1 /*
2 * Copyright (c) 1997, 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/vmClasses.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "gc/shared/collectedHeap.inline.hpp"
29 #include "gc/shared/genCollectedHeap.hpp"
30 #include "gc/shared/slidingForwarding.inline.hpp"
31 #include "gc/shared/space.hpp"
32 #include "gc/shared/space.inline.hpp"
33 #include "gc/shared/spaceDecorator.inline.hpp"
34 #include "memory/iterator.inline.hpp"
35 #include "memory/universe.hpp"
36 #include "oops/oop.inline.hpp"
37 #include "runtime/atomic.hpp"
38 #include "runtime/java.hpp"
39 #include "runtime/prefetch.inline.hpp"
40 #include "runtime/safepoint.hpp"
41 #include "utilities/align.hpp"
42 #include "utilities/copy.hpp"
43 #include "utilities/globalDefinitions.hpp"
44 #include "utilities/macros.hpp"
45 #if INCLUDE_SERIALGC
46 #include "gc/serial/serialBlockOffsetTable.inline.hpp"
47 #include "gc/serial/defNewGeneration.hpp"
48 #endif
49
50 HeapWord* DirtyCardToOopClosure::get_actual_top(HeapWord* top,
51 HeapWord* top_obj) {
52 if (top_obj != nullptr && top_obj < (_sp->toContiguousSpace())->top()) {
53 if (cast_to_oop(top_obj)->is_objArray() || cast_to_oop(top_obj)->is_typeArray()) {
54 // An arrayOop is starting on the dirty card - since we do exact
55 // store checks for objArrays we are done.
56 } else {
57 // Otherwise, it is possible that the object starting on the dirty
58 // card spans the entire card, and that the store happened on a
59 // later card. Figure out where the object ends.
60 assert(_sp->block_size(top_obj) == cast_to_oop(top_obj)->size(),
61 "Block size and object size mismatch");
62 top = top_obj + cast_to_oop(top_obj)->size();
63 }
64 } else {
65 top = (_sp->toContiguousSpace())->top();
66 }
67 return top;
68 }
69
70 void DirtyCardToOopClosure::walk_mem_region(MemRegion mr,
71 HeapWord* bottom,
72 HeapWord* top) {
73 // Note that this assumption won't hold if we have a concurrent
74 // collector in this space, which may have freed up objects after
75 // they were dirtied and before the stop-the-world GC that is
76 // examining cards here.
77 assert(bottom < top, "ought to be at least one obj on a dirty card.");
78
79 walk_mem_region_with_cl(mr, bottom, top, _cl);
80 }
81
82 // We get called with "mr" representing the dirty region
83 // that we want to process. Because of imprecise marking,
84 // we may need to extend the incoming "mr" to the right,
85 // and scan more. However, because we may already have
86 // scanned some of that extended region, we may need to
87 // trim its right-end back some so we do not scan what
88 // we (or another worker thread) may already have scanned
89 // or planning to scan.
90 void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
91 HeapWord* bottom = mr.start();
92 HeapWord* last = mr.last();
93 HeapWord* top = mr.end();
94 HeapWord* bottom_obj;
95 HeapWord* top_obj;
96
97 assert(_last_bottom == nullptr || top <= _last_bottom,
98 "Not decreasing");
99 NOT_PRODUCT(_last_bottom = mr.start());
100
101 bottom_obj = _sp->block_start(bottom);
102 top_obj = _sp->block_start(last);
103
104 assert(bottom_obj <= bottom, "just checking");
105 assert(top_obj <= top, "just checking");
106
107 // Given what we think is the top of the memory region and
108 // the start of the object at the top, get the actual
109 // value of the top.
110 top = get_actual_top(top, top_obj);
111
112 // If the previous call did some part of this region, don't redo.
113 if (_min_done != nullptr && _min_done < top) {
114 top = _min_done;
115 }
116
117 // Top may have been reset, and in fact may be below bottom,
118 // e.g. the dirty card region is entirely in a now free object
119 // -- something that could happen with a concurrent sweeper.
120 bottom = MIN2(bottom, top);
121 MemRegion extended_mr = MemRegion(bottom, top);
122 assert(bottom <= top &&
123 (_min_done == nullptr || top <= _min_done),
124 "overlap!");
125
126 // Walk the region if it is not empty; otherwise there is nothing to do.
127 if (!extended_mr.is_empty()) {
128 walk_mem_region(extended_mr, bottom_obj, top);
129 }
130
131 _min_done = bottom;
132 }
133
134 void DirtyCardToOopClosure::walk_mem_region_with_cl(MemRegion mr,
135 HeapWord* bottom,
136 HeapWord* top,
137 OopIterateClosure* cl) {
138 bottom += cast_to_oop(bottom)->oop_iterate_size(cl, mr);
139 if (bottom < top) {
140 HeapWord* next_obj = bottom + cast_to_oop(bottom)->size();
141 while (next_obj < top) {
142 /* Bottom lies entirely below top, so we can call the */
143 /* non-memRegion version of oop_iterate below. */
144 cast_to_oop(bottom)->oop_iterate(cl);
145 bottom = next_obj;
146 next_obj = bottom + cast_to_oop(bottom)->size();
147 }
148 /* Last object. */
149 cast_to_oop(bottom)->oop_iterate(cl, mr);
150 }
151 }
152
153 void Space::initialize(MemRegion mr,
154 bool clear_space,
155 bool mangle_space) {
156 HeapWord* bottom = mr.start();
157 HeapWord* end = mr.end();
158 assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),
159 "invalid space boundaries");
160 set_bottom(bottom);
161 set_end(end);
162 if (clear_space) clear(mangle_space);
163 }
164
165 void Space::clear(bool mangle_space) {
166 if (ZapUnusedHeapArea && mangle_space) {
167 mangle_unused_area();
168 }
169 }
170
171 ContiguousSpace::ContiguousSpace(): CompactibleSpace(), _top(nullptr) {
172 _mangler = new GenSpaceMangler(this);
173 }
174
175 ContiguousSpace::~ContiguousSpace() {
176 delete _mangler;
177 }
178
179 void ContiguousSpace::initialize(MemRegion mr,
180 bool clear_space,
181 bool mangle_space)
182 {
183 CompactibleSpace::initialize(mr, clear_space, mangle_space);
184 }
185
186 void ContiguousSpace::clear(bool mangle_space) {
187 set_top(bottom());
188 set_saved_mark();
189 CompactibleSpace::clear(mangle_space);
190 }
191
192 bool ContiguousSpace::is_free_block(const HeapWord* p) const {
193 return p >= _top;
194 }
195
196 #if INCLUDE_SERIALGC
197 void TenuredSpace::clear(bool mangle_space) {
198 ContiguousSpace::clear(mangle_space);
199 _offsets.initialize_threshold();
200 }
201
202 void TenuredSpace::set_bottom(HeapWord* new_bottom) {
203 Space::set_bottom(new_bottom);
204 _offsets.set_bottom(new_bottom);
205 }
206
207 void TenuredSpace::set_end(HeapWord* new_end) {
208 // Space should not advertise an increase in size
209 // until after the underlying offset table has been enlarged.
210 _offsets.resize(pointer_delta(new_end, bottom()));
211 Space::set_end(new_end);
212 }
213 #endif // INCLUDE_SERIALGC
214
215 #ifndef PRODUCT
216
217 void ContiguousSpace::set_top_for_allocations(HeapWord* v) {
218 mangler()->set_top_for_allocations(v);
219 }
220 void ContiguousSpace::set_top_for_allocations() {
221 mangler()->set_top_for_allocations(top());
222 }
223 void ContiguousSpace::check_mangled_unused_area(HeapWord* limit) {
224 mangler()->check_mangled_unused_area(limit);
225 }
226
227 void ContiguousSpace::check_mangled_unused_area_complete() {
228 mangler()->check_mangled_unused_area_complete();
229 }
230
231 // Mangled only the unused space that has not previously
232 // been mangled and that has not been allocated since being
233 // mangled.
234 void ContiguousSpace::mangle_unused_area() {
235 mangler()->mangle_unused_area();
236 }
237 void ContiguousSpace::mangle_unused_area_complete() {
238 mangler()->mangle_unused_area_complete();
239 }
240 #endif // NOT_PRODUCT
241
242 void CompactibleSpace::initialize(MemRegion mr,
243 bool clear_space,
244 bool mangle_space) {
245 Space::initialize(mr, clear_space, mangle_space);
246 set_compaction_top(bottom());
247 _next_compaction_space = nullptr;
248 }
249
250 void CompactibleSpace::clear(bool mangle_space) {
251 Space::clear(mangle_space);
252 _compaction_top = bottom();
253 }
254
255 HeapWord* CompactibleSpace::forward(oop q, size_t size,
256 CompactPoint* cp, HeapWord* compact_top, SlidingForwarding* const forwarding) {
257 // q is alive
258 // First check if we should switch compaction space
259 assert(this == cp->space, "'this' should be current compaction space.");
260 size_t compaction_max_size = pointer_delta(end(), compact_top);
261 while (size > compaction_max_size) {
262 // switch to next compaction space
263 cp->space->set_compaction_top(compact_top);
264 cp->space = cp->space->next_compaction_space();
265 if (cp->space == nullptr) {
266 cp->gen = GenCollectedHeap::heap()->young_gen();
267 assert(cp->gen != nullptr, "compaction must succeed");
268 cp->space = cp->gen->first_compaction_space();
269 assert(cp->space != nullptr, "generation must have a first compaction space");
270 }
271 compact_top = cp->space->bottom();
272 cp->space->set_compaction_top(compact_top);
273 cp->space->initialize_threshold();
274 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
275 }
276
277 // store the forwarding pointer into the mark word
278 if (cast_from_oop<HeapWord*>(q) != compact_top) {
279 forwarding->forward_to(q, cast_to_oop(compact_top));
280 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
281 } else {
282 // if the object isn't moving we can just set the mark to the default
283 // mark and handle it specially later on.
284 q->init_mark();
285 assert(!q->is_forwarded(), "should not be forwarded");
286 }
287
288 compact_top += size;
289
290 // We need to update the offset table so that the beginnings of objects can be
291 // found during scavenge. Note that we are updating the offset table based on
292 // where the object will be once the compaction phase finishes.
293 cp->space->alloc_block(compact_top - size, compact_top);
294 return compact_top;
295 }
296
297 #if INCLUDE_SERIALGC
298
299 void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {
300 // Compute the new addresses for the live objects and store it in the mark
301 // Used by universe::mark_sweep_phase2()
302
303 // We're sure to be here before any objects are compacted into this
304 // space, so this is a good time to initialize this:
305 set_compaction_top(bottom());
306
307 if (cp->space == nullptr) {
308 assert(cp->gen != nullptr, "need a generation");
309 assert(cp->gen->first_compaction_space() == this, "just checking");
310 cp->space = cp->gen->first_compaction_space();
311 cp->space->initialize_threshold();
312 cp->space->set_compaction_top(cp->space->bottom());
313 }
314
315 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
316
317 DeadSpacer dead_spacer(this);
318
319 HeapWord* end_of_live = bottom(); // One byte beyond the last byte of the last live object.
320 HeapWord* first_dead = nullptr; // The first dead object.
321
322 const intx interval = PrefetchScanIntervalInBytes;
323
324 HeapWord* cur_obj = bottom();
325 HeapWord* scan_limit = top();
326
327 SlidingForwarding* const forwarding = GenCollectedHeap::heap()->forwarding();
328 while (cur_obj < scan_limit) {
329 if (cast_to_oop(cur_obj)->is_gc_marked()) {
330 // prefetch beyond cur_obj
331 Prefetch::write(cur_obj, interval);
332 size_t size = cast_to_oop(cur_obj)->size();
333 compact_top = cp->space->forward(cast_to_oop(cur_obj), size, cp, compact_top, forwarding);
334 cur_obj += size;
335 end_of_live = cur_obj;
336 } else {
337 // run over all the contiguous dead objects
338 HeapWord* end = cur_obj;
339 do {
340 // prefetch beyond end
341 Prefetch::write(end, interval);
342 end += cast_to_oop(end)->size();
343 } while (end < scan_limit && !cast_to_oop(end)->is_gc_marked());
344
345 // see if we might want to pretend this object is alive so that
346 // we don't have to compact quite as often.
347 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
348 oop obj = cast_to_oop(cur_obj);
349 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top, forwarding);
350 end_of_live = end;
351 } else {
352 // otherwise, it really is a free region.
353
354 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
355 *(HeapWord**)cur_obj = end;
356
357 // see if this is the first dead region.
358 if (first_dead == nullptr) {
359 first_dead = cur_obj;
360 }
361 }
362
363 // move on to the next object
364 cur_obj = end;
365 }
366 }
367
368 assert(cur_obj == scan_limit, "just checking");
369 _end_of_live = end_of_live;
370 if (first_dead != nullptr) {
371 _first_dead = first_dead;
372 } else {
373 _first_dead = end_of_live;
374 }
375
376 // save the compaction_top of the compaction space.
377 cp->space->set_compaction_top(compact_top);
378 }
379
380 void CompactibleSpace::adjust_pointers() {
381 // Check first is there is any work to do.
382 if (used() == 0) {
383 return; // Nothing to do.
384 }
385
386 // adjust all the interior pointers to point at the new locations of objects
387 // Used by MarkSweep::mark_sweep_phase3()
388
389 HeapWord* cur_obj = bottom();
390 HeapWord* const end_of_live = _end_of_live; // Established by prepare_for_compaction().
391 HeapWord* const first_dead = _first_dead; // Established by prepare_for_compaction().
392 const SlidingForwarding* const forwarding = GenCollectedHeap::heap()->forwarding();
393
394 assert(first_dead <= end_of_live, "Stands to reason, no?");
395
396 const intx interval = PrefetchScanIntervalInBytes;
397
398 debug_only(HeapWord* prev_obj = nullptr);
399 while (cur_obj < end_of_live) {
400 Prefetch::write(cur_obj, interval);
401 if (cur_obj < first_dead || cast_to_oop(cur_obj)->is_gc_marked()) {
402 // cur_obj is alive
403 // point all the oops to the new location
404 size_t size = MarkSweep::adjust_pointers(forwarding, cast_to_oop(cur_obj));
405 debug_only(prev_obj = cur_obj);
406 cur_obj += size;
407 } else {
408 debug_only(prev_obj = cur_obj);
409 // cur_obj is not a live object, instead it points at the next live object
410 cur_obj = *(HeapWord**)cur_obj;
411 assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj));
412 }
413 }
414
415 assert(cur_obj == end_of_live, "just checking");
416 }
417
418 void CompactibleSpace::compact() {
419 // Copy all live objects to their new location
420 // Used by MarkSweep::mark_sweep_phase4()
421
422 verify_up_to_first_dead(this);
423
424 HeapWord* const start = bottom();
425 HeapWord* const end_of_live = _end_of_live;
426
427 assert(_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(_first_dead), p2i(end_of_live));
428 if (_first_dead == end_of_live && (start == end_of_live || !cast_to_oop(start)->is_gc_marked())) {
429 // Nothing to compact. The space is either empty or all live object should be left in place.
430 clear_empty_region(this);
431 return;
432 }
433
434 const intx scan_interval = PrefetchScanIntervalInBytes;
435 const intx copy_interval = PrefetchCopyIntervalInBytes;
436
437 assert(start < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(start), p2i(end_of_live));
438 HeapWord* cur_obj = start;
439 if (_first_dead > cur_obj && !cast_to_oop(cur_obj)->is_gc_marked()) {
440 // All object before _first_dead can be skipped. They should not be moved.
441 // A pointer to the first live object is stored at the memory location for _first_dead.
442 cur_obj = *(HeapWord**)(_first_dead);
443 }
444
445 const SlidingForwarding* const forwarding = GenCollectedHeap::heap()->forwarding();
446
447 debug_only(HeapWord* prev_obj = nullptr);
448 while (cur_obj < end_of_live) {
449 if (!cast_to_oop(cur_obj)->is_forwarded()) {
450 debug_only(prev_obj = cur_obj);
451 // The first word of the dead object contains a pointer to the next live object or end of space.
452 cur_obj = *(HeapWord**)cur_obj;
453 assert(cur_obj > prev_obj, "we should be moving forward through memory");
454 } else {
455 // prefetch beyond q
456 Prefetch::read(cur_obj, scan_interval);
457
458 // size and destination
459 size_t size = cast_to_oop(cur_obj)->size();
460 HeapWord* compaction_top = cast_from_oop<HeapWord*>(forwarding->forwardee(cast_to_oop(cur_obj)));
461
462 // prefetch beyond compaction_top
463 Prefetch::write(compaction_top, copy_interval);
464
465 // copy object and reinit its mark
466 assert(cur_obj != compaction_top, "everything in this pass should be moving");
467 Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
468 oop new_obj = cast_to_oop(compaction_top);
469
470 ContinuationGCSupport::transform_stack_chunk(new_obj);
471
472 new_obj->init_mark();
473 assert(new_obj->klass() != nullptr, "should have a class");
474
475 debug_only(prev_obj = cur_obj);
476 cur_obj += size;
477 }
478 }
479
480 clear_empty_region(this);
481 }
482
483 #endif // INCLUDE_SERIALGC
484
485 void Space::print_short() const { print_short_on(tty); }
486
487 void Space::print_short_on(outputStream* st) const {
488 st->print(" space " SIZE_FORMAT "K, %3d%% used", capacity() / K,
489 (int) ((double) used() * 100 / capacity()));
490 }
491
492 void Space::print() const { print_on(tty); }
493
494 void Space::print_on(outputStream* st) const {
495 print_short_on(st);
496 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ")",
497 p2i(bottom()), p2i(end()));
498 }
499
500 void ContiguousSpace::print_on(outputStream* st) const {
501 print_short_on(st);
502 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
503 p2i(bottom()), p2i(top()), p2i(end()));
504 }
505
506 #if INCLUDE_SERIALGC
507 void TenuredSpace::print_on(outputStream* st) const {
508 print_short_on(st);
509 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", "
510 PTR_FORMAT ", " PTR_FORMAT ")",
511 p2i(bottom()), p2i(top()), p2i(_offsets.threshold()), p2i(end()));
512 }
513 #endif
514
515 void ContiguousSpace::verify() const {
516 HeapWord* p = bottom();
517 HeapWord* t = top();
518 HeapWord* prev_p = nullptr;
519 while (p < t) {
520 oopDesc::verify(cast_to_oop(p));
521 prev_p = p;
522 p += cast_to_oop(p)->size();
523 }
524 guarantee(p == top(), "end of last object must match end of space");
525 if (top() != end()) {
526 guarantee(top() == block_start_const(end()-1) &&
527 top() == block_start_const(top()),
528 "top should be start of unallocated block, if it exists");
529 }
530 }
531
532 void Space::oop_iterate(OopIterateClosure* blk) {
533 ObjectToOopClosure blk2(blk);
534 object_iterate(&blk2);
535 }
536
537 bool Space::obj_is_alive(const HeapWord* p) const {
538 assert (block_is_obj(p), "The address should point to an object");
539 return true;
540 }
541
542 void ContiguousSpace::oop_iterate(OopIterateClosure* blk) {
543 if (is_empty()) return;
544 HeapWord* obj_addr = bottom();
545 HeapWord* t = top();
546 // Could call objects iterate, but this is easier.
547 while (obj_addr < t) {
548 obj_addr += cast_to_oop(obj_addr)->oop_iterate_size(blk);
549 }
550 }
551
552 void ContiguousSpace::object_iterate(ObjectClosure* blk) {
553 if (is_empty()) return;
554 object_iterate_from(bottom(), blk);
555 }
556
557 void ContiguousSpace::object_iterate_from(HeapWord* mark, ObjectClosure* blk) {
558 while (mark < top()) {
559 blk->do_object(cast_to_oop(mark));
560 mark += cast_to_oop(mark)->size();
561 }
562 }
563
564 // Very general, slow implementation.
565 HeapWord* ContiguousSpace::block_start_const(const void* p) const {
566 assert(MemRegion(bottom(), end()).contains(p),
567 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
568 p2i(p), p2i(bottom()), p2i(end()));
569 if (p >= top()) {
570 return top();
571 } else {
572 HeapWord* last = bottom();
573 HeapWord* cur = last;
574 while (cur <= p) {
575 last = cur;
576 cur += cast_to_oop(cur)->size();
577 }
578 assert(oopDesc::is_oop(cast_to_oop(last)), PTR_FORMAT " should be an object start", p2i(last));
579 return last;
580 }
581 }
582
583 size_t ContiguousSpace::block_size(const HeapWord* p) const {
584 assert(MemRegion(bottom(), end()).contains(p),
585 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
586 p2i(p), p2i(bottom()), p2i(end()));
587 HeapWord* current_top = top();
588 assert(p <= current_top,
589 "p > current top - p: " PTR_FORMAT ", current top: " PTR_FORMAT,
590 p2i(p), p2i(current_top));
591 assert(p == current_top || oopDesc::is_oop(cast_to_oop(p)),
592 "p (" PTR_FORMAT ") is not a block start - "
593 "current_top: " PTR_FORMAT ", is_oop: %s",
594 p2i(p), p2i(current_top), BOOL_TO_STR(oopDesc::is_oop(cast_to_oop(p))));
595 if (p < current_top) {
596 return cast_to_oop(p)->size();
597 } else {
598 assert(p == current_top, "just checking");
599 return pointer_delta(end(), (HeapWord*) p);
600 }
601 }
602
603 // This version requires locking.
604 inline HeapWord* ContiguousSpace::allocate_impl(size_t size) {
605 assert(Heap_lock->owned_by_self() ||
606 (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()),
607 "not locked");
608 HeapWord* obj = top();
609 if (pointer_delta(end(), obj) >= size) {
610 HeapWord* new_top = obj + size;
611 set_top(new_top);
612 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
613 return obj;
614 } else {
615 return nullptr;
616 }
617 }
618
619 // This version is lock-free.
620 inline HeapWord* ContiguousSpace::par_allocate_impl(size_t size) {
621 do {
622 HeapWord* obj = top();
623 if (pointer_delta(end(), obj) >= size) {
624 HeapWord* new_top = obj + size;
625 HeapWord* result = Atomic::cmpxchg(top_addr(), obj, new_top);
626 // result can be one of two:
627 // the old top value: the exchange succeeded
628 // otherwise: the new value of the top is returned.
629 if (result == obj) {
630 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
631 return obj;
632 }
633 } else {
634 return nullptr;
635 }
636 } while (true);
637 }
638
639 // Requires locking.
640 HeapWord* ContiguousSpace::allocate(size_t size) {
641 return allocate_impl(size);
642 }
643
644 // Lock-free.
645 HeapWord* ContiguousSpace::par_allocate(size_t size) {
646 return par_allocate_impl(size);
647 }
648
649 #if INCLUDE_SERIALGC
650 void TenuredSpace::initialize_threshold() {
651 _offsets.initialize_threshold();
652 }
653
654 void TenuredSpace::alloc_block(HeapWord* start, HeapWord* end) {
655 _offsets.alloc_block(start, end);
656 }
657
658 TenuredSpace::TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
659 MemRegion mr) :
660 _offsets(sharedOffsetArray, mr),
661 _par_alloc_lock(Mutex::safepoint, "TenuredSpaceParAlloc_lock", true)
662 {
663 _offsets.set_contig_space(this);
664 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
665 }
666
667 #define OBJ_SAMPLE_INTERVAL 0
668 #define BLOCK_SAMPLE_INTERVAL 100
669
670 void TenuredSpace::verify() const {
671 HeapWord* p = bottom();
672 HeapWord* prev_p = nullptr;
673 int objs = 0;
674 int blocks = 0;
675
676 if (VerifyObjectStartArray) {
677 _offsets.verify();
678 }
679
680 while (p < top()) {
681 size_t size = cast_to_oop(p)->size();
682 // For a sampling of objects in the space, find it using the
683 // block offset table.
684 if (blocks == BLOCK_SAMPLE_INTERVAL) {
685 guarantee(p == block_start_const(p + (size/2)),
686 "check offset computation");
687 blocks = 0;
688 } else {
689 blocks++;
690 }
691
692 if (objs == OBJ_SAMPLE_INTERVAL) {
693 oopDesc::verify(cast_to_oop(p));
694 objs = 0;
695 } else {
696 objs++;
697 }
698 prev_p = p;
699 p += size;
700 }
701 guarantee(p == top(), "end of last object must match end of space");
702 }
703
704
705 size_t TenuredSpace::allowed_dead_ratio() const {
706 return MarkSweepDeadRatio;
707 }
708 #endif // INCLUDE_SERIALGC