1 /*
2 * Copyright (c) 2000, 2023, 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/classLoaderDataGraph.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/vmSymbols.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "compiler/oopMap.hpp"
33 #include "gc/serial/cardTableRS.hpp"
34 #include "gc/serial/defNewGeneration.hpp"
35 #include "gc/serial/genMarkSweep.hpp"
36 #include "gc/serial/markSweep.hpp"
37 #include "gc/shared/adaptiveSizePolicy.hpp"
38 #include "gc/shared/cardTableBarrierSet.hpp"
39 #include "gc/shared/collectedHeap.inline.hpp"
40 #include "gc/shared/collectorCounters.hpp"
41 #include "gc/shared/continuationGCSupport.inline.hpp"
42 #include "gc/shared/gcId.hpp"
43 #include "gc/shared/gcInitLogger.hpp"
44 #include "gc/shared/gcLocker.hpp"
45 #include "gc/shared/gcPolicyCounters.hpp"
46 #include "gc/shared/gcTrace.hpp"
47 #include "gc/shared/gcTraceTime.inline.hpp"
48 #include "gc/shared/gcVMOperations.hpp"
49 #include "gc/shared/genArguments.hpp"
50 #include "gc/shared/genCollectedHeap.hpp"
51 #include "gc/shared/generationSpec.hpp"
52 #include "gc/shared/locationPrinter.inline.hpp"
53 #include "gc/shared/oopStorage.inline.hpp"
54 #include "gc/shared/oopStorageParState.inline.hpp"
55 #include "gc/shared/oopStorageSet.inline.hpp"
56 #include "gc/shared/scavengableNMethods.hpp"
57 #include "gc/shared/space.hpp"
58 #include "gc/shared/strongRootsScope.hpp"
59 #include "gc/shared/weakProcessor.hpp"
60 #include "gc/shared/workerThread.hpp"
61 #include "memory/iterator.hpp"
62 #include "memory/metaspaceCounters.hpp"
63 #include "memory/metaspaceUtils.hpp"
64 #include "memory/resourceArea.hpp"
65 #include "memory/universe.hpp"
66 #include "oops/oop.inline.hpp"
67 #include "runtime/handles.hpp"
68 #include "runtime/handles.inline.hpp"
69 #include "runtime/java.hpp"
70 #include "runtime/threads.hpp"
71 #include "runtime/vmThread.hpp"
72 #include "services/memoryService.hpp"
73 #include "utilities/autoRestore.hpp"
74 #include "utilities/debug.hpp"
75 #include "utilities/formatBuffer.hpp"
76 #include "utilities/macros.hpp"
77 #include "utilities/stack.inline.hpp"
78 #include "utilities/vmError.hpp"
79 #if INCLUDE_JVMCI
80 #include "jvmci/jvmci.hpp"
81 #endif
82
83 GenCollectedHeap::GenCollectedHeap(Generation::Name young,
84 Generation::Name old,
85 const char* policy_counters_name) :
86 CollectedHeap(),
87 _young_gen(nullptr),
88 _old_gen(nullptr),
89 _young_gen_spec(new GenerationSpec(young,
90 NewSize,
91 MaxNewSize,
92 GenAlignment)),
93 _old_gen_spec(new GenerationSpec(old,
94 OldSize,
95 MaxOldSize,
96 GenAlignment)),
97 _rem_set(nullptr),
98 _soft_ref_gen_policy(),
99 _size_policy(nullptr),
100 _gc_policy_counters(new GCPolicyCounters(policy_counters_name, 2, 2)),
101 _incremental_collection_failed(false),
102 _full_collections_completed(0),
103 _young_manager(nullptr),
104 _old_manager(nullptr) {
105 }
106
107 jint GenCollectedHeap::initialize() {
108 // Allocate space for the heap.
109
110 ReservedHeapSpace heap_rs = allocate(HeapAlignment);
111
112 if (!heap_rs.is_reserved()) {
113 vm_shutdown_during_initialization(
114 "Could not reserve enough space for object heap");
115 return JNI_ENOMEM;
116 }
117
118 initialize_reserved_region(heap_rs);
119
120 _rem_set = create_rem_set(heap_rs.region());
121 _rem_set->initialize();
122 CardTableBarrierSet *bs = new CardTableBarrierSet(_rem_set);
123 bs->initialize();
124 BarrierSet::set_barrier_set(bs);
125
126 ReservedSpace young_rs = heap_rs.first_part(_young_gen_spec->max_size());
127 _young_gen = _young_gen_spec->init(young_rs, rem_set());
128 ReservedSpace old_rs = heap_rs.last_part(_young_gen_spec->max_size());
129
130 old_rs = old_rs.first_part(_old_gen_spec->max_size());
131 _old_gen = _old_gen_spec->init(old_rs, rem_set());
132
133 GCInitLogger::print();
134
135 return JNI_OK;
136 }
137
138 CardTableRS* GenCollectedHeap::create_rem_set(const MemRegion& reserved_region) {
139 return new CardTableRS(reserved_region);
140 }
141
142 void GenCollectedHeap::initialize_size_policy(size_t init_eden_size,
143 size_t init_promo_size,
144 size_t init_survivor_size) {
145 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
146 _size_policy = new AdaptiveSizePolicy(init_eden_size,
147 init_promo_size,
148 init_survivor_size,
149 max_gc_pause_sec,
150 GCTimeRatio);
151 }
152
153 ReservedHeapSpace GenCollectedHeap::allocate(size_t alignment) {
154 // Now figure out the total size.
155 const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
156 assert(alignment % pageSize == 0, "Must be");
157
158 // Check for overflow.
159 size_t total_reserved = _young_gen_spec->max_size() + _old_gen_spec->max_size();
160 if (total_reserved < _young_gen_spec->max_size()) {
161 vm_exit_during_initialization("The size of the object heap + VM data exceeds "
162 "the maximum representable size");
163 }
164 assert(total_reserved % alignment == 0,
165 "Gen size; total_reserved=" SIZE_FORMAT ", alignment="
166 SIZE_FORMAT, total_reserved, alignment);
167
168 ReservedHeapSpace heap_rs = Universe::reserve_heap(total_reserved, alignment);
169 size_t used_page_size = heap_rs.page_size();
170
171 os::trace_page_sizes("Heap",
172 MinHeapSize,
173 total_reserved,
174 used_page_size,
175 heap_rs.base(),
176 heap_rs.size());
177
178 return heap_rs;
179 }
180
181 class GenIsScavengable : public BoolObjectClosure {
182 public:
183 bool do_object_b(oop obj) {
184 return GenCollectedHeap::heap()->is_in_young(obj);
185 }
186 };
187
188 static GenIsScavengable _is_scavengable;
189
190 void GenCollectedHeap::post_initialize() {
191 CollectedHeap::post_initialize();
192 ref_processing_init();
193
194 DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
195
196 initialize_size_policy(def_new_gen->eden()->capacity(),
197 _old_gen->capacity(),
198 def_new_gen->from()->capacity());
199
200 MarkSweep::initialize();
201
202 ScavengableNMethods::initialize(&_is_scavengable);
203 }
204
205 void GenCollectedHeap::ref_processing_init() {
206 _young_gen->ref_processor_init();
207 _old_gen->ref_processor_init();
208 }
209
210 PreGenGCValues GenCollectedHeap::get_pre_gc_values() const {
211 const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
212
213 return PreGenGCValues(def_new_gen->used(),
214 def_new_gen->capacity(),
215 def_new_gen->eden()->used(),
216 def_new_gen->eden()->capacity(),
217 def_new_gen->from()->used(),
218 def_new_gen->from()->capacity(),
219 old_gen()->used(),
220 old_gen()->capacity());
221 }
222
223 GenerationSpec* GenCollectedHeap::young_gen_spec() const {
224 return _young_gen_spec;
225 }
226
227 GenerationSpec* GenCollectedHeap::old_gen_spec() const {
228 return _old_gen_spec;
229 }
230
231 size_t GenCollectedHeap::capacity() const {
232 return _young_gen->capacity() + _old_gen->capacity();
233 }
234
235 size_t GenCollectedHeap::used() const {
236 return _young_gen->used() + _old_gen->used();
237 }
238
239 void GenCollectedHeap::save_used_regions() {
240 _old_gen->save_used_region();
241 _young_gen->save_used_region();
242 }
243
244 size_t GenCollectedHeap::max_capacity() const {
245 return _young_gen->max_capacity() + _old_gen->max_capacity();
246 }
247
248 // Update the _full_collections_completed counter
249 // at the end of a stop-world full GC.
250 unsigned int GenCollectedHeap::update_full_collections_completed() {
251 assert(_full_collections_completed <= _total_full_collections,
252 "Can't complete more collections than were started");
253 _full_collections_completed = _total_full_collections;
254 return _full_collections_completed;
255 }
256
257 // Return true if any of the following is true:
258 // . the allocation won't fit into the current young gen heap
259 // . gc locker is occupied (jni critical section)
260 // . heap memory is tight -- the most recent previous collection
261 // was a full collection because a partial collection (would
262 // have) failed and is likely to fail again
263 bool GenCollectedHeap::should_try_older_generation_allocation(size_t word_size) const {
264 size_t young_capacity = _young_gen->capacity_before_gc();
265 return (word_size > heap_word_size(young_capacity))
266 || GCLocker::is_active_and_needs_gc()
267 || incremental_collection_failed();
268 }
269
270 HeapWord* GenCollectedHeap::expand_heap_and_allocate(size_t size, bool is_tlab) {
271 HeapWord* result = nullptr;
272 if (_old_gen->should_allocate(size, is_tlab)) {
273 result = _old_gen->expand_and_allocate(size, is_tlab);
274 }
275 if (result == nullptr) {
276 if (_young_gen->should_allocate(size, is_tlab)) {
277 result = _young_gen->expand_and_allocate(size, is_tlab);
278 }
279 }
280 assert(result == nullptr || is_in_reserved(result), "result not in heap");
281 return result;
282 }
283
284 HeapWord* GenCollectedHeap::mem_allocate_work(size_t size,
285 bool is_tlab,
286 bool* gc_overhead_limit_was_exceeded) {
287 // In general gc_overhead_limit_was_exceeded should be false so
288 // set it so here and reset it to true only if the gc time
289 // limit is being exceeded as checked below.
290 *gc_overhead_limit_was_exceeded = false;
291
292 HeapWord* result = nullptr;
293
294 // Loop until the allocation is satisfied, or unsatisfied after GC.
295 for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
296
297 // First allocation attempt is lock-free.
298 Generation *young = _young_gen;
299 if (young->should_allocate(size, is_tlab)) {
300 result = young->par_allocate(size, is_tlab);
301 if (result != nullptr) {
302 assert(is_in_reserved(result), "result not in heap");
303 return result;
304 }
305 }
306 uint gc_count_before; // Read inside the Heap_lock locked region.
307 {
308 MutexLocker ml(Heap_lock);
309 log_trace(gc, alloc)("GenCollectedHeap::mem_allocate_work: attempting locked slow path allocation");
310 // Note that only large objects get a shot at being
311 // allocated in later generations.
312 bool first_only = !should_try_older_generation_allocation(size);
313
314 result = attempt_allocation(size, is_tlab, first_only);
315 if (result != nullptr) {
316 assert(is_in_reserved(result), "result not in heap");
317 return result;
318 }
319
320 if (GCLocker::is_active_and_needs_gc()) {
321 if (is_tlab) {
322 return nullptr; // Caller will retry allocating individual object.
323 }
324 if (!is_maximal_no_gc()) {
325 // Try and expand heap to satisfy request.
326 result = expand_heap_and_allocate(size, is_tlab);
327 // Result could be null if we are out of space.
328 if (result != nullptr) {
329 return result;
330 }
331 }
332
333 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
334 return nullptr; // We didn't get to do a GC and we didn't get any memory.
335 }
336
337 // If this thread is not in a jni critical section, we stall
338 // the requestor until the critical section has cleared and
339 // GC allowed. When the critical section clears, a GC is
340 // initiated by the last thread exiting the critical section; so
341 // we retry the allocation sequence from the beginning of the loop,
342 // rather than causing more, now probably unnecessary, GC attempts.
343 JavaThread* jthr = JavaThread::current();
344 if (!jthr->in_critical()) {
345 MutexUnlocker mul(Heap_lock);
346 // Wait for JNI critical section to be exited
347 GCLocker::stall_until_clear();
348 gclocker_stalled_count += 1;
349 continue;
350 } else {
351 if (CheckJNICalls) {
352 fatal("Possible deadlock due to allocating while"
353 " in jni critical section");
354 }
355 return nullptr;
356 }
357 }
358
359 // Read the gc count while the heap lock is held.
360 gc_count_before = total_collections();
361 }
362
363 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
364 VMThread::execute(&op);
365 if (op.prologue_succeeded()) {
366 result = op.result();
367 if (op.gc_locked()) {
368 assert(result == nullptr, "must be null if gc_locked() is true");
369 continue; // Retry and/or stall as necessary.
370 }
371
372 // Allocation has failed and a collection
373 // has been done. If the gc time limit was exceeded the
374 // this time, return null so that an out-of-memory
375 // will be thrown. Clear gc_overhead_limit_exceeded
376 // so that the overhead exceeded does not persist.
377
378 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
379 const bool softrefs_clear = soft_ref_policy()->all_soft_refs_clear();
380
381 if (limit_exceeded && softrefs_clear) {
382 *gc_overhead_limit_was_exceeded = true;
383 size_policy()->set_gc_overhead_limit_exceeded(false);
384 if (op.result() != nullptr) {
385 CollectedHeap::fill_with_object(op.result(), size);
386 }
387 return nullptr;
388 }
389 assert(result == nullptr || is_in_reserved(result),
390 "result not in heap");
391 return result;
392 }
393
394 // Give a warning if we seem to be looping forever.
395 if ((QueuedAllocationWarningCount > 0) &&
396 (try_count % QueuedAllocationWarningCount == 0)) {
397 log_warning(gc, ergo)("GenCollectedHeap::mem_allocate_work retries %d times,"
398 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");
399 }
400 }
401 }
402
403 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
404 bool is_tlab,
405 bool first_only) {
406 HeapWord* res = nullptr;
407
408 if (_young_gen->should_allocate(size, is_tlab)) {
409 res = _young_gen->allocate(size, is_tlab);
410 if (res != nullptr || first_only) {
411 return res;
412 }
413 }
414
415 if (_old_gen->should_allocate(size, is_tlab)) {
416 res = _old_gen->allocate(size, is_tlab);
417 }
418
419 return res;
420 }
421
422 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
423 bool* gc_overhead_limit_was_exceeded) {
424 return mem_allocate_work(size,
425 false /* is_tlab */,
426 gc_overhead_limit_was_exceeded);
427 }
428
429 bool GenCollectedHeap::must_clear_all_soft_refs() {
430 return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
431 _gc_cause == GCCause::_wb_full_gc;
432 }
433
434 void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
435 bool is_tlab, bool run_verification, bool clear_soft_refs) {
436 FormatBuffer<> title("Collect gen: %s", gen->short_name());
437 GCTraceTime(Trace, gc, phases) t1(title);
438 TraceCollectorStats tcs(gen->counters());
439 TraceMemoryManagerStats tmms(gen->gc_manager(), gc_cause());
440
441 gen->stat_record()->invocations++;
442 gen->stat_record()->accumulated_time.start();
443
444 // Must be done anew before each collection because
445 // a previous collection will do mangling and will
446 // change top of some spaces.
447 record_gen_tops_before_GC();
448
449 log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);
450
451 if (run_verification && VerifyBeforeGC) {
452 Universe::verify("Before GC");
453 }
454 COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::clear());
455
456 // Do collection work
457 {
458 // Note on ref discovery: For what appear to be historical reasons,
459 // GCH enables and disabled (by enqueuing) refs discovery.
460 // In the future this should be moved into the generation's
461 // collect method so that ref discovery and enqueueing concerns
462 // are local to a generation. The collect method could return
463 // an appropriate indication in the case that notification on
464 // the ref lock was needed. This will make the treatment of
465 // weak refs more uniform (and indeed remove such concerns
466 // from GCH). XXX
467
468 save_marks(); // save marks for all gens
469 // We want to discover references, but not process them yet.
470 // This mode is disabled in process_discovered_references if the
471 // generation does some collection work, or in
472 // enqueue_discovered_references if the generation returns
473 // without doing any work.
474 ReferenceProcessor* rp = gen->ref_processor();
475 rp->start_discovery(clear_soft_refs);
476
477 gen->collect(full, clear_soft_refs, size, is_tlab);
478
479 rp->disable_discovery();
480 rp->verify_no_references_recorded();
481 }
482
483 COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::update_pointers());
484
485 gen->stat_record()->accumulated_time.stop();
486
487 update_gc_stats(gen, full);
488
489 if (run_verification && VerifyAfterGC) {
490 Universe::verify("After GC");
491 }
492 }
493
494 void GenCollectedHeap::do_collection(bool full,
495 bool clear_all_soft_refs,
496 size_t size,
497 bool is_tlab,
498 GenerationType max_generation) {
499 ResourceMark rm;
500 DEBUG_ONLY(Thread* my_thread = Thread::current();)
501
502 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
503 assert(my_thread->is_VM_thread(), "only VM thread");
504 assert(Heap_lock->is_locked(),
505 "the requesting thread should have the Heap_lock");
506 guarantee(!is_gc_active(), "collection is not reentrant");
507
508 if (GCLocker::check_active_before_gc()) {
509 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
510 }
511
512 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
513 soft_ref_policy()->should_clear_all_soft_refs();
514
515 ClearedAllSoftRefs casr(do_clear_all_soft_refs, soft_ref_policy());
516
517 AutoModifyRestore<bool> temporarily(_is_gc_active, true);
518
519 bool complete = full && (max_generation == OldGen);
520 bool old_collects_young = complete && !ScavengeBeforeFullGC;
521 bool do_young_collection = !old_collects_young && _young_gen->should_collect(full, size, is_tlab);
522
523 const PreGenGCValues pre_gc_values = get_pre_gc_values();
524
525 bool run_verification = total_collections() >= VerifyGCStartAt;
526 bool prepared_for_verification = false;
527 bool do_full_collection = false;
528
529 if (do_young_collection) {
530 GCIdMark gc_id_mark;
531 GCTraceCPUTime tcpu(((DefNewGeneration*)_young_gen)->gc_tracer());
532 GCTraceTime(Info, gc) t("Pause Young", nullptr, gc_cause(), true);
533
534 print_heap_before_gc();
535
536 if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
537 prepare_for_verify();
538 prepared_for_verification = true;
539 }
540
541 gc_prologue(complete);
542 increment_total_collections(complete);
543
544 collect_generation(_young_gen,
545 full,
546 size,
547 is_tlab,
548 run_verification && VerifyGCLevel <= 0,
549 do_clear_all_soft_refs);
550
551 if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
552 size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
553 // Allocation request was met by young GC.
554 size = 0;
555 }
556
557 // Ask if young collection is enough. If so, do the final steps for young collection,
558 // and fallthrough to the end.
559 do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
560 if (!do_full_collection) {
561 // Adjust generation sizes.
562 _young_gen->compute_new_size();
563
564 print_heap_change(pre_gc_values);
565
566 // Track memory usage and detect low memory after GC finishes
567 MemoryService::track_memory_usage();
568
569 gc_epilogue(complete);
570 }
571
572 print_heap_after_gc();
573
574 } else {
575 // No young collection, ask if we need to perform Full collection.
576 do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
577 }
578
579 if (do_full_collection) {
580 GCIdMark gc_id_mark;
581 GCTraceCPUTime tcpu(GenMarkSweep::gc_tracer());
582 GCTraceTime(Info, gc) t("Pause Full", nullptr, gc_cause(), true);
583
584 print_heap_before_gc();
585
586 if (!prepared_for_verification && run_verification &&
587 VerifyGCLevel <= 1 && VerifyBeforeGC) {
588 prepare_for_verify();
589 }
590
591 if (!do_young_collection) {
592 gc_prologue(complete);
593 increment_total_collections(complete);
594 }
595
596 // Accounting quirk: total full collections would be incremented when "complete"
597 // is set, by calling increment_total_collections above. However, we also need to
598 // account Full collections that had "complete" unset.
599 if (!complete) {
600 increment_total_full_collections();
601 }
602
603 CodeCache::on_gc_marking_cycle_start();
604
605 collect_generation(_old_gen,
606 full,
607 size,
608 is_tlab,
609 run_verification && VerifyGCLevel <= 1,
610 do_clear_all_soft_refs);
611
612 CodeCache::on_gc_marking_cycle_finish();
613 CodeCache::arm_all_nmethods();
614
615 // Adjust generation sizes.
616 _old_gen->compute_new_size();
617 _young_gen->compute_new_size();
618
619 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
620 ClassLoaderDataGraph::purge(/*at_safepoint*/true);
621 DEBUG_ONLY(MetaspaceUtils::verify();)
622
623 // Need to clear claim bits for the next mark.
624 ClassLoaderDataGraph::clear_claimed_marks();
625
626 // Resize the metaspace capacity after full collections
627 MetaspaceGC::compute_new_size();
628 update_full_collections_completed();
629
630 print_heap_change(pre_gc_values);
631
632 // Track memory usage and detect low memory after GC finishes
633 MemoryService::track_memory_usage();
634
635 // Need to tell the epilogue code we are done with Full GC, regardless what was
636 // the initial value for "complete" flag.
637 gc_epilogue(true);
638
639 print_heap_after_gc();
640 }
641 }
642
643 bool GenCollectedHeap::should_do_full_collection(size_t size, bool full, bool is_tlab,
644 GenCollectedHeap::GenerationType max_gen) const {
645 return max_gen == OldGen && _old_gen->should_collect(full, size, is_tlab);
646 }
647
648 void GenCollectedHeap::register_nmethod(nmethod* nm) {
649 ScavengableNMethods::register_nmethod(nm);
650 }
651
652 void GenCollectedHeap::unregister_nmethod(nmethod* nm) {
653 ScavengableNMethods::unregister_nmethod(nm);
654 }
655
656 void GenCollectedHeap::verify_nmethod(nmethod* nm) {
657 ScavengableNMethods::verify_nmethod(nm);
658 }
659
660 void GenCollectedHeap::prune_scavengable_nmethods() {
661 ScavengableNMethods::prune_nmethods();
662 }
663
664 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
665 GCCauseSetter x(this, GCCause::_allocation_failure);
666 HeapWord* result = nullptr;
667
668 assert(size != 0, "Precondition violated");
669 if (GCLocker::is_active_and_needs_gc()) {
670 // GC locker is active; instead of a collection we will attempt
671 // to expand the heap, if there's room for expansion.
672 if (!is_maximal_no_gc()) {
673 result = expand_heap_and_allocate(size, is_tlab);
674 }
675 return result; // Could be null if we are out of space.
676 } else if (!incremental_collection_will_fail(false /* don't consult_young */)) {
677 // Do an incremental collection.
678 do_collection(false, // full
679 false, // clear_all_soft_refs
680 size, // size
681 is_tlab, // is_tlab
682 GenCollectedHeap::OldGen); // max_generation
683 } else {
684 log_trace(gc)(" :: Trying full because partial may fail :: ");
685 // Try a full collection; see delta for bug id 6266275
686 // for the original code and why this has been simplified
687 // with from-space allocation criteria modified and
688 // such allocation moved out of the safepoint path.
689 do_collection(true, // full
690 false, // clear_all_soft_refs
691 size, // size
692 is_tlab, // is_tlab
693 GenCollectedHeap::OldGen); // max_generation
694 }
695
696 result = attempt_allocation(size, is_tlab, false /*first_only*/);
697
698 if (result != nullptr) {
699 assert(is_in_reserved(result), "result not in heap");
700 return result;
701 }
702
703 // OK, collection failed, try expansion.
704 result = expand_heap_and_allocate(size, is_tlab);
705 if (result != nullptr) {
706 return result;
707 }
708
709 // If we reach this point, we're really out of memory. Try every trick
710 // we can to reclaim memory. Force collection of soft references. Force
711 // a complete compaction of the heap. Any additional methods for finding
712 // free memory should be here, especially if they are expensive. If this
713 // attempt fails, an OOM exception will be thrown.
714 {
715 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
716
717 do_collection(true, // full
718 true, // clear_all_soft_refs
719 size, // size
720 is_tlab, // is_tlab
721 GenCollectedHeap::OldGen); // max_generation
722 }
723
724 result = attempt_allocation(size, is_tlab, false /* first_only */);
725 if (result != nullptr) {
726 assert(is_in_reserved(result), "result not in heap");
727 return result;
728 }
729
730 assert(!soft_ref_policy()->should_clear_all_soft_refs(),
731 "Flag should have been handled and cleared prior to this point");
732
733 // What else? We might try synchronous finalization later. If the total
734 // space available is large enough for the allocation, then a more
735 // complete compaction phase than we've tried so far might be
736 // appropriate.
737 return nullptr;
738 }
739
740 #ifdef ASSERT
741 class AssertNonScavengableClosure: public OopClosure {
742 public:
743 virtual void do_oop(oop* p) {
744 assert(!GenCollectedHeap::heap()->is_in_partial_collection(*p),
745 "Referent should not be scavengable."); }
746 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
747 };
748 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
749 #endif
750
751 void GenCollectedHeap::process_roots(ScanningOption so,
752 OopClosure* strong_roots,
753 CLDClosure* strong_cld_closure,
754 CLDClosure* weak_cld_closure,
755 CodeBlobToOopClosure* code_roots) {
756 // General roots.
757 assert(code_roots != nullptr, "code root closure should always be set");
758
759 ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
760
761 // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
762 CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? nullptr : code_roots;
763
764 Threads::oops_do(strong_roots, roots_from_code_p);
765
766 OopStorageSet::strong_oops_do(strong_roots);
767
768 if (so & SO_ScavengeCodeCache) {
769 assert(code_roots != nullptr, "must supply closure for code cache");
770
771 // We only visit parts of the CodeCache when scavenging.
772 ScavengableNMethods::nmethods_do(code_roots);
773 }
774 if (so & SO_AllCodeCache) {
775 assert(code_roots != nullptr, "must supply closure for code cache");
776
777 // CMSCollector uses this to do intermediate-strength collections.
778 // We scan the entire code cache, since CodeCache::do_unloading is not called.
779 CodeCache::blobs_do(code_roots);
780 }
781 // Verify that the code cache contents are not subject to
782 // movement by a scavenging collection.
783 DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
784 DEBUG_ONLY(ScavengableNMethods::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
785 }
786
787 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
788 WeakProcessor::oops_do(root_closure);
789 }
790
791 bool GenCollectedHeap::no_allocs_since_save_marks() {
792 return _young_gen->no_allocs_since_save_marks() &&
793 _old_gen->no_allocs_since_save_marks();
794 }
795
796 // public collection interfaces
797 void GenCollectedHeap::collect(GCCause::Cause cause) {
798 // The caller doesn't have the Heap_lock
799 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
800
801 unsigned int gc_count_before;
802 unsigned int full_gc_count_before;
803
804 {
805 MutexLocker ml(Heap_lock);
806 // Read the GC count while holding the Heap_lock
807 gc_count_before = total_collections();
808 full_gc_count_before = total_full_collections();
809 }
810
811 if (GCLocker::should_discard(cause, gc_count_before)) {
812 return;
813 }
814
815 bool should_run_young_gc = (cause == GCCause::_wb_young_gc)
816 || (cause == GCCause::_gc_locker)
817 DEBUG_ONLY(|| (cause == GCCause::_scavenge_alot));
818
819 const GenerationType max_generation = should_run_young_gc
820 ? YoungGen
821 : OldGen;
822
823 VM_GenCollectFull op(gc_count_before, full_gc_count_before,
824 cause, max_generation);
825 VMThread::execute(&op);
826 }
827
828 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
829 do_full_collection(clear_all_soft_refs, OldGen);
830 }
831
832 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
833 GenerationType last_generation) {
834 do_collection(true, // full
835 clear_all_soft_refs, // clear_all_soft_refs
836 0, // size
837 false, // is_tlab
838 last_generation); // last_generation
839 // Hack XXX FIX ME !!!
840 // A scavenge may not have been attempted, or may have
841 // been attempted and failed, because the old gen was too full
842 if (gc_cause() == GCCause::_gc_locker && incremental_collection_failed()) {
843 log_debug(gc, jni)("GC locker: Trying a full collection because scavenge failed");
844 // This time allow the old gen to be collected as well
845 do_collection(true, // full
846 clear_all_soft_refs, // clear_all_soft_refs
847 0, // size
848 false, // is_tlab
849 OldGen); // last_generation
850 }
851 }
852
853 bool GenCollectedHeap::is_in_young(const void* p) const {
854 bool result = p < _old_gen->reserved().start();
855 assert(result == _young_gen->is_in_reserved(p),
856 "incorrect test - result=%d, p=" PTR_FORMAT, result, p2i(p));
857 return result;
858 }
859
860 bool GenCollectedHeap::requires_barriers(stackChunkOop obj) const {
861 return !is_in_young(obj);
862 }
863
864 // Returns "TRUE" iff "p" points into the committed areas of the heap.
865 bool GenCollectedHeap::is_in(const void* p) const {
866 return _young_gen->is_in(p) || _old_gen->is_in(p);
867 }
868
869 #ifdef ASSERT
870 // Don't implement this by using is_in_young(). This method is used
871 // in some cases to check that is_in_young() is correct.
872 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
873 assert(is_in_reserved(p) || p == nullptr,
874 "Does not work if address is non-null and outside of the heap");
875 return p < _young_gen->reserved().end() && p != nullptr;
876 }
877 #endif
878
879 void GenCollectedHeap::oop_iterate(OopIterateClosure* cl) {
880 _young_gen->oop_iterate(cl);
881 _old_gen->oop_iterate(cl);
882 }
883
884 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
885 _young_gen->object_iterate(cl);
886 _old_gen->object_iterate(cl);
887 }
888
889 Space* GenCollectedHeap::space_containing(const void* addr) const {
890 Space* res = _young_gen->space_containing(addr);
891 if (res != nullptr) {
892 return res;
893 }
894 res = _old_gen->space_containing(addr);
895 assert(res != nullptr, "Could not find containing space");
896 return res;
897 }
898
899 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
900 assert(is_in_reserved(addr), "block_start of address outside of heap");
901 if (_young_gen->is_in_reserved(addr)) {
902 assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
903 return _young_gen->block_start(addr);
904 }
905
906 assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
907 assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
908 return _old_gen->block_start(addr);
909 }
910
911 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
912 assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
913 assert(block_start(addr) == addr, "addr must be a block start");
914 if (_young_gen->is_in_reserved(addr)) {
915 return _young_gen->block_is_obj(addr);
916 }
917
918 assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
919 return _old_gen->block_is_obj(addr);
920 }
921
922 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
923 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
924 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
925 return _young_gen->tlab_capacity();
926 }
927
928 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
929 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
930 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
931 return _young_gen->tlab_used();
932 }
933
934 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
935 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
936 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
937 return _young_gen->unsafe_max_tlab_alloc();
938 }
939
940 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t min_size,
941 size_t requested_size,
942 size_t* actual_size) {
943 bool gc_overhead_limit_was_exceeded;
944 HeapWord* result = mem_allocate_work(requested_size /* size */,
945 true /* is_tlab */,
946 &gc_overhead_limit_was_exceeded);
947 if (result != nullptr) {
948 *actual_size = requested_size;
949 }
950
951 return result;
952 }
953
954 // Requires "*prev_ptr" to be non-null. Deletes and a block of minimal size
955 // from the list headed by "*prev_ptr".
956 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
957 bool first = true;
958 size_t min_size = 0; // "first" makes this conceptually infinite.
959 ScratchBlock **smallest_ptr, *smallest;
960 ScratchBlock *cur = *prev_ptr;
961 while (cur) {
962 assert(*prev_ptr == cur, "just checking");
963 if (first || cur->num_words < min_size) {
964 smallest_ptr = prev_ptr;
965 smallest = cur;
966 min_size = smallest->num_words;
967 first = false;
968 }
969 prev_ptr = &cur->next;
970 cur = cur->next;
971 }
972 smallest = *smallest_ptr;
973 *smallest_ptr = smallest->next;
974 return smallest;
975 }
976
977 // Sort the scratch block list headed by res into decreasing size order,
978 // and set "res" to the result.
979 static void sort_scratch_list(ScratchBlock*& list) {
980 ScratchBlock* sorted = nullptr;
981 ScratchBlock* unsorted = list;
982 while (unsorted) {
983 ScratchBlock *smallest = removeSmallestScratch(&unsorted);
984 smallest->next = sorted;
985 sorted = smallest;
986 }
987 list = sorted;
988 }
989
990 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
991 size_t max_alloc_words) {
992 ScratchBlock* res = nullptr;
993 _young_gen->contribute_scratch(res, requestor, max_alloc_words);
994 _old_gen->contribute_scratch(res, requestor, max_alloc_words);
995 sort_scratch_list(res);
996 return res;
997 }
998
999 void GenCollectedHeap::release_scratch() {
1000 _young_gen->reset_scratch();
1001 _old_gen->reset_scratch();
1002 }
1003
1004 void GenCollectedHeap::prepare_for_verify() {
1005 ensure_parsability(false); // no need to retire TLABs
1006 }
1007
1008 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1009 bool old_to_young) {
1010 if (old_to_young) {
1011 cl->do_generation(_old_gen);
1012 cl->do_generation(_young_gen);
1013 } else {
1014 cl->do_generation(_young_gen);
1015 cl->do_generation(_old_gen);
1016 }
1017 }
1018
1019 bool GenCollectedHeap::is_maximal_no_gc() const {
1020 return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
1021 }
1022
1023 void GenCollectedHeap::save_marks() {
1024 _young_gen->save_marks();
1025 _old_gen->save_marks();
1026 }
1027
1028 GenCollectedHeap* GenCollectedHeap::heap() {
1029 // SerialHeap is the only subtype of GenCollectedHeap.
1030 return named_heap<GenCollectedHeap>(CollectedHeap::Serial);
1031 }
1032
1033 #if INCLUDE_SERIALGC
1034 void GenCollectedHeap::prepare_for_compaction() {
1035 // Start by compacting into same gen.
1036 CompactPoint cp(_old_gen);
1037 _old_gen->prepare_for_compaction(&cp);
1038 _young_gen->prepare_for_compaction(&cp);
1039 }
1040 #endif // INCLUDE_SERIALGC
1041
1042 void GenCollectedHeap::verify(VerifyOption option /* ignored */) {
1043 log_debug(gc, verify)("%s", _old_gen->name());
1044 _old_gen->verify();
1045
1046 log_debug(gc, verify)("%s", _young_gen->name());
1047 _young_gen->verify();
1048
1049 log_debug(gc, verify)("RemSet");
1050 rem_set()->verify();
1051 }
1052
1053 void GenCollectedHeap::print_on(outputStream* st) const {
1054 if (_young_gen != nullptr) {
1055 _young_gen->print_on(st);
1056 }
1057 if (_old_gen != nullptr) {
1058 _old_gen->print_on(st);
1059 }
1060 MetaspaceUtils::print_on(st);
1061 }
1062
1063 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1064 }
1065
1066 bool GenCollectedHeap::print_location(outputStream* st, void* addr) const {
1067 return BlockLocationPrinter<GenCollectedHeap>::print_location(st, addr);
1068 }
1069
1070 void GenCollectedHeap::print_tracing_info() const {
1071 if (log_is_enabled(Debug, gc, heap, exit)) {
1072 LogStreamHandle(Debug, gc, heap, exit) lsh;
1073 _young_gen->print_summary_info_on(&lsh);
1074 _old_gen->print_summary_info_on(&lsh);
1075 }
1076 }
1077
1078 void GenCollectedHeap::print_heap_change(const PreGenGCValues& pre_gc_values) const {
1079 const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
1080
1081 log_info(gc, heap)(HEAP_CHANGE_FORMAT" "
1082 HEAP_CHANGE_FORMAT" "
1083 HEAP_CHANGE_FORMAT,
1084 HEAP_CHANGE_FORMAT_ARGS(def_new_gen->short_name(),
1085 pre_gc_values.young_gen_used(),
1086 pre_gc_values.young_gen_capacity(),
1087 def_new_gen->used(),
1088 def_new_gen->capacity()),
1089 HEAP_CHANGE_FORMAT_ARGS("Eden",
1090 pre_gc_values.eden_used(),
1091 pre_gc_values.eden_capacity(),
1092 def_new_gen->eden()->used(),
1093 def_new_gen->eden()->capacity()),
1094 HEAP_CHANGE_FORMAT_ARGS("From",
1095 pre_gc_values.from_used(),
1096 pre_gc_values.from_capacity(),
1097 def_new_gen->from()->used(),
1098 def_new_gen->from()->capacity()));
1099 log_info(gc, heap)(HEAP_CHANGE_FORMAT,
1100 HEAP_CHANGE_FORMAT_ARGS(old_gen()->short_name(),
1101 pre_gc_values.old_gen_used(),
1102 pre_gc_values.old_gen_capacity(),
1103 old_gen()->used(),
1104 old_gen()->capacity()));
1105 MetaspaceUtils::print_metaspace_change(pre_gc_values.metaspace_sizes());
1106 }
1107
1108 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1109 private:
1110 bool _full;
1111 public:
1112 void do_generation(Generation* gen) {
1113 gen->gc_prologue(_full);
1114 }
1115 GenGCPrologueClosure(bool full) : _full(full) {};
1116 };
1117
1118 void GenCollectedHeap::gc_prologue(bool full) {
1119 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1120
1121 // Fill TLAB's and such
1122 ensure_parsability(true); // retire TLABs
1123
1124 // Walk generations
1125 GenGCPrologueClosure blk(full);
1126 generation_iterate(&blk, false); // not old-to-young.
1127 };
1128
1129 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1130 private:
1131 bool _full;
1132 public:
1133 void do_generation(Generation* gen) {
1134 gen->gc_epilogue(_full);
1135 }
1136 GenGCEpilogueClosure(bool full) : _full(full) {};
1137 };
1138
1139 void GenCollectedHeap::gc_epilogue(bool full) {
1140 #if COMPILER2_OR_JVMCI
1141 assert(DerivedPointerTable::is_empty(), "derived pointer present");
1142 #endif // COMPILER2_OR_JVMCI
1143
1144 resize_all_tlabs();
1145
1146 GenGCEpilogueClosure blk(full);
1147 generation_iterate(&blk, false); // not old-to-young.
1148
1149 MetaspaceCounters::update_performance_counters();
1150 };
1151
1152 #ifndef PRODUCT
1153 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1154 private:
1155 public:
1156 void do_generation(Generation* gen) {
1157 gen->record_spaces_top();
1158 }
1159 };
1160
1161 void GenCollectedHeap::record_gen_tops_before_GC() {
1162 if (ZapUnusedHeapArea) {
1163 GenGCSaveTopsBeforeGCClosure blk;
1164 generation_iterate(&blk, false); // not old-to-young.
1165 }
1166 }
1167 #endif // not PRODUCT
1168
1169 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1170 public:
1171 void do_generation(Generation* gen) {
1172 gen->ensure_parsability();
1173 }
1174 };
1175
1176 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1177 CollectedHeap::ensure_parsability(retire_tlabs);
1178 GenEnsureParsabilityClosure ep_cl;
1179 generation_iterate(&ep_cl, false);
1180 }