1 /*
2 * Copyright (c) 2002, 2013, 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 uint PSScavenge::_tenuring_threshold = 0;
63 HeapWord* PSScavenge::_young_generation_boundary = NULL;
64 elapsedTimer PSScavenge::_accumulated_time;
65 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack;
66 Stack<oop, mtGC> 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 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
288 heap->increment_total_collections();
289
290 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
291
292 if ((gc_cause != GCCause::_java_lang_system_gc) ||
293 UseAdaptiveSizePolicyWithSystemGC) {
294 // Gather the feedback data for eden occupancy.
295 young_gen->eden_space()->accumulate_statistics();
296 }
297
298 if (ZapUnusedHeapArea) {
299 // Save information needed to minimize mangling
300 heap->record_gen_tops_before_GC();
301 }
302
303 heap->print_heap_before_gc();
304
305 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
306 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
307
308 size_t prev_used = heap->used();
309 assert(promotion_failed() == false, "Sanity");
310
311 // Fill in TLABs
312 heap->accumulate_statistics_all_tlabs();
313 heap->ensure_parsability(true); // retire TLABs
314
315 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
316 HandleMark hm; // Discard invalid handles created during verification
317 Universe::verify(" VerifyBeforeGC:");
318 }
319
320 {
321 ResourceMark rm;
322 HandleMark hm;
323
324 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
325 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
326 TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
327 TraceCollectorStats tcs(counters());
328 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
329
330 if (TraceGen0Time) accumulated_time()->start();
331
332 // Let the size policy know we're starting
333 size_policy->minor_collection_begin();
334
335 // Verify the object start arrays.
336 if (VerifyObjectStartArray &&
337 VerifyBeforeGC) {
338 old_gen->verify_object_start_array();
339 }
340
341 // Verify no unmarked old->young roots
342 if (VerifyRememberedSets) {
343 CardTableExtension::verify_all_young_refs_imprecise();
344 }
345
346 if (!ScavengeWithObjectsInToSpace) {
347 assert(young_gen->to_space()->is_empty(),
348 "Attempt to scavenge with live objects in to_space");
349 young_gen->to_space()->clear(SpaceDecorator::Mangle);
350 } else if (ZapUnusedHeapArea) {
351 young_gen->to_space()->mangle_unused_area();
352 }
353 save_to_space_top_before_gc();
354
355 COMPILER2_PRESENT(DerivedPointerTable::clear());
356
357 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
358 reference_processor()->setup_policy(false);
359
360 // We track how much was promoted to the next generation for
361 // the AdaptiveSizePolicy.
362 size_t old_gen_used_before = old_gen->used_in_bytes();
363
364 // For PrintGCDetails
365 size_t young_gen_used_before = young_gen->used_in_bytes();
366
367 // Reset our survivor overflow.
368 set_survivor_overflow(false);
369
370 // We need to save the old top values before
371 // creating the promotion_manager. We pass the top
372 // values to the card_table, to prevent it from
373 // straying into the promotion labs.
374 HeapWord* old_top = old_gen->object_space()->top();
375
376 // Release all previously held resources
377 gc_task_manager()->release_all_resources();
378
379 // Set the number of GC threads to be used in this collection
380 gc_task_manager()->set_active_gang();
381 gc_task_manager()->task_idle_workers();
382 // Get the active number of workers here and use that value
383 // throughout the methods.
384 uint active_workers = gc_task_manager()->active_workers();
385 heap->set_par_threads(active_workers);
386
387 PSPromotionManager::pre_scavenge();
388
389 // We'll use the promotion manager again later.
390 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
391 {
392 // TraceTime("Roots");
393 ParallelScavengeHeap::ParStrongRootsScope psrs;
394
395 GCTaskQueue* q = GCTaskQueue::create();
396
397 if (!old_gen->object_space()->is_empty()) {
398 // There are only old-to-young pointers if there are objects
399 // in the old gen.
400 uint stripe_total = active_workers;
401 for(uint i=0; i < stripe_total; i++) {
402 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
403 }
404 }
405
406 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
407 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
408 // We scan the thread roots in parallel
409 Threads::create_thread_roots_tasks(q);
410 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
415 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
416
417 ParallelTaskTerminator terminator(
418 active_workers,
419 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
420 if (active_workers > 1) {
421 for (uint j = 0; j < active_workers; j++) {
422 q->enqueue(new StealTask(&terminator));
423 }
424 }
425
426 gc_task_manager()->execute_and_wait(q);
427 }
428
429 scavenge_midpoint.update();
430
431 // Process reference objects discovered during scavenge
432 {
433 reference_processor()->setup_policy(false); // not always_clear
434 reference_processor()->set_active_mt_degree(active_workers);
435 PSKeepAliveClosure keep_alive(promotion_manager);
436 PSEvacuateFollowersClosure evac_followers(promotion_manager);
437 if (reference_processor()->processing_is_mt()) {
438 PSRefProcTaskExecutor task_executor;
439 reference_processor()->process_discovered_references(
440 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
441 } else {
442 reference_processor()->process_discovered_references(
443 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
444 }
445 }
446
447 // Enqueue reference objects discovered during scavenge.
448 if (reference_processor()->processing_is_mt()) {
449 PSRefProcTaskExecutor task_executor;
450 reference_processor()->enqueue_discovered_references(&task_executor);
451 } else {
452 reference_processor()->enqueue_discovered_references(NULL);
453 }
454
455 // Unlink any dead interned Strings
456 StringTable::unlink(&_is_alive_closure);
457 // Process the remaining live ones
458 PSScavengeRootsClosure root_closure(promotion_manager);
459 StringTable::oops_do(&root_closure);
460
461 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
462 PSPromotionManager::post_scavenge();
463
464 promotion_failure_occurred = promotion_failed();
465 if (promotion_failure_occurred) {
466 clean_up_failed_promotion();
467 if (PrintGC) {
468 gclog_or_tty->print("--");
469 }
470 }
471
472 // Let the size policy know we're done. Note that we count promotion
473 // failure cleanup time as part of the collection (otherwise, we're
474 // implicitly saying it's mutator time).
475 size_policy->minor_collection_end(gc_cause);
476
477 if (!promotion_failure_occurred) {
478 // Swap the survivor spaces.
479
480
481 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
482 young_gen->from_space()->clear(SpaceDecorator::Mangle);
483 young_gen->swap_spaces();
484
485 size_t survived = young_gen->from_space()->used_in_bytes();
486 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
487 size_policy->update_averages(_survivor_overflow, survived, promoted);
488
489 // A successful scavenge should restart the GC time limit count which is
490 // for full GC's.
491 size_policy->reset_gc_overhead_limit_count();
492 if (UseAdaptiveSizePolicy) {
493 // Calculate the new survivor size and tenuring threshold
494
495 if (PrintAdaptiveSizePolicy) {
496 gclog_or_tty->print("AdaptiveSizeStart: ");
497 gclog_or_tty->stamp();
498 gclog_or_tty->print_cr(" collection: %d ",
499 heap->total_collections());
500
501 if (Verbose) {
502 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
503 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
504 }
505 }
506
507
508 if (UsePerfData) {
509 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
510 counters->update_old_eden_size(
511 size_policy->calculated_eden_size_in_bytes());
512 counters->update_old_promo_size(
513 size_policy->calculated_promo_size_in_bytes());
514 counters->update_old_capacity(old_gen->capacity_in_bytes());
515 counters->update_young_capacity(young_gen->capacity_in_bytes());
516 counters->update_survived(survived);
517 counters->update_promoted(promoted);
518 counters->update_survivor_overflowed(_survivor_overflow);
519 }
520
521 size_t survivor_limit =
522 size_policy->max_survivor_size(young_gen->max_size());
523 _tenuring_threshold =
524 size_policy->compute_survivor_space_size_and_threshold(
525 _survivor_overflow,
526 _tenuring_threshold,
527 survivor_limit);
528
529 if (PrintTenuringDistribution) {
530 gclog_or_tty->cr();
531 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)",
532 size_policy->calculated_survivor_size_in_bytes(),
533 _tenuring_threshold, MaxTenuringThreshold);
534 }
535
536 if (UsePerfData) {
537 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
538 counters->update_tenuring_threshold(_tenuring_threshold);
539 counters->update_survivor_size_counters();
540 }
541
542 // Do call at minor collections?
543 // Don't check if the size_policy is ready at this
544 // level. Let the size_policy check that internally.
545 if (UseAdaptiveSizePolicy &&
546 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
547 ((gc_cause != GCCause::_java_lang_system_gc) ||
548 UseAdaptiveSizePolicyWithSystemGC)) {
549
550 // Calculate optimial free space amounts
551 assert(young_gen->max_size() >
552 young_gen->from_space()->capacity_in_bytes() +
553 young_gen->to_space()->capacity_in_bytes(),
554 "Sizes of space in young gen are out-of-bounds");
555 size_t max_eden_size = young_gen->max_size() -
556 young_gen->from_space()->capacity_in_bytes() -
557 young_gen->to_space()->capacity_in_bytes();
558 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
559 young_gen->eden_space()->used_in_bytes(),
560 old_gen->used_in_bytes(),
561 young_gen->eden_space()->capacity_in_bytes(),
562 old_gen->max_gen_size(),
563 max_eden_size,
564 false /* full gc*/,
565 gc_cause,
566 heap->collector_policy());
567
568 }
569 // Resize the young generation at every collection
570 // even if new sizes have not been calculated. This is
571 // to allow resizes that may have been inhibited by the
572 // relative location of the "to" and "from" spaces.
573
574 // Resizing the old gen at minor collects can cause increases
575 // that don't feed back to the generation sizing policy until
576 // a major collection. Don't resize the old gen here.
577
578 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
579 size_policy->calculated_survivor_size_in_bytes());
580
581 if (PrintAdaptiveSizePolicy) {
582 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
583 heap->total_collections());
584 }
585 }
586
587 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
588 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
589 // Also update() will case adaptive NUMA chunk resizing.
590 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
591 young_gen->eden_space()->update();
592
593 heap->gc_policy_counters()->update_counters();
594
595 heap->resize_all_tlabs();
596
597 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
598 }
599
600 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
601
602 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
603
604 CodeCache::prune_scavenge_root_nmethods();
605
606 // Re-verify object start arrays
607 if (VerifyObjectStartArray &&
608 VerifyAfterGC) {
609 old_gen->verify_object_start_array();
610 }
611
612 // Verify all old -> young cards are now precise
613 if (VerifyRememberedSets) {
614 // Precise verification will give false positives. Until this is fixed,
615 // use imprecise verification.
616 // CardTableExtension::verify_all_young_refs_precise();
617 CardTableExtension::verify_all_young_refs_imprecise();
618 }
619
620 if (TraceGen0Time) accumulated_time()->stop();
621
622 if (PrintGC) {
623 if (PrintGCDetails) {
624 // Don't print a GC timestamp here. This is after the GC so
625 // would be confusing.
626 young_gen->print_used_change(young_gen_used_before);
627 }
628 heap->print_heap_change(prev_used);
629 }
630
631 // Track memory usage and detect low memory
632 MemoryService::track_memory_usage();
633 heap->update_counters();
634
635 gc_task_manager()->release_idle_workers();
636 }
637
638 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
639 HandleMark hm; // Discard invalid handles created during verification
640 Universe::verify(" VerifyAfterGC:");
641 }
642
643 heap->print_heap_after_gc();
644
645 if (ZapUnusedHeapArea) {
646 young_gen->eden_space()->check_mangled_unused_area_complete();
647 young_gen->from_space()->check_mangled_unused_area_complete();
648 young_gen->to_space()->check_mangled_unused_area_complete();
649 }
650
651 scavenge_exit.update();
652
653 if (PrintGCTaskTimeStamps) {
654 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
655 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
656 scavenge_exit.ticks());
657 gc_task_manager()->print_task_time_stamps();
658 }
659
660 #ifdef TRACESPINNING
661 ParallelTaskTerminator::print_termination_counts();
662 #endif
663
664 return !promotion_failure_occurred;
665 }
666
667 // This method iterates over all objects in the young generation,
668 // unforwarding markOops. It then restores any preserved mark oops,
669 // and clears the _preserved_mark_stack.
670 void PSScavenge::clean_up_failed_promotion() {
671 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
672 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
673 assert(promotion_failed(), "Sanity");
674
675 PSYoungGen* young_gen = heap->young_gen();
676
677 {
678 ResourceMark rm;
679
680 // Unforward all pointers in the young gen.
681 PSPromotionFailedClosure unforward_closure;
682 young_gen->object_iterate(&unforward_closure);
683
684 if (PrintGC && Verbose) {
685 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
686 }
687
688 // Restore any saved marks.
689 while (!_preserved_oop_stack.is_empty()) {
690 oop obj = _preserved_oop_stack.pop();
691 markOop mark = _preserved_mark_stack.pop();
692 obj->set_mark(mark);
693 }
694
695 // Clear the preserved mark and oop stack caches.
696 _preserved_mark_stack.clear(true);
697 _preserved_oop_stack.clear(true);
698 _promotion_failed = false;
699 }
700
701 // Reset the PromotionFailureALot counters.
702 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
703 }
704
705 // This method is called whenever an attempt to promote an object
706 // fails. Some markOops will need preservation, some will not. Note
707 // that the entire eden is traversed after a failed promotion, with
708 // all forwarded headers replaced by the default markOop. This means
709 // it is not neccessary to preserve most markOops.
710 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
711 _promotion_failed = true;
712 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
713 // Should use per-worker private stakcs hetre rather than
714 // locking a common pair of stacks.
715 ThreadCritical tc;
716 _preserved_oop_stack.push(obj);
717 _preserved_mark_stack.push(obj_mark);
718 }
719 }
720
721 bool PSScavenge::should_attempt_scavenge() {
722 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
723 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
724 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
725
726 if (UsePerfData) {
727 counters->update_scavenge_skipped(not_skipped);
728 }
729
730 PSYoungGen* young_gen = heap->young_gen();
731 PSOldGen* old_gen = heap->old_gen();
732
733 if (!ScavengeWithObjectsInToSpace) {
734 // Do not attempt to promote unless to_space is empty
735 if (!young_gen->to_space()->is_empty()) {
736 _consecutive_skipped_scavenges++;
737 if (UsePerfData) {
738 counters->update_scavenge_skipped(to_space_not_empty);
739 }
740 return false;
741 }
742 }
743
744 // Test to see if the scavenge will likely fail.
745 PSAdaptiveSizePolicy* policy = heap->size_policy();
746
747 // A similar test is done in the policy's should_full_GC(). If this is
748 // changed, decide if that test should also be changed.
749 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
750 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
751 bool result = promotion_estimate < old_gen->free_in_bytes();
752
753 if (PrintGCDetails && Verbose) {
754 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
755 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
756 " padded_average_promoted " SIZE_FORMAT
757 " free in old gen " SIZE_FORMAT,
758 (size_t) policy->average_promoted_in_bytes(),
759 (size_t) policy->padded_average_promoted_in_bytes(),
760 old_gen->free_in_bytes());
761 if (young_gen->used_in_bytes() <
762 (size_t) policy->padded_average_promoted_in_bytes()) {
763 gclog_or_tty->print_cr(" padded_promoted_average is greater"
764 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
765 }
766 }
767
768 if (result) {
769 _consecutive_skipped_scavenges = 0;
770 } else {
771 _consecutive_skipped_scavenges++;
772 if (UsePerfData) {
773 counters->update_scavenge_skipped(promoted_too_large);
774 }
775 }
776 return result;
777 }
778
779 // Used to add tasks
780 GCTaskManager* const PSScavenge::gc_task_manager() {
781 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
782 "shouldn't return NULL");
783 return ParallelScavengeHeap::gc_task_manager();
784 }
785
786 void PSScavenge::initialize() {
787 // Arguments must have been parsed
788
789 if (AlwaysTenure) {
790 _tenuring_threshold = 0;
791 } else if (NeverTenure) {
792 _tenuring_threshold = markOopDesc::max_age + 1;
793 } else {
794 // We want to smooth out our startup times for the AdaptiveSizePolicy
795 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
796 MaxTenuringThreshold;
797 }
798
799 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
800 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
801
802 PSYoungGen* young_gen = heap->young_gen();
803 PSOldGen* old_gen = heap->old_gen();
804
805 // Set boundary between young_gen and old_gen
806 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
807 "old above young");
808 _young_generation_boundary = young_gen->eden_space()->bottom();
809
810 // Initialize ref handling object for scavenging.
811 MemRegion mr = young_gen->reserved();
812
813 _ref_processor =
814 new ReferenceProcessor(mr, // span
815 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
816 (int) ParallelGCThreads, // mt processing degree
817 true, // mt discovery
818 (int) ParallelGCThreads, // mt discovery degree
819 true, // atomic_discovery
820 NULL, // header provides liveness info
821 false); // next field updates do not need write barrier
822
823 // Cache the cardtable
824 BarrierSet* bs = Universe::heap()->barrier_set();
825 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
826 _card_table = (CardTableExtension*)bs;
827
828 _counters = new CollectorCounters("PSScavenge", 0);
829 }