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 _forwarding = new SlidingForwarding(_reserved);
121
122 _rem_set = create_rem_set(heap_rs.region());
123 _rem_set->initialize();
124 CardTableBarrierSet *bs = new CardTableBarrierSet(_rem_set);
125 bs->initialize();
126 BarrierSet::set_barrier_set(bs);
127
128 ReservedSpace young_rs = heap_rs.first_part(_young_gen_spec->max_size());
129 _young_gen = _young_gen_spec->init(young_rs, rem_set());
130 ReservedSpace old_rs = heap_rs.last_part(_young_gen_spec->max_size());
131
132 old_rs = old_rs.first_part(_old_gen_spec->max_size());
133 _old_gen = _old_gen_spec->init(old_rs, rem_set());
134
135 GCInitLogger::print();
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 void GenCollectedHeap::initialize_size_policy(size_t init_eden_size,
145 size_t init_promo_size,
146 size_t init_survivor_size) {
147 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
148 _size_policy = new AdaptiveSizePolicy(init_eden_size,
149 init_promo_size,
150 init_survivor_size,
151 max_gc_pause_sec,
152 GCTimeRatio);
153 }
154
155 ReservedHeapSpace GenCollectedHeap::allocate(size_t alignment) {
156 // Now figure out the total size.
157 const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
158 assert(alignment % pageSize == 0, "Must be");
159
160 // Check for overflow.
161 size_t total_reserved = _young_gen_spec->max_size() + _old_gen_spec->max_size();
162 if (total_reserved < _young_gen_spec->max_size()) {
163 vm_exit_during_initialization("The size of the object heap + VM data exceeds "
164 "the maximum representable size");
165 }
166 assert(total_reserved % alignment == 0,
167 "Gen size; total_reserved=" SIZE_FORMAT ", alignment="
168 SIZE_FORMAT, total_reserved, alignment);
169
170 ReservedHeapSpace heap_rs = Universe::reserve_heap(total_reserved, alignment);
171 size_t used_page_size = heap_rs.page_size();
172
173 os::trace_page_sizes("Heap",
174 MinHeapSize,
175 total_reserved,
176 used_page_size,
177 heap_rs.base(),
178 heap_rs.size());
179
180 return heap_rs;
181 }
182
183 class GenIsScavengable : public BoolObjectClosure {
184 public:
185 bool do_object_b(oop obj) {
186 return GenCollectedHeap::heap()->is_in_young(obj);
187 }
188 };
189
190 static GenIsScavengable _is_scavengable;
191
192 void GenCollectedHeap::post_initialize() {
193 CollectedHeap::post_initialize();
194 ref_processing_init();
195
196 DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
197
198 initialize_size_policy(def_new_gen->eden()->capacity(),
199 _old_gen->capacity(),
200 def_new_gen->from()->capacity());
201
202 MarkSweep::initialize();
203
204 ScavengableNMethods::initialize(&_is_scavengable);
205 }
206
207 void GenCollectedHeap::ref_processing_init() {
208 _young_gen->ref_processor_init();
209 _old_gen->ref_processor_init();
210 }
211
212 PreGenGCValues GenCollectedHeap::get_pre_gc_values() const {
213 const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
214
215 return PreGenGCValues(def_new_gen->used(),
216 def_new_gen->capacity(),
217 def_new_gen->eden()->used(),
218 def_new_gen->eden()->capacity(),
219 def_new_gen->from()->used(),
220 def_new_gen->from()->capacity(),
221 old_gen()->used(),
222 old_gen()->capacity());
223 }
224
225 GenerationSpec* GenCollectedHeap::young_gen_spec() const {
226 return _young_gen_spec;
227 }
228
229 GenerationSpec* GenCollectedHeap::old_gen_spec() const {
230 return _old_gen_spec;
231 }
232
233 size_t GenCollectedHeap::capacity() const {
234 return _young_gen->capacity() + _old_gen->capacity();
235 }
236
237 size_t GenCollectedHeap::used() const {
238 return _young_gen->used() + _old_gen->used();
239 }
240
241 void GenCollectedHeap::save_used_regions() {
242 _old_gen->save_used_region();
243 _young_gen->save_used_region();
244 }
245
246 size_t GenCollectedHeap::max_capacity() const {
247 return _young_gen->max_capacity() + _old_gen->max_capacity();
248 }
249
250 // Update the _full_collections_completed counter
251 // at the end of a stop-world full GC.
252 unsigned int GenCollectedHeap::update_full_collections_completed() {
253 assert(_full_collections_completed <= _total_full_collections,
254 "Can't complete more collections than were started");
255 _full_collections_completed = _total_full_collections;
256 return _full_collections_completed;
257 }
258
259 // Return true if any of the following is true:
260 // . the allocation won't fit into the current young gen heap
261 // . gc locker is occupied (jni critical section)
262 // . heap memory is tight -- the most recent previous collection
263 // was a full collection because a partial collection (would
264 // have) failed and is likely to fail again
265 bool GenCollectedHeap::should_try_older_generation_allocation(size_t word_size) const {
266 size_t young_capacity = _young_gen->capacity_before_gc();
267 return (word_size > heap_word_size(young_capacity))
268 || GCLocker::is_active_and_needs_gc()
269 || incremental_collection_failed();
270 }
271
272 HeapWord* GenCollectedHeap::expand_heap_and_allocate(size_t size, bool is_tlab) {
273 HeapWord* result = nullptr;
274 if (_old_gen->should_allocate(size, is_tlab)) {
275 result = _old_gen->expand_and_allocate(size, is_tlab);
276 }
277 if (result == nullptr) {
278 if (_young_gen->should_allocate(size, is_tlab)) {
279 result = _young_gen->expand_and_allocate(size, is_tlab);
280 }
281 }
282 assert(result == nullptr || is_in_reserved(result), "result not in heap");
283 return result;
284 }
285
286 HeapWord* GenCollectedHeap::mem_allocate_work(size_t size,
287 bool is_tlab,
288 bool* gc_overhead_limit_was_exceeded) {
289 // In general gc_overhead_limit_was_exceeded should be false so
290 // set it so here and reset it to true only if the gc time
291 // limit is being exceeded as checked below.
292 *gc_overhead_limit_was_exceeded = false;
293
294 HeapWord* result = nullptr;
295
296 // Loop until the allocation is satisfied, or unsatisfied after GC.
297 for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
298
299 // First allocation attempt is lock-free.
300 Generation *young = _young_gen;
301 if (young->should_allocate(size, is_tlab)) {
302 result = young->par_allocate(size, is_tlab);
303 if (result != nullptr) {
304 assert(is_in_reserved(result), "result not in heap");
305 return result;
306 }
307 }
308 uint gc_count_before; // Read inside the Heap_lock locked region.
309 {
310 MutexLocker ml(Heap_lock);
311 log_trace(gc, alloc)("GenCollectedHeap::mem_allocate_work: attempting locked slow path allocation");
312 // Note that only large objects get a shot at being
313 // allocated in later generations.
314 bool first_only = !should_try_older_generation_allocation(size);
315
316 result = attempt_allocation(size, is_tlab, first_only);
317 if (result != nullptr) {
318 assert(is_in_reserved(result), "result not in heap");
319 return result;
320 }
321
322 if (GCLocker::is_active_and_needs_gc()) {
323 if (is_tlab) {
324 return nullptr; // Caller will retry allocating individual object.
325 }
326 if (!is_maximal_no_gc()) {
327 // Try and expand heap to satisfy request.
328 result = expand_heap_and_allocate(size, is_tlab);
329 // Result could be null if we are out of space.
330 if (result != nullptr) {
331 return result;
332 }
333 }
334
335 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
336 return nullptr; // We didn't get to do a GC and we didn't get any memory.
337 }
338
339 // If this thread is not in a jni critical section, we stall
340 // the requestor until the critical section has cleared and
341 // GC allowed. When the critical section clears, a GC is
342 // initiated by the last thread exiting the critical section; so
343 // we retry the allocation sequence from the beginning of the loop,
344 // rather than causing more, now probably unnecessary, GC attempts.
345 JavaThread* jthr = JavaThread::current();
346 if (!jthr->in_critical()) {
347 MutexUnlocker mul(Heap_lock);
348 // Wait for JNI critical section to be exited
349 GCLocker::stall_until_clear();
350 gclocker_stalled_count += 1;
351 continue;
352 } else {
353 if (CheckJNICalls) {
354 fatal("Possible deadlock due to allocating while"
355 " in jni critical section");
356 }
357 return nullptr;
358 }
359 }
360
361 // Read the gc count while the heap lock is held.
362 gc_count_before = total_collections();
363 }
364
365 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
366 VMThread::execute(&op);
367 if (op.prologue_succeeded()) {
368 result = op.result();
369 if (op.gc_locked()) {
370 assert(result == nullptr, "must be null if gc_locked() is true");
371 continue; // Retry and/or stall as necessary.
372 }
373
374 // Allocation has failed and a collection
375 // has been done. If the gc time limit was exceeded the
376 // this time, return null so that an out-of-memory
377 // will be thrown. Clear gc_overhead_limit_exceeded
378 // so that the overhead exceeded does not persist.
379
380 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
381 const bool softrefs_clear = soft_ref_policy()->all_soft_refs_clear();
382
383 if (limit_exceeded && softrefs_clear) {
384 *gc_overhead_limit_was_exceeded = true;
385 size_policy()->set_gc_overhead_limit_exceeded(false);
386 if (op.result() != nullptr) {
387 CollectedHeap::fill_with_object(op.result(), size);
388 }
389 return nullptr;
390 }
391 assert(result == nullptr || is_in_reserved(result),
392 "result not in heap");
393 return result;
394 }
395
396 // Give a warning if we seem to be looping forever.
397 if ((QueuedAllocationWarningCount > 0) &&
398 (try_count % QueuedAllocationWarningCount == 0)) {
399 log_warning(gc, ergo)("GenCollectedHeap::mem_allocate_work retries %d times,"
400 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");
401 }
402 }
403 }
404
405 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
406 bool is_tlab,
407 bool first_only) {
408 HeapWord* res = nullptr;
409
410 if (_young_gen->should_allocate(size, is_tlab)) {
411 res = _young_gen->allocate(size, is_tlab);
412 if (res != nullptr || first_only) {
413 return res;
414 }
415 }
416
417 if (_old_gen->should_allocate(size, is_tlab)) {
418 res = _old_gen->allocate(size, is_tlab);
419 }
420
421 return res;
422 }
423
424 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
425 bool* gc_overhead_limit_was_exceeded) {
426 return mem_allocate_work(size,
427 false /* is_tlab */,
428 gc_overhead_limit_was_exceeded);
429 }
430
431 bool GenCollectedHeap::must_clear_all_soft_refs() {
432 return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
433 _gc_cause == GCCause::_wb_full_gc;
434 }
435
436 void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
437 bool is_tlab, bool run_verification, bool clear_soft_refs) {
438 FormatBuffer<> title("Collect gen: %s", gen->short_name());
439 GCTraceTime(Trace, gc, phases) t1(title);
440 TraceCollectorStats tcs(gen->counters());
441 TraceMemoryManagerStats tmms(gen->gc_manager(), gc_cause());
442
443 gen->stat_record()->invocations++;
444 gen->stat_record()->accumulated_time.start();
445
446 // Must be done anew before each collection because
447 // a previous collection will do mangling and will
448 // change top of some spaces.
449 record_gen_tops_before_GC();
450
451 log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);
452
453 if (run_verification && VerifyBeforeGC) {
454 Universe::verify("Before GC");
455 }
456 COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::clear());
457
458 // Do collection work
459 {
460 // Note on ref discovery: For what appear to be historical reasons,
461 // GCH enables and disabled (by enqueuing) refs discovery.
462 // In the future this should be moved into the generation's
463 // collect method so that ref discovery and enqueueing concerns
464 // are local to a generation. The collect method could return
465 // an appropriate indication in the case that notification on
466 // the ref lock was needed. This will make the treatment of
467 // weak refs more uniform (and indeed remove such concerns
468 // from GCH). XXX
469
470 save_marks(); // save marks for all gens
471 // We want to discover references, but not process them yet.
472 // This mode is disabled in process_discovered_references if the
473 // generation does some collection work, or in
474 // enqueue_discovered_references if the generation returns
475 // without doing any work.
476 ReferenceProcessor* rp = gen->ref_processor();
477 rp->start_discovery(clear_soft_refs);
478
479 gen->collect(full, clear_soft_refs, size, is_tlab);
480
481 rp->disable_discovery();
482 rp->verify_no_references_recorded();
483 }
484
485 COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::update_pointers());
486
487 gen->stat_record()->accumulated_time.stop();
488
489 update_gc_stats(gen, full);
490
491 if (run_verification && VerifyAfterGC) {
492 Universe::verify("After GC");
493 }
494 }
495
496 void GenCollectedHeap::do_collection(bool full,
497 bool clear_all_soft_refs,
498 size_t size,
499 bool is_tlab,
500 GenerationType max_generation) {
501 ResourceMark rm;
502 DEBUG_ONLY(Thread* my_thread = Thread::current();)
503
504 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
505 assert(my_thread->is_VM_thread(), "only VM thread");
506 assert(Heap_lock->is_locked(),
507 "the requesting thread should have the Heap_lock");
508 guarantee(!is_gc_active(), "collection is not reentrant");
509
510 if (GCLocker::check_active_before_gc()) {
511 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
512 }
513
514 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
515 soft_ref_policy()->should_clear_all_soft_refs();
516
517 ClearedAllSoftRefs casr(do_clear_all_soft_refs, soft_ref_policy());
518
519 AutoModifyRestore<bool> temporarily(_is_gc_active, true);
520
521 bool complete = full && (max_generation == OldGen);
522 bool old_collects_young = complete && !ScavengeBeforeFullGC;
523 bool do_young_collection = !old_collects_young && _young_gen->should_collect(full, size, is_tlab);
524
525 const PreGenGCValues pre_gc_values = get_pre_gc_values();
526
527 bool run_verification = total_collections() >= VerifyGCStartAt;
528 bool prepared_for_verification = false;
529 bool do_full_collection = false;
530
531 if (do_young_collection) {
532 GCIdMark gc_id_mark;
533 GCTraceCPUTime tcpu(((DefNewGeneration*)_young_gen)->gc_tracer());
534 GCTraceTime(Info, gc) t("Pause Young", nullptr, gc_cause(), true);
535
536 print_heap_before_gc();
537
538 if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
539 prepare_for_verify();
540 prepared_for_verification = true;
541 }
542
543 gc_prologue(complete);
544 increment_total_collections(complete);
545
546 collect_generation(_young_gen,
547 full,
548 size,
549 is_tlab,
550 run_verification && VerifyGCLevel <= 0,
551 do_clear_all_soft_refs);
552
553 if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
554 size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
555 // Allocation request was met by young GC.
556 size = 0;
557 }
558
559 // Ask if young collection is enough. If so, do the final steps for young collection,
560 // and fallthrough to the end.
561 do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
562 if (!do_full_collection) {
563 // Adjust generation sizes.
564 _young_gen->compute_new_size();
565
566 print_heap_change(pre_gc_values);
567
568 // Track memory usage and detect low memory after GC finishes
569 MemoryService::track_memory_usage();
570
571 gc_epilogue(complete);
572 }
573
574 print_heap_after_gc();
575
576 } else {
577 // No young collection, ask if we need to perform Full collection.
578 do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
579 }
580
581 if (do_full_collection) {
582 GCIdMark gc_id_mark;
583 GCTraceCPUTime tcpu(GenMarkSweep::gc_tracer());
584 GCTraceTime(Info, gc) t("Pause Full", nullptr, gc_cause(), true);
585
586 print_heap_before_gc();
587
588 if (!prepared_for_verification && run_verification &&
589 VerifyGCLevel <= 1 && VerifyBeforeGC) {
590 prepare_for_verify();
591 }
592
593 if (!do_young_collection) {
594 gc_prologue(complete);
595 increment_total_collections(complete);
596 }
597
598 // Accounting quirk: total full collections would be incremented when "complete"
599 // is set, by calling increment_total_collections above. However, we also need to
600 // account Full collections that had "complete" unset.
601 if (!complete) {
602 increment_total_full_collections();
603 }
604
605 CodeCache::on_gc_marking_cycle_start();
606
607 collect_generation(_old_gen,
608 full,
609 size,
610 is_tlab,
611 run_verification && VerifyGCLevel <= 1,
612 do_clear_all_soft_refs);
613
614 CodeCache::on_gc_marking_cycle_finish();
615 CodeCache::arm_all_nmethods();
616
617 // Adjust generation sizes.
618 _old_gen->compute_new_size();
619 _young_gen->compute_new_size();
620
621 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
622 ClassLoaderDataGraph::purge(/*at_safepoint*/true);
623 DEBUG_ONLY(MetaspaceUtils::verify();)
624
625 // Need to clear claim bits for the next mark.
626 ClassLoaderDataGraph::clear_claimed_marks();
627
628 // Resize the metaspace capacity after full collections
629 MetaspaceGC::compute_new_size();
630 update_full_collections_completed();
631
632 print_heap_change(pre_gc_values);
633
634 // Track memory usage and detect low memory after GC finishes
635 MemoryService::track_memory_usage();
636
637 // Need to tell the epilogue code we are done with Full GC, regardless what was
638 // the initial value for "complete" flag.
639 gc_epilogue(true);
640
641 print_heap_after_gc();
642 }
643 }
644
645 bool GenCollectedHeap::should_do_full_collection(size_t size, bool full, bool is_tlab,
646 GenCollectedHeap::GenerationType max_gen) const {
647 return max_gen == OldGen && _old_gen->should_collect(full, size, is_tlab);
648 }
649
650 void GenCollectedHeap::register_nmethod(nmethod* nm) {
651 ScavengableNMethods::register_nmethod(nm);
652 }
653
654 void GenCollectedHeap::unregister_nmethod(nmethod* nm) {
655 ScavengableNMethods::unregister_nmethod(nm);
656 }
657
658 void GenCollectedHeap::verify_nmethod(nmethod* nm) {
659 ScavengableNMethods::verify_nmethod(nm);
660 }
661
662 void GenCollectedHeap::prune_scavengable_nmethods() {
663 ScavengableNMethods::prune_nmethods();
664 }
665
666 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
667 GCCauseSetter x(this, GCCause::_allocation_failure);
668 HeapWord* result = nullptr;
669
670 assert(size != 0, "Precondition violated");
671 if (GCLocker::is_active_and_needs_gc()) {
672 // GC locker is active; instead of a collection we will attempt
673 // to expand the heap, if there's room for expansion.
674 if (!is_maximal_no_gc()) {
675 result = expand_heap_and_allocate(size, is_tlab);
676 }
677 return result; // Could be null if we are out of space.
678 } else if (!incremental_collection_will_fail(false /* don't consult_young */)) {
679 // Do an incremental collection.
680 do_collection(false, // full
681 false, // clear_all_soft_refs
682 size, // size
683 is_tlab, // is_tlab
684 GenCollectedHeap::OldGen); // max_generation
685 } else {
686 log_trace(gc)(" :: Trying full because partial may fail :: ");
687 // Try a full collection; see delta for bug id 6266275
688 // for the original code and why this has been simplified
689 // with from-space allocation criteria modified and
690 // such allocation moved out of the safepoint path.
691 do_collection(true, // full
692 false, // clear_all_soft_refs
693 size, // size
694 is_tlab, // is_tlab
695 GenCollectedHeap::OldGen); // max_generation
696 }
697
698 result = attempt_allocation(size, is_tlab, false /*first_only*/);
699
700 if (result != nullptr) {
701 assert(is_in_reserved(result), "result not in heap");
702 return result;
703 }
704
705 // OK, collection failed, try expansion.
706 result = expand_heap_and_allocate(size, is_tlab);
707 if (result != nullptr) {
708 return result;
709 }
710
711 // If we reach this point, we're really out of memory. Try every trick
712 // we can to reclaim memory. Force collection of soft references. Force
713 // a complete compaction of the heap. Any additional methods for finding
714 // free memory should be here, especially if they are expensive. If this
715 // attempt fails, an OOM exception will be thrown.
716 {
717 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
718
719 do_collection(true, // full
720 true, // clear_all_soft_refs
721 size, // size
722 is_tlab, // is_tlab
723 GenCollectedHeap::OldGen); // max_generation
724 }
725
726 result = attempt_allocation(size, is_tlab, false /* first_only */);
727 if (result != nullptr) {
728 assert(is_in_reserved(result), "result not in heap");
729 return result;
730 }
731
732 assert(!soft_ref_policy()->should_clear_all_soft_refs(),
733 "Flag should have been handled and cleared prior to this point");
734
735 // What else? We might try synchronous finalization later. If the total
736 // space available is large enough for the allocation, then a more
737 // complete compaction phase than we've tried so far might be
738 // appropriate.
739 return nullptr;
740 }
741
742 #ifdef ASSERT
743 class AssertNonScavengableClosure: public OopClosure {
744 public:
745 virtual void do_oop(oop* p) {
746 assert(!GenCollectedHeap::heap()->is_in_partial_collection(*p),
747 "Referent should not be scavengable."); }
748 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
749 };
750 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
751 #endif
752
753 void GenCollectedHeap::process_roots(ScanningOption so,
754 OopClosure* strong_roots,
755 CLDClosure* strong_cld_closure,
756 CLDClosure* weak_cld_closure,
757 CodeBlobToOopClosure* code_roots) {
758 // General roots.
759 assert(code_roots != nullptr, "code root closure should always be set");
760
761 ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
762
763 // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
764 CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? nullptr : code_roots;
765
766 Threads::oops_do(strong_roots, roots_from_code_p);
767
768 OopStorageSet::strong_oops_do(strong_roots);
769
770 if (so & SO_ScavengeCodeCache) {
771 assert(code_roots != nullptr, "must supply closure for code cache");
772
773 // We only visit parts of the CodeCache when scavenging.
774 ScavengableNMethods::nmethods_do(code_roots);
775 }
776 if (so & SO_AllCodeCache) {
777 assert(code_roots != nullptr, "must supply closure for code cache");
778
779 // CMSCollector uses this to do intermediate-strength collections.
780 // We scan the entire code cache, since CodeCache::do_unloading is not called.
781 CodeCache::blobs_do(code_roots);
782 }
783 // Verify that the code cache contents are not subject to
784 // movement by a scavenging collection.
785 DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
786 DEBUG_ONLY(ScavengableNMethods::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
787 }
788
789 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
790 WeakProcessor::oops_do(root_closure);
791 }
792
793 bool GenCollectedHeap::no_allocs_since_save_marks() {
794 return _young_gen->no_allocs_since_save_marks() &&
795 _old_gen->no_allocs_since_save_marks();
796 }
797
798 // public collection interfaces
799 void GenCollectedHeap::collect(GCCause::Cause cause) {
800 // The caller doesn't have the Heap_lock
801 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
802
803 unsigned int gc_count_before;
804 unsigned int full_gc_count_before;
805
806 {
807 MutexLocker ml(Heap_lock);
808 // Read the GC count while holding the Heap_lock
809 gc_count_before = total_collections();
810 full_gc_count_before = total_full_collections();
811 }
812
813 if (GCLocker::should_discard(cause, gc_count_before)) {
814 return;
815 }
816
817 bool should_run_young_gc = (cause == GCCause::_wb_young_gc)
818 || (cause == GCCause::_gc_locker)
819 DEBUG_ONLY(|| (cause == GCCause::_scavenge_alot));
820
821 const GenerationType max_generation = should_run_young_gc
822 ? YoungGen
823 : OldGen;
824
825 VM_GenCollectFull op(gc_count_before, full_gc_count_before,
826 cause, max_generation);
827 VMThread::execute(&op);
828 }
829
830 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
831 do_full_collection(clear_all_soft_refs, OldGen);
832 }
833
834 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
835 GenerationType last_generation) {
836 do_collection(true, // full
837 clear_all_soft_refs, // clear_all_soft_refs
838 0, // size
839 false, // is_tlab
840 last_generation); // last_generation
841 // Hack XXX FIX ME !!!
842 // A scavenge may not have been attempted, or may have
843 // been attempted and failed, because the old gen was too full
844 if (gc_cause() == GCCause::_gc_locker && incremental_collection_failed()) {
845 log_debug(gc, jni)("GC locker: Trying a full collection because scavenge failed");
846 // This time allow the old gen to be collected as well
847 do_collection(true, // full
848 clear_all_soft_refs, // clear_all_soft_refs
849 0, // size
850 false, // is_tlab
851 OldGen); // last_generation
852 }
853 }
854
855 bool GenCollectedHeap::is_in_young(const void* p) const {
856 bool result = p < _old_gen->reserved().start();
857 assert(result == _young_gen->is_in_reserved(p),
858 "incorrect test - result=%d, p=" PTR_FORMAT, result, p2i(p));
859 return result;
860 }
861
862 bool GenCollectedHeap::requires_barriers(stackChunkOop obj) const {
863 return !is_in_young(obj);
864 }
865
866 // Returns "TRUE" iff "p" points into the committed areas of the heap.
867 bool GenCollectedHeap::is_in(const void* p) const {
868 return _young_gen->is_in(p) || _old_gen->is_in(p);
869 }
870
871 #ifdef ASSERT
872 // Don't implement this by using is_in_young(). This method is used
873 // in some cases to check that is_in_young() is correct.
874 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
875 assert(is_in_reserved(p) || p == nullptr,
876 "Does not work if address is non-null and outside of the heap");
877 return p < _young_gen->reserved().end() && p != nullptr;
878 }
879 #endif
880
881 void GenCollectedHeap::oop_iterate(OopIterateClosure* cl) {
882 _young_gen->oop_iterate(cl);
883 _old_gen->oop_iterate(cl);
884 }
885
886 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
887 _young_gen->object_iterate(cl);
888 _old_gen->object_iterate(cl);
889 }
890
891 Space* GenCollectedHeap::space_containing(const void* addr) const {
892 Space* res = _young_gen->space_containing(addr);
893 if (res != nullptr) {
894 return res;
895 }
896 res = _old_gen->space_containing(addr);
897 assert(res != nullptr, "Could not find containing space");
898 return res;
899 }
900
901 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
902 assert(is_in_reserved(addr), "block_start of address outside of heap");
903 if (_young_gen->is_in_reserved(addr)) {
904 assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
905 return _young_gen->block_start(addr);
906 }
907
908 assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
909 assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
910 return _old_gen->block_start(addr);
911 }
912
913 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
914 assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
915 assert(block_start(addr) == addr, "addr must be a block start");
916 if (_young_gen->is_in_reserved(addr)) {
917 return _young_gen->block_is_obj(addr);
918 }
919
920 assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
921 return _old_gen->block_is_obj(addr);
922 }
923
924 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
925 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
926 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
927 return _young_gen->tlab_capacity();
928 }
929
930 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
931 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
932 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
933 return _young_gen->tlab_used();
934 }
935
936 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
937 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
938 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
939 return _young_gen->unsafe_max_tlab_alloc();
940 }
941
942 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t min_size,
943 size_t requested_size,
944 size_t* actual_size) {
945 bool gc_overhead_limit_was_exceeded;
946 HeapWord* result = mem_allocate_work(requested_size /* size */,
947 true /* is_tlab */,
948 &gc_overhead_limit_was_exceeded);
949 if (result != nullptr) {
950 *actual_size = requested_size;
951 }
952
953 return result;
954 }
955
956 // Requires "*prev_ptr" to be non-null. Deletes and a block of minimal size
957 // from the list headed by "*prev_ptr".
958 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
959 bool first = true;
960 size_t min_size = 0; // "first" makes this conceptually infinite.
961 ScratchBlock **smallest_ptr, *smallest;
962 ScratchBlock *cur = *prev_ptr;
963 while (cur) {
964 assert(*prev_ptr == cur, "just checking");
965 if (first || cur->num_words < min_size) {
966 smallest_ptr = prev_ptr;
967 smallest = cur;
968 min_size = smallest->num_words;
969 first = false;
970 }
971 prev_ptr = &cur->next;
972 cur = cur->next;
973 }
974 smallest = *smallest_ptr;
975 *smallest_ptr = smallest->next;
976 return smallest;
977 }
978
979 // Sort the scratch block list headed by res into decreasing size order,
980 // and set "res" to the result.
981 static void sort_scratch_list(ScratchBlock*& list) {
982 ScratchBlock* sorted = nullptr;
983 ScratchBlock* unsorted = list;
984 while (unsorted) {
985 ScratchBlock *smallest = removeSmallestScratch(&unsorted);
986 smallest->next = sorted;
987 sorted = smallest;
988 }
989 list = sorted;
990 }
991
992 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
993 size_t max_alloc_words) {
994 ScratchBlock* res = nullptr;
995 _young_gen->contribute_scratch(res, requestor, max_alloc_words);
996 _old_gen->contribute_scratch(res, requestor, max_alloc_words);
997 sort_scratch_list(res);
998 return res;
999 }
1000
1001 void GenCollectedHeap::release_scratch() {
1002 _young_gen->reset_scratch();
1003 _old_gen->reset_scratch();
1004 }
1005
1006 void GenCollectedHeap::prepare_for_verify() {
1007 ensure_parsability(false); // no need to retire TLABs
1008 }
1009
1010 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1011 bool old_to_young) {
1012 if (old_to_young) {
1013 cl->do_generation(_old_gen);
1014 cl->do_generation(_young_gen);
1015 } else {
1016 cl->do_generation(_young_gen);
1017 cl->do_generation(_old_gen);
1018 }
1019 }
1020
1021 bool GenCollectedHeap::is_maximal_no_gc() const {
1022 return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
1023 }
1024
1025 void GenCollectedHeap::save_marks() {
1026 _young_gen->save_marks();
1027 _old_gen->save_marks();
1028 }
1029
1030 GenCollectedHeap* GenCollectedHeap::heap() {
1031 // SerialHeap is the only subtype of GenCollectedHeap.
1032 return named_heap<GenCollectedHeap>(CollectedHeap::Serial);
1033 }
1034
1035 #if INCLUDE_SERIALGC
1036 void GenCollectedHeap::prepare_for_compaction() {
1037 // Start by compacting into same gen.
1038 CompactPoint cp(_old_gen);
1039 _forwarding->clear();
1040 _old_gen->prepare_for_compaction(&cp);
1041 _young_gen->prepare_for_compaction(&cp);
1042 }
1043 #endif // INCLUDE_SERIALGC
1044
1045 void GenCollectedHeap::verify(VerifyOption option /* ignored */) {
1046 log_debug(gc, verify)("%s", _old_gen->name());
1047 _old_gen->verify();
1048
1049 log_debug(gc, verify)("%s", _young_gen->name());
1050 _young_gen->verify();
1051
1052 log_debug(gc, verify)("RemSet");
1053 rem_set()->verify();
1054 }
1055
1056 void GenCollectedHeap::print_on(outputStream* st) const {
1057 if (_young_gen != nullptr) {
1058 _young_gen->print_on(st);
1059 }
1060 if (_old_gen != nullptr) {
1061 _old_gen->print_on(st);
1062 }
1063 MetaspaceUtils::print_on(st);
1064 }
1065
1066 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1067 }
1068
1069 bool GenCollectedHeap::print_location(outputStream* st, void* addr) const {
1070 return BlockLocationPrinter<GenCollectedHeap>::print_location(st, addr);
1071 }
1072
1073 void GenCollectedHeap::print_tracing_info() const {
1074 if (log_is_enabled(Debug, gc, heap, exit)) {
1075 LogStreamHandle(Debug, gc, heap, exit) lsh;
1076 _young_gen->print_summary_info_on(&lsh);
1077 _old_gen->print_summary_info_on(&lsh);
1078 }
1079 }
1080
1081 void GenCollectedHeap::print_heap_change(const PreGenGCValues& pre_gc_values) const {
1082 const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
1083
1084 log_info(gc, heap)(HEAP_CHANGE_FORMAT" "
1085 HEAP_CHANGE_FORMAT" "
1086 HEAP_CHANGE_FORMAT,
1087 HEAP_CHANGE_FORMAT_ARGS(def_new_gen->short_name(),
1088 pre_gc_values.young_gen_used(),
1089 pre_gc_values.young_gen_capacity(),
1090 def_new_gen->used(),
1091 def_new_gen->capacity()),
1092 HEAP_CHANGE_FORMAT_ARGS("Eden",
1093 pre_gc_values.eden_used(),
1094 pre_gc_values.eden_capacity(),
1095 def_new_gen->eden()->used(),
1096 def_new_gen->eden()->capacity()),
1097 HEAP_CHANGE_FORMAT_ARGS("From",
1098 pre_gc_values.from_used(),
1099 pre_gc_values.from_capacity(),
1100 def_new_gen->from()->used(),
1101 def_new_gen->from()->capacity()));
1102 log_info(gc, heap)(HEAP_CHANGE_FORMAT,
1103 HEAP_CHANGE_FORMAT_ARGS(old_gen()->short_name(),
1104 pre_gc_values.old_gen_used(),
1105 pre_gc_values.old_gen_capacity(),
1106 old_gen()->used(),
1107 old_gen()->capacity()));
1108 MetaspaceUtils::print_metaspace_change(pre_gc_values.metaspace_sizes());
1109 }
1110
1111 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1112 private:
1113 bool _full;
1114 public:
1115 void do_generation(Generation* gen) {
1116 gen->gc_prologue(_full);
1117 }
1118 GenGCPrologueClosure(bool full) : _full(full) {};
1119 };
1120
1121 void GenCollectedHeap::gc_prologue(bool full) {
1122 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1123
1124 // Fill TLAB's and such
1125 ensure_parsability(true); // retire TLABs
1126
1127 // Walk generations
1128 GenGCPrologueClosure blk(full);
1129 generation_iterate(&blk, false); // not old-to-young.
1130 };
1131
1132 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1133 private:
1134 bool _full;
1135 public:
1136 void do_generation(Generation* gen) {
1137 gen->gc_epilogue(_full);
1138 }
1139 GenGCEpilogueClosure(bool full) : _full(full) {};
1140 };
1141
1142 void GenCollectedHeap::gc_epilogue(bool full) {
1143 #if COMPILER2_OR_JVMCI
1144 assert(DerivedPointerTable::is_empty(), "derived pointer present");
1145 #endif // COMPILER2_OR_JVMCI
1146
1147 resize_all_tlabs();
1148
1149 GenGCEpilogueClosure blk(full);
1150 generation_iterate(&blk, false); // not old-to-young.
1151
1152 MetaspaceCounters::update_performance_counters();
1153 };
1154
1155 #ifndef PRODUCT
1156 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1157 private:
1158 public:
1159 void do_generation(Generation* gen) {
1160 gen->record_spaces_top();
1161 }
1162 };
1163
1164 void GenCollectedHeap::record_gen_tops_before_GC() {
1165 if (ZapUnusedHeapArea) {
1166 GenGCSaveTopsBeforeGCClosure blk;
1167 generation_iterate(&blk, false); // not old-to-young.
1168 }
1169 }
1170 #endif // not PRODUCT
1171
1172 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1173 public:
1174 void do_generation(Generation* gen) {
1175 gen->ensure_parsability();
1176 }
1177 };
1178
1179 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1180 CollectedHeap::ensure_parsability(retire_tlabs);
1181 GenEnsureParsabilityClosure ep_cl;
1182 generation_iterate(&ep_cl, false);
1183 }