1 /*
2 * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/vmClasses.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "gc/shared/blockOffsetTable.inline.hpp"
29 #include "gc/shared/collectedHeap.inline.hpp"
30 #include "gc/shared/genCollectedHeap.hpp"
31 #include "gc/shared/genOopClosures.inline.hpp"
32 #include "gc/shared/space.hpp"
33 #include "gc/shared/space.inline.hpp"
34 #include "gc/shared/spaceDecorator.inline.hpp"
35 #include "memory/iterator.inline.hpp"
36 #include "memory/universe.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/atomic.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/prefetch.inline.hpp"
41 #include "runtime/safepoint.hpp"
42 #include "utilities/align.hpp"
43 #include "utilities/copy.hpp"
44 #include "utilities/globalDefinitions.hpp"
45 #include "utilities/macros.hpp"
46 #if INCLUDE_SERIALGC
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 void OffsetTableContigSpace::clear(bool mangle_space) {
293 ContiguousSpace::clear(mangle_space);
294 _offsets.initialize_threshold();
295 }
296
297 void OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
298 Space::set_bottom(new_bottom);
299 _offsets.set_bottom(new_bottom);
300 }
301
302 void OffsetTableContigSpace::set_end(HeapWord* new_end) {
303 // Space should not advertise an increase in size
304 // until after the underlying offset table has been enlarged.
305 _offsets.resize(pointer_delta(new_end, bottom()));
306 Space::set_end(new_end);
307 }
308
309 #ifndef PRODUCT
310
311 void ContiguousSpace::set_top_for_allocations(HeapWord* v) {
312 mangler()->set_top_for_allocations(v);
313 }
314 void ContiguousSpace::set_top_for_allocations() {
315 mangler()->set_top_for_allocations(top());
316 }
317 void ContiguousSpace::check_mangled_unused_area(HeapWord* limit) {
318 mangler()->check_mangled_unused_area(limit);
319 }
320
321 void ContiguousSpace::check_mangled_unused_area_complete() {
322 mangler()->check_mangled_unused_area_complete();
323 }
324
325 // Mangled only the unused space that has not previously
326 // been mangled and that has not been allocated since being
327 // mangled.
328 void ContiguousSpace::mangle_unused_area() {
329 mangler()->mangle_unused_area();
330 }
331 void ContiguousSpace::mangle_unused_area_complete() {
332 mangler()->mangle_unused_area_complete();
333 }
334 #endif // NOT_PRODUCT
335
336 void CompactibleSpace::initialize(MemRegion mr,
337 bool clear_space,
338 bool mangle_space) {
339 Space::initialize(mr, clear_space, mangle_space);
340 set_compaction_top(bottom());
341 _next_compaction_space = NULL;
342 }
343
344 void CompactibleSpace::clear(bool mangle_space) {
345 Space::clear(mangle_space);
346 _compaction_top = bottom();
347 }
348
349 HeapWord* CompactibleSpace::forward(oop q, size_t size,
350 CompactPoint* cp, HeapWord* compact_top) {
351 // q is alive
352 // First check if we should switch compaction space
353 assert(this == cp->space, "'this' should be current compaction space.");
354 size_t compaction_max_size = pointer_delta(end(), compact_top);
355 while (size > compaction_max_size) {
356 // switch to next compaction space
357 cp->space->set_compaction_top(compact_top);
358 cp->space = cp->space->next_compaction_space();
359 if (cp->space == NULL) {
360 cp->gen = GenCollectedHeap::heap()->young_gen();
361 assert(cp->gen != NULL, "compaction must succeed");
362 cp->space = cp->gen->first_compaction_space();
363 assert(cp->space != NULL, "generation must have a first compaction space");
364 }
365 compact_top = cp->space->bottom();
366 cp->space->set_compaction_top(compact_top);
367 cp->space->initialize_threshold();
368 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
369 }
370
371 // store the forwarding pointer into the mark word
372 if (cast_from_oop<HeapWord*>(q) != compact_top) {
373 q->forward_to(cast_to_oop(compact_top));
374 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
375 } else {
376 // if the object isn't moving we can just set the mark to the default
377 // mark and handle it specially later on.
378 q->init_mark();
379 assert(!q->is_forwarded(), "should not be forwarded");
380 }
381
382 compact_top += size;
383
384 // We need to update the offset table so that the beginnings of objects can be
385 // found during scavenge. Note that we are updating the offset table based on
386 // where the object will be once the compaction phase finishes.
387 cp->space->alloc_block(compact_top - size, compact_top);
388 return compact_top;
389 }
390
391 #if INCLUDE_SERIALGC
392
393 void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {
394 // Compute the new addresses for the live objects and store it in the mark
395 // Used by universe::mark_sweep_phase2()
396
397 // We're sure to be here before any objects are compacted into this
398 // space, so this is a good time to initialize this:
399 set_compaction_top(bottom());
400
401 if (cp->space == NULL) {
402 assert(cp->gen != NULL, "need a generation");
403 assert(cp->gen->first_compaction_space() == this, "just checking");
404 cp->space = cp->gen->first_compaction_space();
405 cp->space->initialize_threshold();
406 cp->space->set_compaction_top(cp->space->bottom());
407 }
408
409 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
410
411 DeadSpacer dead_spacer(this);
412
413 HeapWord* end_of_live = bottom(); // One byte beyond the last byte of the last live object.
414 HeapWord* first_dead = NULL; // The first dead object.
415
416 const intx interval = PrefetchScanIntervalInBytes;
417
418 HeapWord* cur_obj = bottom();
419 HeapWord* scan_limit = top();
420
421 while (cur_obj < scan_limit) {
422 if (cast_to_oop(cur_obj)->is_gc_marked()) {
423 // prefetch beyond cur_obj
424 Prefetch::write(cur_obj, interval);
425 size_t size = cast_to_oop(cur_obj)->size();
426 compact_top = cp->space->forward(cast_to_oop(cur_obj), size, cp, compact_top);
427 cur_obj += size;
428 end_of_live = cur_obj;
429 } else {
430 // run over all the contiguous dead objects
431 HeapWord* end = cur_obj;
432 do {
433 // prefetch beyond end
434 Prefetch::write(end, interval);
435 end += cast_to_oop(end)->size();
436 } while (end < scan_limit && !cast_to_oop(end)->is_gc_marked());
437
438 // see if we might want to pretend this object is alive so that
439 // we don't have to compact quite as often.
440 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
441 oop obj = cast_to_oop(cur_obj);
442 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top);
443 end_of_live = end;
444 } else {
445 // otherwise, it really is a free region.
446
447 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
448 *(HeapWord**)cur_obj = end;
449
450 // see if this is the first dead region.
451 if (first_dead == NULL) {
452 first_dead = cur_obj;
453 }
454 }
455
456 // move on to the next object
457 cur_obj = end;
458 }
459 }
460
461 assert(cur_obj == scan_limit, "just checking");
462 _end_of_live = end_of_live;
463 if (first_dead != NULL) {
464 _first_dead = first_dead;
465 } else {
466 _first_dead = end_of_live;
467 }
468
469 // save the compaction_top of the compaction space.
470 cp->space->set_compaction_top(compact_top);
471 }
472
473 void CompactibleSpace::adjust_pointers() {
474 // Check first is there is any work to do.
475 if (used() == 0) {
476 return; // Nothing to do.
477 }
478
479 // adjust all the interior pointers to point at the new locations of objects
480 // Used by MarkSweep::mark_sweep_phase3()
481
482 HeapWord* cur_obj = bottom();
483 HeapWord* const end_of_live = _end_of_live; // Established by prepare_for_compaction().
484 HeapWord* const first_dead = _first_dead; // Established by prepare_for_compaction().
485
486 assert(first_dead <= end_of_live, "Stands to reason, no?");
487
488 const intx interval = PrefetchScanIntervalInBytes;
489
490 debug_only(HeapWord* prev_obj = NULL);
491 while (cur_obj < end_of_live) {
492 Prefetch::write(cur_obj, interval);
493 if (cur_obj < first_dead || cast_to_oop(cur_obj)->is_gc_marked()) {
494 // cur_obj is alive
495 // point all the oops to the new location
496 size_t size = MarkSweep::adjust_pointers(cast_to_oop(cur_obj));
497 debug_only(prev_obj = cur_obj);
498 cur_obj += size;
499 } else {
500 debug_only(prev_obj = cur_obj);
501 // cur_obj is not a live object, instead it points at the next live object
502 cur_obj = *(HeapWord**)cur_obj;
503 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));
504 }
505 }
506
507 assert(cur_obj == end_of_live, "just checking");
508 }
509
510 void CompactibleSpace::compact() {
511 // Copy all live objects to their new location
512 // Used by MarkSweep::mark_sweep_phase4()
513
514 verify_up_to_first_dead(this);
515
516 HeapWord* const start = bottom();
517 HeapWord* const end_of_live = _end_of_live;
518
519 assert(_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(_first_dead), p2i(end_of_live));
520 if (_first_dead == end_of_live && (start == end_of_live || !cast_to_oop(start)->is_gc_marked())) {
521 // Nothing to compact. The space is either empty or all live object should be left in place.
522 clear_empty_region(this);
523 return;
524 }
525
526 const intx scan_interval = PrefetchScanIntervalInBytes;
527 const intx copy_interval = PrefetchCopyIntervalInBytes;
528
529 assert(start < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(start), p2i(end_of_live));
530 HeapWord* cur_obj = start;
531 if (_first_dead > cur_obj && !cast_to_oop(cur_obj)->is_gc_marked()) {
532 // All object before _first_dead can be skipped. They should not be moved.
533 // A pointer to the first live object is stored at the memory location for _first_dead.
534 cur_obj = *(HeapWord**)(_first_dead);
535 }
536
537 debug_only(HeapWord* prev_obj = NULL);
538 while (cur_obj < end_of_live) {
539 if (!cast_to_oop(cur_obj)->is_forwarded()) {
540 debug_only(prev_obj = cur_obj);
541 // The first word of the dead object contains a pointer to the next live object or end of space.
542 cur_obj = *(HeapWord**)cur_obj;
543 assert(cur_obj > prev_obj, "we should be moving forward through memory");
544 } else {
545 // prefetch beyond q
546 Prefetch::read(cur_obj, scan_interval);
547
548 // size and destination
549 size_t size = cast_to_oop(cur_obj)->size();
550 HeapWord* compaction_top = cast_from_oop<HeapWord*>(cast_to_oop(cur_obj)->forwardee());
551
552 // prefetch beyond compaction_top
553 Prefetch::write(compaction_top, copy_interval);
554
555 // copy object and reinit its mark
556 assert(cur_obj != compaction_top, "everything in this pass should be moving");
557 Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
558 cast_to_oop(compaction_top)->init_mark();
559 assert(cast_to_oop(compaction_top)->klass() != NULL, "should have a class");
560
561 debug_only(prev_obj = cur_obj);
562 cur_obj += size;
563 }
564 }
565
566 clear_empty_region(this);
567 }
568
569 #endif // INCLUDE_SERIALGC
570
571 void Space::print_short() const { print_short_on(tty); }
572
573 void Space::print_short_on(outputStream* st) const {
574 st->print(" space " SIZE_FORMAT "K, %3d%% used", capacity() / K,
575 (int) ((double) used() * 100 / capacity()));
576 }
577
578 void Space::print() const { print_on(tty); }
579
580 void Space::print_on(outputStream* st) const {
581 print_short_on(st);
582 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ")",
583 p2i(bottom()), p2i(end()));
584 }
585
586 void ContiguousSpace::print_on(outputStream* st) const {
587 print_short_on(st);
588 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
589 p2i(bottom()), p2i(top()), p2i(end()));
590 }
591
592 void OffsetTableContigSpace::print_on(outputStream* st) const {
593 print_short_on(st);
594 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
595 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
596 p2i(bottom()), p2i(top()), p2i(_offsets.threshold()), p2i(end()));
597 }
598
599 void ContiguousSpace::verify() const {
600 HeapWord* p = bottom();
601 HeapWord* t = top();
602 HeapWord* prev_p = NULL;
603 while (p < t) {
604 oopDesc::verify(cast_to_oop(p));
605 prev_p = p;
606 p += cast_to_oop(p)->size();
607 }
608 guarantee(p == top(), "end of last object must match end of space");
609 if (top() != end()) {
610 guarantee(top() == block_start_const(end()-1) &&
611 top() == block_start_const(top()),
612 "top should be start of unallocated block, if it exists");
613 }
614 }
615
616 void Space::oop_iterate(OopIterateClosure* blk) {
617 ObjectToOopClosure blk2(blk);
618 object_iterate(&blk2);
619 }
620
621 bool Space::obj_is_alive(const HeapWord* p) const {
622 assert (block_is_obj(p), "The address should point to an object");
623 return true;
624 }
625
626 void ContiguousSpace::oop_iterate(OopIterateClosure* blk) {
627 if (is_empty()) return;
628 HeapWord* obj_addr = bottom();
629 HeapWord* t = top();
630 // Could call objects iterate, but this is easier.
631 while (obj_addr < t) {
632 obj_addr += cast_to_oop(obj_addr)->oop_iterate_size(blk);
633 }
634 }
635
636 void ContiguousSpace::object_iterate(ObjectClosure* blk) {
637 if (is_empty()) return;
638 object_iterate_from(bottom(), blk);
639 }
640
641 void ContiguousSpace::object_iterate_from(HeapWord* mark, ObjectClosure* blk) {
642 while (mark < top()) {
643 blk->do_object(cast_to_oop(mark));
644 mark += cast_to_oop(mark)->size();
645 }
646 }
647
648 // Very general, slow implementation.
649 HeapWord* ContiguousSpace::block_start_const(const void* p) const {
650 assert(MemRegion(bottom(), end()).contains(p),
651 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
652 p2i(p), p2i(bottom()), p2i(end()));
653 if (p >= top()) {
654 return top();
655 } else {
656 HeapWord* last = bottom();
657 HeapWord* cur = last;
658 while (cur <= p) {
659 last = cur;
660 cur += cast_to_oop(cur)->size();
661 }
662 assert(oopDesc::is_oop(cast_to_oop(last)), PTR_FORMAT " should be an object start", p2i(last));
663 return last;
664 }
665 }
666
667 size_t ContiguousSpace::block_size(const HeapWord* p) const {
668 assert(MemRegion(bottom(), end()).contains(p),
669 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
670 p2i(p), p2i(bottom()), p2i(end()));
671 HeapWord* current_top = top();
672 assert(p <= current_top,
673 "p > current top - p: " PTR_FORMAT ", current top: " PTR_FORMAT,
674 p2i(p), p2i(current_top));
675 assert(p == current_top || oopDesc::is_oop(cast_to_oop(p)),
676 "p (" PTR_FORMAT ") is not a block start - "
677 "current_top: " PTR_FORMAT ", is_oop: %s",
678 p2i(p), p2i(current_top), BOOL_TO_STR(oopDesc::is_oop(cast_to_oop(p))));
679 if (p < current_top) {
680 return cast_to_oop(p)->size();
681 } else {
682 assert(p == current_top, "just checking");
683 return pointer_delta(end(), (HeapWord*) p);
684 }
685 }
686
687 // This version requires locking.
688 inline HeapWord* ContiguousSpace::allocate_impl(size_t size) {
689 assert(Heap_lock->owned_by_self() ||
690 (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()),
691 "not locked");
692 HeapWord* obj = top();
693 if (pointer_delta(end(), obj) >= size) {
694 HeapWord* new_top = obj + size;
695 set_top(new_top);
696 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
697 return obj;
698 } else {
699 return NULL;
700 }
701 }
702
703 // This version is lock-free.
704 inline HeapWord* ContiguousSpace::par_allocate_impl(size_t size) {
705 do {
706 HeapWord* obj = top();
707 if (pointer_delta(end(), obj) >= size) {
708 HeapWord* new_top = obj + size;
709 HeapWord* result = Atomic::cmpxchg(top_addr(), obj, new_top);
710 // result can be one of two:
711 // the old top value: the exchange succeeded
712 // otherwise: the new value of the top is returned.
713 if (result == obj) {
714 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
715 return obj;
716 }
717 } else {
718 return NULL;
719 }
720 } while (true);
721 }
722
723 // Requires locking.
724 HeapWord* ContiguousSpace::allocate(size_t size) {
725 return allocate_impl(size);
726 }
727
728 // Lock-free.
729 HeapWord* ContiguousSpace::par_allocate(size_t size) {
730 return par_allocate_impl(size);
731 }
732
733 void OffsetTableContigSpace::initialize_threshold() {
734 _offsets.initialize_threshold();
735 }
736
737 void OffsetTableContigSpace::alloc_block(HeapWord* start, HeapWord* end) {
738 _offsets.alloc_block(start, end);
739 }
740
741 OffsetTableContigSpace::OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
742 MemRegion mr) :
743 _offsets(sharedOffsetArray, mr),
744 _par_alloc_lock(Mutex::safepoint, "OffsetTableContigSpaceParAlloc_lock", true)
745 {
746 _offsets.set_contig_space(this);
747 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
748 }
749
750 #define OBJ_SAMPLE_INTERVAL 0
751 #define BLOCK_SAMPLE_INTERVAL 100
752
753 void OffsetTableContigSpace::verify() const {
754 HeapWord* p = bottom();
755 HeapWord* prev_p = NULL;
756 int objs = 0;
757 int blocks = 0;
758
759 if (VerifyObjectStartArray) {
760 _offsets.verify();
761 }
762
763 while (p < top()) {
764 size_t size = cast_to_oop(p)->size();
765 // For a sampling of objects in the space, find it using the
766 // block offset table.
767 if (blocks == BLOCK_SAMPLE_INTERVAL) {
768 guarantee(p == block_start_const(p + (size/2)),
769 "check offset computation");
770 blocks = 0;
771 } else {
772 blocks++;
773 }
774
775 if (objs == OBJ_SAMPLE_INTERVAL) {
776 oopDesc::verify(cast_to_oop(p));
777 objs = 0;
778 } else {
779 objs++;
780 }
781 prev_p = p;
782 p += size;
783 }
784 guarantee(p == top(), "end of last object must match end of space");
785 }
786
787
788 size_t TenuredSpace::allowed_dead_ratio() const {
789 return MarkSweepDeadRatio;
790 }