1 /*
  2  * Copyright (c) 2001, 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 "cds/cdsConfig.hpp"
 27 #include "classfile/classLoaderData.hpp"
 28 #include "classfile/vmClasses.hpp"
 29 #include "gc/shared/allocTracer.hpp"
 30 #include "gc/shared/barrierSet.hpp"
 31 #include "gc/shared/collectedHeap.hpp"
 32 #include "gc/shared/collectedHeap.inline.hpp"
 33 #include "gc/shared/gcLocker.inline.hpp"
 34 #include "gc/shared/gcHeapSummary.hpp"
 35 #include "gc/shared/stringdedup/stringDedup.hpp"
 36 #include "gc/shared/gcTrace.hpp"
 37 #include "gc/shared/gcTraceTime.inline.hpp"
 38 #include "gc/shared/gcVMOperations.hpp"
 39 #include "gc/shared/gcWhen.hpp"
 40 #include "gc/shared/gc_globals.hpp"
 41 #include "gc/shared/memAllocator.hpp"
 42 #include "gc/shared/tlab_globals.hpp"
 43 #include "logging/log.hpp"
 44 #include "logging/logStream.hpp"
 45 #include "memory/classLoaderMetaspace.hpp"
 46 #include "memory/metaspace.hpp"
 47 #include "memory/metaspaceUtils.hpp"
 48 #include "memory/resourceArea.hpp"
 49 #include "memory/universe.hpp"
 50 #include "oops/instanceMirrorKlass.hpp"
 51 #include "oops/oop.inline.hpp"
 52 #include "runtime/handles.inline.hpp"
 53 #include "runtime/init.hpp"
 54 #include "runtime/javaThread.hpp"
 55 #include "runtime/perfData.hpp"
 56 #include "runtime/threadSMR.hpp"
 57 #include "runtime/vmThread.hpp"
 58 #include "services/heapDumper.hpp"
 59 #include "utilities/align.hpp"
 60 #include "utilities/copy.hpp"
 61 #include "utilities/events.hpp"
 62 
 63 class ClassLoaderData;
 64 
 65 size_t CollectedHeap::_lab_alignment_reserve = SIZE_MAX;
 66 Klass* CollectedHeap::_filler_object_klass = nullptr;
 67 size_t CollectedHeap::_filler_array_max_size = 0;
 68 size_t CollectedHeap::_stack_chunk_max_size = 0;
 69 
 70 class GCMessage : public FormatBuffer<1024> {
 71  public:
 72   bool is_before;
 73 };
 74 
 75 template <>
 76 void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {
 77   st->print_cr("GC heap %s", m.is_before ? "before" : "after");
 78   st->print_raw(m);
 79 }
 80 
 81 class GCHeapLog : public EventLogBase<GCMessage> {
 82  private:
 83   void log_heap(CollectedHeap* heap, bool before);
 84 
 85  public:
 86   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History", "gc") {}
 87 
 88   void log_heap_before(CollectedHeap* heap) {
 89     log_heap(heap, true);
 90   }
 91   void log_heap_after(CollectedHeap* heap) {
 92     log_heap(heap, false);
 93   }
 94 };
 95 
 96 void GCHeapLog::log_heap(CollectedHeap* heap, bool before) {
 97   if (!should_log()) {
 98     return;
 99   }
100 
101   double timestamp = fetch_timestamp();
102   MutexLocker ml(&_mutex, Mutex::_no_safepoint_check_flag);
103   int index = compute_log_index();
104   _records[index].thread = nullptr; // Its the GC thread so it's not that interesting.
105   _records[index].timestamp = timestamp;
106   _records[index].data.is_before = before;
107   stringStream st(_records[index].data.buffer(), _records[index].data.size());
108 
109   st.print_cr("{Heap %s GC invocations=%u (full %u):",
110                  before ? "before" : "after",
111                  heap->total_collections(),
112                  heap->total_full_collections());
113 
114   heap->print_on(&st);
115   st.print_cr("}");
116 }
117 
118 ParallelObjectIterator::ParallelObjectIterator(uint thread_num) :
119   _impl(Universe::heap()->parallel_object_iterator(thread_num))
120 {}
121 
122 ParallelObjectIterator::~ParallelObjectIterator() {
123   delete _impl;
124 }
125 
126 void ParallelObjectIterator::object_iterate(ObjectClosure* cl, uint worker_id) {
127   _impl->object_iterate(cl, worker_id);
128 }
129 
130 size_t CollectedHeap::unused() const {
131   MutexLocker ml(Heap_lock);
132   return capacity() - used();
133 }
134 
135 VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {
136   size_t capacity_in_words = capacity() / HeapWordSize;
137 
138   return VirtualSpaceSummary(
139     _reserved.start(), _reserved.start() + capacity_in_words, _reserved.end());
140 }
141 
142 GCHeapSummary CollectedHeap::create_heap_summary() {
143   VirtualSpaceSummary heap_space = create_heap_space_summary();
144   return GCHeapSummary(heap_space, used());
145 }
146 
147 MetaspaceSummary CollectedHeap::create_metaspace_summary() {
148   const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
149     MetaspaceUtils::chunk_free_list_summary(Metaspace::NonClassType);
150   const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =
151     MetaspaceUtils::chunk_free_list_summary(Metaspace::ClassType);
152   return MetaspaceSummary(MetaspaceGC::capacity_until_GC(),
153                           MetaspaceUtils::get_combined_statistics(),
154                           ms_chunk_free_list_summary, class_chunk_free_list_summary);
155 }
156 
157 bool CollectedHeap::contains_null(const oop* p) const {
158   return *p == nullptr;
159 }
160 
161 void CollectedHeap::print_heap_before_gc() {
162   LogTarget(Debug, gc, heap) lt;
163   if (lt.is_enabled()) {
164     LogStream ls(lt);
165     ls.print_cr("Heap before GC invocations=%u (full %u):", total_collections(), total_full_collections());
166     ResourceMark rm;
167     print_on(&ls);
168   }
169 
170   if (_gc_heap_log != nullptr) {
171     _gc_heap_log->log_heap_before(this);
172   }
173 }
174 
175 void CollectedHeap::print_heap_after_gc() {
176   LogTarget(Debug, gc, heap) lt;
177   if (lt.is_enabled()) {
178     LogStream ls(lt);
179     ls.print_cr("Heap after GC invocations=%u (full %u):", total_collections(), total_full_collections());
180     ResourceMark rm;
181     print_on(&ls);
182   }
183 
184   if (_gc_heap_log != nullptr) {
185     _gc_heap_log->log_heap_after(this);
186   }
187 }
188 
189 void CollectedHeap::print() const { print_on(tty); }
190 
191 void CollectedHeap::print_on_error(outputStream* st) const {
192   st->print_cr("Heap:");
193   print_extended_on(st);
194   st->cr();
195 
196   BarrierSet* bs = BarrierSet::barrier_set();
197   if (bs != nullptr) {
198     bs->print_on(st);
199   }
200 }
201 
202 void CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
203   const GCHeapSummary& heap_summary = create_heap_summary();
204   gc_tracer->report_gc_heap_summary(when, heap_summary);
205 
206   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
207   gc_tracer->report_metaspace_summary(when, metaspace_summary);
208 }
209 
210 void CollectedHeap::trace_heap_before_gc(const GCTracer* gc_tracer) {
211   trace_heap(GCWhen::BeforeGC, gc_tracer);
212 }
213 
214 void CollectedHeap::trace_heap_after_gc(const GCTracer* gc_tracer) {
215   trace_heap(GCWhen::AfterGC, gc_tracer);
216 }
217 
218 // Default implementation, for collectors that don't support the feature.
219 bool CollectedHeap::supports_concurrent_gc_breakpoints() const {
220   return false;
221 }
222 
223 bool CollectedHeap::is_oop(oop object) const {
224   if (!is_object_aligned(object)) {
225     return false;
226   }
227 
228   if (!is_in(object)) {
229     return false;
230   }
231 
232   if (!Metaspace::contains(object->klass_raw())) {
233     return false;
234   }
235 
236   return true;
237 }
238 
239 // Memory state functions.
240 
241 
242 CollectedHeap::CollectedHeap() :
243   _capacity_at_last_gc(0),
244   _used_at_last_gc(0),
245   _soft_ref_policy(),
246   _is_gc_active(false),
247   _last_whole_heap_examined_time_ns(os::javaTimeNanos()),
248   _total_collections(0),
249   _total_full_collections(0),
250   _gc_cause(GCCause::_no_gc),
251   _gc_lastcause(GCCause::_no_gc)
252 {
253   // If the minimum object size is greater than MinObjAlignment, we can
254   // end up with a shard at the end of the buffer that's smaller than
255   // the smallest object.  We can't allow that because the buffer must
256   // look like it's full of objects when we retire it, so we make
257   // sure we have enough space for a filler int array object.
258   size_t min_size = min_dummy_object_size();
259   _lab_alignment_reserve = min_size > (size_t)MinObjAlignment ? align_object_size(min_size) : 0;
260 
261   const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
262   const size_t elements_per_word = HeapWordSize / sizeof(jint);
263   _filler_array_max_size = align_object_size(filler_array_hdr_size() +
264                                              max_len / elements_per_word);
265 
266   NOT_PRODUCT(_promotion_failure_alot_count = 0;)
267   NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
268 
269   if (UsePerfData) {
270     EXCEPTION_MARK;
271 
272     // create the gc cause jvmstat counters
273     _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
274                              80, GCCause::to_string(_gc_cause), CHECK);
275 
276     _perf_gc_lastcause =
277                 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
278                              80, GCCause::to_string(_gc_lastcause), CHECK);
279   }
280 
281   // Create the ring log
282   if (LogEvents) {
283     _gc_heap_log = new GCHeapLog();
284   } else {
285     _gc_heap_log = nullptr;
286   }
287 }
288 
289 // This interface assumes that it's being called by the
290 // vm thread. It collects the heap assuming that the
291 // heap lock is already held and that we are executing in
292 // the context of the vm thread.
293 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
294   Thread* thread = Thread::current();
295   assert(thread->is_VM_thread(), "Precondition#1");
296   assert(Heap_lock->is_locked(), "Precondition#2");
297   GCCauseSetter gcs(this, cause);
298   switch (cause) {
299     case GCCause::_codecache_GC_threshold:
300     case GCCause::_codecache_GC_aggressive:
301     case GCCause::_heap_inspection:
302     case GCCause::_heap_dump:
303     case GCCause::_metadata_GC_threshold: {
304       HandleMark hm(thread);
305       do_full_collection(false);        // don't clear all soft refs
306       break;
307     }
308     case GCCause::_metadata_GC_clear_soft_refs: {
309       HandleMark hm(thread);
310       do_full_collection(true);         // do clear all soft refs
311       break;
312     }
313     default:
314       ShouldNotReachHere(); // Unexpected use of this function
315   }
316 }
317 
318 MetaWord* CollectedHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
319                                                             size_t word_size,
320                                                             Metaspace::MetadataType mdtype) {
321   uint loop_count = 0;
322   uint gc_count = 0;
323   uint full_gc_count = 0;
324 
325   assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
326 
327   do {
328     MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype);
329     if (result != nullptr) {
330       return result;
331     }
332 
333     if (GCLocker::is_active_and_needs_gc()) {
334       // If the GCLocker is active, just expand and allocate.
335       // If that does not succeed, wait if this thread is not
336       // in a critical section itself.
337       result = loader_data->metaspace_non_null()->expand_and_allocate(word_size, mdtype);
338       if (result != nullptr) {
339         return result;
340       }
341       JavaThread* jthr = JavaThread::current();
342       if (!jthr->in_critical()) {
343         // Wait for JNI critical section to be exited
344         GCLocker::stall_until_clear();
345         // The GC invoked by the last thread leaving the critical
346         // section will be a young collection and a full collection
347         // is (currently) needed for unloading classes so continue
348         // to the next iteration to get a full GC.
349         continue;
350       } else {
351         if (CheckJNICalls) {
352           fatal("Possible deadlock due to allocating while"
353                 " in jni critical section");
354         }
355         return nullptr;
356       }
357     }
358 
359     {  // Need lock to get self consistent gc_count's
360       MutexLocker ml(Heap_lock);
361       gc_count      = Universe::heap()->total_collections();
362       full_gc_count = Universe::heap()->total_full_collections();
363     }
364 
365     // Generate a VM operation
366     VM_CollectForMetadataAllocation op(loader_data,
367                                        word_size,
368                                        mdtype,
369                                        gc_count,
370                                        full_gc_count,
371                                        GCCause::_metadata_GC_threshold);
372     VMThread::execute(&op);
373 
374     // If GC was locked out, try again. Check before checking success because the
375     // prologue could have succeeded and the GC still have been locked out.
376     if (op.gc_locked()) {
377       continue;
378     }
379 
380     if (op.prologue_succeeded()) {
381       return op.result();
382     }
383     loop_count++;
384     if ((QueuedAllocationWarningCount > 0) &&
385         (loop_count % QueuedAllocationWarningCount == 0)) {
386       log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times,"
387                             " size=" SIZE_FORMAT, loop_count, word_size);
388     }
389   } while (true);  // Until a GC is done
390 }
391 
392 MemoryUsage CollectedHeap::memory_usage() {
393   return MemoryUsage(InitialHeapSize, used(), capacity(), max_capacity());
394 }
395 
396 void CollectedHeap::set_gc_cause(GCCause::Cause v) {
397   if (UsePerfData) {
398     _gc_lastcause = _gc_cause;
399     _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
400     _perf_gc_cause->set_value(GCCause::to_string(v));
401   }
402   _gc_cause = v;
403 }
404 
405 size_t CollectedHeap::max_tlab_size() const {
406   // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].
407   // This restriction could be removed by enabling filling with multiple arrays.
408   // If we compute that the reasonable way as
409   //    header_size + ((sizeof(jint) * max_jint) / HeapWordSize)
410   // we'll overflow on the multiply, so we do the divide first.
411   // We actually lose a little by dividing first,
412   // but that just makes the TLAB  somewhat smaller than the biggest array,
413   // which is fine, since we'll be able to fill that.
414   size_t max_int_size = typeArrayOopDesc::header_size(T_INT) +
415               sizeof(jint) *
416               ((juint) max_jint / (size_t) HeapWordSize);
417   return align_down(max_int_size, MinObjAlignment);
418 }
419 
420 size_t CollectedHeap::filler_array_hdr_size() {
421   return align_object_offset(arrayOopDesc::header_size(T_INT)); // align to Long
422 }
423 
424 size_t CollectedHeap::filler_array_min_size() {
425   return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
426 }
427 
428 void CollectedHeap::zap_filler_array_with(HeapWord* start, size_t words, juint value) {
429   Copy::fill_to_words(start + filler_array_hdr_size(),
430                       words - filler_array_hdr_size(), value);
431 }
432 
433 #ifdef ASSERT
434 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
435 {
436   assert(words >= min_fill_size(), "too small to fill");
437   assert(is_object_aligned(words), "unaligned size");
438 }
439 
440 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
441 {
442   if (ZapFillerObjects && zap) {
443     zap_filler_array_with(start, words, 0XDEAFBABE);
444   }
445 }
446 #endif // ASSERT
447 
448 void
449 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
450 {
451   assert(words >= filler_array_min_size(), "too small for an array");
452   assert(words <= filler_array_max_size(), "too big for a single object");
453 
454   const size_t payload_size = words - filler_array_hdr_size();
455   const size_t len = payload_size * HeapWordSize / sizeof(jint);
456   assert((int)len >= 0, "size too large " SIZE_FORMAT " becomes %d", words, (int)len);
457 
458   ObjArrayAllocator allocator(Universe::fillerArrayKlassObj(), words, (int)len, /* do_zero */ false);
459   allocator.initialize(start);
460   if (CDSConfig::is_dumping_heap()) {
461     // This array is written into the CDS archive. Make sure it
462     // has deterministic contents.
463     zap_filler_array_with(start, words, 0);
464   } else {
465     DEBUG_ONLY(zap_filler_array(start, words, zap);)
466   }
467 }
468 
469 void
470 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
471 {
472   assert(words <= filler_array_max_size(), "too big for a single object");
473 
474   if (words >= filler_array_min_size()) {
475     fill_with_array(start, words, zap);
476   } else if (words > 0) {
477     assert(words == min_fill_size(), "unaligned size");
478     ObjAllocator allocator(CollectedHeap::filler_object_klass(), words);
479     allocator.initialize(start);
480   }
481 }
482 
483 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
484 {
485   DEBUG_ONLY(fill_args_check(start, words);)
486   HandleMark hm(Thread::current());  // Free handles before leaving.
487   fill_with_object_impl(start, words, zap);
488 }
489 
490 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
491 {
492   DEBUG_ONLY(fill_args_check(start, words);)
493   HandleMark hm(Thread::current());  // Free handles before leaving.
494 
495   // Multiple objects may be required depending on the filler array maximum size. Fill
496   // the range up to that with objects that are filler_array_max_size sized. The
497   // remainder is filled with a single object.
498   const size_t min = min_fill_size();
499   const size_t max = filler_array_max_size();
500   while (words > max) {
501     const size_t cur = (words - max) >= min ? max : max - min;
502     fill_with_array(start, cur, zap);
503     start += cur;
504     words -= cur;
505   }
506 
507   fill_with_object_impl(start, words, zap);
508 }
509 
510 void CollectedHeap::fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap) {
511   CollectedHeap::fill_with_object(start, end, zap);
512 }
513 
514 HeapWord* CollectedHeap::allocate_new_tlab(size_t min_size,
515                                            size_t requested_size,
516                                            size_t* actual_size) {
517   guarantee(false, "thread-local allocation buffers not supported");
518   return nullptr;
519 }
520 
521 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
522   assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
523          "Should only be called at a safepoint or at start-up");
524 
525   ThreadLocalAllocStats stats;
526 
527   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next();) {
528     BarrierSet::barrier_set()->make_parsable(thread);
529     if (UseTLAB) {
530       if (retire_tlabs) {
531         thread->tlab().retire(&stats);
532       } else {
533         thread->tlab().make_parsable();
534       }
535     }
536   }
537 
538   stats.publish();
539 }
540 
541 void CollectedHeap::resize_all_tlabs() {
542   assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
543          "Should only resize tlabs at safepoint");
544 
545   if (UseTLAB && ResizeTLAB) {
546     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
547       thread->tlab().resize();
548     }
549   }
550 }
551 
552 jlong CollectedHeap::millis_since_last_whole_heap_examined() {
553   return (os::javaTimeNanos() - _last_whole_heap_examined_time_ns) / NANOSECS_PER_MILLISEC;
554 }
555 
556 void CollectedHeap::record_whole_heap_examined_timestamp() {
557   _last_whole_heap_examined_time_ns = os::javaTimeNanos();
558 }
559 
560 void CollectedHeap::full_gc_dump(GCTimer* timer, bool before) {
561   assert(timer != nullptr, "timer is null");
562   static uint count = 0;
563   if ((HeapDumpBeforeFullGC && before) || (HeapDumpAfterFullGC && !before)) {
564     if (FullGCHeapDumpLimit == 0 || count < FullGCHeapDumpLimit) {
565       GCTraceTime(Info, gc) tm(before ? "Heap Dump (before full gc)" : "Heap Dump (after full gc)", timer);
566       HeapDumper::dump_heap();
567       count++;
568     }
569   }
570 
571   LogTarget(Trace, gc, classhisto) lt;
572   if (lt.is_enabled()) {
573     GCTraceTime(Trace, gc, classhisto) tm(before ? "Class Histogram (before full gc)" : "Class Histogram (after full gc)", timer);
574     ResourceMark rm;
575     LogStream ls(lt);
576     VM_GC_HeapInspection inspector(&ls, false /* ! full gc */);
577     inspector.doit();
578   }
579 }
580 
581 void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {
582   full_gc_dump(timer, true);
583 }
584 
585 void CollectedHeap::post_full_gc_dump(GCTimer* timer) {
586   full_gc_dump(timer, false);
587 }
588 
589 void CollectedHeap::initialize_reserved_region(const ReservedHeapSpace& rs) {
590   // It is important to do this in a way such that concurrent readers can't
591   // temporarily think something is in the heap.  (Seen this happen in asserts.)
592   _reserved.set_word_size(0);
593   _reserved.set_start((HeapWord*)rs.base());
594   _reserved.set_end((HeapWord*)rs.end());
595 }
596 
597 void CollectedHeap::post_initialize() {
598   StringDedup::initialize();
599   initialize_serviceability();
600 }
601 
602 #ifndef PRODUCT
603 
604 bool CollectedHeap::promotion_should_fail(volatile size_t* count) {
605   // Access to count is not atomic; the value does not have to be exact.
606   if (PromotionFailureALot) {
607     const size_t gc_num = total_collections();
608     const size_t elapsed_gcs = gc_num - _promotion_failure_alot_gc_number;
609     if (elapsed_gcs >= PromotionFailureALotInterval) {
610       // Test for unsigned arithmetic wrap-around.
611       if (++*count >= PromotionFailureALotCount) {
612         *count = 0;
613         return true;
614       }
615     }
616   }
617   return false;
618 }
619 
620 bool CollectedHeap::promotion_should_fail() {
621   return promotion_should_fail(&_promotion_failure_alot_count);
622 }
623 
624 void CollectedHeap::reset_promotion_should_fail(volatile size_t* count) {
625   if (PromotionFailureALot) {
626     _promotion_failure_alot_gc_number = total_collections();
627     *count = 0;
628   }
629 }
630 
631 void CollectedHeap::reset_promotion_should_fail() {
632   reset_promotion_should_fail(&_promotion_failure_alot_count);
633 }
634 
635 #endif  // #ifndef PRODUCT
636 
637 // It's the caller's responsibility to ensure glitch-freedom
638 // (if required).
639 void CollectedHeap::update_capacity_and_used_at_gc() {
640   _capacity_at_last_gc = capacity();
641   _used_at_last_gc     = used();
642 }