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