1 /*
2 * Copyright (c) 1997, 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/vmClasses.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "gc/shared/collectedHeap.inline.hpp"
29 #include "gc/shared/genCollectedHeap.hpp"
30 #include "gc/shared/genOopClosures.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 != NULL) {
53 if (_sp->block_is_obj(top_obj)) {
54 if (_precision == CardTable::ObjHeadPreciseArray) {
55 if (cast_to_oop(top_obj)->is_objArray() || cast_to_oop(top_obj)->is_typeArray()) {
56 // An arrayOop is starting on the dirty card - since we do exact
57 // store checks for objArrays we are done.
58 } else {
59 // Otherwise, it is possible that the object starting on the dirty
60 // card spans the entire card, and that the store happened on a
61 // later card. Figure out where the object ends.
62 // Use the block_size() method of the space over which
63 // the iteration is being done. That space (e.g. CMS) may have
64 // specific requirements on object sizes which will
65 // be reflected in the block_size() method.
66 top = top_obj + cast_to_oop(top_obj)->size();
67 }
68 }
69 } else {
70 top = top_obj;
71 }
72 } else {
73 assert(top == _sp->end(), "only case where top_obj == NULL");
74 }
75 return top;
76 }
77
78 void DirtyCardToOopClosure::walk_mem_region(MemRegion mr,
79 HeapWord* bottom,
80 HeapWord* top) {
81 // 1. Blocks may or may not be objects.
82 // 2. Even when a block_is_obj(), it may not entirely
83 // occupy the block if the block quantum is larger than
84 // the object size.
85 // We can and should try to optimize by calling the non-MemRegion
86 // version of oop_iterate() for all but the extremal objects
87 // (for which we need to call the MemRegion version of
88 // oop_iterate()) To be done post-beta XXX
89 for (; bottom < top; bottom += _sp->block_size(bottom)) {
90 // As in the case of contiguous space above, we'd like to
91 // just use the value returned by oop_iterate to increment the
92 // current pointer; unfortunately, that won't work in CMS because
93 // we'd need an interface change (it seems) to have the space
94 // "adjust the object size" (for instance pad it up to its
95 // block alignment or minimum block size restrictions. XXX
96 if (_sp->block_is_obj(bottom) &&
97 !_sp->obj_allocated_since_save_marks(cast_to_oop(bottom))) {
98 cast_to_oop(bottom)->oop_iterate(_cl, mr);
99 }
100 }
101 }
102
103 // We get called with "mr" representing the dirty region
104 // that we want to process. Because of imprecise marking,
105 // we may need to extend the incoming "mr" to the right,
106 // and scan more. However, because we may already have
107 // scanned some of that extended region, we may need to
108 // trim its right-end back some so we do not scan what
109 // we (or another worker thread) may already have scanned
110 // or planning to scan.
111 void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
112 HeapWord* bottom = mr.start();
113 HeapWord* last = mr.last();
114 HeapWord* top = mr.end();
115 HeapWord* bottom_obj;
116 HeapWord* top_obj;
117
118 assert(_precision == CardTable::ObjHeadPreciseArray ||
119 _precision == CardTable::Precise,
120 "Only ones we deal with for now.");
121
122 assert(_precision != CardTable::ObjHeadPreciseArray ||
123 _last_bottom == NULL || top <= _last_bottom,
124 "Not decreasing");
125 NOT_PRODUCT(_last_bottom = mr.start());
126
127 bottom_obj = _sp->block_start(bottom);
128 top_obj = _sp->block_start(last);
129
130 assert(bottom_obj <= bottom, "just checking");
131 assert(top_obj <= top, "just checking");
132
133 // Given what we think is the top of the memory region and
134 // the start of the object at the top, get the actual
135 // value of the top.
136 top = get_actual_top(top, top_obj);
137
138 // If the previous call did some part of this region, don't redo.
139 if (_precision == CardTable::ObjHeadPreciseArray &&
140 _min_done != NULL &&
141 _min_done < top) {
142 top = _min_done;
143 }
144
145 // Top may have been reset, and in fact may be below bottom,
146 // e.g. the dirty card region is entirely in a now free object
147 // -- something that could happen with a concurrent sweeper.
148 bottom = MIN2(bottom, top);
149 MemRegion extended_mr = MemRegion(bottom, top);
150 assert(bottom <= top &&
151 (_precision != CardTable::ObjHeadPreciseArray ||
152 _min_done == NULL ||
153 top <= _min_done),
154 "overlap!");
155
156 // Walk the region if it is not empty; otherwise there is nothing to do.
157 if (!extended_mr.is_empty()) {
158 walk_mem_region(extended_mr, bottom_obj, top);
159 }
160
161 _min_done = bottom;
162 }
163
164 DirtyCardToOopClosure* Space::new_dcto_cl(OopIterateClosure* cl,
165 CardTable::PrecisionStyle precision,
166 HeapWord* boundary) {
167 return new DirtyCardToOopClosure(this, cl, precision, boundary);
168 }
169
170 HeapWord* ContiguousSpaceDCTOC::get_actual_top(HeapWord* top,
171 HeapWord* top_obj) {
172 if (top_obj != NULL && top_obj < (_sp->toContiguousSpace())->top()) {
173 if (_precision == CardTable::ObjHeadPreciseArray) {
174 if (cast_to_oop(top_obj)->is_objArray() || cast_to_oop(top_obj)->is_typeArray()) {
175 // An arrayOop is starting on the dirty card - since we do exact
176 // store checks for objArrays we are done.
177 } else {
178 // Otherwise, it is possible that the object starting on the dirty
179 // card spans the entire card, and that the store happened on a
180 // later card. Figure out where the object ends.
181 assert(_sp->block_size(top_obj) == cast_to_oop(top_obj)->size(),
182 "Block size and object size mismatch");
183 top = top_obj + cast_to_oop(top_obj)->size();
184 }
185 }
186 } else {
187 top = (_sp->toContiguousSpace())->top();
188 }
189 return top;
190 }
191
192 void FilteringDCTOC::walk_mem_region(MemRegion mr,
193 HeapWord* bottom,
194 HeapWord* top) {
195 // Note that this assumption won't hold if we have a concurrent
196 // collector in this space, which may have freed up objects after
197 // they were dirtied and before the stop-the-world GC that is
198 // examining cards here.
199 assert(bottom < top, "ought to be at least one obj on a dirty card.");
200
201 if (_boundary != NULL) {
202 // We have a boundary outside of which we don't want to look
203 // at objects, so create a filtering closure around the
204 // oop closure before walking the region.
205 FilteringClosure filter(_boundary, _cl);
206 walk_mem_region_with_cl(mr, bottom, top, &filter);
207 } else {
208 // No boundary, simply walk the heap with the oop closure.
209 walk_mem_region_with_cl(mr, bottom, top, _cl);
210 }
211
212 }
213
214 // We must replicate this so that the static type of "FilteringClosure"
215 // (see above) is apparent at the oop_iterate calls.
216 #define ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
217 void ContiguousSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr, \
218 HeapWord* bottom, \
219 HeapWord* top, \
220 ClosureType* cl) { \
221 bottom += cast_to_oop(bottom)->oop_iterate_size(cl, mr); \
222 if (bottom < top) { \
223 HeapWord* next_obj = bottom + cast_to_oop(bottom)->size(); \
224 while (next_obj < top) { \
225 /* Bottom lies entirely below top, so we can call the */ \
226 /* non-memRegion version of oop_iterate below. */ \
227 cast_to_oop(bottom)->oop_iterate(cl); \
228 bottom = next_obj; \
229 next_obj = bottom + cast_to_oop(bottom)->size(); \
230 } \
231 /* Last object. */ \
232 cast_to_oop(bottom)->oop_iterate(cl, mr); \
233 } \
234 }
235
236 // (There are only two of these, rather than N, because the split is due
237 // only to the introduction of the FilteringClosure, a local part of the
238 // impl of this abstraction.)
239 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(OopIterateClosure)
240 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
241
242 DirtyCardToOopClosure*
243 ContiguousSpace::new_dcto_cl(OopIterateClosure* cl,
244 CardTable::PrecisionStyle precision,
245 HeapWord* boundary) {
246 return new ContiguousSpaceDCTOC(this, cl, precision, boundary);
247 }
248
249 void Space::initialize(MemRegion mr,
250 bool clear_space,
251 bool mangle_space) {
252 HeapWord* bottom = mr.start();
253 HeapWord* end = mr.end();
254 assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),
255 "invalid space boundaries");
256 set_bottom(bottom);
257 set_end(end);
258 if (clear_space) clear(mangle_space);
259 }
260
261 void Space::clear(bool mangle_space) {
262 if (ZapUnusedHeapArea && mangle_space) {
263 mangle_unused_area();
264 }
265 }
266
267 ContiguousSpace::ContiguousSpace(): CompactibleSpace(), _top(NULL) {
268 _mangler = new GenSpaceMangler(this);
269 }
270
271 ContiguousSpace::~ContiguousSpace() {
272 delete _mangler;
273 }
274
275 void ContiguousSpace::initialize(MemRegion mr,
276 bool clear_space,
277 bool mangle_space)
278 {
279 CompactibleSpace::initialize(mr, clear_space, mangle_space);
280 }
281
282 void ContiguousSpace::clear(bool mangle_space) {
283 set_top(bottom());
284 set_saved_mark();
285 CompactibleSpace::clear(mangle_space);
286 }
287
288 bool ContiguousSpace::is_free_block(const HeapWord* p) const {
289 return p >= _top;
290 }
291
292 #if INCLUDE_SERIALGC
293 void OffsetTableContigSpace::clear(bool mangle_space) {
294 ContiguousSpace::clear(mangle_space);
295 _offsets.initialize_threshold();
296 }
297
298 void OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
299 Space::set_bottom(new_bottom);
300 _offsets.set_bottom(new_bottom);
301 }
302
303 void OffsetTableContigSpace::set_end(HeapWord* new_end) {
304 // Space should not advertise an increase in size
305 // until after the underlying offset table has been enlarged.
306 _offsets.resize(pointer_delta(new_end, bottom()));
307 Space::set_end(new_end);
308 }
309 #endif // INCLUDE_SERIALGC
310
311 #ifndef PRODUCT
312
313 void ContiguousSpace::set_top_for_allocations(HeapWord* v) {
314 mangler()->set_top_for_allocations(v);
315 }
316 void ContiguousSpace::set_top_for_allocations() {
317 mangler()->set_top_for_allocations(top());
318 }
319 void ContiguousSpace::check_mangled_unused_area(HeapWord* limit) {
320 mangler()->check_mangled_unused_area(limit);
321 }
322
323 void ContiguousSpace::check_mangled_unused_area_complete() {
324 mangler()->check_mangled_unused_area_complete();
325 }
326
327 // Mangled only the unused space that has not previously
328 // been mangled and that has not been allocated since being
329 // mangled.
330 void ContiguousSpace::mangle_unused_area() {
331 mangler()->mangle_unused_area();
332 }
333 void ContiguousSpace::mangle_unused_area_complete() {
334 mangler()->mangle_unused_area_complete();
335 }
336 #endif // NOT_PRODUCT
337
338 void CompactibleSpace::initialize(MemRegion mr,
339 bool clear_space,
340 bool mangle_space) {
341 Space::initialize(mr, clear_space, mangle_space);
342 set_compaction_top(bottom());
343 _next_compaction_space = NULL;
344 }
345
346 void CompactibleSpace::clear(bool mangle_space) {
347 Space::clear(mangle_space);
348 _compaction_top = bottom();
349 }
350
351 HeapWord* CompactibleSpace::forward(oop q, size_t size,
352 CompactPoint* cp, HeapWord* compact_top) {
353 // q is alive
354 // First check if we should switch compaction space
355 assert(this == cp->space, "'this' should be current compaction space.");
356 size_t compaction_max_size = pointer_delta(end(), compact_top);
357 while (size > compaction_max_size) {
358 // switch to next compaction space
359 cp->space->set_compaction_top(compact_top);
360 cp->space = cp->space->next_compaction_space();
361 if (cp->space == NULL) {
362 cp->gen = GenCollectedHeap::heap()->young_gen();
363 assert(cp->gen != NULL, "compaction must succeed");
364 cp->space = cp->gen->first_compaction_space();
365 assert(cp->space != NULL, "generation must have a first compaction space");
366 }
367 compact_top = cp->space->bottom();
368 cp->space->set_compaction_top(compact_top);
369 cp->space->initialize_threshold();
370 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
371 }
372
373 // store the forwarding pointer into the mark word
374 if (cast_from_oop<HeapWord*>(q) != compact_top) {
375 q->forward_to(cast_to_oop(compact_top));
376 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
377 } else {
378 // if the object isn't moving we can just set the mark to the default
379 // mark and handle it specially later on.
380 q->init_mark();
381 assert(!q->is_forwarded(), "should not be forwarded");
382 }
383
384 compact_top += size;
385
386 // We need to update the offset table so that the beginnings of objects can be
387 // found during scavenge. Note that we are updating the offset table based on
388 // where the object will be once the compaction phase finishes.
389 cp->space->alloc_block(compact_top - size, compact_top);
390 return compact_top;
391 }
392
393 #if INCLUDE_SERIALGC
394
395 void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {
396 // Compute the new addresses for the live objects and store it in the mark
397 // Used by universe::mark_sweep_phase2()
398
399 // We're sure to be here before any objects are compacted into this
400 // space, so this is a good time to initialize this:
401 set_compaction_top(bottom());
402
403 if (cp->space == NULL) {
404 assert(cp->gen != NULL, "need a generation");
405 assert(cp->gen->first_compaction_space() == this, "just checking");
406 cp->space = cp->gen->first_compaction_space();
407 cp->space->initialize_threshold();
408 cp->space->set_compaction_top(cp->space->bottom());
409 }
410
411 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
412
413 DeadSpacer dead_spacer(this);
414
415 HeapWord* end_of_live = bottom(); // One byte beyond the last byte of the last live object.
416 HeapWord* first_dead = NULL; // The first dead object.
417
418 const intx interval = PrefetchScanIntervalInBytes;
419
420 HeapWord* cur_obj = bottom();
421 HeapWord* scan_limit = top();
422
423 while (cur_obj < scan_limit) {
424 if (cast_to_oop(cur_obj)->is_gc_marked()) {
425 // prefetch beyond cur_obj
426 Prefetch::write(cur_obj, interval);
427 size_t size = cast_to_oop(cur_obj)->size();
428 compact_top = cp->space->forward(cast_to_oop(cur_obj), size, cp, compact_top);
429 cur_obj += size;
430 end_of_live = cur_obj;
431 } else {
432 // run over all the contiguous dead objects
433 HeapWord* end = cur_obj;
434 do {
435 // prefetch beyond end
436 Prefetch::write(end, interval);
437 end += cast_to_oop(end)->size();
438 } while (end < scan_limit && !cast_to_oop(end)->is_gc_marked());
439
440 // see if we might want to pretend this object is alive so that
441 // we don't have to compact quite as often.
442 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
443 oop obj = cast_to_oop(cur_obj);
444 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top);
445 end_of_live = end;
446 } else {
447 // otherwise, it really is a free region.
448
449 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
450 *(HeapWord**)cur_obj = end;
451
452 // see if this is the first dead region.
453 if (first_dead == NULL) {
454 first_dead = cur_obj;
455 }
456 }
457
458 // move on to the next object
459 cur_obj = end;
460 }
461 }
462
463 assert(cur_obj == scan_limit, "just checking");
464 _end_of_live = end_of_live;
465 if (first_dead != NULL) {
466 _first_dead = first_dead;
467 } else {
468 _first_dead = end_of_live;
469 }
470
471 // save the compaction_top of the compaction space.
472 cp->space->set_compaction_top(compact_top);
473 }
474
475 void CompactibleSpace::adjust_pointers() {
476 // Check first is there is any work to do.
477 if (used() == 0) {
478 return; // Nothing to do.
479 }
480
481 // adjust all the interior pointers to point at the new locations of objects
482 // Used by MarkSweep::mark_sweep_phase3()
483
484 HeapWord* cur_obj = bottom();
485 HeapWord* const end_of_live = _end_of_live; // Established by prepare_for_compaction().
486 HeapWord* const first_dead = _first_dead; // Established by prepare_for_compaction().
487
488 assert(first_dead <= end_of_live, "Stands to reason, no?");
489
490 const intx interval = PrefetchScanIntervalInBytes;
491
492 debug_only(HeapWord* prev_obj = NULL);
493 while (cur_obj < end_of_live) {
494 Prefetch::write(cur_obj, interval);
495 if (cur_obj < first_dead || cast_to_oop(cur_obj)->is_gc_marked()) {
496 // cur_obj is alive
497 // point all the oops to the new location
498 size_t size = MarkSweep::adjust_pointers(cast_to_oop(cur_obj));
499 debug_only(prev_obj = cur_obj);
500 cur_obj += size;
501 } else {
502 debug_only(prev_obj = cur_obj);
503 // cur_obj is not a live object, instead it points at the next live object
504 cur_obj = *(HeapWord**)cur_obj;
505 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));
506 }
507 }
508
509 assert(cur_obj == end_of_live, "just checking");
510 }
511
512 void CompactibleSpace::compact() {
513 // Copy all live objects to their new location
514 // Used by MarkSweep::mark_sweep_phase4()
515
516 verify_up_to_first_dead(this);
517
518 HeapWord* const start = bottom();
519 HeapWord* const end_of_live = _end_of_live;
520
521 assert(_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(_first_dead), p2i(end_of_live));
522 if (_first_dead == end_of_live && (start == end_of_live || !cast_to_oop(start)->is_gc_marked())) {
523 // Nothing to compact. The space is either empty or all live object should be left in place.
524 clear_empty_region(this);
525 return;
526 }
527
528 const intx scan_interval = PrefetchScanIntervalInBytes;
529 const intx copy_interval = PrefetchCopyIntervalInBytes;
530
531 assert(start < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(start), p2i(end_of_live));
532 HeapWord* cur_obj = start;
533 if (_first_dead > cur_obj && !cast_to_oop(cur_obj)->is_gc_marked()) {
534 // All object before _first_dead can be skipped. They should not be moved.
535 // A pointer to the first live object is stored at the memory location for _first_dead.
536 cur_obj = *(HeapWord**)(_first_dead);
537 }
538
539 debug_only(HeapWord* prev_obj = NULL);
540 while (cur_obj < end_of_live) {
541 if (!cast_to_oop(cur_obj)->is_forwarded()) {
542 debug_only(prev_obj = cur_obj);
543 // The first word of the dead object contains a pointer to the next live object or end of space.
544 cur_obj = *(HeapWord**)cur_obj;
545 assert(cur_obj > prev_obj, "we should be moving forward through memory");
546 } else {
547 // prefetch beyond q
548 Prefetch::read(cur_obj, scan_interval);
549
550 // size and destination
551 size_t size = cast_to_oop(cur_obj)->size();
552 HeapWord* compaction_top = cast_from_oop<HeapWord*>(cast_to_oop(cur_obj)->forwardee());
553
554 // prefetch beyond compaction_top
555 Prefetch::write(compaction_top, copy_interval);
556
557 // copy object and reinit its mark
558 assert(cur_obj != compaction_top, "everything in this pass should be moving");
559 Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
560 oop new_obj = cast_to_oop(compaction_top);
561
562 ContinuationGCSupport::transform_stack_chunk(new_obj);
563
564 new_obj->init_mark();
565 assert(new_obj->klass() != NULL, "should have a class");
566
567 debug_only(prev_obj = cur_obj);
568 cur_obj += size;
569 }
570 }
571
572 clear_empty_region(this);
573 }
574
575 #endif // INCLUDE_SERIALGC
576
577 void Space::print_short() const { print_short_on(tty); }
578
579 void Space::print_short_on(outputStream* st) const {
580 st->print(" space " SIZE_FORMAT "K, %3d%% used", capacity() / K,
581 (int) ((double) used() * 100 / capacity()));
582 }
583
584 void Space::print() const { print_on(tty); }
585
586 void Space::print_on(outputStream* st) const {
587 print_short_on(st);
588 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ")",
589 p2i(bottom()), p2i(end()));
590 }
591
592 void ContiguousSpace::print_on(outputStream* st) const {
593 print_short_on(st);
594 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
595 p2i(bottom()), p2i(top()), p2i(end()));
596 }
597
598 #if INCLUDE_SERIALGC
599 void OffsetTableContigSpace::print_on(outputStream* st) const {
600 print_short_on(st);
601 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", "
602 PTR_FORMAT ", " PTR_FORMAT ")",
603 p2i(bottom()), p2i(top()), p2i(_offsets.threshold()), p2i(end()));
604 }
605 #endif
606
607 void ContiguousSpace::verify() const {
608 HeapWord* p = bottom();
609 HeapWord* t = top();
610 HeapWord* prev_p = NULL;
611 while (p < t) {
612 oopDesc::verify(cast_to_oop(p));
613 prev_p = p;
614 p += cast_to_oop(p)->size();
615 }
616 guarantee(p == top(), "end of last object must match end of space");
617 if (top() != end()) {
618 guarantee(top() == block_start_const(end()-1) &&
619 top() == block_start_const(top()),
620 "top should be start of unallocated block, if it exists");
621 }
622 }
623
624 void Space::oop_iterate(OopIterateClosure* blk) {
625 ObjectToOopClosure blk2(blk);
626 object_iterate(&blk2);
627 }
628
629 bool Space::obj_is_alive(const HeapWord* p) const {
630 assert (block_is_obj(p), "The address should point to an object");
631 return true;
632 }
633
634 void ContiguousSpace::oop_iterate(OopIterateClosure* blk) {
635 if (is_empty()) return;
636 HeapWord* obj_addr = bottom();
637 HeapWord* t = top();
638 // Could call objects iterate, but this is easier.
639 while (obj_addr < t) {
640 obj_addr += cast_to_oop(obj_addr)->oop_iterate_size(blk);
641 }
642 }
643
644 void ContiguousSpace::object_iterate(ObjectClosure* blk) {
645 if (is_empty()) return;
646 object_iterate_from(bottom(), blk);
647 }
648
649 void ContiguousSpace::object_iterate_from(HeapWord* mark, ObjectClosure* blk) {
650 while (mark < top()) {
651 blk->do_object(cast_to_oop(mark));
652 mark += cast_to_oop(mark)->size();
653 }
654 }
655
656 // Very general, slow implementation.
657 HeapWord* ContiguousSpace::block_start_const(const void* p) const {
658 assert(MemRegion(bottom(), end()).contains(p),
659 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
660 p2i(p), p2i(bottom()), p2i(end()));
661 if (p >= top()) {
662 return top();
663 } else {
664 HeapWord* last = bottom();
665 HeapWord* cur = last;
666 while (cur <= p) {
667 last = cur;
668 cur += cast_to_oop(cur)->size();
669 }
670 assert(oopDesc::is_oop(cast_to_oop(last)), PTR_FORMAT " should be an object start", p2i(last));
671 return last;
672 }
673 }
674
675 size_t ContiguousSpace::block_size(const HeapWord* p) const {
676 assert(MemRegion(bottom(), end()).contains(p),
677 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
678 p2i(p), p2i(bottom()), p2i(end()));
679 HeapWord* current_top = top();
680 assert(p <= current_top,
681 "p > current top - p: " PTR_FORMAT ", current top: " PTR_FORMAT,
682 p2i(p), p2i(current_top));
683 assert(p == current_top || oopDesc::is_oop(cast_to_oop(p)),
684 "p (" PTR_FORMAT ") is not a block start - "
685 "current_top: " PTR_FORMAT ", is_oop: %s",
686 p2i(p), p2i(current_top), BOOL_TO_STR(oopDesc::is_oop(cast_to_oop(p))));
687 if (p < current_top) {
688 return cast_to_oop(p)->size();
689 } else {
690 assert(p == current_top, "just checking");
691 return pointer_delta(end(), (HeapWord*) p);
692 }
693 }
694
695 // This version requires locking.
696 inline HeapWord* ContiguousSpace::allocate_impl(size_t size) {
697 assert(Heap_lock->owned_by_self() ||
698 (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()),
699 "not locked");
700 HeapWord* obj = top();
701 if (pointer_delta(end(), obj) >= size) {
702 HeapWord* new_top = obj + size;
703 set_top(new_top);
704 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
705 return obj;
706 } else {
707 return NULL;
708 }
709 }
710
711 // This version is lock-free.
712 inline HeapWord* ContiguousSpace::par_allocate_impl(size_t size) {
713 do {
714 HeapWord* obj = top();
715 if (pointer_delta(end(), obj) >= size) {
716 HeapWord* new_top = obj + size;
717 HeapWord* result = Atomic::cmpxchg(top_addr(), obj, new_top);
718 // result can be one of two:
719 // the old top value: the exchange succeeded
720 // otherwise: the new value of the top is returned.
721 if (result == obj) {
722 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
723 return obj;
724 }
725 } else {
726 return NULL;
727 }
728 } while (true);
729 }
730
731 // Requires locking.
732 HeapWord* ContiguousSpace::allocate(size_t size) {
733 return allocate_impl(size);
734 }
735
736 // Lock-free.
737 HeapWord* ContiguousSpace::par_allocate(size_t size) {
738 return par_allocate_impl(size);
739 }
740
741 #if INCLUDE_SERIALGC
742 void OffsetTableContigSpace::initialize_threshold() {
743 _offsets.initialize_threshold();
744 }
745
746 void OffsetTableContigSpace::alloc_block(HeapWord* start, HeapWord* end) {
747 _offsets.alloc_block(start, end);
748 }
749
750 OffsetTableContigSpace::OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
751 MemRegion mr) :
752 _offsets(sharedOffsetArray, mr),
753 _par_alloc_lock(Mutex::safepoint, "OffsetTableContigSpaceParAlloc_lock", true)
754 {
755 _offsets.set_contig_space(this);
756 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
757 }
758
759 #define OBJ_SAMPLE_INTERVAL 0
760 #define BLOCK_SAMPLE_INTERVAL 100
761
762 void OffsetTableContigSpace::verify() const {
763 HeapWord* p = bottom();
764 HeapWord* prev_p = NULL;
765 int objs = 0;
766 int blocks = 0;
767
768 if (VerifyObjectStartArray) {
769 _offsets.verify();
770 }
771
772 while (p < top()) {
773 size_t size = cast_to_oop(p)->size();
774 // For a sampling of objects in the space, find it using the
775 // block offset table.
776 if (blocks == BLOCK_SAMPLE_INTERVAL) {
777 guarantee(p == block_start_const(p + (size/2)),
778 "check offset computation");
779 blocks = 0;
780 } else {
781 blocks++;
782 }
783
784 if (objs == OBJ_SAMPLE_INTERVAL) {
785 oopDesc::verify(cast_to_oop(p));
786 objs = 0;
787 } else {
788 objs++;
789 }
790 prev_p = p;
791 p += size;
792 }
793 guarantee(p == top(), "end of last object must match end of space");
794 }
795
796
797 size_t TenuredSpace::allowed_dead_ratio() const {
798 return MarkSweepDeadRatio;
799 }
800 #endif // INCLUDE_SERIALGC