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/isGCActiveMark.hpp"
38 #include "gc_implementation/shared/spaceDecorator.hpp"
39 #include "gc_interface/gcCause.hpp"
40 #include "memory/collectorPolicy.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/referencePolicy.hpp"
43 #include "memory/referenceProcessor.hpp"
44 #include "memory/resourceArea.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "oops/oop.psgc.inline.hpp"
47 #include "runtime/biasedLocking.hpp"
48 #include "runtime/fprofiler.hpp"
49 #include "runtime/handles.inline.hpp"
50 #include "runtime/threadCritical.hpp"
51 #include "runtime/vmThread.hpp"
52 #include "runtime/vm_operations.hpp"
53 #include "services/memoryService.hpp"
54 #include "utilities/stack.inline.hpp"
55
56
57 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
58 int PSScavenge::_consecutive_skipped_scavenges = 0;
59 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
60 CardTableExtension* PSScavenge::_card_table = NULL;
61 bool PSScavenge::_survivor_overflow = false;
62 int PSScavenge::_tenuring_threshold = 0;
63 HeapWord* PSScavenge::_young_generation_boundary = NULL;
64 elapsedTimer PSScavenge::_accumulated_time;
65 Stack<markOop> PSScavenge::_preserved_mark_stack;
66 Stack<oop> PSScavenge::_preserved_oop_stack;
67 CollectorCounters* PSScavenge::_counters = NULL;
68 bool PSScavenge::_promotion_failed = false;
69
70 // Define before use
71 class PSIsAliveClosure: public BoolObjectClosure {
72 public:
73 void do_object(oop p) {
74 assert(false, "Do not call.");
75 }
76 bool do_object_b(oop p) {
77 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
78 }
79 };
80
81 PSIsAliveClosure PSScavenge::_is_alive_closure;
82
83 class PSKeepAliveClosure: public OopClosure {
84 protected:
85 MutableSpace* _to_space;
86 PSPromotionManager* _promotion_manager;
87
88 public:
89 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
90 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
91 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
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 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, 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(!Universe::heap()->is_gc_active(), "not reentrant");
222
223 ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
224 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
225
226 PSAdaptiveSizePolicy* policy = heap->size_policy();
227 IsGCActiveMark mark;
228
229 const bool scavenge_done = PSScavenge::invoke_no_policy();
230 const bool need_full_gc = !scavenge_done ||
231 policy->should_full_GC(heap->old_gen()->free_in_bytes());
232 bool full_gc_done = false;
233
234 if (UsePerfData) {
235 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
236 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
237 counters->update_full_follows_scavenge(ffs_val);
238 }
239
240 if (need_full_gc) {
241 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
242 CollectorPolicy* cp = heap->collector_policy();
243 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
244
245 if (UseParallelOldGC) {
246 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
247 } else {
248 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
249 }
250 }
251
252 return full_gc_done;
253 }
254
255 // This method contains no policy. You should probably
256 // be calling invoke() instead.
257 bool PSScavenge::invoke_no_policy() {
258 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
259 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
260
261 assert(_preserved_mark_stack.is_empty(), "should be empty");
262 assert(_preserved_oop_stack.is_empty(), "should be empty");
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*)Universe::heap();
275 GCCause::Cause gc_cause = heap->gc_cause();
276 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
277
278 // Check for potential problems.
279 if (!should_attempt_scavenge()) {
280 return false;
281 }
282
283 bool promotion_failure_occurred = false;
284
285 PSYoungGen* young_gen = heap->young_gen();
286 PSOldGen* old_gen = heap->old_gen();
287 PSPermGen* perm_gen = heap->perm_gen();
288 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
289 heap->increment_total_collections();
290
291 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
292
293 if ((gc_cause != GCCause::_java_lang_system_gc) ||
294 UseAdaptiveSizePolicyWithSystemGC) {
295 // Gather the feedback data for eden occupancy.
296 young_gen->eden_space()->accumulate_statistics();
297 }
298
299 if (ZapUnusedHeapArea) {
300 // Save information needed to minimize mangling
301 heap->record_gen_tops_before_GC();
302 }
303
304 heap->print_heap_before_gc();
305
306 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
307 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
308
309 size_t prev_used = heap->used();
310 assert(promotion_failed() == false, "Sanity");
311
312 // Fill in TLABs
313 heap->accumulate_statistics_all_tlabs();
314 heap->ensure_parsability(true); // retire TLABs
315
316 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
317 HandleMark hm; // Discard invalid handles created during verification
318 gclog_or_tty->print(" VerifyBeforeGC:");
319 Universe::verify(true);
320 }
321
322 {
323 ResourceMark rm;
324 HandleMark hm;
325
326 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
327 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
328 TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
329 TraceCollectorStats tcs(counters());
330 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
331
332 if (TraceGen0Time) accumulated_time()->start();
333
334 // Let the size policy know we're starting
335 size_policy->minor_collection_begin();
336
337 // Verify the object start arrays.
338 if (VerifyObjectStartArray &&
339 VerifyBeforeGC) {
340 old_gen->verify_object_start_array();
341 perm_gen->verify_object_start_array();
342 }
343
344 // Verify no unmarked old->young roots
345 if (VerifyRememberedSets) {
346 CardTableExtension::verify_all_young_refs_imprecise();
347 }
348
349 if (!ScavengeWithObjectsInToSpace) {
350 assert(young_gen->to_space()->is_empty(),
351 "Attempt to scavenge with live objects in to_space");
352 young_gen->to_space()->clear(SpaceDecorator::Mangle);
353 } else if (ZapUnusedHeapArea) {
354 young_gen->to_space()->mangle_unused_area();
355 }
356 save_to_space_top_before_gc();
357
358 COMPILER2_PRESENT(DerivedPointerTable::clear());
359
360 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
361 reference_processor()->setup_policy(false);
362
363 // We track how much was promoted to the next generation for
364 // the AdaptiveSizePolicy.
365 size_t old_gen_used_before = old_gen->used_in_bytes();
366
367 // For PrintGCDetails
368 size_t young_gen_used_before = young_gen->used_in_bytes();
369
370 // Reset our survivor overflow.
371 set_survivor_overflow(false);
372
373 // We need to save the old/perm top values before
374 // creating the promotion_manager. We pass the top
375 // values to the card_table, to prevent it from
376 // straying into the promotion labs.
377 HeapWord* old_top = old_gen->object_space()->top();
378 HeapWord* perm_top = perm_gen->object_space()->top();
379
380 // Release all previously held resources
381 gc_task_manager()->release_all_resources();
382
383 // Set the number of GC threads to be used in this collection
384 gc_task_manager()->set_active_gang();
385 gc_task_manager()->task_idle_workers();
386 // Get the active number of workers here and use that value
387 // throughout the methods.
388 uint active_workers = gc_task_manager()->active_workers();
389 heap->set_par_threads(active_workers);
390
391 PSPromotionManager::pre_scavenge();
392
393 // We'll use the promotion manager again later.
394 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
395 {
396 // TraceTime("Roots");
397 ParallelScavengeHeap::ParStrongRootsScope psrs;
398
399 GCTaskQueue* q = GCTaskQueue::create();
400
401 uint stripe_total = active_workers;
402 for(uint i=0; i < stripe_total; i++) {
403 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
404 }
405
406 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
407
408 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
409 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
410 // We scan the thread roots in parallel
411 Threads::create_thread_roots_tasks(q);
412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
415 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
416 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
417 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
418
419 ParallelTaskTerminator terminator(
420 active_workers,
421 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
422 if (active_workers > 1) {
423 for (uint j = 0; j < active_workers; j++) {
424 q->enqueue(new StealTask(&terminator));
425 }
426 }
427
428 gc_task_manager()->execute_and_wait(q);
429 }
430
431 scavenge_midpoint.update();
432
433 // Process reference objects discovered during scavenge
434 {
435 reference_processor()->setup_policy(false); // not always_clear
436 reference_processor()->set_active_mt_degree(active_workers);
437 PSKeepAliveClosure keep_alive(promotion_manager);
438 PSEvacuateFollowersClosure evac_followers(promotion_manager);
439 if (reference_processor()->processing_is_mt()) {
440 PSRefProcTaskExecutor task_executor;
441 reference_processor()->process_discovered_references(
442 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
443 } else {
444 reference_processor()->process_discovered_references(
445 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
446 }
447 }
448
449 // Enqueue reference objects discovered during scavenge.
450 if (reference_processor()->processing_is_mt()) {
451 PSRefProcTaskExecutor task_executor;
452 reference_processor()->enqueue_discovered_references(&task_executor);
453 } else {
454 reference_processor()->enqueue_discovered_references(NULL);
455 }
456
457 if (!JavaObjectsInPerm) {
458 // Unlink any dead interned Strings
459 StringTable::unlink(&_is_alive_closure);
460 // Process the remaining live ones
461 PSScavengeRootsClosure root_closure(promotion_manager);
462 StringTable::oops_do(&root_closure);
463 }
464
465 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
466 PSPromotionManager::post_scavenge();
467
468 promotion_failure_occurred = promotion_failed();
469 if (promotion_failure_occurred) {
470 clean_up_failed_promotion();
471 if (PrintGC) {
472 gclog_or_tty->print("--");
473 }
474 }
475
476 // Let the size policy know we're done. Note that we count promotion
477 // failure cleanup time as part of the collection (otherwise, we're
478 // implicitly saying it's mutator time).
479 size_policy->minor_collection_end(gc_cause);
480
481 if (!promotion_failure_occurred) {
482 // Swap the survivor spaces.
483
484
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: %d young_gen_capacity: %d"
507 " perm_gen_capacity: %d ",
508 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
509 perm_gen->capacity_in_bytes());
510 }
511 }
512
513
514 if (UsePerfData) {
515 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
516 counters->update_old_eden_size(
517 size_policy->calculated_eden_size_in_bytes());
518 counters->update_old_promo_size(
519 size_policy->calculated_promo_size_in_bytes());
520 counters->update_old_capacity(old_gen->capacity_in_bytes());
521 counters->update_young_capacity(young_gen->capacity_in_bytes());
522 counters->update_survived(survived);
523 counters->update_promoted(promoted);
524 counters->update_survivor_overflowed(_survivor_overflow);
525 }
526
527 size_t survivor_limit =
528 size_policy->max_survivor_size(young_gen->max_size());
529 _tenuring_threshold =
530 size_policy->compute_survivor_space_size_and_threshold(
531 _survivor_overflow,
532 _tenuring_threshold,
533 survivor_limit);
534
535 if (PrintTenuringDistribution) {
536 gclog_or_tty->cr();
537 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
538 size_policy->calculated_survivor_size_in_bytes(),
539 _tenuring_threshold, MaxTenuringThreshold);
540 }
541
542 if (UsePerfData) {
543 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
544 counters->update_tenuring_threshold(_tenuring_threshold);
545 counters->update_survivor_size_counters();
546 }
547
548 // Do call at minor collections?
549 // Don't check if the size_policy is ready at this
550 // level. Let the size_policy check that internally.
551 if (UseAdaptiveSizePolicy &&
552 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
553 ((gc_cause != GCCause::_java_lang_system_gc) ||
554 UseAdaptiveSizePolicyWithSystemGC)) {
555
556 // Calculate optimial free space amounts
557 assert(young_gen->max_size() >
558 young_gen->from_space()->capacity_in_bytes() +
559 young_gen->to_space()->capacity_in_bytes(),
560 "Sizes of space in young gen are out-of-bounds");
561 size_t max_eden_size = young_gen->max_size() -
562 young_gen->from_space()->capacity_in_bytes() -
563 young_gen->to_space()->capacity_in_bytes();
564 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
565 young_gen->eden_space()->used_in_bytes(),
566 old_gen->used_in_bytes(),
567 perm_gen->used_in_bytes(),
568 young_gen->eden_space()->capacity_in_bytes(),
569 old_gen->max_gen_size(),
570 max_eden_size,
571 false /* full gc*/,
572 gc_cause,
573 heap->collector_policy());
574
575 }
576 // Resize the young generation at every collection
577 // even if new sizes have not been calculated. This is
578 // to allow resizes that may have been inhibited by the
579 // relative location of the "to" and "from" spaces.
580
581 // Resizing the old gen at minor collects can cause increases
582 // that don't feed back to the generation sizing policy until
583 // a major collection. Don't resize the old gen here.
584
585 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
586 size_policy->calculated_survivor_size_in_bytes());
587
588 if (PrintAdaptiveSizePolicy) {
589 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
590 heap->total_collections());
591 }
592 }
593
594 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
595 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
596 // Also update() will case adaptive NUMA chunk resizing.
597 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
598 young_gen->eden_space()->update();
599
600 heap->gc_policy_counters()->update_counters();
601
602 heap->resize_all_tlabs();
603
604 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
605 }
606
607 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
608
609 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
610
611 CodeCache::prune_scavenge_root_nmethods();
612
613 // Re-verify object start arrays
614 if (VerifyObjectStartArray &&
615 VerifyAfterGC) {
616 old_gen->verify_object_start_array();
617 perm_gen->verify_object_start_array();
618 }
619
620 // Verify all old -> young cards are now precise
621 if (VerifyRememberedSets) {
622 // Precise verification will give false positives. Until this is fixed,
623 // use imprecise verification.
624 // CardTableExtension::verify_all_young_refs_precise();
625 CardTableExtension::verify_all_young_refs_imprecise();
626 }
627
628 if (TraceGen0Time) accumulated_time()->stop();
629
630 if (PrintGC) {
631 if (PrintGCDetails) {
632 // Don't print a GC timestamp here. This is after the GC so
633 // would be confusing.
634 young_gen->print_used_change(young_gen_used_before);
635 }
636 heap->print_heap_change(prev_used);
637 }
638
639 // Track memory usage and detect low memory
640 MemoryService::track_memory_usage();
641 heap->update_counters();
642
643 gc_task_manager()->release_idle_workers();
644 }
645
646 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
647 HandleMark hm; // Discard invalid handles created during verification
648 gclog_or_tty->print(" VerifyAfterGC:");
649 Universe::verify(false);
650 }
651
652 heap->print_heap_after_gc();
653
654 if (ZapUnusedHeapArea) {
655 young_gen->eden_space()->check_mangled_unused_area_complete();
656 young_gen->from_space()->check_mangled_unused_area_complete();
657 young_gen->to_space()->check_mangled_unused_area_complete();
658 }
659
660 scavenge_exit.update();
661
662 if (PrintGCTaskTimeStamps) {
663 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
664 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
665 scavenge_exit.ticks());
666 gc_task_manager()->print_task_time_stamps();
667 }
668
669 #ifdef TRACESPINNING
670 ParallelTaskTerminator::print_termination_counts();
671 #endif
672
673 return !promotion_failure_occurred;
674 }
675
676 // This method iterates over all objects in the young generation,
677 // unforwarding markOops. It then restores any preserved mark oops,
678 // and clears the _preserved_mark_stack.
679 void PSScavenge::clean_up_failed_promotion() {
680 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
681 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
682 assert(promotion_failed(), "Sanity");
683
684 PSYoungGen* young_gen = heap->young_gen();
685
686 {
687 ResourceMark rm;
688
689 // Unforward all pointers in the young gen.
690 PSPromotionFailedClosure unforward_closure;
691 young_gen->object_iterate(&unforward_closure);
692
693 if (PrintGC && Verbose) {
694 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
695 }
696
697 // Restore any saved marks.
698 while (!_preserved_oop_stack.is_empty()) {
699 oop obj = _preserved_oop_stack.pop();
700 markOop mark = _preserved_mark_stack.pop();
701 obj->set_mark(mark);
702 }
703
704 // Clear the preserved mark and oop stack caches.
705 _preserved_mark_stack.clear(true);
706 _preserved_oop_stack.clear(true);
707 _promotion_failed = false;
708 }
709
710 // Reset the PromotionFailureALot counters.
711 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
712 }
713
714 // This method is called whenever an attempt to promote an object
715 // fails. Some markOops will need preservation, some will not. Note
716 // that the entire eden is traversed after a failed promotion, with
717 // all forwarded headers replaced by the default markOop. This means
718 // it is not neccessary to preserve most markOops.
719 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
720 _promotion_failed = true;
721 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
722 // Should use per-worker private stakcs hetre rather than
723 // locking a common pair of stacks.
724 ThreadCritical tc;
725 _preserved_oop_stack.push(obj);
726 _preserved_mark_stack.push(obj_mark);
727 }
728 }
729
730 bool PSScavenge::should_attempt_scavenge() {
731 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
732 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
733 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
734
735 if (UsePerfData) {
736 counters->update_scavenge_skipped(not_skipped);
737 }
738
739 PSYoungGen* young_gen = heap->young_gen();
740 PSOldGen* old_gen = heap->old_gen();
741
742 if (!ScavengeWithObjectsInToSpace) {
743 // Do not attempt to promote unless to_space is empty
744 if (!young_gen->to_space()->is_empty()) {
745 _consecutive_skipped_scavenges++;
746 if (UsePerfData) {
747 counters->update_scavenge_skipped(to_space_not_empty);
748 }
749 return false;
750 }
751 }
752
753 // Test to see if the scavenge will likely fail.
754 PSAdaptiveSizePolicy* policy = heap->size_policy();
755
756 // A similar test is done in the policy's should_full_GC(). If this is
757 // changed, decide if that test should also be changed.
758 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
759 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
760 bool result = promotion_estimate < old_gen->free_in_bytes();
761
762 if (PrintGCDetails && Verbose) {
763 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
764 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
765 " padded_average_promoted " SIZE_FORMAT
766 " free in old gen " SIZE_FORMAT,
767 (size_t) policy->average_promoted_in_bytes(),
768 (size_t) policy->padded_average_promoted_in_bytes(),
769 old_gen->free_in_bytes());
770 if (young_gen->used_in_bytes() <
771 (size_t) policy->padded_average_promoted_in_bytes()) {
772 gclog_or_tty->print_cr(" padded_promoted_average is greater"
773 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
774 }
775 }
776
777 if (result) {
778 _consecutive_skipped_scavenges = 0;
779 } else {
780 _consecutive_skipped_scavenges++;
781 if (UsePerfData) {
782 counters->update_scavenge_skipped(promoted_too_large);
783 }
784 }
785 return result;
786 }
787
788 // Used to add tasks
789 GCTaskManager* const PSScavenge::gc_task_manager() {
790 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
791 "shouldn't return NULL");
792 return ParallelScavengeHeap::gc_task_manager();
793 }
794
795 void PSScavenge::initialize() {
796 // Arguments must have been parsed
797
798 if (AlwaysTenure) {
799 _tenuring_threshold = 0;
800 } else if (NeverTenure) {
801 _tenuring_threshold = markOopDesc::max_age + 1;
802 } else {
803 // We want to smooth out our startup times for the AdaptiveSizePolicy
804 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
805 MaxTenuringThreshold;
806 }
807
808 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
809 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
810
811 PSYoungGen* young_gen = heap->young_gen();
812 PSOldGen* old_gen = heap->old_gen();
813 PSPermGen* perm_gen = heap->perm_gen();
814
815 // Set boundary between young_gen and old_gen
816 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
817 "perm above old");
818 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
819 "old above young");
820 _young_generation_boundary = young_gen->eden_space()->bottom();
821
822 // Initialize ref handling object for scavenging.
823 MemRegion mr = young_gen->reserved();
824
825 _ref_processor =
826 new ReferenceProcessor(mr, // span
827 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
828 (int) ParallelGCThreads, // mt processing degree
829 true, // mt discovery
830 (int) ParallelGCThreads, // mt discovery degree
831 true, // atomic_discovery
832 NULL, // header provides liveness info
833 false); // next field updates do not need write barrier
834
835 // Cache the cardtable
836 BarrierSet* bs = Universe::heap()->barrier_set();
837 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
838 _card_table = (CardTableExtension*)bs;
839
840 _counters = new CollectorCounters("PSScavenge", 0);
841 }