Fri, 17 May 2013 17:24:20 +0200
7176220: 'Full GC' events miss date stamp information occasionally
Summary: Move date stamp logic into GCTraceTime
Reviewed-by: brutisso, tschatzl
1 /*
2 * Copyright (c) 2000, 2014, 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
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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).
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23 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "classfile/vmSymbols.hpp"
29 #include "code/icBuffer.hpp"
30 #include "gc_implementation/shared/collectorCounters.hpp"
31 #include "gc_implementation/shared/gcTrace.hpp"
32 #include "gc_implementation/shared/gcTraceTime.hpp"
33 #include "gc_implementation/shared/vmGCOperations.hpp"
34 #include "gc_interface/collectedHeap.inline.hpp"
35 #include "memory/filemap.hpp"
36 #include "memory/gcLocker.inline.hpp"
37 #include "memory/genCollectedHeap.hpp"
38 #include "memory/genOopClosures.inline.hpp"
39 #include "memory/generation.inline.hpp"
40 #include "memory/generationSpec.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "memory/sharedHeap.hpp"
43 #include "memory/space.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/oop.inline2.hpp"
46 #include "runtime/biasedLocking.hpp"
47 #include "runtime/fprofiler.hpp"
48 #include "runtime/handles.hpp"
49 #include "runtime/handles.inline.hpp"
50 #include "runtime/java.hpp"
51 #include "runtime/vmThread.hpp"
52 #include "services/memoryService.hpp"
53 #include "utilities/vmError.hpp"
54 #include "utilities/workgroup.hpp"
55 #include "utilities/macros.hpp"
56 #if INCLUDE_ALL_GCS
57 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
58 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
59 #endif // INCLUDE_ALL_GCS
61 GenCollectedHeap* GenCollectedHeap::_gch;
62 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
64 // The set of potentially parallel tasks in root scanning.
65 enum GCH_strong_roots_tasks {
66 // We probably want to parallelize both of these internally, but for now...
67 GCH_PS_younger_gens,
68 // Leave this one last.
69 GCH_PS_NumElements
70 };
72 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
73 SharedHeap(policy),
74 _gen_policy(policy),
75 _gen_process_roots_tasks(new SubTasksDone(GCH_PS_NumElements)),
76 _full_collections_completed(0)
77 {
78 if (_gen_process_roots_tasks == NULL ||
79 !_gen_process_roots_tasks->valid()) {
80 vm_exit_during_initialization("Failed necessary allocation.");
81 }
82 assert(policy != NULL, "Sanity check");
83 }
85 jint GenCollectedHeap::initialize() {
86 CollectedHeap::pre_initialize();
88 int i;
89 _n_gens = gen_policy()->number_of_generations();
91 // While there are no constraints in the GC code that HeapWordSize
92 // be any particular value, there are multiple other areas in the
93 // system which believe this to be true (e.g. oop->object_size in some
94 // cases incorrectly returns the size in wordSize units rather than
95 // HeapWordSize).
96 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
98 // The heap must be at least as aligned as generations.
99 size_t gen_alignment = Generation::GenGrain;
101 _gen_specs = gen_policy()->generations();
103 // Make sure the sizes are all aligned.
104 for (i = 0; i < _n_gens; i++) {
105 _gen_specs[i]->align(gen_alignment);
106 }
108 // Allocate space for the heap.
110 char* heap_address;
111 size_t total_reserved = 0;
112 int n_covered_regions = 0;
113 ReservedSpace heap_rs;
115 size_t heap_alignment = collector_policy()->heap_alignment();
117 heap_address = allocate(heap_alignment, &total_reserved,
118 &n_covered_regions, &heap_rs);
120 if (!heap_rs.is_reserved()) {
121 vm_shutdown_during_initialization(
122 "Could not reserve enough space for object heap");
123 return JNI_ENOMEM;
124 }
126 _reserved = MemRegion((HeapWord*)heap_rs.base(),
127 (HeapWord*)(heap_rs.base() + heap_rs.size()));
129 // It is important to do this in a way such that concurrent readers can't
130 // temporarily think somethings in the heap. (Seen this happen in asserts.)
131 _reserved.set_word_size(0);
132 _reserved.set_start((HeapWord*)heap_rs.base());
133 size_t actual_heap_size = heap_rs.size();
134 _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
136 _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
137 set_barrier_set(rem_set()->bs());
139 _gch = this;
141 for (i = 0; i < _n_gens; i++) {
142 ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false);
143 _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
144 heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
145 }
146 clear_incremental_collection_failed();
148 #if INCLUDE_ALL_GCS
149 // If we are running CMS, create the collector responsible
150 // for collecting the CMS generations.
151 if (collector_policy()->is_concurrent_mark_sweep_policy()) {
152 bool success = create_cms_collector();
153 if (!success) return JNI_ENOMEM;
154 }
155 #endif // INCLUDE_ALL_GCS
157 return JNI_OK;
158 }
161 char* GenCollectedHeap::allocate(size_t alignment,
162 size_t* _total_reserved,
163 int* _n_covered_regions,
164 ReservedSpace* heap_rs){
165 const char overflow_msg[] = "The size of the object heap + VM data exceeds "
166 "the maximum representable size";
168 // Now figure out the total size.
169 size_t total_reserved = 0;
170 int n_covered_regions = 0;
171 const size_t pageSize = UseLargePages ?
172 os::large_page_size() : os::vm_page_size();
174 assert(alignment % pageSize == 0, "Must be");
176 for (int i = 0; i < _n_gens; i++) {
177 total_reserved += _gen_specs[i]->max_size();
178 if (total_reserved < _gen_specs[i]->max_size()) {
179 vm_exit_during_initialization(overflow_msg);
180 }
181 n_covered_regions += _gen_specs[i]->n_covered_regions();
182 }
183 assert(total_reserved % alignment == 0,
184 err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment="
185 SIZE_FORMAT, total_reserved, alignment));
187 // Needed until the cardtable is fixed to have the right number
188 // of covered regions.
189 n_covered_regions += 2;
191 *_total_reserved = total_reserved;
192 *_n_covered_regions = n_covered_regions;
194 *heap_rs = Universe::reserve_heap(total_reserved, alignment);
195 return heap_rs->base();
196 }
199 void GenCollectedHeap::post_initialize() {
200 SharedHeap::post_initialize();
201 TwoGenerationCollectorPolicy *policy =
202 (TwoGenerationCollectorPolicy *)collector_policy();
203 guarantee(policy->is_two_generation_policy(), "Illegal policy type");
204 DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
205 assert(def_new_gen->kind() == Generation::DefNew ||
206 def_new_gen->kind() == Generation::ParNew ||
207 def_new_gen->kind() == Generation::ASParNew,
208 "Wrong generation kind");
210 Generation* old_gen = get_gen(1);
211 assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
212 old_gen->kind() == Generation::ASConcurrentMarkSweep ||
213 old_gen->kind() == Generation::MarkSweepCompact,
214 "Wrong generation kind");
216 policy->initialize_size_policy(def_new_gen->eden()->capacity(),
217 old_gen->capacity(),
218 def_new_gen->from()->capacity());
219 policy->initialize_gc_policy_counters();
220 }
222 void GenCollectedHeap::ref_processing_init() {
223 SharedHeap::ref_processing_init();
224 for (int i = 0; i < _n_gens; i++) {
225 _gens[i]->ref_processor_init();
226 }
227 }
229 size_t GenCollectedHeap::capacity() const {
230 size_t res = 0;
231 for (int i = 0; i < _n_gens; i++) {
232 res += _gens[i]->capacity();
233 }
234 return res;
235 }
237 size_t GenCollectedHeap::used() const {
238 size_t res = 0;
239 for (int i = 0; i < _n_gens; i++) {
240 res += _gens[i]->used();
241 }
242 return res;
243 }
245 // Save the "used_region" for generations level and lower.
246 void GenCollectedHeap::save_used_regions(int level) {
247 assert(level < _n_gens, "Illegal level parameter");
248 for (int i = level; i >= 0; i--) {
249 _gens[i]->save_used_region();
250 }
251 }
253 size_t GenCollectedHeap::max_capacity() const {
254 size_t res = 0;
255 for (int i = 0; i < _n_gens; i++) {
256 res += _gens[i]->max_capacity();
257 }
258 return res;
259 }
261 // Update the _full_collections_completed counter
262 // at the end of a stop-world full GC.
263 unsigned int GenCollectedHeap::update_full_collections_completed() {
264 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
265 assert(_full_collections_completed <= _total_full_collections,
266 "Can't complete more collections than were started");
267 _full_collections_completed = _total_full_collections;
268 ml.notify_all();
269 return _full_collections_completed;
270 }
272 // Update the _full_collections_completed counter, as appropriate,
273 // at the end of a concurrent GC cycle. Note the conditional update
274 // below to allow this method to be called by a concurrent collector
275 // without synchronizing in any manner with the VM thread (which
276 // may already have initiated a STW full collection "concurrently").
277 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
278 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
279 assert((_full_collections_completed <= _total_full_collections) &&
280 (count <= _total_full_collections),
281 "Can't complete more collections than were started");
282 if (count > _full_collections_completed) {
283 _full_collections_completed = count;
284 ml.notify_all();
285 }
286 return _full_collections_completed;
287 }
290 #ifndef PRODUCT
291 // Override of memory state checking method in CollectedHeap:
292 // Some collectors (CMS for example) can't have badHeapWordVal written
293 // in the first two words of an object. (For instance , in the case of
294 // CMS these words hold state used to synchronize between certain
295 // (concurrent) GC steps and direct allocating mutators.)
296 // The skip_header_HeapWords() method below, allows us to skip
297 // over the requisite number of HeapWord's. Note that (for
298 // generational collectors) this means that those many words are
299 // skipped in each object, irrespective of the generation in which
300 // that object lives. The resultant loss of precision seems to be
301 // harmless and the pain of avoiding that imprecision appears somewhat
302 // higher than we are prepared to pay for such rudimentary debugging
303 // support.
304 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
305 size_t size) {
306 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
307 // We are asked to check a size in HeapWords,
308 // but the memory is mangled in juint words.
309 juint* start = (juint*) (addr + skip_header_HeapWords());
310 juint* end = (juint*) (addr + size);
311 for (juint* slot = start; slot < end; slot += 1) {
312 assert(*slot == badHeapWordVal,
313 "Found non badHeapWordValue in pre-allocation check");
314 }
315 }
316 }
317 #endif
319 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
320 bool is_tlab,
321 bool first_only) {
322 HeapWord* res;
323 for (int i = 0; i < _n_gens; i++) {
324 if (_gens[i]->should_allocate(size, is_tlab)) {
325 res = _gens[i]->allocate(size, is_tlab);
326 if (res != NULL) return res;
327 else if (first_only) break;
328 }
329 }
330 // Otherwise...
331 return NULL;
332 }
334 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
335 bool* gc_overhead_limit_was_exceeded) {
336 return collector_policy()->mem_allocate_work(size,
337 false /* is_tlab */,
338 gc_overhead_limit_was_exceeded);
339 }
341 bool GenCollectedHeap::must_clear_all_soft_refs() {
342 return _gc_cause == GCCause::_last_ditch_collection;
343 }
345 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
346 return UseConcMarkSweepGC &&
347 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
348 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
349 }
351 void GenCollectedHeap::do_collection(bool full,
352 bool clear_all_soft_refs,
353 size_t size,
354 bool is_tlab,
355 int max_level) {
356 bool prepared_for_verification = false;
357 ResourceMark rm;
358 DEBUG_ONLY(Thread* my_thread = Thread::current();)
360 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
361 assert(my_thread->is_VM_thread() ||
362 my_thread->is_ConcurrentGC_thread(),
363 "incorrect thread type capability");
364 assert(Heap_lock->is_locked(),
365 "the requesting thread should have the Heap_lock");
366 guarantee(!is_gc_active(), "collection is not reentrant");
367 assert(max_level < n_gens(), "sanity check");
369 if (GC_locker::check_active_before_gc()) {
370 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
371 }
373 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
374 collector_policy()->should_clear_all_soft_refs();
376 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
378 const size_t metadata_prev_used = MetaspaceAux::used_bytes();
380 print_heap_before_gc();
382 {
383 FlagSetting fl(_is_gc_active, true);
385 bool complete = full && (max_level == (n_gens()-1));
386 const char* gc_cause_prefix = complete ? "Full GC" : "GC";
387 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
388 // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
389 // so we can assume here that the next GC id is what we want.
390 GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek());
392 gc_prologue(complete);
393 increment_total_collections(complete);
395 size_t gch_prev_used = used();
397 int starting_level = 0;
398 if (full) {
399 // Search for the oldest generation which will collect all younger
400 // generations, and start collection loop there.
401 for (int i = max_level; i >= 0; i--) {
402 if (_gens[i]->full_collects_younger_generations()) {
403 starting_level = i;
404 break;
405 }
406 }
407 }
409 bool must_restore_marks_for_biased_locking = false;
411 int max_level_collected = starting_level;
412 for (int i = starting_level; i <= max_level; i++) {
413 if (_gens[i]->should_collect(full, size, is_tlab)) {
414 if (i == n_gens() - 1) { // a major collection is to happen
415 if (!complete) {
416 // The full_collections increment was missed above.
417 increment_total_full_collections();
418 }
419 pre_full_gc_dump(NULL); // do any pre full gc dumps
420 }
421 // Timer for individual generations. Last argument is false: no CR
422 // FIXME: We should try to start the timing earlier to cover more of the GC pause
423 // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
424 // so we can assume here that the next GC id is what we want.
425 GCTraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, NULL, GCId::peek());
426 TraceCollectorStats tcs(_gens[i]->counters());
427 TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());
429 size_t prev_used = _gens[i]->used();
430 _gens[i]->stat_record()->invocations++;
431 _gens[i]->stat_record()->accumulated_time.start();
433 // Must be done anew before each collection because
434 // a previous collection will do mangling and will
435 // change top of some spaces.
436 record_gen_tops_before_GC();
438 if (PrintGC && Verbose) {
439 gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
440 i,
441 _gens[i]->stat_record()->invocations,
442 size*HeapWordSize);
443 }
445 if (VerifyBeforeGC && i >= VerifyGCLevel &&
446 total_collections() >= VerifyGCStartAt) {
447 HandleMark hm; // Discard invalid handles created during verification
448 if (!prepared_for_verification) {
449 prepare_for_verify();
450 prepared_for_verification = true;
451 }
452 Universe::verify(" VerifyBeforeGC:");
453 }
454 COMPILER2_PRESENT(DerivedPointerTable::clear());
456 if (!must_restore_marks_for_biased_locking &&
457 _gens[i]->performs_in_place_marking()) {
458 // We perform this mark word preservation work lazily
459 // because it's only at this point that we know whether we
460 // absolutely have to do it; we want to avoid doing it for
461 // scavenge-only collections where it's unnecessary
462 must_restore_marks_for_biased_locking = true;
463 BiasedLocking::preserve_marks();
464 }
466 // Do collection work
467 {
468 // Note on ref discovery: For what appear to be historical reasons,
469 // GCH enables and disabled (by enqueing) refs discovery.
470 // In the future this should be moved into the generation's
471 // collect method so that ref discovery and enqueueing concerns
472 // are local to a generation. The collect method could return
473 // an appropriate indication in the case that notification on
474 // the ref lock was needed. This will make the treatment of
475 // weak refs more uniform (and indeed remove such concerns
476 // from GCH). XXX
478 HandleMark hm; // Discard invalid handles created during gc
479 save_marks(); // save marks for all gens
480 // We want to discover references, but not process them yet.
481 // This mode is disabled in process_discovered_references if the
482 // generation does some collection work, or in
483 // enqueue_discovered_references if the generation returns
484 // without doing any work.
485 ReferenceProcessor* rp = _gens[i]->ref_processor();
486 // If the discovery of ("weak") refs in this generation is
487 // atomic wrt other collectors in this configuration, we
488 // are guaranteed to have empty discovered ref lists.
489 if (rp->discovery_is_atomic()) {
490 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
491 rp->setup_policy(do_clear_all_soft_refs);
492 } else {
493 // collect() below will enable discovery as appropriate
494 }
495 _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
496 if (!rp->enqueuing_is_done()) {
497 rp->enqueue_discovered_references();
498 } else {
499 rp->set_enqueuing_is_done(false);
500 }
501 rp->verify_no_references_recorded();
502 }
503 max_level_collected = i;
505 // Determine if allocation request was met.
506 if (size > 0) {
507 if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
508 if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
509 size = 0;
510 }
511 }
512 }
514 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
516 _gens[i]->stat_record()->accumulated_time.stop();
518 update_gc_stats(i, full);
520 if (VerifyAfterGC && i >= VerifyGCLevel &&
521 total_collections() >= VerifyGCStartAt) {
522 HandleMark hm; // Discard invalid handles created during verification
523 Universe::verify(" VerifyAfterGC:");
524 }
526 if (PrintGCDetails) {
527 gclog_or_tty->print(":");
528 _gens[i]->print_heap_change(prev_used);
529 }
530 }
531 }
533 // Update "complete" boolean wrt what actually transpired --
534 // for instance, a promotion failure could have led to
535 // a whole heap collection.
536 complete = complete || (max_level_collected == n_gens() - 1);
538 if (complete) { // We did a "major" collection
539 // FIXME: See comment at pre_full_gc_dump call
540 post_full_gc_dump(NULL); // do any post full gc dumps
541 }
543 if (PrintGCDetails) {
544 print_heap_change(gch_prev_used);
546 // Print metaspace info for full GC with PrintGCDetails flag.
547 if (complete) {
548 MetaspaceAux::print_metaspace_change(metadata_prev_used);
549 }
550 }
552 for (int j = max_level_collected; j >= 0; j -= 1) {
553 // Adjust generation sizes.
554 _gens[j]->compute_new_size();
555 }
557 if (complete) {
558 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
559 ClassLoaderDataGraph::purge();
560 MetaspaceAux::verify_metrics();
561 // Resize the metaspace capacity after full collections
562 MetaspaceGC::compute_new_size();
563 update_full_collections_completed();
564 }
566 // Track memory usage and detect low memory after GC finishes
567 MemoryService::track_memory_usage();
569 gc_epilogue(complete);
571 if (must_restore_marks_for_biased_locking) {
572 BiasedLocking::restore_marks();
573 }
574 }
576 AdaptiveSizePolicy* sp = gen_policy()->size_policy();
577 AdaptiveSizePolicyOutput(sp, total_collections());
579 print_heap_after_gc();
581 #ifdef TRACESPINNING
582 ParallelTaskTerminator::print_termination_counts();
583 #endif
584 }
586 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
587 return collector_policy()->satisfy_failed_allocation(size, is_tlab);
588 }
590 void GenCollectedHeap::set_par_threads(uint t) {
591 SharedHeap::set_par_threads(t);
592 _gen_process_roots_tasks->set_n_threads(t);
593 }
595 void GenCollectedHeap::
596 gen_process_roots(int level,
597 bool younger_gens_as_roots,
598 bool activate_scope,
599 SharedHeap::ScanningOption so,
600 OopsInGenClosure* not_older_gens,
601 OopsInGenClosure* weak_roots,
602 OopsInGenClosure* older_gens,
603 CLDClosure* cld_closure,
604 CLDClosure* weak_cld_closure,
605 CodeBlobClosure* code_closure) {
607 // General roots.
608 SharedHeap::process_roots(activate_scope, so,
609 not_older_gens, weak_roots,
610 cld_closure, weak_cld_closure,
611 code_closure);
613 if (younger_gens_as_roots) {
614 if (!_gen_process_roots_tasks->is_task_claimed(GCH_PS_younger_gens)) {
615 for (int i = 0; i < level; i++) {
616 not_older_gens->set_generation(_gens[i]);
617 _gens[i]->oop_iterate(not_older_gens);
618 }
619 not_older_gens->reset_generation();
620 }
621 }
622 // When collection is parallel, all threads get to cooperate to do
623 // older-gen scanning.
624 for (int i = level+1; i < _n_gens; i++) {
625 older_gens->set_generation(_gens[i]);
626 rem_set()->younger_refs_iterate(_gens[i], older_gens);
627 older_gens->reset_generation();
628 }
630 _gen_process_roots_tasks->all_tasks_completed();
631 }
633 void GenCollectedHeap::
634 gen_process_roots(int level,
635 bool younger_gens_as_roots,
636 bool activate_scope,
637 SharedHeap::ScanningOption so,
638 bool only_strong_roots,
639 OopsInGenClosure* not_older_gens,
640 OopsInGenClosure* older_gens,
641 CLDClosure* cld_closure) {
643 const bool is_adjust_phase = !only_strong_roots && !younger_gens_as_roots;
645 bool is_moving_collection = false;
646 if (level == 0 || is_adjust_phase) {
647 // young collections are always moving
648 is_moving_collection = true;
649 }
651 MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection);
652 CodeBlobClosure* code_closure = &mark_code_closure;
654 gen_process_roots(level,
655 younger_gens_as_roots,
656 activate_scope, so,
657 not_older_gens, only_strong_roots ? NULL : not_older_gens,
658 older_gens,
659 cld_closure, only_strong_roots ? NULL : cld_closure,
660 code_closure);
662 }
664 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
665 SharedHeap::process_weak_roots(root_closure);
666 // "Local" "weak" refs
667 for (int i = 0; i < _n_gens; i++) {
668 _gens[i]->ref_processor()->weak_oops_do(root_closure);
669 }
670 }
672 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \
673 void GenCollectedHeap:: \
674 oop_since_save_marks_iterate(int level, \
675 OopClosureType* cur, \
676 OopClosureType* older) { \
677 _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \
678 for (int i = level+1; i < n_gens(); i++) { \
679 _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \
680 } \
681 }
683 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
685 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
687 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
688 for (int i = level; i < _n_gens; i++) {
689 if (!_gens[i]->no_allocs_since_save_marks()) return false;
690 }
691 return true;
692 }
694 bool GenCollectedHeap::supports_inline_contig_alloc() const {
695 return _gens[0]->supports_inline_contig_alloc();
696 }
698 HeapWord** GenCollectedHeap::top_addr() const {
699 return _gens[0]->top_addr();
700 }
702 HeapWord** GenCollectedHeap::end_addr() const {
703 return _gens[0]->end_addr();
704 }
706 // public collection interfaces
708 void GenCollectedHeap::collect(GCCause::Cause cause) {
709 if (should_do_concurrent_full_gc(cause)) {
710 #if INCLUDE_ALL_GCS
711 // mostly concurrent full collection
712 collect_mostly_concurrent(cause);
713 #else // INCLUDE_ALL_GCS
714 ShouldNotReachHere();
715 #endif // INCLUDE_ALL_GCS
716 } else if (cause == GCCause::_wb_young_gc) {
717 // minor collection for WhiteBox API
718 collect(cause, 0);
719 } else {
720 #ifdef ASSERT
721 if (cause == GCCause::_scavenge_alot) {
722 // minor collection only
723 collect(cause, 0);
724 } else {
725 // Stop-the-world full collection
726 collect(cause, n_gens() - 1);
727 }
728 #else
729 // Stop-the-world full collection
730 collect(cause, n_gens() - 1);
731 #endif
732 }
733 }
735 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
736 // The caller doesn't have the Heap_lock
737 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
738 MutexLocker ml(Heap_lock);
739 collect_locked(cause, max_level);
740 }
742 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
743 // The caller has the Heap_lock
744 assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
745 collect_locked(cause, n_gens() - 1);
746 }
748 // this is the private collection interface
749 // The Heap_lock is expected to be held on entry.
751 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
752 // Read the GC count while holding the Heap_lock
753 unsigned int gc_count_before = total_collections();
754 unsigned int full_gc_count_before = total_full_collections();
755 {
756 MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
757 VM_GenCollectFull op(gc_count_before, full_gc_count_before,
758 cause, max_level);
759 VMThread::execute(&op);
760 }
761 }
763 #if INCLUDE_ALL_GCS
764 bool GenCollectedHeap::create_cms_collector() {
766 assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
767 (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)),
768 "Unexpected generation kinds");
769 // Skip two header words in the block content verification
770 NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
771 CMSCollector* collector = new CMSCollector(
772 (ConcurrentMarkSweepGeneration*)_gens[1],
773 _rem_set->as_CardTableRS(),
774 (ConcurrentMarkSweepPolicy*) collector_policy());
776 if (collector == NULL || !collector->completed_initialization()) {
777 if (collector) {
778 delete collector; // Be nice in embedded situation
779 }
780 vm_shutdown_during_initialization("Could not create CMS collector");
781 return false;
782 }
783 return true; // success
784 }
786 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
787 assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
789 MutexLocker ml(Heap_lock);
790 // Read the GC counts while holding the Heap_lock
791 unsigned int full_gc_count_before = total_full_collections();
792 unsigned int gc_count_before = total_collections();
793 {
794 MutexUnlocker mu(Heap_lock);
795 VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
796 VMThread::execute(&op);
797 }
798 }
799 #endif // INCLUDE_ALL_GCS
801 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
802 do_full_collection(clear_all_soft_refs, _n_gens - 1);
803 }
805 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
806 int max_level) {
807 int local_max_level;
808 if (!incremental_collection_will_fail(false /* don't consult_young */) &&
809 gc_cause() == GCCause::_gc_locker) {
810 local_max_level = 0;
811 } else {
812 local_max_level = max_level;
813 }
815 do_collection(true /* full */,
816 clear_all_soft_refs /* clear_all_soft_refs */,
817 0 /* size */,
818 false /* is_tlab */,
819 local_max_level /* max_level */);
820 // Hack XXX FIX ME !!!
821 // A scavenge may not have been attempted, or may have
822 // been attempted and failed, because the old gen was too full
823 if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
824 incremental_collection_will_fail(false /* don't consult_young */)) {
825 if (PrintGCDetails) {
826 gclog_or_tty->print_cr("GC locker: Trying a full collection "
827 "because scavenge failed");
828 }
829 // This time allow the old gen to be collected as well
830 do_collection(true /* full */,
831 clear_all_soft_refs /* clear_all_soft_refs */,
832 0 /* size */,
833 false /* is_tlab */,
834 n_gens() - 1 /* max_level */);
835 }
836 }
838 bool GenCollectedHeap::is_in_young(oop p) {
839 bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
840 assert(result == _gens[0]->is_in_reserved(p),
841 err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, p2i((void*)p)));
842 return result;
843 }
845 // Returns "TRUE" iff "p" points into the committed areas of the heap.
846 bool GenCollectedHeap::is_in(const void* p) const {
847 #ifndef ASSERT
848 guarantee(VerifyBeforeGC ||
849 VerifyDuringGC ||
850 VerifyBeforeExit ||
851 VerifyDuringStartup ||
852 PrintAssembly ||
853 tty->count() != 0 || // already printing
854 VerifyAfterGC ||
855 VMError::fatal_error_in_progress(), "too expensive");
857 #endif
858 // This might be sped up with a cache of the last generation that
859 // answered yes.
860 for (int i = 0; i < _n_gens; i++) {
861 if (_gens[i]->is_in(p)) return true;
862 }
863 // Otherwise...
864 return false;
865 }
867 #ifdef ASSERT
868 // Don't implement this by using is_in_young(). This method is used
869 // in some cases to check that is_in_young() is correct.
870 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
871 assert(is_in_reserved(p) || p == NULL,
872 "Does not work if address is non-null and outside of the heap");
873 return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
874 }
875 #endif
877 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
878 for (int i = 0; i < _n_gens; i++) {
879 _gens[i]->oop_iterate(cl);
880 }
881 }
883 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
884 for (int i = 0; i < _n_gens; i++) {
885 _gens[i]->object_iterate(cl);
886 }
887 }
889 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
890 for (int i = 0; i < _n_gens; i++) {
891 _gens[i]->safe_object_iterate(cl);
892 }
893 }
895 Space* GenCollectedHeap::space_containing(const void* addr) const {
896 for (int i = 0; i < _n_gens; i++) {
897 Space* res = _gens[i]->space_containing(addr);
898 if (res != NULL) return res;
899 }
900 // Otherwise...
901 assert(false, "Could not find containing space");
902 return NULL;
903 }
906 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
907 assert(is_in_reserved(addr), "block_start of address outside of heap");
908 for (int i = 0; i < _n_gens; i++) {
909 if (_gens[i]->is_in_reserved(addr)) {
910 assert(_gens[i]->is_in(addr),
911 "addr should be in allocated part of generation");
912 return _gens[i]->block_start(addr);
913 }
914 }
915 assert(false, "Some generation should contain the address");
916 return NULL;
917 }
919 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
920 assert(is_in_reserved(addr), "block_size of address outside of heap");
921 for (int i = 0; i < _n_gens; i++) {
922 if (_gens[i]->is_in_reserved(addr)) {
923 assert(_gens[i]->is_in(addr),
924 "addr should be in allocated part of generation");
925 return _gens[i]->block_size(addr);
926 }
927 }
928 assert(false, "Some generation should contain the address");
929 return 0;
930 }
932 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
933 assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
934 assert(block_start(addr) == addr, "addr must be a block start");
935 for (int i = 0; i < _n_gens; i++) {
936 if (_gens[i]->is_in_reserved(addr)) {
937 return _gens[i]->block_is_obj(addr);
938 }
939 }
940 assert(false, "Some generation should contain the address");
941 return false;
942 }
944 bool GenCollectedHeap::supports_tlab_allocation() const {
945 for (int i = 0; i < _n_gens; i += 1) {
946 if (_gens[i]->supports_tlab_allocation()) {
947 return true;
948 }
949 }
950 return false;
951 }
953 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
954 size_t result = 0;
955 for (int i = 0; i < _n_gens; i += 1) {
956 if (_gens[i]->supports_tlab_allocation()) {
957 result += _gens[i]->tlab_capacity();
958 }
959 }
960 return result;
961 }
963 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
964 size_t result = 0;
965 for (int i = 0; i < _n_gens; i += 1) {
966 if (_gens[i]->supports_tlab_allocation()) {
967 result += _gens[i]->tlab_used();
968 }
969 }
970 return result;
971 }
973 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
974 size_t result = 0;
975 for (int i = 0; i < _n_gens; i += 1) {
976 if (_gens[i]->supports_tlab_allocation()) {
977 result += _gens[i]->unsafe_max_tlab_alloc();
978 }
979 }
980 return result;
981 }
983 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
984 bool gc_overhead_limit_was_exceeded;
985 return collector_policy()->mem_allocate_work(size /* size */,
986 true /* is_tlab */,
987 &gc_overhead_limit_was_exceeded);
988 }
990 // Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size
991 // from the list headed by "*prev_ptr".
992 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
993 bool first = true;
994 size_t min_size = 0; // "first" makes this conceptually infinite.
995 ScratchBlock **smallest_ptr, *smallest;
996 ScratchBlock *cur = *prev_ptr;
997 while (cur) {
998 assert(*prev_ptr == cur, "just checking");
999 if (first || cur->num_words < min_size) {
1000 smallest_ptr = prev_ptr;
1001 smallest = cur;
1002 min_size = smallest->num_words;
1003 first = false;
1004 }
1005 prev_ptr = &cur->next;
1006 cur = cur->next;
1007 }
1008 smallest = *smallest_ptr;
1009 *smallest_ptr = smallest->next;
1010 return smallest;
1011 }
1013 // Sort the scratch block list headed by res into decreasing size order,
1014 // and set "res" to the result.
1015 static void sort_scratch_list(ScratchBlock*& list) {
1016 ScratchBlock* sorted = NULL;
1017 ScratchBlock* unsorted = list;
1018 while (unsorted) {
1019 ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1020 smallest->next = sorted;
1021 sorted = smallest;
1022 }
1023 list = sorted;
1024 }
1026 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1027 size_t max_alloc_words) {
1028 ScratchBlock* res = NULL;
1029 for (int i = 0; i < _n_gens; i++) {
1030 _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1031 }
1032 sort_scratch_list(res);
1033 return res;
1034 }
1036 void GenCollectedHeap::release_scratch() {
1037 for (int i = 0; i < _n_gens; i++) {
1038 _gens[i]->reset_scratch();
1039 }
1040 }
1042 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1043 void do_generation(Generation* gen) {
1044 gen->prepare_for_verify();
1045 }
1046 };
1048 void GenCollectedHeap::prepare_for_verify() {
1049 ensure_parsability(false); // no need to retire TLABs
1050 GenPrepareForVerifyClosure blk;
1051 generation_iterate(&blk, false);
1052 }
1055 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1056 bool old_to_young) {
1057 if (old_to_young) {
1058 for (int i = _n_gens-1; i >= 0; i--) {
1059 cl->do_generation(_gens[i]);
1060 }
1061 } else {
1062 for (int i = 0; i < _n_gens; i++) {
1063 cl->do_generation(_gens[i]);
1064 }
1065 }
1066 }
1068 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1069 for (int i = 0; i < _n_gens; i++) {
1070 _gens[i]->space_iterate(cl, true);
1071 }
1072 }
1074 bool GenCollectedHeap::is_maximal_no_gc() const {
1075 for (int i = 0; i < _n_gens; i++) {
1076 if (!_gens[i]->is_maximal_no_gc()) {
1077 return false;
1078 }
1079 }
1080 return true;
1081 }
1083 void GenCollectedHeap::save_marks() {
1084 for (int i = 0; i < _n_gens; i++) {
1085 _gens[i]->save_marks();
1086 }
1087 }
1089 GenCollectedHeap* GenCollectedHeap::heap() {
1090 assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1091 assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1092 return _gch;
1093 }
1096 void GenCollectedHeap::prepare_for_compaction() {
1097 guarantee(_n_gens = 2, "Wrong number of generations");
1098 Generation* old_gen = _gens[1];
1099 // Start by compacting into same gen.
1100 CompactPoint cp(old_gen);
1101 old_gen->prepare_for_compaction(&cp);
1102 Generation* young_gen = _gens[0];
1103 young_gen->prepare_for_compaction(&cp);
1104 }
1106 GCStats* GenCollectedHeap::gc_stats(int level) const {
1107 return _gens[level]->gc_stats();
1108 }
1110 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) {
1111 for (int i = _n_gens-1; i >= 0; i--) {
1112 Generation* g = _gens[i];
1113 if (!silent) {
1114 gclog_or_tty->print("%s", g->name());
1115 gclog_or_tty->print(" ");
1116 }
1117 g->verify();
1118 }
1119 if (!silent) {
1120 gclog_or_tty->print("remset ");
1121 }
1122 rem_set()->verify();
1123 }
1125 void GenCollectedHeap::print_on(outputStream* st) const {
1126 for (int i = 0; i < _n_gens; i++) {
1127 _gens[i]->print_on(st);
1128 }
1129 MetaspaceAux::print_on(st);
1130 }
1132 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1133 if (workers() != NULL) {
1134 workers()->threads_do(tc);
1135 }
1136 #if INCLUDE_ALL_GCS
1137 if (UseConcMarkSweepGC) {
1138 ConcurrentMarkSweepThread::threads_do(tc);
1139 }
1140 #endif // INCLUDE_ALL_GCS
1141 }
1143 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1144 #if INCLUDE_ALL_GCS
1145 if (UseParNewGC) {
1146 workers()->print_worker_threads_on(st);
1147 }
1148 if (UseConcMarkSweepGC) {
1149 ConcurrentMarkSweepThread::print_all_on(st);
1150 }
1151 #endif // INCLUDE_ALL_GCS
1152 }
1154 void GenCollectedHeap::print_on_error(outputStream* st) const {
1155 this->CollectedHeap::print_on_error(st);
1157 #if INCLUDE_ALL_GCS
1158 if (UseConcMarkSweepGC) {
1159 st->cr();
1160 CMSCollector::print_on_error(st);
1161 }
1162 #endif // INCLUDE_ALL_GCS
1163 }
1165 void GenCollectedHeap::print_tracing_info() const {
1166 if (TraceGen0Time) {
1167 get_gen(0)->print_summary_info();
1168 }
1169 if (TraceGen1Time) {
1170 get_gen(1)->print_summary_info();
1171 }
1172 }
1174 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1175 if (PrintGCDetails && Verbose) {
1176 gclog_or_tty->print(" " SIZE_FORMAT
1177 "->" SIZE_FORMAT
1178 "(" SIZE_FORMAT ")",
1179 prev_used, used(), capacity());
1180 } else {
1181 gclog_or_tty->print(" " SIZE_FORMAT "K"
1182 "->" SIZE_FORMAT "K"
1183 "(" SIZE_FORMAT "K)",
1184 prev_used / K, used() / K, capacity() / K);
1185 }
1186 }
1188 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1189 private:
1190 bool _full;
1191 public:
1192 void do_generation(Generation* gen) {
1193 gen->gc_prologue(_full);
1194 }
1195 GenGCPrologueClosure(bool full) : _full(full) {};
1196 };
1198 void GenCollectedHeap::gc_prologue(bool full) {
1199 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1201 always_do_update_barrier = false;
1202 // Fill TLAB's and such
1203 CollectedHeap::accumulate_statistics_all_tlabs();
1204 ensure_parsability(true); // retire TLABs
1206 // Walk generations
1207 GenGCPrologueClosure blk(full);
1208 generation_iterate(&blk, false); // not old-to-young.
1209 };
1211 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1212 private:
1213 bool _full;
1214 public:
1215 void do_generation(Generation* gen) {
1216 gen->gc_epilogue(_full);
1217 }
1218 GenGCEpilogueClosure(bool full) : _full(full) {};
1219 };
1221 void GenCollectedHeap::gc_epilogue(bool full) {
1222 #ifdef COMPILER2
1223 assert(DerivedPointerTable::is_empty(), "derived pointer present");
1224 size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1225 guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1226 #endif /* COMPILER2 */
1228 resize_all_tlabs();
1230 GenGCEpilogueClosure blk(full);
1231 generation_iterate(&blk, false); // not old-to-young.
1233 if (!CleanChunkPoolAsync) {
1234 Chunk::clean_chunk_pool();
1235 }
1237 MetaspaceCounters::update_performance_counters();
1238 CompressedClassSpaceCounters::update_performance_counters();
1240 always_do_update_barrier = UseConcMarkSweepGC;
1241 };
1243 #ifndef PRODUCT
1244 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1245 private:
1246 public:
1247 void do_generation(Generation* gen) {
1248 gen->record_spaces_top();
1249 }
1250 };
1252 void GenCollectedHeap::record_gen_tops_before_GC() {
1253 if (ZapUnusedHeapArea) {
1254 GenGCSaveTopsBeforeGCClosure blk;
1255 generation_iterate(&blk, false); // not old-to-young.
1256 }
1257 }
1258 #endif // not PRODUCT
1260 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1261 public:
1262 void do_generation(Generation* gen) {
1263 gen->ensure_parsability();
1264 }
1265 };
1267 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1268 CollectedHeap::ensure_parsability(retire_tlabs);
1269 GenEnsureParsabilityClosure ep_cl;
1270 generation_iterate(&ep_cl, false);
1271 }
1273 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
1274 oop obj,
1275 size_t obj_size) {
1276 guarantee(old_gen->level() == 1, "We only get here with an old generation");
1277 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1278 HeapWord* result = NULL;
1280 result = old_gen->expand_and_allocate(obj_size, false);
1282 if (result != NULL) {
1283 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1284 }
1285 return oop(result);
1286 }
1288 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1289 jlong _time; // in ms
1290 jlong _now; // in ms
1292 public:
1293 GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1295 jlong time() { return _time; }
1297 void do_generation(Generation* gen) {
1298 _time = MIN2(_time, gen->time_of_last_gc(_now));
1299 }
1300 };
1302 jlong GenCollectedHeap::millis_since_last_gc() {
1303 // We need a monotonically non-deccreasing time in ms but
1304 // os::javaTimeMillis() does not guarantee monotonicity.
1305 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1306 GenTimeOfLastGCClosure tolgc_cl(now);
1307 // iterate over generations getting the oldest
1308 // time that a generation was collected
1309 generation_iterate(&tolgc_cl, false);
1311 // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1312 // provided the underlying platform provides such a time source
1313 // (and it is bug free). So we still have to guard against getting
1314 // back a time later than 'now'.
1315 jlong retVal = now - tolgc_cl.time();
1316 if (retVal < 0) {
1317 NOT_PRODUCT(warning("time warp: "INT64_FORMAT, (int64_t) retVal);)
1318 return 0;
1319 }
1320 return retVal;
1321 }