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