330 HandleMark hm;
331
332 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
333 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
334 GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
335 TraceCollectorStats tcs(counters());
336 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
337
338 if (TraceGen0Time) accumulated_time()->start();
339
340 // Let the size policy know we're starting
341 size_policy->minor_collection_begin();
342
343 // Verify the object start arrays.
344 if (VerifyObjectStartArray &&
345 VerifyBeforeGC) {
346 old_gen->verify_object_start_array();
347 }
348
349 // Verify no unmarked old->young roots
350 if (VerifyRememberedSets) {
351 CardTableExtension::verify_all_young_refs_imprecise();
352 }
353
354 if (!ScavengeWithObjectsInToSpace) {
355 assert(young_gen->to_space()->is_empty(),
356 "Attempt to scavenge with live objects in to_space");
357 young_gen->to_space()->clear(SpaceDecorator::Mangle);
358 } else if (ZapUnusedHeapArea) {
359 young_gen->to_space()->mangle_unused_area();
360 }
361 save_to_space_top_before_gc();
362
363 COMPILER2_PRESENT(DerivedPointerTable::clear());
364
365 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
366 reference_processor()->setup_policy(false);
367
368 // We track how much was promoted to the next generation for
369 // the AdaptiveSizePolicy.
370 size_t old_gen_used_before = old_gen->used_in_bytes();
371
372 // For PrintGCDetails
373 size_t young_gen_used_before = young_gen->used_in_bytes();
374
375 // Reset our survivor overflow.
376 set_survivor_overflow(false);
377
378 // We need to save the old top values before
379 // creating the promotion_manager. We pass the top
380 // values to the card_table, to prevent it from
381 // straying into the promotion labs.
382 HeapWord* old_top = old_gen->object_space()->top();
383
384 // Release all previously held resources
385 gc_task_manager()->release_all_resources();
386
387 // Set the number of GC threads to be used in this collection
388 gc_task_manager()->set_active_gang();
389 gc_task_manager()->task_idle_workers();
390 // Get the active number of workers here and use that value
391 // throughout the methods.
392 uint active_workers = gc_task_manager()->active_workers();
393 heap->set_par_threads(active_workers);
394
395 PSPromotionManager::pre_scavenge();
396
397 // We'll use the promotion manager again later.
398 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
399 {
400 GCTraceTime tm("Scavenge", false, false, &_gc_timer);
401 ParallelScavengeHeap::ParStrongRootsScope psrs;
402
403 GCTaskQueue* q = GCTaskQueue::create();
404
405 if (!old_gen->object_space()->is_empty()) {
406 // There are only old-to-young pointers if there are objects
407 // in the old gen.
408 uint stripe_total = active_workers;
409 for(uint i=0; i < stripe_total; i++) {
410 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
411 }
412 }
413
414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
415 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
416 // We scan the thread roots in parallel
417 Threads::create_thread_roots_tasks(q);
418 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
419 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
420 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
421 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
422 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
423 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
424 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
425
426 ParallelTaskTerminator terminator(
427 active_workers,
428 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
429 if (active_workers > 1) {
430 for (uint j = 0; j < active_workers; j++) {
431 q->enqueue(new StealTask(&terminator));
432 }
433 }
434
435 gc_task_manager()->execute_and_wait(q);
436 }
437
438 scavenge_midpoint.update();
439
440 // Process reference objects discovered during scavenge
441 {
442 GCTraceTime tm("References", false, false, &_gc_timer);
443
444 reference_processor()->setup_policy(false); // not always_clear
445 reference_processor()->set_active_mt_degree(active_workers);
446 PSKeepAliveClosure keep_alive(promotion_manager);
447 PSEvacuateFollowersClosure evac_followers(promotion_manager);
448 ReferenceProcessorStats stats;
449 if (reference_processor()->processing_is_mt()) {
450 PSRefProcTaskExecutor task_executor;
451 stats = reference_processor()->process_discovered_references(
452 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
453 &_gc_timer);
454 } else {
455 stats = reference_processor()->process_discovered_references(
456 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
457 }
458
459 _gc_tracer.report_gc_reference_stats(stats);
460
461 // Enqueue reference objects discovered during scavenge.
462 if (reference_processor()->processing_is_mt()) {
463 PSRefProcTaskExecutor task_executor;
464 reference_processor()->enqueue_discovered_references(&task_executor);
465 } else {
466 reference_processor()->enqueue_discovered_references(NULL);
467 }
468 }
469
470 {
471 GCTraceTime tm("StringTable", false, false, &_gc_timer);
472 // Unlink any dead interned Strings and process the remaining live ones.
473 PSScavengeRootsClosure root_closure(promotion_manager);
474 StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
475 }
476
477 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
478 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
479 if (promotion_failure_occurred) {
480 clean_up_failed_promotion();
481 if (PrintGC) {
482 gclog_or_tty->print("--");
483 }
484 }
485
486 // Let the size policy know we're done. Note that we count promotion
487 // failure cleanup time as part of the collection (otherwise, we're
488 // implicitly saying it's mutator time).
489 size_policy->minor_collection_end(gc_cause);
490
491 if (!promotion_failure_occurred) {
492 // Swap the survivor spaces.
493 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
494 young_gen->from_space()->clear(SpaceDecorator::Mangle);
495 young_gen->swap_spaces();
496
497 size_t survived = young_gen->from_space()->used_in_bytes();
498 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
499 size_policy->update_averages(_survivor_overflow, survived, promoted);
500
501 // A successful scavenge should restart the GC time limit count which is
502 // for full GC's.
503 size_policy->reset_gc_overhead_limit_count();
504 if (UseAdaptiveSizePolicy) {
505 // Calculate the new survivor size and tenuring threshold
506
507 if (PrintAdaptiveSizePolicy) {
508 gclog_or_tty->print("AdaptiveSizeStart: ");
509 gclog_or_tty->stamp();
510 gclog_or_tty->print_cr(" collection: %d ",
511 heap->total_collections());
512
513 if (Verbose) {
514 gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
515 " young_gen_capacity: " SIZE_FORMAT,
516 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
517 }
518 }
519
520
521 if (UsePerfData) {
522 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
523 counters->update_old_eden_size(
524 size_policy->calculated_eden_size_in_bytes());
525 counters->update_old_promo_size(
526 size_policy->calculated_promo_size_in_bytes());
527 counters->update_old_capacity(old_gen->capacity_in_bytes());
528 counters->update_young_capacity(young_gen->capacity_in_bytes());
529 counters->update_survived(survived);
530 counters->update_promoted(promoted);
531 counters->update_survivor_overflowed(_survivor_overflow);
532 }
533
534 size_t max_young_size = young_gen->max_size();
535
536 // Deciding a free ratio in the young generation is tricky, so if
537 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
538 // that the old generation size may have been limited because of them) we
539 // should then limit our young generation size using NewRatio to have it
540 // follow the old generation size.
541 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
542 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
543 }
544
545 size_t survivor_limit =
546 size_policy->max_survivor_size(max_young_size);
547 _tenuring_threshold =
548 size_policy->compute_survivor_space_size_and_threshold(
549 _survivor_overflow,
550 _tenuring_threshold,
551 survivor_limit);
552
553 if (PrintTenuringDistribution) {
554 gclog_or_tty->cr();
555 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold "
556 UINTX_FORMAT " (max threshold " UINTX_FORMAT ")",
557 size_policy->calculated_survivor_size_in_bytes(),
558 _tenuring_threshold, MaxTenuringThreshold);
559 }
560
561 if (UsePerfData) {
562 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
563 counters->update_tenuring_threshold(_tenuring_threshold);
564 counters->update_survivor_size_counters();
565 }
566
567 // Do call at minor collections?
568 // Don't check if the size_policy is ready at this
569 // level. Let the size_policy check that internally.
570 if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
571 ((gc_cause != GCCause::_java_lang_system_gc) ||
572 UseAdaptiveSizePolicyWithSystemGC)) {
573
574 // Calculate optimal free space amounts
575 assert(young_gen->max_size() >
576 young_gen->from_space()->capacity_in_bytes() +
577 young_gen->to_space()->capacity_in_bytes(),
578 "Sizes of space in young gen are out-of-bounds");
579
580 size_t young_live = young_gen->used_in_bytes();
581 size_t eden_live = young_gen->eden_space()->used_in_bytes();
582 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
583 size_t max_old_gen_size = old_gen->max_gen_size();
584 size_t max_eden_size = max_young_size -
585 young_gen->from_space()->capacity_in_bytes() -
586 young_gen->to_space()->capacity_in_bytes();
587
588 // Used for diagnostics
589 size_policy->clear_generation_free_space_flags();
590
591 size_policy->compute_eden_space_size(young_live,
592 eden_live,
593 cur_eden,
594 max_eden_size,
595 false /* not full gc*/);
596
597 size_policy->check_gc_overhead_limit(young_live,
598 eden_live,
599 max_old_gen_size,
600 max_eden_size,
601 false /* not full gc*/,
602 gc_cause,
603 heap->collector_policy());
604
605 size_policy->decay_supplemental_growth(false /* not full gc*/);
606 }
607 // Resize the young generation at every collection
608 // even if new sizes have not been calculated. This is
609 // to allow resizes that may have been inhibited by the
610 // relative location of the "to" and "from" spaces.
611
612 // Resizing the old gen at minor collects can cause increases
613 // that don't feed back to the generation sizing policy until
614 // a major collection. Don't resize the old gen here.
615
616 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
617 size_policy->calculated_survivor_size_in_bytes());
618
619 if (PrintAdaptiveSizePolicy) {
620 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
621 heap->total_collections());
622 }
623 }
624
625 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
626 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
627 // Also update() will case adaptive NUMA chunk resizing.
628 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
629 young_gen->eden_space()->update();
630
631 heap->gc_policy_counters()->update_counters();
632
633 heap->resize_all_tlabs();
634
635 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
636 }
637
638 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
639
640 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
641
642 {
643 GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);
644
645 CodeCache::prune_scavenge_root_nmethods();
646 }
647
648 // Re-verify object start arrays
649 if (VerifyObjectStartArray &&
650 VerifyAfterGC) {
651 old_gen->verify_object_start_array();
652 }
653
654 // Verify all old -> young cards are now precise
655 if (VerifyRememberedSets) {
656 // Precise verification will give false positives. Until this is fixed,
657 // use imprecise verification.
658 // CardTableExtension::verify_all_young_refs_precise();
659 CardTableExtension::verify_all_young_refs_imprecise();
660 }
661
662 if (TraceGen0Time) accumulated_time()->stop();
663
664 if (PrintGC) {
665 if (PrintGCDetails) {
666 // Don't print a GC timestamp here. This is after the GC so
667 // would be confusing.
668 young_gen->print_used_change(young_gen_used_before);
669 }
670 heap->print_heap_change(prev_used);
671 }
672
673 // Track memory usage and detect low memory
674 MemoryService::track_memory_usage();
675 heap->update_counters();
676
677 gc_task_manager()->release_idle_workers();
678 }
679
680 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
681 HandleMark hm; // Discard invalid handles created during verification
682 Universe::verify(" VerifyAfterGC:");
683 }
684
685 heap->print_heap_after_gc();
686 heap->trace_heap_after_gc(&_gc_tracer);
687 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
688
689 if (ZapUnusedHeapArea) {
690 young_gen->eden_space()->check_mangled_unused_area_complete();
691 young_gen->from_space()->check_mangled_unused_area_complete();
692 young_gen->to_space()->check_mangled_unused_area_complete();
693 }
694
695 scavenge_exit.update();
696
697 if (PrintGCTaskTimeStamps) {
698 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
699 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
700 scavenge_exit.ticks());
701 gc_task_manager()->print_task_time_stamps();
702 }
703
704 #ifdef TRACESPINNING
705 ParallelTaskTerminator::print_termination_counts();
706 #endif
707
708
709 _gc_timer.register_gc_end();
710
711 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
712
713 return !promotion_failure_occurred;
714 }
715
716 // This method iterates over all objects in the young generation,
717 // unforwarding markOops. It then restores any preserved mark oops,
718 // and clears the _preserved_mark_stack.
719 void PSScavenge::clean_up_failed_promotion() {
720 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
721 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
722
723 PSYoungGen* young_gen = heap->young_gen();
724
725 {
726 ResourceMark rm;
727
728 // Unforward all pointers in the young gen.
729 PSPromotionFailedClosure unforward_closure;
730 young_gen->object_iterate(&unforward_closure);
731
732 if (PrintGC && Verbose) {
733 gclog_or_tty->print_cr("Restoring " SIZE_FORMAT " marks", _preserved_oop_stack.size());
734 }
735
736 // Restore any saved marks.
737 while (!_preserved_oop_stack.is_empty()) {
738 oop obj = _preserved_oop_stack.pop();
739 markOop mark = _preserved_mark_stack.pop();
740 obj->set_mark(mark);
741 }
742
743 // Clear the preserved mark and oop stack caches.
744 _preserved_mark_stack.clear(true);
745 _preserved_oop_stack.clear(true);
746 }
747
748 // Reset the PromotionFailureALot counters.
749 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
750 }
751
752 // This method is called whenever an attempt to promote an object
753 // fails. Some markOops will need preservation, some will not. Note
754 // that the entire eden is traversed after a failed promotion, with
755 // all forwarded headers replaced by the default markOop. This means
756 // it is not necessary to preserve most markOops.
757 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
758 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
759 // Should use per-worker private stacks here rather than
760 // locking a common pair of stacks.
761 ThreadCritical tc;
762 _preserved_oop_stack.push(obj);
763 _preserved_mark_stack.push(obj_mark);
764 }
765 }
766
767 bool PSScavenge::should_attempt_scavenge() {
768 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
769 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
770 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
771
772 if (UsePerfData) {
773 counters->update_scavenge_skipped(not_skipped);
774 }
775
776 PSYoungGen* young_gen = heap->young_gen();
777 PSOldGen* old_gen = heap->old_gen();
778
779 if (!ScavengeWithObjectsInToSpace) {
780 // Do not attempt to promote unless to_space is empty
781 if (!young_gen->to_space()->is_empty()) {
782 _consecutive_skipped_scavenges++;
783 if (UsePerfData) {
784 counters->update_scavenge_skipped(to_space_not_empty);
785 }
786 return false;
787 }
788 }
789
790 // Test to see if the scavenge will likely fail.
791 PSAdaptiveSizePolicy* policy = heap->size_policy();
792
793 // A similar test is done in the policy's should_full_GC(). If this is
794 // changed, decide if that test should also be changed.
795 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
796 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
797 bool result = promotion_estimate < old_gen->free_in_bytes();
798
799 if (PrintGCDetails && Verbose) {
800 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
801 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
802 " padded_average_promoted " SIZE_FORMAT
803 " free in old gen " SIZE_FORMAT,
804 (size_t) policy->average_promoted_in_bytes(),
805 (size_t) policy->padded_average_promoted_in_bytes(),
806 old_gen->free_in_bytes());
807 if (young_gen->used_in_bytes() <
808 (size_t) policy->padded_average_promoted_in_bytes()) {
809 gclog_or_tty->print_cr(" padded_promoted_average is greater"
810 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
811 }
812 }
813
814 if (result) {
815 _consecutive_skipped_scavenges = 0;
816 } else {
817 _consecutive_skipped_scavenges++;
818 if (UsePerfData) {
819 counters->update_scavenge_skipped(promoted_too_large);
820 }
821 }
822 return result;
823 }
824
825 // Used to add tasks
826 GCTaskManager* const PSScavenge::gc_task_manager() {
827 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
828 "shouldn't return NULL");
829 return ParallelScavengeHeap::gc_task_manager();
830 }
831
832 void PSScavenge::initialize() {
833 // Arguments must have been parsed
834
835 if (AlwaysTenure || NeverTenure) {
836 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
837 err_msg("MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is ", MaxTenuringThreshold));
838 _tenuring_threshold = MaxTenuringThreshold;
839 } else {
840 // We want to smooth out our startup times for the AdaptiveSizePolicy
841 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
842 MaxTenuringThreshold;
843 }
844
845 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
846 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
847
848 PSYoungGen* young_gen = heap->young_gen();
849 PSOldGen* old_gen = heap->old_gen();
850
851 // Set boundary between young_gen and old_gen
852 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
853 "old above young");
854 set_young_generation_boundary(young_gen->eden_space()->bottom());
855
856 // Initialize ref handling object for scavenging.
857 MemRegion mr = young_gen->reserved();
858
859 _ref_processor =
860 new ReferenceProcessor(mr, // span
861 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
862 (int) ParallelGCThreads, // mt processing degree
863 true, // mt discovery
864 (int) ParallelGCThreads, // mt discovery degree
865 true, // atomic_discovery
866 NULL, // header provides liveness info
867 false); // next field updates do not need write barrier
868
869 // Cache the cardtable
870 BarrierSet* bs = Universe::heap()->barrier_set();
871 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
872 _card_table = (CardTableExtension*)bs;
873
874 _counters = new CollectorCounters("PSScavenge", 0);
875 }