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