1 /*
2 * Copyright (c) 2001, 2021, 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/classLoaderData.hpp"
27 #include "classfile/vmClasses.hpp"
28 #include "gc/shared/allocTracer.hpp"
29 #include "gc/shared/barrierSet.hpp"
30 #include "gc/shared/collectedHeap.hpp"
31 #include "gc/shared/collectedHeap.inline.hpp"
32 #include "gc/shared/gcLocker.inline.hpp"
33 #include "gc/shared/gcHeapSummary.hpp"
34 #include "gc/shared/stringdedup/stringDedup.hpp"
35 #include "gc/shared/gcTrace.hpp"
36 #include "gc/shared/gcTraceTime.inline.hpp"
37 #include "gc/shared/gcVMOperations.hpp"
38 #include "gc/shared/gcWhen.hpp"
39 #include "gc/shared/gc_globals.hpp"
40 #include "gc/shared/memAllocator.hpp"
41 #include "gc/shared/tlab_globals.hpp"
42 #include "logging/log.hpp"
43 #include "logging/logStream.hpp"
44 #include "memory/classLoaderMetaspace.hpp"
45 #include "memory/metaspaceUtils.hpp"
46 #include "memory/resourceArea.hpp"
47 #include "memory/universe.hpp"
48 #include "oops/instanceMirrorKlass.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "runtime/handles.inline.hpp"
51 #include "runtime/init.hpp"
52 #include "runtime/perfData.hpp"
53 #include "runtime/thread.inline.hpp"
54 #include "runtime/threadSMR.hpp"
55 #include "runtime/vmThread.hpp"
56 #include "services/heapDumper.hpp"
57 #include "utilities/align.hpp"
58 #include "utilities/copy.hpp"
59 #include "utilities/events.hpp"
60
61 class ClassLoaderData;
62
63 size_t CollectedHeap::_filler_array_max_size = 0;
64
65 class GCMessage : public FormatBuffer<1024> {
66 public:
67 bool is_before;
68 };
69
70 template <>
71 void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {
72 st->print_cr("GC heap %s", m.is_before ? "before" : "after");
73 st->print_raw(m);
74 }
75
76 class GCHeapLog : public EventLogBase<GCMessage> {
77 private:
78 void log_heap(CollectedHeap* heap, bool before);
79
80 public:
81 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History", "gc") {}
82
83 void log_heap_before(CollectedHeap* heap) {
84 log_heap(heap, true);
85 }
86 void log_heap_after(CollectedHeap* heap) {
87 log_heap(heap, false);
88 }
89 };
90
91 void GCHeapLog::log_heap(CollectedHeap* heap, bool before) {
92 if (!should_log()) {
93 return;
94 }
95
96 double timestamp = fetch_timestamp();
97 MutexLocker ml(&_mutex, Mutex::_no_safepoint_check_flag);
98 int index = compute_log_index();
99 _records[index].thread = NULL; // Its the GC thread so it's not that interesting.
100 _records[index].timestamp = timestamp;
101 _records[index].data.is_before = before;
102 stringStream st(_records[index].data.buffer(), _records[index].data.size());
103
104 st.print_cr("{Heap %s GC invocations=%u (full %u):",
105 before ? "before" : "after",
106 heap->total_collections(),
107 heap->total_full_collections());
108
109 heap->print_on(&st);
110 st.print_cr("}");
111 }
112
113 size_t CollectedHeap::unused() const {
114 MutexLocker ml(Heap_lock);
115 return capacity() - used();
116 }
117
118 VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {
119 size_t capacity_in_words = capacity() / HeapWordSize;
120
121 return VirtualSpaceSummary(
122 _reserved.start(), _reserved.start() + capacity_in_words, _reserved.end());
123 }
124
125 GCHeapSummary CollectedHeap::create_heap_summary() {
126 VirtualSpaceSummary heap_space = create_heap_space_summary();
127 return GCHeapSummary(heap_space, used());
128 }
129
130 MetaspaceSummary CollectedHeap::create_metaspace_summary() {
131 const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
132 MetaspaceUtils::chunk_free_list_summary(Metaspace::NonClassType);
133 const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =
134 MetaspaceUtils::chunk_free_list_summary(Metaspace::ClassType);
135 return MetaspaceSummary(MetaspaceGC::capacity_until_GC(),
136 MetaspaceUtils::get_combined_statistics(),
137 ms_chunk_free_list_summary, class_chunk_free_list_summary);
138 }
139
140 void CollectedHeap::print_heap_before_gc() {
141 LogTarget(Debug, gc, heap) lt;
142 if (lt.is_enabled()) {
143 LogStream ls(lt);
144 ls.print_cr("Heap before GC invocations=%u (full %u):", total_collections(), total_full_collections());
145 ResourceMark rm;
146 print_on(&ls);
147 }
148
149 if (_gc_heap_log != NULL) {
150 _gc_heap_log->log_heap_before(this);
151 }
152 }
153
154 void CollectedHeap::print_heap_after_gc() {
155 LogTarget(Debug, gc, heap) lt;
156 if (lt.is_enabled()) {
157 LogStream ls(lt);
158 ls.print_cr("Heap after GC invocations=%u (full %u):", total_collections(), total_full_collections());
159 ResourceMark rm;
160 print_on(&ls);
161 }
162
163 if (_gc_heap_log != NULL) {
164 _gc_heap_log->log_heap_after(this);
165 }
166 }
167
168 void CollectedHeap::print() const { print_on(tty); }
169
170 void CollectedHeap::print_on_error(outputStream* st) const {
171 st->print_cr("Heap:");
172 print_extended_on(st);
173 st->cr();
174
175 BarrierSet* bs = BarrierSet::barrier_set();
176 if (bs != NULL) {
177 bs->print_on(st);
178 }
179 }
180
181 void CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
182 const GCHeapSummary& heap_summary = create_heap_summary();
183 gc_tracer->report_gc_heap_summary(when, heap_summary);
184
185 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
186 gc_tracer->report_metaspace_summary(when, metaspace_summary);
187 }
188
189 void CollectedHeap::trace_heap_before_gc(const GCTracer* gc_tracer) {
190 trace_heap(GCWhen::BeforeGC, gc_tracer);
191 }
192
193 void CollectedHeap::trace_heap_after_gc(const GCTracer* gc_tracer) {
194 trace_heap(GCWhen::AfterGC, gc_tracer);
195 }
196
197 // Default implementation, for collectors that don't support the feature.
198 bool CollectedHeap::supports_concurrent_gc_breakpoints() const {
199 return false;
200 }
201
202 bool CollectedHeap::is_oop(oop object) const {
203 if (!is_object_aligned(object)) {
204 return false;
205 }
206
207 if (!is_in(object)) {
208 return false;
209 }
210
211 return true;
212 }
213
214 // Memory state functions.
215
216
217 CollectedHeap::CollectedHeap() :
218 _capacity_at_last_gc(0),
219 _used_at_last_gc(0),
220 _is_gc_active(false),
221 _last_whole_heap_examined_time_ns(os::javaTimeNanos()),
222 _total_collections(0),
223 _total_full_collections(0),
224 _gc_cause(GCCause::_no_gc),
225 _gc_lastcause(GCCause::_no_gc)
226 {
227 const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
228 const size_t elements_per_word = HeapWordSize / sizeof(jint);
229 int header_size_in_bytes = arrayOopDesc::base_offset_in_bytes(T_INT);
230 assert(header_size_in_bytes % sizeof(jint) == 0, "must be aligned to int");
231 int header_size_in_ints = header_size_in_bytes / sizeof(jint);
232 _filler_array_max_size = align_object_size((header_size_in_ints + max_len) / elements_per_word);
233
234 NOT_PRODUCT(_promotion_failure_alot_count = 0;)
235 NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
236
237 if (UsePerfData) {
238 EXCEPTION_MARK;
239
240 // create the gc cause jvmstat counters
241 _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
242 80, GCCause::to_string(_gc_cause), CHECK);
243
244 _perf_gc_lastcause =
245 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
246 80, GCCause::to_string(_gc_lastcause), CHECK);
247 }
248
249 // Create the ring log
250 if (LogEvents) {
251 _gc_heap_log = new GCHeapLog();
252 } else {
253 _gc_heap_log = NULL;
254 }
255 }
256
257 // This interface assumes that it's being called by the
258 // vm thread. It collects the heap assuming that the
259 // heap lock is already held and that we are executing in
260 // the context of the vm thread.
261 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
262 Thread* thread = Thread::current();
263 assert(thread->is_VM_thread(), "Precondition#1");
264 assert(Heap_lock->is_locked(), "Precondition#2");
265 GCCauseSetter gcs(this, cause);
266 switch (cause) {
267 case GCCause::_heap_inspection:
268 case GCCause::_heap_dump:
269 case GCCause::_metadata_GC_threshold : {
270 HandleMark hm(thread);
271 do_full_collection(false); // don't clear all soft refs
272 break;
273 }
274 case GCCause::_archive_time_gc:
275 case GCCause::_metadata_GC_clear_soft_refs: {
276 HandleMark hm(thread);
277 do_full_collection(true); // do clear all soft refs
278 break;
279 }
280 default:
281 ShouldNotReachHere(); // Unexpected use of this function
282 }
283 }
284
285 MetaWord* CollectedHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
286 size_t word_size,
287 Metaspace::MetadataType mdtype) {
288 uint loop_count = 0;
289 uint gc_count = 0;
290 uint full_gc_count = 0;
291
292 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
293
294 do {
295 MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype);
296 if (result != NULL) {
297 return result;
298 }
299
300 if (GCLocker::is_active_and_needs_gc()) {
301 // If the GCLocker is active, just expand and allocate.
302 // If that does not succeed, wait if this thread is not
303 // in a critical section itself.
304 result = loader_data->metaspace_non_null()->expand_and_allocate(word_size, mdtype);
305 if (result != NULL) {
306 return result;
307 }
308 JavaThread* jthr = JavaThread::current();
309 if (!jthr->in_critical()) {
310 // Wait for JNI critical section to be exited
311 GCLocker::stall_until_clear();
312 // The GC invoked by the last thread leaving the critical
313 // section will be a young collection and a full collection
314 // is (currently) needed for unloading classes so continue
315 // to the next iteration to get a full GC.
316 continue;
317 } else {
318 if (CheckJNICalls) {
319 fatal("Possible deadlock due to allocating while"
320 " in jni critical section");
321 }
322 return NULL;
323 }
324 }
325
326 { // Need lock to get self consistent gc_count's
327 MutexLocker ml(Heap_lock);
328 gc_count = Universe::heap()->total_collections();
329 full_gc_count = Universe::heap()->total_full_collections();
330 }
331
332 // Generate a VM operation
333 VM_CollectForMetadataAllocation op(loader_data,
334 word_size,
335 mdtype,
336 gc_count,
337 full_gc_count,
338 GCCause::_metadata_GC_threshold);
339 VMThread::execute(&op);
340
341 // If GC was locked out, try again. Check before checking success because the
342 // prologue could have succeeded and the GC still have been locked out.
343 if (op.gc_locked()) {
344 continue;
345 }
346
347 if (op.prologue_succeeded()) {
348 return op.result();
349 }
350 loop_count++;
351 if ((QueuedAllocationWarningCount > 0) &&
352 (loop_count % QueuedAllocationWarningCount == 0)) {
353 log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times,"
354 " size=" SIZE_FORMAT, loop_count, word_size);
355 }
356 } while (true); // Until a GC is done
357 }
358
359 MemoryUsage CollectedHeap::memory_usage() {
360 return MemoryUsage(InitialHeapSize, used(), capacity(), max_capacity());
361 }
362
363 void CollectedHeap::set_gc_cause(GCCause::Cause v) {
364 if (UsePerfData) {
365 _gc_lastcause = _gc_cause;
366 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
367 _perf_gc_cause->set_value(GCCause::to_string(v));
368 }
369 _gc_cause = v;
370 }
371
372 #ifndef PRODUCT
373 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
374 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
375 // please note mismatch between size (in 32/64 bit words), and ju_addr that always point to a 32 bit word
376 for (juint* ju_addr = reinterpret_cast<juint*>(addr); ju_addr < reinterpret_cast<juint*>(addr + size); ++ju_addr) {
377 assert(*ju_addr == badHeapWordVal, "Found non badHeapWordValue in pre-allocation check");
378 }
379 }
380 }
381 #endif // PRODUCT
382
383 size_t CollectedHeap::max_tlab_size() const {
384 // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].
385 // This restriction could be removed by enabling filling with multiple arrays.
386 // If we compute that the reasonable way as
387 // header_size + ((sizeof(jint) * max_jint) / HeapWordSize)
388 // we'll overflow on the multiply, so we do the divide first.
389 // We actually lose a little by dividing first,
390 // but that just makes the TLAB somewhat smaller than the biggest array,
391 // which is fine, since we'll be able to fill that.
392 int header_size_in_bytes = typeArrayOopDesc::base_offset_in_bytes(T_INT);
393 assert(header_size_in_bytes % sizeof(jint) == 0, "header size must align to int");
394 size_t max_int_size = header_size_in_bytes / HeapWordSize +
395 sizeof(jint) *
396 ((juint) max_jint / (size_t) HeapWordSize);
397 return align_down(max_int_size, MinObjAlignment);
398 }
399
400 size_t CollectedHeap::filler_array_min_size() {
401 int aligned_header_size_words = align_up(arrayOopDesc::base_offset_in_bytes(T_INT), HeapWordSize) / HeapWordSize;
402 return align_object_size(aligned_header_size_words); // align to MinObjAlignment
403 }
404
405 #ifdef ASSERT
406 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
407 {
408 assert(words >= min_fill_size(), "too small to fill");
409 assert(is_object_aligned(words), "unaligned size");
410 }
411
412 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
413 {
414 if (ZapFillerObjects && zap) {
415 int payload_start = align_up(arrayOopDesc::base_offset_in_bytes(T_INT), HeapWordSize) / HeapWordSize;
416 Copy::fill_to_words(start + payload_start,
417 words - payload_start, 0XDEAFBABE);
418 }
419 }
420 #endif // ASSERT
421
422 void
423 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
424 {
425 assert(words >= filler_array_min_size(), "too small for an array");
426 assert(words <= filler_array_max_size(), "too big for a single object");
427
428 const size_t payload_size_bytes = words * HeapWordSize - arrayOopDesc::base_offset_in_bytes(T_INT);
429 assert(payload_size_bytes % sizeof(jint) == 0, "must be int aligned");
430 const size_t len = payload_size_bytes / sizeof(jint);
431 assert((int)len >= 0, "size too large " SIZE_FORMAT " becomes %d", words, (int)len);
432
433 ObjArrayAllocator allocator(Universe::intArrayKlassObj(), words, (int)len, /* do_zero */ false);
434 allocator.initialize(start);
435 DEBUG_ONLY(zap_filler_array(start, words, zap);)
436 }
437
438 void
439 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
440 {
441 assert(words <= filler_array_max_size(), "too big for a single object");
442
443 if (words >= filler_array_min_size()) {
444 fill_with_array(start, words, zap);
445 } else if (words > 0) {
446 assert(words == min_fill_size(), "unaligned size");
447 ObjAllocator allocator(vmClasses::Object_klass(), words);
448 allocator.initialize(start);
449 }
450 }
451
452 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
453 {
454 DEBUG_ONLY(fill_args_check(start, words);)
455 HandleMark hm(Thread::current()); // Free handles before leaving.
456 fill_with_object_impl(start, words, zap);
457 }
458
459 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
460 {
461 DEBUG_ONLY(fill_args_check(start, words);)
462 HandleMark hm(Thread::current()); // Free handles before leaving.
463
464 // Multiple objects may be required depending on the filler array maximum size. Fill
465 // the range up to that with objects that are filler_array_max_size sized. The
466 // remainder is filled with a single object.
467 const size_t min = min_fill_size();
468 const size_t max = filler_array_max_size();
469 while (words > max) {
470 const size_t cur = (words - max) >= min ? max : max - min;
471 fill_with_array(start, cur, zap);
472 start += cur;
473 words -= cur;
474 }
475
476 fill_with_object_impl(start, words, zap);
477 }
478
479 void CollectedHeap::fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap) {
480 CollectedHeap::fill_with_object(start, end, zap);
481 }
482
483 size_t CollectedHeap::min_dummy_object_size() const {
484 return oopDesc::header_size();
485 }
486
487 size_t CollectedHeap::tlab_alloc_reserve() const {
488 size_t min_size = min_dummy_object_size();
489 return min_size > (size_t)MinObjAlignment ? align_object_size(min_size) : 0;
490 }
491
492 HeapWord* CollectedHeap::allocate_new_tlab(size_t min_size,
493 size_t requested_size,
494 size_t* actual_size) {
495 guarantee(false, "thread-local allocation buffers not supported");
496 return NULL;
497 }
498
499 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
500 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
501 "Should only be called at a safepoint or at start-up");
502
503 ThreadLocalAllocStats stats;
504
505 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next();) {
506 BarrierSet::barrier_set()->make_parsable(thread);
507 if (UseTLAB) {
508 if (retire_tlabs) {
509 thread->tlab().retire(&stats);
510 } else {
511 thread->tlab().make_parsable();
512 }
513 }
514 }
515
516 stats.publish();
517 }
518
519 void CollectedHeap::resize_all_tlabs() {
520 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
521 "Should only resize tlabs at safepoint");
522
523 if (UseTLAB && ResizeTLAB) {
524 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
525 thread->tlab().resize();
526 }
527 }
528 }
529
530 jlong CollectedHeap::millis_since_last_whole_heap_examined() {
531 return (os::javaTimeNanos() - _last_whole_heap_examined_time_ns) / NANOSECS_PER_MILLISEC;
532 }
533
534 void CollectedHeap::record_whole_heap_examined_timestamp() {
535 _last_whole_heap_examined_time_ns = os::javaTimeNanos();
536 }
537
538 void CollectedHeap::full_gc_dump(GCTimer* timer, bool before) {
539 assert(timer != NULL, "timer is null");
540 if ((HeapDumpBeforeFullGC && before) || (HeapDumpAfterFullGC && !before)) {
541 GCTraceTime(Info, gc) tm(before ? "Heap Dump (before full gc)" : "Heap Dump (after full gc)", timer);
542 HeapDumper::dump_heap();
543 }
544
545 LogTarget(Trace, gc, classhisto) lt;
546 if (lt.is_enabled()) {
547 GCTraceTime(Trace, gc, classhisto) tm(before ? "Class Histogram (before full gc)" : "Class Histogram (after full gc)", timer);
548 ResourceMark rm;
549 LogStream ls(lt);
550 VM_GC_HeapInspection inspector(&ls, false /* ! full gc */);
551 inspector.doit();
552 }
553 }
554
555 void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {
556 full_gc_dump(timer, true);
557 }
558
559 void CollectedHeap::post_full_gc_dump(GCTimer* timer) {
560 full_gc_dump(timer, false);
561 }
562
563 void CollectedHeap::initialize_reserved_region(const ReservedHeapSpace& rs) {
564 // It is important to do this in a way such that concurrent readers can't
565 // temporarily think something is in the heap. (Seen this happen in asserts.)
566 _reserved.set_word_size(0);
567 _reserved.set_start((HeapWord*)rs.base());
568 _reserved.set_end((HeapWord*)rs.end());
569 }
570
571 void CollectedHeap::post_initialize() {
572 StringDedup::initialize();
573 initialize_serviceability();
574 }
575
576 #ifndef PRODUCT
577
578 bool CollectedHeap::promotion_should_fail(volatile size_t* count) {
579 // Access to count is not atomic; the value does not have to be exact.
580 if (PromotionFailureALot) {
581 const size_t gc_num = total_collections();
582 const size_t elapsed_gcs = gc_num - _promotion_failure_alot_gc_number;
583 if (elapsed_gcs >= PromotionFailureALotInterval) {
584 // Test for unsigned arithmetic wrap-around.
585 if (++*count >= PromotionFailureALotCount) {
586 *count = 0;
587 return true;
588 }
589 }
590 }
591 return false;
592 }
593
594 bool CollectedHeap::promotion_should_fail() {
595 return promotion_should_fail(&_promotion_failure_alot_count);
596 }
597
598 void CollectedHeap::reset_promotion_should_fail(volatile size_t* count) {
599 if (PromotionFailureALot) {
600 _promotion_failure_alot_gc_number = total_collections();
601 *count = 0;
602 }
603 }
604
605 void CollectedHeap::reset_promotion_should_fail() {
606 reset_promotion_should_fail(&_promotion_failure_alot_count);
607 }
608
609 #endif // #ifndef PRODUCT
610
611 bool CollectedHeap::supports_object_pinning() const {
612 return false;
613 }
614
615 oop CollectedHeap::pin_object(JavaThread* thread, oop obj) {
616 ShouldNotReachHere();
617 return NULL;
618 }
619
620 void CollectedHeap::unpin_object(JavaThread* thread, oop obj) {
621 ShouldNotReachHere();
622 }
623
624 bool CollectedHeap::is_archived_object(oop object) const {
625 return false;
626 }
627
628 uint32_t CollectedHeap::hash_oop(oop obj) const {
629 const uintptr_t addr = cast_from_oop<uintptr_t>(obj);
630 return static_cast<uint32_t>(addr >> LogMinObjAlignment);
631 }
632
633 // It's the caller's responsibility to ensure glitch-freedom
634 // (if required).
635 void CollectedHeap::update_capacity_and_used_at_gc() {
636 _capacity_at_last_gc = capacity();
637 _used_at_last_gc = used();
638 }