1 /*
2 * Copyright (c) 2002, 2012, 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/symbolTable.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
30 #include "gc_implementation/parallelScavenge/generationSizer.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 int PSScavenge::_tenuring_threshold = 0;
67 HeapWord* PSScavenge::_young_generation_boundary = NULL;
68 elapsedTimer PSScavenge::_accumulated_time;
69 STWGCTimer PSScavenge::_gc_timer;
70 ParallelScavengeTracer PSScavenge::_gc_tracer;
71 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack;
72 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack;
73 CollectorCounters* PSScavenge::_counters = NULL;
74
75 // Define before use
76 class PSIsAliveClosure: public BoolObjectClosure {
77 public:
78 void do_object(oop p) {
79 assert(false, "Do not call.");
80 }
81 bool do_object_b(oop p) {
82 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
83 }
84 };
85
86 PSIsAliveClosure PSScavenge::_is_alive_closure;
87
88 class PSKeepAliveClosure: public OopClosure {
89 protected:
90 MutableSpace* _to_space;
91 PSPromotionManager* _promotion_manager;
92
93 public:
94 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
95 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
96 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
97 _to_space = heap->young_gen()->to_space();
98
99 assert(_promotion_manager != NULL, "Sanity");
100 }
101
102 template <class T> void do_oop_work(T* p) {
103 assert (!oopDesc::is_null(*p), "expected non-null ref");
104 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
105 "expected an oop while scanning weak refs");
106
107 // Weak refs may be visited more than once.
108 if (PSScavenge::should_scavenge(p, _to_space)) {
109 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);
110 }
111 }
112 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
113 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
114 };
115
116 class PSEvacuateFollowersClosure: public VoidClosure {
117 private:
118 PSPromotionManager* _promotion_manager;
119 public:
120 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
121
122 virtual void do_void() {
123 assert(_promotion_manager != NULL, "Sanity");
124 _promotion_manager->drain_stacks(true);
125 guarantee(_promotion_manager->stacks_empty(),
126 "stacks should be empty at this point");
127 }
128 };
129
130 class PSPromotionFailedClosure : public ObjectClosure {
131 virtual void do_object(oop obj) {
132 if (obj->is_forwarded()) {
133 obj->init_mark();
134 }
135 }
136 };
137
138 class PSRefProcTaskProxy: public GCTask {
139 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
140 ProcessTask & _rp_task;
141 uint _work_id;
142 public:
143 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
144 : _rp_task(rp_task),
145 _work_id(work_id)
146 { }
147
148 private:
149 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
150 virtual void do_it(GCTaskManager* manager, uint which);
151 };
152
153 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
154 {
155 PSPromotionManager* promotion_manager =
156 PSPromotionManager::gc_thread_promotion_manager(which);
157 assert(promotion_manager != NULL, "sanity check");
158 PSKeepAliveClosure keep_alive(promotion_manager);
159 PSEvacuateFollowersClosure evac_followers(promotion_manager);
160 PSIsAliveClosure is_alive;
161 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
162 }
163
164 class PSRefEnqueueTaskProxy: public GCTask {
165 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
166 EnqueueTask& _enq_task;
167 uint _work_id;
168
169 public:
170 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
171 : _enq_task(enq_task),
172 _work_id(work_id)
173 { }
174
175 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
176 virtual void do_it(GCTaskManager* manager, uint which)
177 {
178 _enq_task.work(_work_id);
179 }
180 };
181
182 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
183 virtual void execute(ProcessTask& task);
184 virtual void execute(EnqueueTask& task);
185 };
186
187 void PSRefProcTaskExecutor::execute(ProcessTask& task)
188 {
189 GCTaskQueue* q = GCTaskQueue::create();
190 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
191 for(uint i=0; i < manager->active_workers(); i++) {
192 q->enqueue(new PSRefProcTaskProxy(task, i));
193 }
194 ParallelTaskTerminator terminator(manager->active_workers(),
195 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
196 if (task.marks_oops_alive() && manager->active_workers() > 1) {
197 for (uint j = 0; j < manager->active_workers(); j++) {
198 q->enqueue(new StealTask(&terminator));
199 }
200 }
201 manager->execute_and_wait(q);
202 }
203
204
205 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
206 {
207 GCTaskQueue* q = GCTaskQueue::create();
208 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
209 for(uint i=0; i < manager->active_workers(); i++) {
210 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
211 }
212 manager->execute_and_wait(q);
213 }
214
215 // This method contains all heap specific policy for invoking scavenge.
216 // PSScavenge::invoke_no_policy() will do nothing but attempt to
217 // scavenge. It will not clean up after failed promotions, bail out if
218 // we've exceeded policy time limits, or any other special behavior.
219 // All such policy should be placed here.
220 //
221 // Note that this method should only be called from the vm_thread while
222 // at a safepoint!
223 bool PSScavenge::invoke() {
224 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
225 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
226 assert(!Universe::heap()->is_gc_active(), "not reentrant");
227
228 ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
229 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
230
231 PSAdaptiveSizePolicy* policy = heap->size_policy();
232 IsGCActiveMark mark;
233
234 const bool scavenge_done = PSScavenge::invoke_no_policy();
235 const bool need_full_gc = !scavenge_done ||
236 policy->should_full_GC(heap->old_gen()->free_in_bytes());
237 bool full_gc_done = false;
238
239 if (UsePerfData) {
240 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
241 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
242 counters->update_full_follows_scavenge(ffs_val);
243 }
244
245 if (need_full_gc) {
246 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
247 CollectorPolicy* cp = heap->collector_policy();
248 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
249
250 if (UseParallelOldGC) {
251 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
252 } else {
253 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
254 }
255 }
256
257 return full_gc_done;
258 }
259
260 // This method contains no policy. You should probably
261 // be calling invoke() instead.
262 bool PSScavenge::invoke_no_policy() {
263 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
264 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
265
266 assert(_preserved_mark_stack.is_empty(), "should be empty");
267 assert(_preserved_oop_stack.is_empty(), "should be empty");
268
269 _gc_timer.register_gc_start();
270
271 TimeStamp scavenge_entry;
272 TimeStamp scavenge_midpoint;
273 TimeStamp scavenge_exit;
274
275 scavenge_entry.update();
276
277 if (GC_locker::check_active_before_gc()) {
278 return false;
279 }
280
281 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
282 GCCause::Cause gc_cause = heap->gc_cause();
283 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
284
285 // Check for potential problems.
286 if (!should_attempt_scavenge()) {
287 return false;
288 }
289
290 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
291
292 bool promotion_failure_occurred = false;
293
294 PSYoungGen* young_gen = heap->young_gen();
295 PSOldGen* old_gen = heap->old_gen();
296 PSPermGen* perm_gen = heap->perm_gen();
297 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
298
299 heap->increment_total_collections();
300
301 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
302
303 if ((gc_cause != GCCause::_java_lang_system_gc) ||
304 UseAdaptiveSizePolicyWithSystemGC) {
305 // Gather the feedback data for eden occupancy.
306 young_gen->eden_space()->accumulate_statistics();
307 }
308
309 if (ZapUnusedHeapArea) {
310 // Save information needed to minimize mangling
311 heap->record_gen_tops_before_GC();
312 }
313
314 heap->print_heap_before_gc();
315 heap->trace_heap_before_gc(&_gc_tracer);
316
317 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
318 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
319
320 size_t prev_used = heap->used();
321
322 // Fill in TLABs
323 heap->accumulate_statistics_all_tlabs();
324 heap->ensure_parsability(true); // retire TLABs
325
326 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
327 HandleMark hm; // Discard invalid handles created during verification
328 Universe::verify(" VerifyBeforeGC:");
329 }
330
331 {
332 ResourceMark rm;
333 HandleMark hm;
334
335 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
336 GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
337 TraceCollectorStats tcs(counters());
338 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
339
340 if (TraceGen0Time) accumulated_time()->start();
341
342 // Let the size policy know we're starting
343 size_policy->minor_collection_begin();
344
345 // Verify the object start arrays.
346 if (VerifyObjectStartArray &&
347 VerifyBeforeGC) {
348 old_gen->verify_object_start_array();
349 perm_gen->verify_object_start_array();
350 }
351
352 // Verify no unmarked old->young roots
353 if (VerifyRememberedSets) {
354 CardTableExtension::verify_all_young_refs_imprecise();
355 }
356
357 if (!ScavengeWithObjectsInToSpace) {
358 assert(young_gen->to_space()->is_empty(),
359 "Attempt to scavenge with live objects in to_space");
360 young_gen->to_space()->clear(SpaceDecorator::Mangle);
361 } else if (ZapUnusedHeapArea) {
362 young_gen->to_space()->mangle_unused_area();
363 }
364 save_to_space_top_before_gc();
365
366 COMPILER2_PRESENT(DerivedPointerTable::clear());
367
368 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
369 reference_processor()->setup_policy(false);
370
371 // We track how much was promoted to the next generation for
372 // the AdaptiveSizePolicy.
373 size_t old_gen_used_before = old_gen->used_in_bytes();
374
375 // For PrintGCDetails
376 size_t young_gen_used_before = young_gen->used_in_bytes();
377
378 // Reset our survivor overflow.
379 set_survivor_overflow(false);
380
381 // We need to save the old/perm top values before
382 // creating the promotion_manager. We pass the top
383 // values to the card_table, to prevent it from
384 // straying into the promotion labs.
385 HeapWord* old_top = old_gen->object_space()->top();
386 HeapWord* perm_top = perm_gen->object_space()->top();
387
388 // Release all previously held resources
389 gc_task_manager()->release_all_resources();
390
391 // Set the number of GC threads to be used in this collection
392 gc_task_manager()->set_active_gang();
393 gc_task_manager()->task_idle_workers();
394 // Get the active number of workers here and use that value
395 // throughout the methods.
396 uint active_workers = gc_task_manager()->active_workers();
397 heap->set_par_threads(active_workers);
398
399 PSPromotionManager::pre_scavenge();
400
401 // We'll use the promotion manager again later.
402 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
403 {
404 GCTraceTime tm("Scavenge", false, false, &_gc_timer);
405 ParallelScavengeHeap::ParStrongRootsScope psrs;
406
407 GCTaskQueue* q = GCTaskQueue::create();
408
409 uint stripe_total = active_workers;
410 for(uint i=0; i < stripe_total; i++) {
411 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
412 }
413
414 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
415
416 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
417 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
418 // We scan the thread roots in parallel
419 Threads::create_thread_roots_tasks(q);
420 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
421 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
422 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
423 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
424 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
425 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
426
427 ParallelTaskTerminator terminator(
428 active_workers,
429 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
430 if (active_workers > 1) {
431 for (uint j = 0; j < active_workers; j++) {
432 q->enqueue(new StealTask(&terminator));
433 }
434 }
435
436 gc_task_manager()->execute_and_wait(q);
437 }
438
439 scavenge_midpoint.update();
440
441 // Process reference objects discovered during scavenge
442 {
443 GCTraceTime tm("References", false, false, &_gc_timer);
444
445 reference_processor()->setup_policy(false); // not always_clear
446 reference_processor()->set_active_mt_degree(active_workers);
447 PSKeepAliveClosure keep_alive(promotion_manager);
448 PSEvacuateFollowersClosure evac_followers(promotion_manager);
449 ReferenceProcessorStats stats;
450 if (reference_processor()->processing_is_mt()) {
451 PSRefProcTaskExecutor task_executor;
452 stats = reference_processor()->process_discovered_references(
453 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
454 &_gc_timer);
455 } else {
456 stats = reference_processor()->process_discovered_references(
457 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
458 }
459
460 _gc_tracer.report_gc_reference_stats(stats);
461
462 // Enqueue reference objects discovered during scavenge.
463 if (reference_processor()->processing_is_mt()) {
464 PSRefProcTaskExecutor task_executor;
465 reference_processor()->enqueue_discovered_references(&task_executor);
466 } else {
467 reference_processor()->enqueue_discovered_references(NULL);
468 }
469 }
470
471 if (!JavaObjectsInPerm) {
472 GCTraceTime tm("StringTable", false, false, &_gc_timer);
473 // Unlink any dead interned Strings
474 StringTable::unlink(&_is_alive_closure);
475 // Process the remaining live ones
476 PSScavengeRootsClosure root_closure(promotion_manager);
477 StringTable::oops_do(&root_closure);
478 }
479
480 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
481 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
482 if (promotion_failure_occurred) {
483 clean_up_failed_promotion();
484 if (PrintGC) {
485 gclog_or_tty->print("--");
486 }
487 }
488
489 // Let the size policy know we're done. Note that we count promotion
490 // failure cleanup time as part of the collection (otherwise, we're
491 // implicitly saying it's mutator time).
492 size_policy->minor_collection_end(gc_cause);
493
494 if (!promotion_failure_occurred) {
495 // Swap the survivor spaces.
496 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
497 young_gen->from_space()->clear(SpaceDecorator::Mangle);
498 young_gen->swap_spaces();
499
500 size_t survived = young_gen->from_space()->used_in_bytes();
501 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
502 size_policy->update_averages(_survivor_overflow, survived, promoted);
503
504 // A successful scavenge should restart the GC time limit count which is
505 // for full GC's.
506 size_policy->reset_gc_overhead_limit_count();
507 if (UseAdaptiveSizePolicy) {
508 // Calculate the new survivor size and tenuring threshold
509
510 if (PrintAdaptiveSizePolicy) {
511 gclog_or_tty->print("AdaptiveSizeStart: ");
512 gclog_or_tty->stamp();
513 gclog_or_tty->print_cr(" collection: %d ",
514 heap->total_collections());
515
516 if (Verbose) {
517 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
518 " perm_gen_capacity: %d ",
519 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
520 perm_gen->capacity_in_bytes());
521 }
522 }
523
524
525 if (UsePerfData) {
526 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
527 counters->update_old_eden_size(
528 size_policy->calculated_eden_size_in_bytes());
529 counters->update_old_promo_size(
530 size_policy->calculated_promo_size_in_bytes());
531 counters->update_old_capacity(old_gen->capacity_in_bytes());
532 counters->update_young_capacity(young_gen->capacity_in_bytes());
533 counters->update_survived(survived);
534 counters->update_promoted(promoted);
535 counters->update_survivor_overflowed(_survivor_overflow);
536 }
537
538 size_t survivor_limit =
539 size_policy->max_survivor_size(young_gen->max_size());
540 _tenuring_threshold =
541 size_policy->compute_survivor_space_size_and_threshold(
542 _survivor_overflow,
543 _tenuring_threshold,
544 survivor_limit);
545
546 if (PrintTenuringDistribution) {
547 gclog_or_tty->cr();
548 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
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 (UseAdaptiveSizePolicy &&
563 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
564 ((gc_cause != GCCause::_java_lang_system_gc) ||
565 UseAdaptiveSizePolicyWithSystemGC)) {
566
567 // Calculate optimial free space amounts
568 assert(young_gen->max_size() >
569 young_gen->from_space()->capacity_in_bytes() +
570 young_gen->to_space()->capacity_in_bytes(),
571 "Sizes of space in young gen are out-of-bounds");
572 size_t max_eden_size = young_gen->max_size() -
573 young_gen->from_space()->capacity_in_bytes() -
574 young_gen->to_space()->capacity_in_bytes();
575 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
576 young_gen->eden_space()->used_in_bytes(),
577 old_gen->used_in_bytes(),
578 perm_gen->used_in_bytes(),
579 young_gen->eden_space()->capacity_in_bytes(),
580 old_gen->max_gen_size(),
581 max_eden_size,
582 false /* full gc*/,
583 gc_cause,
584 heap->collector_policy());
585
586 }
587 // Resize the young generation at every collection
588 // even if new sizes have not been calculated. This is
589 // to allow resizes that may have been inhibited by the
590 // relative location of the "to" and "from" spaces.
591
592 // Resizing the old gen at minor collects can cause increases
593 // that don't feed back to the generation sizing policy until
594 // a major collection. Don't resize the old gen here.
595
596 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
597 size_policy->calculated_survivor_size_in_bytes());
598
599 if (PrintAdaptiveSizePolicy) {
600 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
601 heap->total_collections());
602 }
603 }
604
605 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
606 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
607 // Also update() will case adaptive NUMA chunk resizing.
608 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
609 young_gen->eden_space()->update();
610
611 heap->gc_policy_counters()->update_counters();
612
613 heap->resize_all_tlabs();
614
615 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
616 }
617
618 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
619
620 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
621
622 {
623 GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);
624
625 CodeCache::prune_scavenge_root_nmethods();
626 }
627
628 // Re-verify object start arrays
629 if (VerifyObjectStartArray &&
630 VerifyAfterGC) {
631 old_gen->verify_object_start_array();
632 perm_gen->verify_object_start_array();
633 }
634
635 // Verify all old -> young cards are now precise
636 if (VerifyRememberedSets) {
637 // Precise verification will give false positives. Until this is fixed,
638 // use imprecise verification.
639 // CardTableExtension::verify_all_young_refs_precise();
640 CardTableExtension::verify_all_young_refs_imprecise();
641 }
642
643 if (TraceGen0Time) accumulated_time()->stop();
644
645 if (PrintGC) {
646 if (PrintGCDetails) {
647 // Don't print a GC timestamp here. This is after the GC so
648 // would be confusing.
649 young_gen->print_used_change(young_gen_used_before);
650 }
651 heap->print_heap_change(prev_used);
652 }
653
654 // Track memory usage and detect low memory
655 MemoryService::track_memory_usage();
656 heap->update_counters();
657
658 gc_task_manager()->release_idle_workers();
659 }
660
661 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
662 HandleMark hm; // Discard invalid handles created during verification
663 Universe::verify(" VerifyAfterGC:");
664 }
665
666 heap->print_heap_after_gc();
667 heap->trace_heap_after_gc(&_gc_tracer);
668 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
669
670 if (ZapUnusedHeapArea) {
671 young_gen->eden_space()->check_mangled_unused_area_complete();
672 young_gen->from_space()->check_mangled_unused_area_complete();
673 young_gen->to_space()->check_mangled_unused_area_complete();
674 }
675
676 scavenge_exit.update();
677
678 if (PrintGCTaskTimeStamps) {
679 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
680 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
681 scavenge_exit.ticks());
682 gc_task_manager()->print_task_time_stamps();
683 }
684
685 #ifdef TRACESPINNING
686 ParallelTaskTerminator::print_termination_counts();
687 #endif
688
689
690 _gc_timer.register_gc_end();
691
692 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
693
694 return !promotion_failure_occurred;
695 }
696
697 // This method iterates over all objects in the young generation,
698 // unforwarding markOops. It then restores any preserved mark oops,
699 // and clears the _preserved_mark_stack.
700 void PSScavenge::clean_up_failed_promotion() {
701 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
702 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
703
704 PSYoungGen* young_gen = heap->young_gen();
705
706 {
707 ResourceMark rm;
708
709 // Unforward all pointers in the young gen.
710 PSPromotionFailedClosure unforward_closure;
711 young_gen->object_iterate(&unforward_closure);
712
713 if (PrintGC && Verbose) {
714 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
715 }
716
717 // Restore any saved marks.
718 while (!_preserved_oop_stack.is_empty()) {
719 oop obj = _preserved_oop_stack.pop();
720 markOop mark = _preserved_mark_stack.pop();
721 obj->set_mark(mark);
722 }
723
724 // Clear the preserved mark and oop stack caches.
725 _preserved_mark_stack.clear(true);
726 _preserved_oop_stack.clear(true);
727 }
728
729 // Reset the PromotionFailureALot counters.
730 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
731 }
732
733 // This method is called whenever an attempt to promote an object
734 // fails. Some markOops will need preservation, some will not. Note
735 // that the entire eden is traversed after a failed promotion, with
736 // all forwarded headers replaced by the default markOop. This means
737 // it is not necessary to preserve most markOops.
738 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
739 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
740 // Should use per-worker private stacks here rather than
741 // locking a common pair of stacks.
742 ThreadCritical tc;
743 _preserved_oop_stack.push(obj);
744 _preserved_mark_stack.push(obj_mark);
745 }
746 }
747
748 bool PSScavenge::should_attempt_scavenge() {
749 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
750 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
751 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
752
753 if (UsePerfData) {
754 counters->update_scavenge_skipped(not_skipped);
755 }
756
757 PSYoungGen* young_gen = heap->young_gen();
758 PSOldGen* old_gen = heap->old_gen();
759
760 if (!ScavengeWithObjectsInToSpace) {
761 // Do not attempt to promote unless to_space is empty
762 if (!young_gen->to_space()->is_empty()) {
763 _consecutive_skipped_scavenges++;
764 if (UsePerfData) {
765 counters->update_scavenge_skipped(to_space_not_empty);
766 }
767 return false;
768 }
769 }
770
771 // Test to see if the scavenge will likely fail.
772 PSAdaptiveSizePolicy* policy = heap->size_policy();
773
774 // A similar test is done in the policy's should_full_GC(). If this is
775 // changed, decide if that test should also be changed.
776 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
777 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
778 bool result = promotion_estimate < old_gen->free_in_bytes();
779
780 if (PrintGCDetails && Verbose) {
781 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
782 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
783 " padded_average_promoted " SIZE_FORMAT
784 " free in old gen " SIZE_FORMAT,
785 (size_t) policy->average_promoted_in_bytes(),
786 (size_t) policy->padded_average_promoted_in_bytes(),
787 old_gen->free_in_bytes());
788 if (young_gen->used_in_bytes() <
789 (size_t) policy->padded_average_promoted_in_bytes()) {
790 gclog_or_tty->print_cr(" padded_promoted_average is greater"
791 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
792 }
793 }
794
795 if (result) {
796 _consecutive_skipped_scavenges = 0;
797 } else {
798 _consecutive_skipped_scavenges++;
799 if (UsePerfData) {
800 counters->update_scavenge_skipped(promoted_too_large);
801 }
802 }
803 return result;
804 }
805
806 // Used to add tasks
807 GCTaskManager* const PSScavenge::gc_task_manager() {
808 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
809 "shouldn't return NULL");
810 return ParallelScavengeHeap::gc_task_manager();
811 }
812
813 void PSScavenge::initialize() {
814 // Arguments must have been parsed
815
816 if (AlwaysTenure) {
817 _tenuring_threshold = 0;
818 } else if (NeverTenure) {
819 _tenuring_threshold = markOopDesc::max_age + 1;
820 } else {
821 // We want to smooth out our startup times for the AdaptiveSizePolicy
822 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
823 MaxTenuringThreshold;
824 }
825
826 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
827 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
828
829 PSYoungGen* young_gen = heap->young_gen();
830 PSOldGen* old_gen = heap->old_gen();
831 PSPermGen* perm_gen = heap->perm_gen();
832
833 // Set boundary between young_gen and old_gen
834 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
835 "perm above old");
836 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
837 "old above young");
838 _young_generation_boundary = young_gen->eden_space()->bottom();
839
840 // Initialize ref handling object for scavenging.
841 MemRegion mr = young_gen->reserved();
842
843 _ref_processor =
844 new ReferenceProcessor(mr, // span
845 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
846 (int) ParallelGCThreads, // mt processing degree
847 true, // mt discovery
848 (int) ParallelGCThreads, // mt discovery degree
849 true, // atomic_discovery
850 NULL, // header provides liveness info
851 false); // next field updates do not need write barrier
852
853 // Cache the cardtable
854 BarrierSet* bs = Universe::heap()->barrier_set();
855 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
856 _card_table = (CardTableExtension*)bs;
857
858 _counters = new CollectorCounters("PSScavenge", 0);
859 }