1 /*
2 * Copyright (c) 2000, 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 "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/vmGCOperations.hpp"
32 #include "gc_interface/collectedHeap.inline.hpp"
33 #include "memory/filemap.hpp"
34 #include "memory/gcLocker.inline.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/genOopClosures.inline.hpp"
37 #include "memory/generation.inline.hpp"
38 #include "memory/generationSpec.hpp"
39 #include "memory/resourceArea.hpp"
40 #include "memory/sharedHeap.hpp"
41 #include "memory/space.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "oops/oop.inline2.hpp"
44 #include "runtime/biasedLocking.hpp"
45 #include "runtime/fprofiler.hpp"
46 #include "runtime/handles.hpp"
47 #include "runtime/handles.inline.hpp"
48 #include "runtime/java.hpp"
49 #include "runtime/vmThread.hpp"
50 #include "services/memoryService.hpp"
51 #include "utilities/vmError.hpp"
52 #include "utilities/workgroup.hpp"
53 #include "utilities/macros.hpp"
54 #if INCLUDE_ALL_GCS
55 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
56 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
57 #endif // INCLUDE_ALL_GCS
58
59 GenCollectedHeap* GenCollectedHeap::_gch;
60 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
61
62 // The set of potentially parallel tasks in strong root scanning.
63 enum GCH_process_strong_roots_tasks {
64 // We probably want to parallelize both of these internally, but for now...
65 GCH_PS_younger_gens,
66 // Leave this one last.
67 GCH_PS_NumElements
68 };
69
70 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
71 SharedHeap(policy),
72 _gen_policy(policy),
73 _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
74 _full_collections_completed(0)
75 {
76 if (_gen_process_strong_tasks == NULL ||
77 !_gen_process_strong_tasks->valid()) {
78 vm_exit_during_initialization("Failed necessary allocation.");
79 }
80 assert(policy != NULL, "Sanity check");
81 }
82
83 jint GenCollectedHeap::initialize() {
84 CollectedHeap::pre_initialize();
85
86 int i;
87 _n_gens = gen_policy()->number_of_generations();
88
89 // While there are no constraints in the GC code that HeapWordSize
90 // be any particular value, there are multiple other areas in the
91 // system which believe this to be true (e.g. oop->object_size in some
92 // cases incorrectly returns the size in wordSize units rather than
93 // HeapWordSize).
94 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
95
96 // The heap must be at least as aligned as generations.
97 size_t alignment = Generation::GenGrain;
98
99 _gen_specs = gen_policy()->generations();
100
101 // Make sure the sizes are all aligned.
102 for (i = 0; i < _n_gens; i++) {
103 _gen_specs[i]->align(alignment);
104 }
105
106 // Allocate space for the heap.
107
108 char* heap_address;
109 size_t total_reserved = 0;
110 int n_covered_regions = 0;
111 ReservedSpace heap_rs(0);
112
113 heap_address = allocate(alignment, &total_reserved,
114 &n_covered_regions, &heap_rs);
115
116 if (!heap_rs.is_reserved()) {
117 vm_shutdown_during_initialization(
118 "Could not reserve enough space for object heap");
119 return JNI_ENOMEM;
120 }
121
122 _reserved = MemRegion((HeapWord*)heap_rs.base(),
123 (HeapWord*)(heap_rs.base() + heap_rs.size()));
124
125 // It is important to do this in a way such that concurrent readers can't
126 // temporarily think somethings in the heap. (Seen this happen in asserts.)
127 _reserved.set_word_size(0);
128 _reserved.set_start((HeapWord*)heap_rs.base());
129 size_t actual_heap_size = heap_rs.size();
130 _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
131
132 _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
133 set_barrier_set(rem_set()->bs());
134
135 _gch = this;
136
137 for (i = 0; i < _n_gens; i++) {
138 ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false);
139 _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
140 heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
141 }
142 clear_incremental_collection_failed();
143
144 #if INCLUDE_ALL_GCS
145 // If we are running CMS, create the collector responsible
146 // for collecting the CMS generations.
147 if (collector_policy()->is_concurrent_mark_sweep_policy()) {
148 bool success = create_cms_collector();
149 if (!success) return JNI_ENOMEM;
150 }
151 #endif // INCLUDE_ALL_GCS
152
153 return JNI_OK;
154 }
155
156
157 char* GenCollectedHeap::allocate(size_t alignment,
158 size_t* _total_reserved,
159 int* _n_covered_regions,
160 ReservedSpace* heap_rs){
161 const char overflow_msg[] = "The size of the object heap + VM data exceeds "
162 "the maximum representable size";
163
164 // Now figure out the total size.
165 size_t total_reserved = 0;
166 int n_covered_regions = 0;
167 const size_t pageSize = UseLargePages ?
168 os::large_page_size() : os::vm_page_size();
169
170 for (int i = 0; i < _n_gens; i++) {
171 total_reserved += _gen_specs[i]->max_size();
172 if (total_reserved < _gen_specs[i]->max_size()) {
173 vm_exit_during_initialization(overflow_msg);
174 }
175 n_covered_regions += _gen_specs[i]->n_covered_regions();
176 }
177 assert(total_reserved % pageSize == 0,
178 err_msg("Gen size; total_reserved=" SIZE_FORMAT ", pageSize="
179 SIZE_FORMAT, total_reserved, pageSize));
180
181 // Needed until the cardtable is fixed to have the right number
182 // of covered regions.
183 n_covered_regions += 2;
184
185 if (UseLargePages) {
186 assert(total_reserved != 0, "total_reserved cannot be 0");
187 total_reserved = round_to(total_reserved, os::large_page_size());
188 if (total_reserved < os::large_page_size()) {
189 vm_exit_during_initialization(overflow_msg);
190 }
191 }
192
193 *_total_reserved = total_reserved;
194 *_n_covered_regions = n_covered_regions;
195 *heap_rs = Universe::reserve_heap(total_reserved, alignment);
196 return heap_rs->base();
197 }
198
199
200 void GenCollectedHeap::post_initialize() {
201 SharedHeap::post_initialize();
202 TwoGenerationCollectorPolicy *policy =
203 (TwoGenerationCollectorPolicy *)collector_policy();
204 guarantee(policy->is_two_generation_policy(), "Illegal policy type");
205 DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
206 assert(def_new_gen->kind() == Generation::DefNew ||
207 def_new_gen->kind() == Generation::ParNew ||
208 def_new_gen->kind() == Generation::ASParNew,
209 "Wrong generation kind");
210
211 Generation* old_gen = get_gen(1);
212 assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
213 old_gen->kind() == Generation::ASConcurrentMarkSweep ||
214 old_gen->kind() == Generation::MarkSweepCompact,
215 "Wrong generation kind");
216
217 policy->initialize_size_policy(def_new_gen->eden()->capacity(),
218 old_gen->capacity(),
219 def_new_gen->from()->capacity());
220 policy->initialize_gc_policy_counters();
221 }
222
223 void GenCollectedHeap::ref_processing_init() {
224 SharedHeap::ref_processing_init();
225 for (int i = 0; i < _n_gens; i++) {
226 _gens[i]->ref_processor_init();
227 }
228 }
229
230 size_t GenCollectedHeap::capacity() const {
231 size_t res = 0;
232 for (int i = 0; i < _n_gens; i++) {
233 res += _gens[i]->capacity();
234 }
235 return res;
236 }
237
238 size_t GenCollectedHeap::used() const {
239 size_t res = 0;
240 for (int i = 0; i < _n_gens; i++) {
241 res += _gens[i]->used();
242 }
243 return res;
244 }
245
246 // Save the "used_region" for generations level and lower.
247 void GenCollectedHeap::save_used_regions(int level) {
248 assert(level < _n_gens, "Illegal level parameter");
249 for (int i = level; i >= 0; i--) {
250 _gens[i]->save_used_region();
251 }
252 }
253
254 size_t GenCollectedHeap::max_capacity() const {
255 size_t res = 0;
256 for (int i = 0; i < _n_gens; i++) {
257 res += _gens[i]->max_capacity();
258 }
259 return res;
260 }
261
262 // Update the _full_collections_completed counter
263 // at the end of a stop-world full GC.
264 unsigned int GenCollectedHeap::update_full_collections_completed() {
265 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
266 assert(_full_collections_completed <= _total_full_collections,
267 "Can't complete more collections than were started");
268 _full_collections_completed = _total_full_collections;
269 ml.notify_all();
270 return _full_collections_completed;
271 }
272
273 // Update the _full_collections_completed counter, as appropriate,
274 // at the end of a concurrent GC cycle. Note the conditional update
275 // below to allow this method to be called by a concurrent collector
276 // without synchronizing in any manner with the VM thread (which
277 // may already have initiated a STW full collection "concurrently").
278 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
279 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
280 assert((_full_collections_completed <= _total_full_collections) &&
281 (count <= _total_full_collections),
282 "Can't complete more collections than were started");
283 if (count > _full_collections_completed) {
284 _full_collections_completed = count;
285 ml.notify_all();
286 }
287 return _full_collections_completed;
288 }
289
290
291 #ifndef PRODUCT
292 // Override of memory state checking method in CollectedHeap:
293 // Some collectors (CMS for example) can't have badHeapWordVal written
294 // in the first two words of an object. (For instance , in the case of
295 // CMS these words hold state used to synchronize between certain
296 // (concurrent) GC steps and direct allocating mutators.)
297 // The skip_header_HeapWords() method below, allows us to skip
298 // over the requisite number of HeapWord's. Note that (for
299 // generational collectors) this means that those many words are
300 // skipped in each object, irrespective of the generation in which
301 // that object lives. The resultant loss of precision seems to be
302 // harmless and the pain of avoiding that imprecision appears somewhat
303 // higher than we are prepared to pay for such rudimentary debugging
304 // support.
305 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
306 size_t size) {
307 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
308 // We are asked to check a size in HeapWords,
309 // but the memory is mangled in juint words.
310 juint* start = (juint*) (addr + skip_header_HeapWords());
311 juint* end = (juint*) (addr + size);
312 for (juint* slot = start; slot < end; slot += 1) {
313 assert(*slot == badHeapWordVal,
314 "Found non badHeapWordValue in pre-allocation check");
315 }
316 }
317 }
318 #endif
319
320 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
321 bool is_tlab,
322 bool first_only) {
323 HeapWord* res;
324 for (int i = 0; i < _n_gens; i++) {
325 if (_gens[i]->should_allocate(size, is_tlab)) {
326 res = _gens[i]->allocate(size, is_tlab);
327 if (res != NULL) return res;
328 else if (first_only) break;
329 }
330 }
331 // Otherwise...
332 return NULL;
333 }
334
335 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
336 bool* gc_overhead_limit_was_exceeded) {
337 return collector_policy()->mem_allocate_work(size,
338 false /* is_tlab */,
339 gc_overhead_limit_was_exceeded);
340 }
341
342 bool GenCollectedHeap::must_clear_all_soft_refs() {
343 return _gc_cause == GCCause::_last_ditch_collection;
344 }
345
346 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
347 return UseConcMarkSweepGC &&
348 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
349 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
350 }
351
352 void GenCollectedHeap::do_collection(bool full,
353 bool clear_all_soft_refs,
354 size_t size,
355 bool is_tlab,
356 int max_level) {
357 bool prepared_for_verification = false;
358 ResourceMark rm;
359 DEBUG_ONLY(Thread* my_thread = Thread::current();)
360
361 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
362 assert(my_thread->is_VM_thread() ||
363 my_thread->is_ConcurrentGC_thread(),
364 "incorrect thread type capability");
365 assert(Heap_lock->is_locked(),
366 "the requesting thread should have the Heap_lock");
367 guarantee(!is_gc_active(), "collection is not reentrant");
368 assert(max_level < n_gens(), "sanity check");
369
370 if (GC_locker::check_active_before_gc()) {
371 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
372 }
373
374 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
375 collector_policy()->should_clear_all_soft_refs();
376
377 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
378
379 const size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
380
381 print_heap_before_gc();
382
383 {
384 FlagSetting fl(_is_gc_active, true);
385
386 bool complete = full && (max_level == (n_gens()-1));
387 const char* gc_cause_prefix = complete ? "Full GC" : "GC";
388 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
389 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
390 TraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, gclog_or_tty);
391
392 gc_prologue(complete);
393 increment_total_collections(complete);
394
395 size_t gch_prev_used = used();
396
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 }
408
409 bool must_restore_marks_for_biased_locking = false;
410
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(); // do any pre full gc dumps
420 }
421 // Timer for individual generations. Last argument is false: no CR
422 TraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, gclog_or_tty);
423 TraceCollectorStats tcs(_gens[i]->counters());
424 TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());
425
426 size_t prev_used = _gens[i]->used();
427 _gens[i]->stat_record()->invocations++;
428 _gens[i]->stat_record()->accumulated_time.start();
429
430 // Must be done anew before each collection because
431 // a previous collection will do mangling and will
432 // change top of some spaces.
433 record_gen_tops_before_GC();
434
435 if (PrintGC && Verbose) {
436 gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
437 i,
438 _gens[i]->stat_record()->invocations,
439 size*HeapWordSize);
440 }
441
442 if (VerifyBeforeGC && i >= VerifyGCLevel &&
443 total_collections() >= VerifyGCStartAt) {
444 HandleMark hm; // Discard invalid handles created during verification
445 if (!prepared_for_verification) {
446 prepare_for_verify();
447 prepared_for_verification = true;
448 }
449 Universe::verify(" VerifyBeforeGC:");
450 }
451 COMPILER2_PRESENT(DerivedPointerTable::clear());
452
453 if (!must_restore_marks_for_biased_locking &&
454 _gens[i]->performs_in_place_marking()) {
455 // We perform this mark word preservation work lazily
456 // because it's only at this point that we know whether we
457 // absolutely have to do it; we want to avoid doing it for
458 // scavenge-only collections where it's unnecessary
459 must_restore_marks_for_biased_locking = true;
460 BiasedLocking::preserve_marks();
461 }
462
463 // Do collection work
464 {
465 // Note on ref discovery: For what appear to be historical reasons,
466 // GCH enables and disabled (by enqueing) refs discovery.
467 // In the future this should be moved into the generation's
468 // collect method so that ref discovery and enqueueing concerns
469 // are local to a generation. The collect method could return
470 // an appropriate indication in the case that notification on
471 // the ref lock was needed. This will make the treatment of
472 // weak refs more uniform (and indeed remove such concerns
473 // from GCH). XXX
474
475 HandleMark hm; // Discard invalid handles created during gc
476 save_marks(); // save marks for all gens
477 // We want to discover references, but not process them yet.
478 // This mode is disabled in process_discovered_references if the
479 // generation does some collection work, or in
480 // enqueue_discovered_references if the generation returns
481 // without doing any work.
482 ReferenceProcessor* rp = _gens[i]->ref_processor();
483 // If the discovery of ("weak") refs in this generation is
484 // atomic wrt other collectors in this configuration, we
485 // are guaranteed to have empty discovered ref lists.
486 if (rp->discovery_is_atomic()) {
487 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
488 rp->setup_policy(do_clear_all_soft_refs);
489 } else {
490 // collect() below will enable discovery as appropriate
491 }
492 _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
493 if (!rp->enqueuing_is_done()) {
494 rp->enqueue_discovered_references();
495 } else {
496 rp->set_enqueuing_is_done(false);
497 }
498 rp->verify_no_references_recorded();
499 }
500 max_level_collected = i;
501
502 // Determine if allocation request was met.
503 if (size > 0) {
504 if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
505 if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
506 size = 0;
507 }
508 }
509 }
510
511 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
512
513 _gens[i]->stat_record()->accumulated_time.stop();
514
515 update_gc_stats(i, full);
516
517 if (VerifyAfterGC && i >= VerifyGCLevel &&
518 total_collections() >= VerifyGCStartAt) {
519 HandleMark hm; // Discard invalid handles created during verification
520 Universe::verify(" VerifyAfterGC:");
521 }
522
523 if (PrintGCDetails) {
524 gclog_or_tty->print(":");
525 _gens[i]->print_heap_change(prev_used);
526 }
527 }
528 }
529
530 // Update "complete" boolean wrt what actually transpired --
531 // for instance, a promotion failure could have led to
532 // a whole heap collection.
533 complete = complete || (max_level_collected == n_gens() - 1);
534
535 if (complete) { // We did a "major" collection
536 post_full_gc_dump(); // do any post full gc dumps
537 }
538
539 if (PrintGCDetails) {
540 print_heap_change(gch_prev_used);
541
542 // Print metaspace info for full GC with PrintGCDetails flag.
543 if (complete) {
544 MetaspaceAux::print_metaspace_change(metadata_prev_used);
545 }
546 }
547
548 for (int j = max_level_collected; j >= 0; j -= 1) {
549 // Adjust generation sizes.
550 _gens[j]->compute_new_size();
551 }
552
553 if (complete) {
554 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
555 ClassLoaderDataGraph::purge();
556 MetaspaceAux::verify_metrics();
557 // Resize the metaspace capacity after full collections
558 MetaspaceGC::compute_new_size();
559 update_full_collections_completed();
560 }
561
562 // Track memory usage and detect low memory after GC finishes
563 MemoryService::track_memory_usage();
564
565 gc_epilogue(complete);
566
567 if (must_restore_marks_for_biased_locking) {
568 BiasedLocking::restore_marks();
569 }
570 }
571
572 AdaptiveSizePolicy* sp = gen_policy()->size_policy();
573 AdaptiveSizePolicyOutput(sp, total_collections());
574
575 print_heap_after_gc();
576
577 #ifdef TRACESPINNING
578 ParallelTaskTerminator::print_termination_counts();
579 #endif
580 }
581
582 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
583 return collector_policy()->satisfy_failed_allocation(size, is_tlab);
584 }
585
586 void GenCollectedHeap::set_par_threads(uint t) {
587 SharedHeap::set_par_threads(t);
588 _gen_process_strong_tasks->set_n_threads(t);
589 }
590
591 void GenCollectedHeap::
592 gen_process_strong_roots(int level,
593 bool younger_gens_as_roots,
594 bool activate_scope,
595 bool is_scavenging,
596 SharedHeap::ScanningOption so,
597 OopsInGenClosure* not_older_gens,
598 bool do_code_roots,
599 OopsInGenClosure* older_gens,
600 KlassClosure* klass_closure) {
601 // General strong roots.
602
603 if (!do_code_roots) {
604 SharedHeap::process_strong_roots(activate_scope, is_scavenging, so,
605 not_older_gens, NULL, klass_closure);
606 } else {
607 bool do_code_marking = (activate_scope || nmethod::oops_do_marking_is_active());
608 CodeBlobToOopClosure code_roots(not_older_gens, /*do_marking=*/ do_code_marking);
609 SharedHeap::process_strong_roots(activate_scope, is_scavenging, so,
610 not_older_gens, &code_roots, klass_closure);
611 }
612
613 if (younger_gens_as_roots) {
614 if (!_gen_process_strong_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 }
629
630 _gen_process_strong_tasks->all_tasks_completed();
631 }
632
633 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
634 CodeBlobClosure* code_roots) {
635 SharedHeap::process_weak_roots(root_closure, code_roots);
636 // "Local" "weak" refs
637 for (int i = 0; i < _n_gens; i++) {
638 _gens[i]->ref_processor()->weak_oops_do(root_closure);
639 }
640 }
641
642 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \
643 void GenCollectedHeap:: \
644 oop_since_save_marks_iterate(int level, \
645 OopClosureType* cur, \
646 OopClosureType* older) { \
647 _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \
648 for (int i = level+1; i < n_gens(); i++) { \
649 _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \
650 } \
651 }
652
653 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
654
655 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
656
657 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
658 for (int i = level; i < _n_gens; i++) {
659 if (!_gens[i]->no_allocs_since_save_marks()) return false;
660 }
661 return true;
662 }
663
664 bool GenCollectedHeap::supports_inline_contig_alloc() const {
665 return _gens[0]->supports_inline_contig_alloc();
666 }
667
668 HeapWord** GenCollectedHeap::top_addr() const {
669 return _gens[0]->top_addr();
670 }
671
672 HeapWord** GenCollectedHeap::end_addr() const {
673 return _gens[0]->end_addr();
674 }
675
676 size_t GenCollectedHeap::unsafe_max_alloc() {
677 return _gens[0]->unsafe_max_alloc_nogc();
678 }
679
680 // public collection interfaces
681
682 void GenCollectedHeap::collect(GCCause::Cause cause) {
683 if (should_do_concurrent_full_gc(cause)) {
684 #if INCLUDE_ALL_GCS
685 // mostly concurrent full collection
686 collect_mostly_concurrent(cause);
687 #else // INCLUDE_ALL_GCS
688 ShouldNotReachHere();
689 #endif // INCLUDE_ALL_GCS
690 } else {
691 #ifdef ASSERT
692 if (cause == GCCause::_scavenge_alot) {
693 // minor collection only
694 collect(cause, 0);
695 } else {
696 // Stop-the-world full collection
697 collect(cause, n_gens() - 1);
698 }
699 #else
700 // Stop-the-world full collection
701 collect(cause, n_gens() - 1);
702 #endif
703 }
704 }
705
706 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
707 // The caller doesn't have the Heap_lock
708 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
709 MutexLocker ml(Heap_lock);
710 collect_locked(cause, max_level);
711 }
712
713 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
714 // The caller has the Heap_lock
715 assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
716 collect_locked(cause, n_gens() - 1);
717 }
718
719 // this is the private collection interface
720 // The Heap_lock is expected to be held on entry.
721
722 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
723 // Read the GC count while holding the Heap_lock
724 unsigned int gc_count_before = total_collections();
725 unsigned int full_gc_count_before = total_full_collections();
726 {
727 MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
728 VM_GenCollectFull op(gc_count_before, full_gc_count_before,
729 cause, max_level);
730 VMThread::execute(&op);
731 }
732 }
733
734 #if INCLUDE_ALL_GCS
735 bool GenCollectedHeap::create_cms_collector() {
736
737 assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
738 (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)),
739 "Unexpected generation kinds");
740 // Skip two header words in the block content verification
741 NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
742 CMSCollector* collector = new CMSCollector(
743 (ConcurrentMarkSweepGeneration*)_gens[1],
744 _rem_set->as_CardTableRS(),
745 (ConcurrentMarkSweepPolicy*) collector_policy());
746
747 if (collector == NULL || !collector->completed_initialization()) {
748 if (collector) {
749 delete collector; // Be nice in embedded situation
750 }
751 vm_shutdown_during_initialization("Could not create CMS collector");
752 return false;
753 }
754 return true; // success
755 }
756
757 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
758 assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
759
760 MutexLocker ml(Heap_lock);
761 // Read the GC counts while holding the Heap_lock
762 unsigned int full_gc_count_before = total_full_collections();
763 unsigned int gc_count_before = total_collections();
764 {
765 MutexUnlocker mu(Heap_lock);
766 VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
767 VMThread::execute(&op);
768 }
769 }
770 #endif // INCLUDE_ALL_GCS
771
772 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
773 do_full_collection(clear_all_soft_refs, _n_gens - 1);
774 }
775
776 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
777 int max_level) {
778 int local_max_level;
779 if (!incremental_collection_will_fail(false /* don't consult_young */) &&
780 gc_cause() == GCCause::_gc_locker) {
781 local_max_level = 0;
782 } else {
783 local_max_level = max_level;
784 }
785
786 do_collection(true /* full */,
787 clear_all_soft_refs /* clear_all_soft_refs */,
788 0 /* size */,
789 false /* is_tlab */,
790 local_max_level /* max_level */);
791 // Hack XXX FIX ME !!!
792 // A scavenge may not have been attempted, or may have
793 // been attempted and failed, because the old gen was too full
794 if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
795 incremental_collection_will_fail(false /* don't consult_young */)) {
796 if (PrintGCDetails) {
797 gclog_or_tty->print_cr("GC locker: Trying a full collection "
798 "because scavenge failed");
799 }
800 // This time allow the old gen to be collected as well
801 do_collection(true /* full */,
802 clear_all_soft_refs /* clear_all_soft_refs */,
803 0 /* size */,
804 false /* is_tlab */,
805 n_gens() - 1 /* max_level */);
806 }
807 }
808
809 bool GenCollectedHeap::is_in_young(oop p) {
810 bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
811 assert(result == _gens[0]->is_in_reserved(p),
812 err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, (void*)p));
813 return result;
814 }
815
816 // Returns "TRUE" iff "p" points into the committed areas of the heap.
817 bool GenCollectedHeap::is_in(const void* p) const {
818 #ifndef ASSERT
819 guarantee(VerifyBeforeGC ||
820 VerifyDuringGC ||
821 VerifyBeforeExit ||
822 VerifyDuringStartup ||
823 PrintAssembly ||
824 tty->count() != 0 || // already printing
825 VerifyAfterGC ||
826 VMError::fatal_error_in_progress(), "too expensive");
827
828 #endif
829 // This might be sped up with a cache of the last generation that
830 // answered yes.
831 for (int i = 0; i < _n_gens; i++) {
832 if (_gens[i]->is_in(p)) return true;
833 }
834 // Otherwise...
835 return false;
836 }
837
838 #ifdef ASSERT
839 // Don't implement this by using is_in_young(). This method is used
840 // in some cases to check that is_in_young() is correct.
841 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
842 assert(is_in_reserved(p) || p == NULL,
843 "Does not work if address is non-null and outside of the heap");
844 return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
845 }
846 #endif
847
848 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
849 for (int i = 0; i < _n_gens; i++) {
850 _gens[i]->oop_iterate(cl);
851 }
852 }
853
854 void GenCollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
855 for (int i = 0; i < _n_gens; i++) {
856 _gens[i]->oop_iterate(mr, cl);
857 }
858 }
859
860 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
861 for (int i = 0; i < _n_gens; i++) {
862 _gens[i]->object_iterate(cl);
863 }
864 }
865
866 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
867 for (int i = 0; i < _n_gens; i++) {
868 _gens[i]->safe_object_iterate(cl);
869 }
870 }
871
872 Space* GenCollectedHeap::space_containing(const void* addr) const {
873 for (int i = 0; i < _n_gens; i++) {
874 Space* res = _gens[i]->space_containing(addr);
875 if (res != NULL) return res;
876 }
877 // Otherwise...
878 assert(false, "Could not find containing space");
879 return NULL;
880 }
881
882
883 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
884 assert(is_in_reserved(addr), "block_start of address outside of heap");
885 for (int i = 0; i < _n_gens; i++) {
886 if (_gens[i]->is_in_reserved(addr)) {
887 assert(_gens[i]->is_in(addr),
888 "addr should be in allocated part of generation");
889 return _gens[i]->block_start(addr);
890 }
891 }
892 assert(false, "Some generation should contain the address");
893 return NULL;
894 }
895
896 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
897 assert(is_in_reserved(addr), "block_size of address outside of heap");
898 for (int i = 0; i < _n_gens; i++) {
899 if (_gens[i]->is_in_reserved(addr)) {
900 assert(_gens[i]->is_in(addr),
901 "addr should be in allocated part of generation");
902 return _gens[i]->block_size(addr);
903 }
904 }
905 assert(false, "Some generation should contain the address");
906 return 0;
907 }
908
909 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
910 assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
911 assert(block_start(addr) == addr, "addr must be a block start");
912 for (int i = 0; i < _n_gens; i++) {
913 if (_gens[i]->is_in_reserved(addr)) {
914 return _gens[i]->block_is_obj(addr);
915 }
916 }
917 assert(false, "Some generation should contain the address");
918 return false;
919 }
920
921 bool GenCollectedHeap::supports_tlab_allocation() const {
922 for (int i = 0; i < _n_gens; i += 1) {
923 if (_gens[i]->supports_tlab_allocation()) {
924 return true;
925 }
926 }
927 return false;
928 }
929
930 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
931 size_t result = 0;
932 for (int i = 0; i < _n_gens; i += 1) {
933 if (_gens[i]->supports_tlab_allocation()) {
934 result += _gens[i]->tlab_capacity();
935 }
936 }
937 return result;
938 }
939
940 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
941 size_t result = 0;
942 for (int i = 0; i < _n_gens; i += 1) {
943 if (_gens[i]->supports_tlab_allocation()) {
944 result += _gens[i]->unsafe_max_tlab_alloc();
945 }
946 }
947 return result;
948 }
949
950 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
951 bool gc_overhead_limit_was_exceeded;
952 return collector_policy()->mem_allocate_work(size /* size */,
953 true /* is_tlab */,
954 &gc_overhead_limit_was_exceeded);
955 }
956
957 // Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size
958 // from the list headed by "*prev_ptr".
959 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
960 bool first = true;
961 size_t min_size = 0; // "first" makes this conceptually infinite.
962 ScratchBlock **smallest_ptr, *smallest;
963 ScratchBlock *cur = *prev_ptr;
964 while (cur) {
965 assert(*prev_ptr == cur, "just checking");
966 if (first || cur->num_words < min_size) {
967 smallest_ptr = prev_ptr;
968 smallest = cur;
969 min_size = smallest->num_words;
970 first = false;
971 }
972 prev_ptr = &cur->next;
973 cur = cur->next;
974 }
975 smallest = *smallest_ptr;
976 *smallest_ptr = smallest->next;
977 return smallest;
978 }
979
980 // Sort the scratch block list headed by res into decreasing size order,
981 // and set "res" to the result.
982 static void sort_scratch_list(ScratchBlock*& list) {
983 ScratchBlock* sorted = NULL;
984 ScratchBlock* unsorted = list;
985 while (unsorted) {
986 ScratchBlock *smallest = removeSmallestScratch(&unsorted);
987 smallest->next = sorted;
988 sorted = smallest;
989 }
990 list = sorted;
991 }
992
993 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
994 size_t max_alloc_words) {
995 ScratchBlock* res = NULL;
996 for (int i = 0; i < _n_gens; i++) {
997 _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
998 }
999 sort_scratch_list(res);
1000 return res;
1001 }
1002
1003 void GenCollectedHeap::release_scratch() {
1004 for (int i = 0; i < _n_gens; i++) {
1005 _gens[i]->reset_scratch();
1006 }
1007 }
1008
1009 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1010 void do_generation(Generation* gen) {
1011 gen->prepare_for_verify();
1012 }
1013 };
1014
1015 void GenCollectedHeap::prepare_for_verify() {
1016 ensure_parsability(false); // no need to retire TLABs
1017 GenPrepareForVerifyClosure blk;
1018 generation_iterate(&blk, false);
1019 }
1020
1021
1022 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1023 bool old_to_young) {
1024 if (old_to_young) {
1025 for (int i = _n_gens-1; i >= 0; i--) {
1026 cl->do_generation(_gens[i]);
1027 }
1028 } else {
1029 for (int i = 0; i < _n_gens; i++) {
1030 cl->do_generation(_gens[i]);
1031 }
1032 }
1033 }
1034
1035 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1036 for (int i = 0; i < _n_gens; i++) {
1037 _gens[i]->space_iterate(cl, true);
1038 }
1039 }
1040
1041 bool GenCollectedHeap::is_maximal_no_gc() const {
1042 for (int i = 0; i < _n_gens; i++) {
1043 if (!_gens[i]->is_maximal_no_gc()) {
1044 return false;
1045 }
1046 }
1047 return true;
1048 }
1049
1050 void GenCollectedHeap::save_marks() {
1051 for (int i = 0; i < _n_gens; i++) {
1052 _gens[i]->save_marks();
1053 }
1054 }
1055
1056 void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
1057 for (int i = 0; i <= collectedGen; i++) {
1058 _gens[i]->compute_new_size();
1059 }
1060 }
1061
1062 GenCollectedHeap* GenCollectedHeap::heap() {
1063 assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1064 assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1065 return _gch;
1066 }
1067
1068
1069 void GenCollectedHeap::prepare_for_compaction() {
1070 Generation* scanning_gen = _gens[_n_gens-1];
1071 // Start by compacting into same gen.
1072 CompactPoint cp(scanning_gen, NULL, NULL);
1073 while (scanning_gen != NULL) {
1074 scanning_gen->prepare_for_compaction(&cp);
1075 scanning_gen = prev_gen(scanning_gen);
1076 }
1077 }
1078
1079 GCStats* GenCollectedHeap::gc_stats(int level) const {
1080 return _gens[level]->gc_stats();
1081 }
1082
1083 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) {
1084 for (int i = _n_gens-1; i >= 0; i--) {
1085 Generation* g = _gens[i];
1086 if (!silent) {
1087 gclog_or_tty->print(g->name());
1088 gclog_or_tty->print(" ");
1089 }
1090 g->verify();
1091 }
1092 if (!silent) {
1093 gclog_or_tty->print("remset ");
1094 }
1095 rem_set()->verify();
1096 }
1097
1098 void GenCollectedHeap::print_on(outputStream* st) const {
1099 for (int i = 0; i < _n_gens; i++) {
1100 _gens[i]->print_on(st);
1101 }
1102 MetaspaceAux::print_on(st);
1103 }
1104
1105 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1106 if (workers() != NULL) {
1107 workers()->threads_do(tc);
1108 }
1109 #if INCLUDE_ALL_GCS
1110 if (UseConcMarkSweepGC) {
1111 ConcurrentMarkSweepThread::threads_do(tc);
1112 }
1113 #endif // INCLUDE_ALL_GCS
1114 }
1115
1116 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1117 #if INCLUDE_ALL_GCS
1118 if (UseParNewGC) {
1119 workers()->print_worker_threads_on(st);
1120 }
1121 if (UseConcMarkSweepGC) {
1122 ConcurrentMarkSweepThread::print_all_on(st);
1123 }
1124 #endif // INCLUDE_ALL_GCS
1125 }
1126
1127 void GenCollectedHeap::print_on_error(outputStream* st) const {
1128 this->CollectedHeap::print_on_error(st);
1129
1130 #if INCLUDE_ALL_GCS
1131 if (UseConcMarkSweepGC) {
1132 st->cr();
1133 CMSCollector::print_on_error(st);
1134 }
1135 #endif // INCLUDE_ALL_GCS
1136 }
1137
1138 void GenCollectedHeap::print_tracing_info() const {
1139 if (TraceGen0Time) {
1140 get_gen(0)->print_summary_info();
1141 }
1142 if (TraceGen1Time) {
1143 get_gen(1)->print_summary_info();
1144 }
1145 }
1146
1147 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1148 if (PrintGCDetails && Verbose) {
1149 gclog_or_tty->print(" " SIZE_FORMAT
1150 "->" SIZE_FORMAT
1151 "(" SIZE_FORMAT ")",
1152 prev_used, used(), capacity());
1153 } else {
1154 gclog_or_tty->print(" " SIZE_FORMAT "K"
1155 "->" SIZE_FORMAT "K"
1156 "(" SIZE_FORMAT "K)",
1157 prev_used / K, used() / K, capacity() / K);
1158 }
1159 }
1160
1161 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1162 private:
1163 bool _full;
1164 public:
1165 void do_generation(Generation* gen) {
1166 gen->gc_prologue(_full);
1167 }
1168 GenGCPrologueClosure(bool full) : _full(full) {};
1169 };
1170
1171 void GenCollectedHeap::gc_prologue(bool full) {
1172 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1173
1174 always_do_update_barrier = false;
1175 // Fill TLAB's and such
1176 CollectedHeap::accumulate_statistics_all_tlabs();
1177 ensure_parsability(true); // retire TLABs
1178
1179 // Walk generations
1180 GenGCPrologueClosure blk(full);
1181 generation_iterate(&blk, false); // not old-to-young.
1182 };
1183
1184 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1185 private:
1186 bool _full;
1187 public:
1188 void do_generation(Generation* gen) {
1189 gen->gc_epilogue(_full);
1190 }
1191 GenGCEpilogueClosure(bool full) : _full(full) {};
1192 };
1193
1194 void GenCollectedHeap::gc_epilogue(bool full) {
1195 #ifdef COMPILER2
1196 assert(DerivedPointerTable::is_empty(), "derived pointer present");
1197 size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1198 guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1199 #endif /* COMPILER2 */
1200
1201 resize_all_tlabs();
1202
1203 GenGCEpilogueClosure blk(full);
1204 generation_iterate(&blk, false); // not old-to-young.
1205
1206 if (!CleanChunkPoolAsync) {
1207 Chunk::clean_chunk_pool();
1208 }
1209
1210 MetaspaceCounters::update_performance_counters();
1211
1212 always_do_update_barrier = UseConcMarkSweepGC;
1213 };
1214
1215 #ifndef PRODUCT
1216 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1217 private:
1218 public:
1219 void do_generation(Generation* gen) {
1220 gen->record_spaces_top();
1221 }
1222 };
1223
1224 void GenCollectedHeap::record_gen_tops_before_GC() {
1225 if (ZapUnusedHeapArea) {
1226 GenGCSaveTopsBeforeGCClosure blk;
1227 generation_iterate(&blk, false); // not old-to-young.
1228 }
1229 }
1230 #endif // not PRODUCT
1231
1232 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1233 public:
1234 void do_generation(Generation* gen) {
1235 gen->ensure_parsability();
1236 }
1237 };
1238
1239 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1240 CollectedHeap::ensure_parsability(retire_tlabs);
1241 GenEnsureParsabilityClosure ep_cl;
1242 generation_iterate(&ep_cl, false);
1243 }
1244
1245 oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
1246 oop obj,
1247 size_t obj_size) {
1248 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1249 HeapWord* result = NULL;
1250
1251 // First give each higher generation a chance to allocate the promoted object.
1252 Generation* allocator = next_gen(gen);
1253 if (allocator != NULL) {
1254 do {
1255 result = allocator->allocate(obj_size, false);
1256 } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
1257 }
1258
1259 if (result == NULL) {
1260 // Then give gen and higher generations a chance to expand and allocate the
1261 // object.
1262 do {
1263 result = gen->expand_and_allocate(obj_size, false);
1264 } while (result == NULL && (gen = next_gen(gen)) != NULL);
1265 }
1266
1267 if (result != NULL) {
1268 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1269 }
1270 return oop(result);
1271 }
1272
1273 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1274 jlong _time; // in ms
1275 jlong _now; // in ms
1276
1277 public:
1278 GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1279
1280 jlong time() { return _time; }
1281
1282 void do_generation(Generation* gen) {
1283 _time = MIN2(_time, gen->time_of_last_gc(_now));
1284 }
1285 };
1286
1287 jlong GenCollectedHeap::millis_since_last_gc() {
1288 // We need a monotonically non-deccreasing time in ms but
1289 // os::javaTimeMillis() does not guarantee monotonicity.
1290 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1291 GenTimeOfLastGCClosure tolgc_cl(now);
1292 // iterate over generations getting the oldest
1293 // time that a generation was collected
1294 generation_iterate(&tolgc_cl, false);
1295
1296 // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1297 // provided the underlying platform provides such a time source
1298 // (and it is bug free). So we still have to guard against getting
1299 // back a time later than 'now'.
1300 jlong retVal = now - tolgc_cl.time();
1301 if (retVal < 0) {
1302 NOT_PRODUCT(warning("time warp: "INT64_FORMAT, retVal);)
1303 return 0;
1304 }
1305 return retVal;
1306 }