1 /*
2 * Copyright (c) 2001, 2022, 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 ParallelObjectIterator::ParallelObjectIterator(uint thread_num) :
114 _impl(Universe::heap()->parallel_object_iterator(thread_num))
115 {}
116
117 ParallelObjectIterator::~ParallelObjectIterator() {
118 delete _impl;
119 }
120
121 void ParallelObjectIterator::object_iterate(ObjectClosure* cl, uint worker_id) {
122 _impl->object_iterate(cl, worker_id);
123 }
124
125 size_t CollectedHeap::unused() const {
126 MutexLocker ml(Heap_lock);
127 return capacity() - used();
128 }
129
130 VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {
131 size_t capacity_in_words = capacity() / HeapWordSize;
132
133 return VirtualSpaceSummary(
134 _reserved.start(), _reserved.start() + capacity_in_words, _reserved.end());
135 }
136
137 GCHeapSummary CollectedHeap::create_heap_summary() {
138 VirtualSpaceSummary heap_space = create_heap_space_summary();
139 return GCHeapSummary(heap_space, used());
140 }
141
142 MetaspaceSummary CollectedHeap::create_metaspace_summary() {
143 const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
144 MetaspaceUtils::chunk_free_list_summary(Metaspace::NonClassType);
145 const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =
146 MetaspaceUtils::chunk_free_list_summary(Metaspace::ClassType);
147 return MetaspaceSummary(MetaspaceGC::capacity_until_GC(),
148 MetaspaceUtils::get_combined_statistics(),
149 ms_chunk_free_list_summary, class_chunk_free_list_summary);
150 }
151
152 void CollectedHeap::print_heap_before_gc() {
153 LogTarget(Debug, gc, heap) lt;
154 if (lt.is_enabled()) {
155 LogStream ls(lt);
156 ls.print_cr("Heap before GC invocations=%u (full %u):", total_collections(), total_full_collections());
157 ResourceMark rm;
158 print_on(&ls);
159 }
160
161 if (_gc_heap_log != NULL) {
162 _gc_heap_log->log_heap_before(this);
163 }
164 }
165
166 void CollectedHeap::print_heap_after_gc() {
167 LogTarget(Debug, gc, heap) lt;
168 if (lt.is_enabled()) {
169 LogStream ls(lt);
170 ls.print_cr("Heap after GC invocations=%u (full %u):", total_collections(), total_full_collections());
171 ResourceMark rm;
172 print_on(&ls);
173 }
174
175 if (_gc_heap_log != NULL) {
176 _gc_heap_log->log_heap_after(this);
177 }
178 }
179
180 void CollectedHeap::print() const { print_on(tty); }
181
182 void CollectedHeap::print_on_error(outputStream* st) const {
183 st->print_cr("Heap:");
184 print_extended_on(st);
185 st->cr();
186
187 BarrierSet* bs = BarrierSet::barrier_set();
188 if (bs != NULL) {
189 bs->print_on(st);
190 }
191 }
192
193 void CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
194 const GCHeapSummary& heap_summary = create_heap_summary();
195 gc_tracer->report_gc_heap_summary(when, heap_summary);
196
197 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
198 gc_tracer->report_metaspace_summary(when, metaspace_summary);
199 }
200
201 void CollectedHeap::trace_heap_before_gc(const GCTracer* gc_tracer) {
202 trace_heap(GCWhen::BeforeGC, gc_tracer);
203 }
204
205 void CollectedHeap::trace_heap_after_gc(const GCTracer* gc_tracer) {
206 trace_heap(GCWhen::AfterGC, gc_tracer);
207 }
208
209 // Default implementation, for collectors that don't support the feature.
210 bool CollectedHeap::supports_concurrent_gc_breakpoints() const {
211 return false;
212 }
213
214 bool CollectedHeap::is_oop(oop object) const {
215 if (!is_object_aligned(object)) {
216 return false;
217 }
218
219 if (!is_in(object)) {
220 return false;
221 }
222
223 if (is_in(object->klass_or_null())) {
224 return false;
225 }
226
227 return true;
228 }
229
230 // Memory state functions.
231
232
233 CollectedHeap::CollectedHeap() :
234 _capacity_at_last_gc(0),
235 _used_at_last_gc(0),
236 _is_gc_active(false),
237 _last_whole_heap_examined_time_ns(os::javaTimeNanos()),
238 _total_collections(0),
239 _total_full_collections(0),
240 _gc_cause(GCCause::_no_gc),
241 _gc_lastcause(GCCause::_no_gc)
242 {
243 const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
244 const size_t elements_per_word = HeapWordSize / sizeof(jint);
245 _filler_array_max_size = align_object_size(filler_array_hdr_size() +
246 max_len / elements_per_word);
247
248 NOT_PRODUCT(_promotion_failure_alot_count = 0;)
249 NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
250
251 if (UsePerfData) {
252 EXCEPTION_MARK;
253
254 // create the gc cause jvmstat counters
255 _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
256 80, GCCause::to_string(_gc_cause), CHECK);
257
258 _perf_gc_lastcause =
259 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
260 80, GCCause::to_string(_gc_lastcause), CHECK);
261 }
262
263 // Create the ring log
264 if (LogEvents) {
265 _gc_heap_log = new GCHeapLog();
266 } else {
267 _gc_heap_log = NULL;
268 }
269 }
270
271 // This interface assumes that it's being called by the
272 // vm thread. It collects the heap assuming that the
273 // heap lock is already held and that we are executing in
274 // the context of the vm thread.
275 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
276 Thread* thread = Thread::current();
277 assert(thread->is_VM_thread(), "Precondition#1");
278 assert(Heap_lock->is_locked(), "Precondition#2");
279 GCCauseSetter gcs(this, cause);
280 switch (cause) {
281 case GCCause::_heap_inspection:
282 case GCCause::_heap_dump:
283 case GCCause::_metadata_GC_threshold : {
284 HandleMark hm(thread);
285 do_full_collection(false); // don't clear all soft refs
286 break;
287 }
288 case GCCause::_archive_time_gc:
289 case GCCause::_metadata_GC_clear_soft_refs: {
290 HandleMark hm(thread);
291 do_full_collection(true); // do clear all soft refs
292 break;
293 }
294 default:
295 ShouldNotReachHere(); // Unexpected use of this function
296 }
297 }
298
299 MetaWord* CollectedHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
300 size_t word_size,
301 Metaspace::MetadataType mdtype) {
302 uint loop_count = 0;
303 uint gc_count = 0;
304 uint full_gc_count = 0;
305
306 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
307
308 do {
309 MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype);
310 if (result != NULL) {
311 return result;
312 }
313
314 if (GCLocker::is_active_and_needs_gc()) {
315 // If the GCLocker is active, just expand and allocate.
316 // If that does not succeed, wait if this thread is not
317 // in a critical section itself.
318 result = loader_data->metaspace_non_null()->expand_and_allocate(word_size, mdtype);
319 if (result != NULL) {
320 return result;
321 }
322 JavaThread* jthr = JavaThread::current();
323 if (!jthr->in_critical()) {
324 // Wait for JNI critical section to be exited
325 GCLocker::stall_until_clear();
326 // The GC invoked by the last thread leaving the critical
327 // section will be a young collection and a full collection
328 // is (currently) needed for unloading classes so continue
329 // to the next iteration to get a full GC.
330 continue;
331 } else {
332 if (CheckJNICalls) {
333 fatal("Possible deadlock due to allocating while"
334 " in jni critical section");
335 }
336 return NULL;
337 }
338 }
339
340 { // Need lock to get self consistent gc_count's
341 MutexLocker ml(Heap_lock);
342 gc_count = Universe::heap()->total_collections();
343 full_gc_count = Universe::heap()->total_full_collections();
344 }
345
346 // Generate a VM operation
347 VM_CollectForMetadataAllocation op(loader_data,
348 word_size,
349 mdtype,
350 gc_count,
351 full_gc_count,
352 GCCause::_metadata_GC_threshold);
353 VMThread::execute(&op);
354
355 // If GC was locked out, try again. Check before checking success because the
356 // prologue could have succeeded and the GC still have been locked out.
357 if (op.gc_locked()) {
358 continue;
359 }
360
361 if (op.prologue_succeeded()) {
362 return op.result();
363 }
364 loop_count++;
365 if ((QueuedAllocationWarningCount > 0) &&
366 (loop_count % QueuedAllocationWarningCount == 0)) {
367 log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times,"
368 " size=" SIZE_FORMAT, loop_count, word_size);
369 }
370 } while (true); // Until a GC is done
371 }
372
373 MemoryUsage CollectedHeap::memory_usage() {
374 return MemoryUsage(InitialHeapSize, used(), capacity(), max_capacity());
375 }
376
377 void CollectedHeap::set_gc_cause(GCCause::Cause v) {
378 if (UsePerfData) {
379 _gc_lastcause = _gc_cause;
380 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
381 _perf_gc_cause->set_value(GCCause::to_string(v));
382 }
383 _gc_cause = v;
384 }
385
386 #ifndef PRODUCT
387 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
388 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
389 // please note mismatch between size (in 32/64 bit words), and ju_addr that always point to a 32 bit word
390 for (juint* ju_addr = reinterpret_cast<juint*>(addr); ju_addr < reinterpret_cast<juint*>(addr + size); ++ju_addr) {
391 assert(*ju_addr == badHeapWordVal, "Found non badHeapWordValue in pre-allocation check");
392 }
393 }
394 }
395 #endif // PRODUCT
396
397 size_t CollectedHeap::max_tlab_size() const {
398 // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].
399 // This restriction could be removed by enabling filling with multiple arrays.
400 // If we compute that the reasonable way as
401 // header_size + ((sizeof(jint) * max_jint) / HeapWordSize)
402 // we'll overflow on the multiply, so we do the divide first.
403 // We actually lose a little by dividing first,
404 // but that just makes the TLAB somewhat smaller than the biggest array,
405 // which is fine, since we'll be able to fill that.
406 size_t max_int_size = typeArrayOopDesc::header_size(T_INT) +
407 sizeof(jint) *
408 ((juint) max_jint / (size_t) HeapWordSize);
409 return align_down(max_int_size, MinObjAlignment);
410 }
411
412 size_t CollectedHeap::filler_array_hdr_size() {
413 return align_object_offset(arrayOopDesc::header_size(T_INT)); // align to Long
414 }
415
416 size_t CollectedHeap::filler_array_min_size() {
417 return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
418 }
419
420 void CollectedHeap::zap_filler_array_with(HeapWord* start, size_t words, juint value) {
421 Copy::fill_to_words(start + filler_array_hdr_size(),
422 words - filler_array_hdr_size(), value);
423 }
424
425 #ifdef ASSERT
426 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
427 {
428 assert(words >= min_fill_size(), "too small to fill");
429 assert(is_object_aligned(words), "unaligned size");
430 }
431
432 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
433 {
434 if (ZapFillerObjects && zap) {
435 zap_filler_array_with(start, words, 0XDEAFBABE);
436 }
437 }
438 #endif // ASSERT
439
440 void
441 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
442 {
443 assert(words >= filler_array_min_size(), "too small for an array");
444 assert(words <= filler_array_max_size(), "too big for a single object");
445
446 const size_t payload_size = words - filler_array_hdr_size();
447 const size_t len = payload_size * HeapWordSize / sizeof(jint);
448 assert((int)len >= 0, "size too large " SIZE_FORMAT " becomes %d", words, (int)len);
449
450 ObjArrayAllocator allocator(Universe::intArrayKlassObj(), words, (int)len, /* do_zero */ false);
451 allocator.initialize(start);
452 if (DumpSharedSpaces) {
453 // This array is written into the CDS archive. Make sure it
454 // has deterministic contents.
455 zap_filler_array_with(start, words, 0);
456 } else {
457 DEBUG_ONLY(zap_filler_array(start, words, zap);)
458 }
459 }
460
461 void
462 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
463 {
464 assert(words <= filler_array_max_size(), "too big for a single object");
465
466 if (words >= filler_array_min_size()) {
467 fill_with_array(start, words, zap);
468 } else if (words > 0) {
469 assert(words == min_fill_size(), "unaligned size");
470 ObjAllocator allocator(vmClasses::Object_klass(), words);
471 allocator.initialize(start);
472 }
473 }
474
475 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
476 {
477 DEBUG_ONLY(fill_args_check(start, words);)
478 HandleMark hm(Thread::current()); // Free handles before leaving.
479 fill_with_object_impl(start, words, zap);
480 }
481
482 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
483 {
484 DEBUG_ONLY(fill_args_check(start, words);)
485 HandleMark hm(Thread::current()); // Free handles before leaving.
486
487 // Multiple objects may be required depending on the filler array maximum size. Fill
488 // the range up to that with objects that are filler_array_max_size sized. The
489 // remainder is filled with a single object.
490 const size_t min = min_fill_size();
491 const size_t max = filler_array_max_size();
492 while (words > max) {
493 const size_t cur = (words - max) >= min ? max : max - min;
494 fill_with_array(start, cur, zap);
495 start += cur;
496 words -= cur;
497 }
498
499 fill_with_object_impl(start, words, zap);
500 }
501
502 void CollectedHeap::fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap) {
503 CollectedHeap::fill_with_object(start, end, zap);
504 }
505
506 size_t CollectedHeap::tlab_alloc_reserve() const {
507 size_t min_size = min_dummy_object_size();
508 return min_size > (size_t)MinObjAlignment ? align_object_size(min_size) : 0;
509 }
510
511 HeapWord* CollectedHeap::allocate_new_tlab(size_t min_size,
512 size_t requested_size,
513 size_t* actual_size) {
514 guarantee(false, "thread-local allocation buffers not supported");
515 return NULL;
516 }
517
518 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
519 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
520 "Should only be called at a safepoint or at start-up");
521
522 ThreadLocalAllocStats stats;
523
524 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next();) {
525 BarrierSet::barrier_set()->make_parsable(thread);
526 if (UseTLAB) {
527 if (retire_tlabs) {
528 thread->tlab().retire(&stats);
529 } else {
530 thread->tlab().make_parsable();
531 }
532 }
533 }
534
535 stats.publish();
536 }
537
538 void CollectedHeap::resize_all_tlabs() {
539 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
540 "Should only resize tlabs at safepoint");
541
542 if (UseTLAB && ResizeTLAB) {
543 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
544 thread->tlab().resize();
545 }
546 }
547 }
548
549 jlong CollectedHeap::millis_since_last_whole_heap_examined() {
550 return (os::javaTimeNanos() - _last_whole_heap_examined_time_ns) / NANOSECS_PER_MILLISEC;
551 }
552
553 void CollectedHeap::record_whole_heap_examined_timestamp() {
554 _last_whole_heap_examined_time_ns = os::javaTimeNanos();
555 }
556
557 void CollectedHeap::full_gc_dump(GCTimer* timer, bool before) {
558 assert(timer != NULL, "timer is null");
559 if ((HeapDumpBeforeFullGC && before) || (HeapDumpAfterFullGC && !before)) {
560 GCTraceTime(Info, gc) tm(before ? "Heap Dump (before full gc)" : "Heap Dump (after full gc)", timer);
561 HeapDumper::dump_heap();
562 }
563
564 LogTarget(Trace, gc, classhisto) lt;
565 if (lt.is_enabled()) {
566 GCTraceTime(Trace, gc, classhisto) tm(before ? "Class Histogram (before full gc)" : "Class Histogram (after full gc)", timer);
567 ResourceMark rm;
568 LogStream ls(lt);
569 VM_GC_HeapInspection inspector(&ls, false /* ! full gc */);
570 inspector.doit();
571 }
572 }
573
574 void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {
575 full_gc_dump(timer, true);
576 }
577
578 void CollectedHeap::post_full_gc_dump(GCTimer* timer) {
579 full_gc_dump(timer, false);
580 }
581
582 void CollectedHeap::initialize_reserved_region(const ReservedHeapSpace& rs) {
583 // It is important to do this in a way such that concurrent readers can't
584 // temporarily think something is in the heap. (Seen this happen in asserts.)
585 _reserved.set_word_size(0);
586 _reserved.set_start((HeapWord*)rs.base());
587 _reserved.set_end((HeapWord*)rs.end());
588 }
589
590 void CollectedHeap::post_initialize() {
591 StringDedup::initialize();
592 initialize_serviceability();
593 }
594
595 #ifndef PRODUCT
596
597 bool CollectedHeap::promotion_should_fail(volatile size_t* count) {
598 // Access to count is not atomic; the value does not have to be exact.
599 if (PromotionFailureALot) {
600 const size_t gc_num = total_collections();
601 const size_t elapsed_gcs = gc_num - _promotion_failure_alot_gc_number;
602 if (elapsed_gcs >= PromotionFailureALotInterval) {
603 // Test for unsigned arithmetic wrap-around.
604 if (++*count >= PromotionFailureALotCount) {
605 *count = 0;
606 return true;
607 }
608 }
609 }
610 return false;
611 }
612
613 bool CollectedHeap::promotion_should_fail() {
614 return promotion_should_fail(&_promotion_failure_alot_count);
615 }
616
617 void CollectedHeap::reset_promotion_should_fail(volatile size_t* count) {
618 if (PromotionFailureALot) {
619 _promotion_failure_alot_gc_number = total_collections();
620 *count = 0;
621 }
622 }
623
624 void CollectedHeap::reset_promotion_should_fail() {
625 reset_promotion_should_fail(&_promotion_failure_alot_count);
626 }
627
628 #endif // #ifndef PRODUCT
629
630 bool CollectedHeap::supports_object_pinning() const {
631 return false;
632 }
633
634 oop CollectedHeap::pin_object(JavaThread* thread, oop obj) {
635 ShouldNotReachHere();
636 return NULL;
637 }
638
639 void CollectedHeap::unpin_object(JavaThread* thread, oop obj) {
640 ShouldNotReachHere();
641 }
642
643 bool CollectedHeap::is_archived_object(oop object) const {
644 return false;
645 }
646
647 uint32_t CollectedHeap::hash_oop(oop obj) const {
648 const uintptr_t addr = cast_from_oop<uintptr_t>(obj);
649 return static_cast<uint32_t>(addr >> LogMinObjAlignment);
650 }
651
652 // It's the caller's responsibility to ensure glitch-freedom
653 // (if required).
654 void CollectedHeap::update_capacity_and_used_at_gc() {
655 _capacity_at_last_gc = capacity();
656 _used_at_last_gc = used();
657 }