1 /*
2 * Copyright (c) 1997, 2016, 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/systemDictionary.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "gc/serial/defNewGeneration.hpp"
29 #include "gc/shared/blockOffsetTable.inline.hpp"
30 #include "gc/shared/collectedHeap.inline.hpp"
31 #include "gc/shared/genCollectedHeap.hpp"
32 #include "gc/shared/genOopClosures.inline.hpp"
33 #include "gc/shared/space.hpp"
34 #include "gc/shared/space.inline.hpp"
35 #include "gc/shared/spaceDecorator.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/atomic.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/orderAccess.inline.hpp"
41 #include "runtime/prefetch.inline.hpp"
42 #include "runtime/safepoint.hpp"
43 #include "utilities/copy.hpp"
44 #include "utilities/globalDefinitions.hpp"
45 #include "utilities/macros.hpp"
46
47 HeapWord* DirtyCardToOopClosure::get_actual_top(HeapWord* top,
48 HeapWord* top_obj) {
49 if (top_obj != NULL) {
50 if (_sp->block_is_obj(top_obj)) {
51 if (_precision == CardTableModRefBS::ObjHeadPreciseArray) {
52 if (oop(top_obj)->is_objArray() || 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 // Use the block_size() method of the space over which
60 // the iteration is being done. That space (e.g. CMS) may have
61 // specific requirements on object sizes which will
62 // be reflected in the block_size() method.
63 top = top_obj + oop(top_obj)->size();
64 }
65 }
66 } else {
67 top = top_obj;
68 }
69 } else {
70 assert(top == _sp->end(), "only case where top_obj == NULL");
71 }
72 return top;
73 }
74
75 void DirtyCardToOopClosure::walk_mem_region(MemRegion mr,
76 HeapWord* bottom,
77 HeapWord* top) {
78 // 1. Blocks may or may not be objects.
79 // 2. Even when a block_is_obj(), it may not entirely
80 // occupy the block if the block quantum is larger than
81 // the object size.
82 // We can and should try to optimize by calling the non-MemRegion
83 // version of oop_iterate() for all but the extremal objects
84 // (for which we need to call the MemRegion version of
85 // oop_iterate()) To be done post-beta XXX
86 for (; bottom < top; bottom += _sp->block_size(bottom)) {
87 // As in the case of contiguous space above, we'd like to
88 // just use the value returned by oop_iterate to increment the
89 // current pointer; unfortunately, that won't work in CMS because
90 // we'd need an interface change (it seems) to have the space
91 // "adjust the object size" (for instance pad it up to its
92 // block alignment or minimum block size restrictions. XXX
93 if (_sp->block_is_obj(bottom) &&
94 !_sp->obj_allocated_since_save_marks(oop(bottom))) {
95 oop(bottom)->oop_iterate(_cl, mr);
96 }
97 }
98 }
99
100 // We get called with "mr" representing the dirty region
101 // that we want to process. Because of imprecise marking,
102 // we may need to extend the incoming "mr" to the right,
103 // and scan more. However, because we may already have
104 // scanned some of that extended region, we may need to
105 // trim its right-end back some so we do not scan what
106 // we (or another worker thread) may already have scanned
107 // or planning to scan.
108 void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
109
110 // Some collectors need to do special things whenever their dirty
111 // cards are processed. For instance, CMS must remember mutator updates
112 // (i.e. dirty cards) so as to re-scan mutated objects.
113 // Such work can be piggy-backed here on dirty card scanning, so as to make
114 // it slightly more efficient than doing a complete non-destructive pre-scan
115 // of the card table.
116 MemRegionClosure* pCl = _sp->preconsumptionDirtyCardClosure();
117 if (pCl != NULL) {
118 pCl->do_MemRegion(mr);
119 }
120
121 HeapWord* bottom = mr.start();
122 HeapWord* last = mr.last();
123 HeapWord* top = mr.end();
124 HeapWord* bottom_obj;
125 HeapWord* top_obj;
126
127 assert(_precision == CardTableModRefBS::ObjHeadPreciseArray ||
128 _precision == CardTableModRefBS::Precise,
129 "Only ones we deal with for now.");
130
131 assert(_precision != CardTableModRefBS::ObjHeadPreciseArray ||
132 _cl->idempotent() || _last_bottom == NULL ||
133 top <= _last_bottom,
134 "Not decreasing");
135 NOT_PRODUCT(_last_bottom = mr.start());
136
137 bottom_obj = _sp->block_start(bottom);
138 top_obj = _sp->block_start(last);
139
140 assert(bottom_obj <= bottom, "just checking");
141 assert(top_obj <= top, "just checking");
142
143 // Given what we think is the top of the memory region and
144 // the start of the object at the top, get the actual
145 // value of the top.
146 top = get_actual_top(top, top_obj);
147
148 // If the previous call did some part of this region, don't redo.
149 if (_precision == CardTableModRefBS::ObjHeadPreciseArray &&
150 _min_done != NULL &&
151 _min_done < top) {
152 top = _min_done;
153 }
154
155 // Top may have been reset, and in fact may be below bottom,
156 // e.g. the dirty card region is entirely in a now free object
157 // -- something that could happen with a concurrent sweeper.
158 bottom = MIN2(bottom, top);
159 MemRegion extended_mr = MemRegion(bottom, top);
160 assert(bottom <= top &&
161 (_precision != CardTableModRefBS::ObjHeadPreciseArray ||
162 _min_done == NULL ||
163 top <= _min_done),
164 "overlap!");
165
166 // Walk the region if it is not empty; otherwise there is nothing to do.
167 if (!extended_mr.is_empty()) {
168 walk_mem_region(extended_mr, bottom_obj, top);
169 }
170
171 // An idempotent closure might be applied in any order, so we don't
172 // record a _min_done for it.
173 if (!_cl->idempotent()) {
174 _min_done = bottom;
175 } else {
176 assert(_min_done == _last_explicit_min_done,
177 "Don't update _min_done for idempotent cl");
178 }
179 }
180
181 DirtyCardToOopClosure* Space::new_dcto_cl(ExtendedOopClosure* cl,
182 CardTableModRefBS::PrecisionStyle precision,
183 HeapWord* boundary,
184 bool parallel) {
185 return new DirtyCardToOopClosure(this, cl, precision, boundary);
186 }
187
188 HeapWord* ContiguousSpaceDCTOC::get_actual_top(HeapWord* top,
189 HeapWord* top_obj) {
190 if (top_obj != NULL && top_obj < (_sp->toContiguousSpace())->top()) {
191 if (_precision == CardTableModRefBS::ObjHeadPreciseArray) {
192 if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {
193 // An arrayOop is starting on the dirty card - since we do exact
194 // store checks for objArrays we are done.
195 } else {
196 // Otherwise, it is possible that the object starting on the dirty
197 // card spans the entire card, and that the store happened on a
198 // later card. Figure out where the object ends.
199 assert(_sp->block_size(top_obj) == (size_t) oop(top_obj)->size(),
200 "Block size and object size mismatch");
201 top = top_obj + oop(top_obj)->size();
202 }
203 }
204 } else {
205 top = (_sp->toContiguousSpace())->top();
206 }
207 return top;
208 }
209
210 void FilteringDCTOC::walk_mem_region(MemRegion mr,
211 HeapWord* bottom,
212 HeapWord* top) {
213 // Note that this assumption won't hold if we have a concurrent
214 // collector in this space, which may have freed up objects after
215 // they were dirtied and before the stop-the-world GC that is
216 // examining cards here.
217 assert(bottom < top, "ought to be at least one obj on a dirty card.");
218
219 if (_boundary != NULL) {
220 // We have a boundary outside of which we don't want to look
221 // at objects, so create a filtering closure around the
222 // oop closure before walking the region.
223 FilteringClosure filter(_boundary, _cl);
224 walk_mem_region_with_cl(mr, bottom, top, &filter);
225 } else {
226 // No boundary, simply walk the heap with the oop closure.
227 walk_mem_region_with_cl(mr, bottom, top, _cl);
228 }
229
230 }
231
232 // We must replicate this so that the static type of "FilteringClosure"
233 // (see above) is apparent at the oop_iterate calls.
234 #define ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
235 void ContiguousSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr, \
236 HeapWord* bottom, \
237 HeapWord* top, \
238 ClosureType* cl) { \
239 bottom += oop(bottom)->oop_iterate_size(cl, mr); \
240 if (bottom < top) { \
241 HeapWord* next_obj = bottom + oop(bottom)->size(); \
242 while (next_obj < top) { \
243 /* Bottom lies entirely below top, so we can call the */ \
244 /* non-memRegion version of oop_iterate below. */ \
245 oop(bottom)->oop_iterate(cl); \
246 bottom = next_obj; \
247 next_obj = bottom + oop(bottom)->size(); \
248 } \
249 /* Last object. */ \
250 oop(bottom)->oop_iterate(cl, mr); \
251 } \
252 }
253
254 // (There are only two of these, rather than N, because the split is due
255 // only to the introduction of the FilteringClosure, a local part of the
256 // impl of this abstraction.)
257 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
258 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
259
260 DirtyCardToOopClosure*
261 ContiguousSpace::new_dcto_cl(ExtendedOopClosure* cl,
262 CardTableModRefBS::PrecisionStyle precision,
263 HeapWord* boundary,
264 bool parallel) {
265 return new ContiguousSpaceDCTOC(this, cl, precision, boundary);
266 }
267
268 void Space::initialize(MemRegion mr,
269 bool clear_space,
270 bool mangle_space) {
271 HeapWord* bottom = mr.start();
272 HeapWord* end = mr.end();
273 assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),
274 "invalid space boundaries");
275 set_bottom(bottom);
276 set_end(end);
277 if (clear_space) clear(mangle_space);
278 }
279
280 void Space::clear(bool mangle_space) {
281 if (ZapUnusedHeapArea && mangle_space) {
282 mangle_unused_area();
283 }
284 }
285
286 ContiguousSpace::ContiguousSpace(): CompactibleSpace(), _top(NULL),
287 _concurrent_iteration_safe_limit(NULL) {
288 _mangler = new GenSpaceMangler(this);
289 }
290
291 ContiguousSpace::~ContiguousSpace() {
292 delete _mangler;
293 }
294
295 void ContiguousSpace::initialize(MemRegion mr,
296 bool clear_space,
297 bool mangle_space)
298 {
299 CompactibleSpace::initialize(mr, clear_space, mangle_space);
300 set_concurrent_iteration_safe_limit(top());
301 }
302
303 void ContiguousSpace::clear(bool mangle_space) {
304 set_top(bottom());
305 set_saved_mark();
306 CompactibleSpace::clear(mangle_space);
307 }
308
309 bool ContiguousSpace::is_free_block(const HeapWord* p) const {
310 return p >= _top;
311 }
312
313 void OffsetTableContigSpace::clear(bool mangle_space) {
314 ContiguousSpace::clear(mangle_space);
315 _offsets.initialize_threshold();
316 }
317
318 void OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
319 Space::set_bottom(new_bottom);
320 _offsets.set_bottom(new_bottom);
321 }
322
323 void OffsetTableContigSpace::set_end(HeapWord* new_end) {
324 // Space should not advertise an increase in size
325 // until after the underlying offset table has been enlarged.
326 _offsets.resize(pointer_delta(new_end, bottom()));
327 Space::set_end(new_end);
328 }
329
330 #ifndef PRODUCT
331
332 void ContiguousSpace::set_top_for_allocations(HeapWord* v) {
333 mangler()->set_top_for_allocations(v);
334 }
335 void ContiguousSpace::set_top_for_allocations() {
336 mangler()->set_top_for_allocations(top());
337 }
338 void ContiguousSpace::check_mangled_unused_area(HeapWord* limit) {
339 mangler()->check_mangled_unused_area(limit);
340 }
341
342 void ContiguousSpace::check_mangled_unused_area_complete() {
343 mangler()->check_mangled_unused_area_complete();
344 }
345
346 // Mangled only the unused space that has not previously
347 // been mangled and that has not been allocated since being
348 // mangled.
349 void ContiguousSpace::mangle_unused_area() {
350 mangler()->mangle_unused_area();
351 }
352 void ContiguousSpace::mangle_unused_area_complete() {
353 mangler()->mangle_unused_area_complete();
354 }
355 #endif // NOT_PRODUCT
356
357 void CompactibleSpace::initialize(MemRegion mr,
358 bool clear_space,
359 bool mangle_space) {
360 Space::initialize(mr, clear_space, mangle_space);
361 set_compaction_top(bottom());
362 _next_compaction_space = NULL;
363 }
364
365 void CompactibleSpace::clear(bool mangle_space) {
366 Space::clear(mangle_space);
367 _compaction_top = bottom();
368 }
369
370 HeapWord* CompactibleSpace::forward(oop q, size_t size,
371 CompactPoint* cp, HeapWord* compact_top) {
372 // q is alive
373 // First check if we should switch compaction space
374 assert(this == cp->space, "'this' should be current compaction space.");
375 size_t compaction_max_size = pointer_delta(end(), compact_top);
376 while (size > compaction_max_size) {
377 // switch to next compaction space
378 cp->space->set_compaction_top(compact_top);
379 cp->space = cp->space->next_compaction_space();
380 if (cp->space == NULL) {
381 cp->gen = GenCollectedHeap::heap()->young_gen();
382 assert(cp->gen != NULL, "compaction must succeed");
383 cp->space = cp->gen->first_compaction_space();
384 assert(cp->space != NULL, "generation must have a first compaction space");
385 }
386 compact_top = cp->space->bottom();
387 cp->space->set_compaction_top(compact_top);
388 cp->threshold = cp->space->initialize_threshold();
389 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
390 }
391
392 // store the forwarding pointer into the mark word
393 if ((HeapWord*)q != compact_top) {
394 q->forward_to(oop(compact_top));
395 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
396 } else {
397 // if the object isn't moving we can just set the mark to the default
398 // mark and handle it specially later on.
399 q->init_mark();
400 assert(q->forwardee() == NULL, "should be forwarded to NULL");
401 }
402
403 compact_top += size;
404
405 // we need to update the offset table so that the beginnings of objects can be
406 // found during scavenge. Note that we are updating the offset table based on
407 // where the object will be once the compaction phase finishes.
408 if (compact_top > cp->threshold)
409 cp->threshold =
410 cp->space->cross_threshold(compact_top - size, compact_top);
411 return compact_top;
412 }
413
414 void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {
415 scan_and_forward(this, cp);
416 }
417
418 void CompactibleSpace::adjust_pointers() {
419 // Check first is there is any work to do.
420 if (used() == 0) {
421 return; // Nothing to do.
422 }
423
424 scan_and_adjust_pointers(this);
425 }
426
427 void CompactibleSpace::compact() {
428 scan_and_compact(this);
429 }
430
431 void Space::print_short() const { print_short_on(tty); }
432
433 void Space::print_short_on(outputStream* st) const {
434 st->print(" space " SIZE_FORMAT "K, %3d%% used", capacity() / K,
435 (int) ((double) used() * 100 / capacity()));
436 }
437
438 void Space::print() const { print_on(tty); }
439
440 void Space::print_on(outputStream* st) const {
441 print_short_on(st);
442 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ")",
443 p2i(bottom()), p2i(end()));
444 }
445
446 void ContiguousSpace::print_on(outputStream* st) const {
447 print_short_on(st);
448 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
449 p2i(bottom()), p2i(top()), p2i(end()));
450 }
451
452 void OffsetTableContigSpace::print_on(outputStream* st) const {
453 print_short_on(st);
454 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
455 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
456 p2i(bottom()), p2i(top()), p2i(_offsets.threshold()), p2i(end()));
457 }
458
459 void ContiguousSpace::verify() const {
460 HeapWord* p = bottom();
461 HeapWord* t = top();
462 HeapWord* prev_p = NULL;
463 while (p < t) {
464 oop(p)->verify();
465 prev_p = p;
466 p += oop(p)->size();
467 }
468 guarantee(p == top(), "end of last object must match end of space");
469 if (top() != end()) {
470 guarantee(top() == block_start_const(end()-1) &&
471 top() == block_start_const(top()),
472 "top should be start of unallocated block, if it exists");
473 }
474 }
475
476 void Space::oop_iterate(ExtendedOopClosure* blk) {
477 ObjectToOopClosure blk2(blk);
478 object_iterate(&blk2);
479 }
480
481 bool Space::obj_is_alive(const HeapWord* p) const {
482 assert (block_is_obj(p), "The address should point to an object");
483 return true;
484 }
485
486 #if INCLUDE_ALL_GCS
487 #define ContigSpace_PAR_OOP_ITERATE_DEFN(OopClosureType, nv_suffix) \
488 \
489 void ContiguousSpace::par_oop_iterate(MemRegion mr, OopClosureType* blk) {\
490 HeapWord* obj_addr = mr.start(); \
491 HeapWord* t = mr.end(); \
492 while (obj_addr < t) { \
493 assert(oop(obj_addr)->is_oop(), "Should be an oop"); \
494 obj_addr += oop(obj_addr)->oop_iterate_size(blk); \
495 } \
496 }
497
498 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DEFN)
499
500 #undef ContigSpace_PAR_OOP_ITERATE_DEFN
501 #endif // INCLUDE_ALL_GCS
502
503 void ContiguousSpace::oop_iterate(ExtendedOopClosure* blk) {
504 if (is_empty()) return;
505 HeapWord* obj_addr = bottom();
506 HeapWord* t = top();
507 // Could call objects iterate, but this is easier.
508 while (obj_addr < t) {
509 obj_addr += oop(obj_addr)->oop_iterate_size(blk);
510 }
511 }
512
513 void ContiguousSpace::object_iterate(ObjectClosure* blk) {
514 if (is_empty()) return;
515 object_iterate_from(bottom(), blk);
516 }
517
518 // For a ContiguousSpace object_iterate() and safe_object_iterate()
519 // are the same.
520 void ContiguousSpace::safe_object_iterate(ObjectClosure* blk) {
521 object_iterate(blk);
522 }
523
524 void ContiguousSpace::object_iterate_from(HeapWord* mark, ObjectClosure* blk) {
525 while (mark < top()) {
526 blk->do_object(oop(mark));
527 mark += oop(mark)->size();
528 }
529 }
530
531 HeapWord*
532 ContiguousSpace::object_iterate_careful(ObjectClosureCareful* blk) {
533 HeapWord * limit = concurrent_iteration_safe_limit();
534 assert(limit <= top(), "sanity check");
535 for (HeapWord* p = bottom(); p < limit;) {
536 size_t size = blk->do_object_careful(oop(p));
537 if (size == 0) {
538 return p; // failed at p
539 } else {
540 p += size;
541 }
542 }
543 return NULL; // all done
544 }
545
546 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
547 \
548 void ContiguousSpace:: \
549 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
550 HeapWord* t; \
551 HeapWord* p = saved_mark_word(); \
552 assert(p != NULL, "expected saved mark"); \
553 \
554 const intx interval = PrefetchScanIntervalInBytes; \
555 do { \
556 t = top(); \
557 while (p < t) { \
558 Prefetch::write(p, interval); \
559 debug_only(HeapWord* prev = p); \
560 oop m = oop(p); \
561 p += m->oop_iterate_size(blk); \
562 } \
563 } while (t < top()); \
564 \
565 set_saved_mark_word(p); \
566 }
567
568 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN)
569
570 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN
571
572 // Very general, slow implementation.
573 HeapWord* ContiguousSpace::block_start_const(const void* p) const {
574 assert(MemRegion(bottom(), end()).contains(p),
575 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
576 p2i(p), p2i(bottom()), p2i(end()));
577 if (p >= top()) {
578 return top();
579 } else {
580 HeapWord* last = bottom();
581 HeapWord* cur = last;
582 while (cur <= p) {
583 last = cur;
584 cur += oop(cur)->size();
585 }
586 assert(oop(last)->is_oop(), PTR_FORMAT " should be an object start", p2i(last));
587 return last;
588 }
589 }
590
591 size_t ContiguousSpace::block_size(const HeapWord* p) const {
592 assert(MemRegion(bottom(), end()).contains(p),
593 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
594 p2i(p), p2i(bottom()), p2i(end()));
595 HeapWord* current_top = top();
596 assert(p <= current_top,
597 "p > current top - p: " PTR_FORMAT ", current top: " PTR_FORMAT,
598 p2i(p), p2i(current_top));
599 assert(p == current_top || oop(p)->is_oop(),
600 "p (" PTR_FORMAT ") is not a block start - "
601 "current_top: " PTR_FORMAT ", is_oop: %s",
602 p2i(p), p2i(current_top), BOOL_TO_STR(oop(p)->is_oop()));
603 if (p < current_top) {
604 return oop(p)->size();
605 } else {
606 assert(p == current_top, "just checking");
607 return pointer_delta(end(), (HeapWord*) p);
608 }
609 }
610
611 // This version requires locking.
612 inline HeapWord* ContiguousSpace::allocate_impl(size_t size) {
613 assert(Heap_lock->owned_by_self() ||
614 (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()),
615 "not locked");
616 HeapWord* obj = top();
617 if (pointer_delta(end(), obj) >= size) {
618 HeapWord* new_top = obj + size;
619 set_top(new_top);
620 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
621 return obj;
622 } else {
623 return NULL;
624 }
625 }
626
627 // This version is lock-free.
628 inline HeapWord* ContiguousSpace::par_allocate_impl(size_t size) {
629 do {
630 HeapWord* obj = top();
631 if (pointer_delta(end(), obj) >= size) {
632 HeapWord* new_top = obj + size;
633 HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
634 // result can be one of two:
635 // the old top value: the exchange succeeded
636 // otherwise: the new value of the top is returned.
637 if (result == obj) {
638 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
639 return obj;
640 }
641 } else {
642 return NULL;
643 }
644 } while (true);
645 }
646
647 HeapWord* ContiguousSpace::allocate_aligned(size_t size) {
648 assert(Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()), "not locked");
649 HeapWord* end_value = end();
650
651 HeapWord* obj = CollectedHeap::align_allocation_or_fail(top(), end_value, SurvivorAlignmentInBytes);
652 if (obj == NULL) {
653 return NULL;
654 }
655
656 if (pointer_delta(end_value, obj) >= size) {
657 HeapWord* new_top = obj + size;
658 set_top(new_top);
659 assert(::is_aligned(obj, SurvivorAlignmentInBytes) && is_aligned(new_top),
660 "checking alignment");
661 return obj;
662 } else {
663 set_top(obj);
664 return NULL;
665 }
666 }
667
668 // Requires locking.
669 HeapWord* ContiguousSpace::allocate(size_t size) {
670 return allocate_impl(size);
671 }
672
673 // Lock-free.
674 HeapWord* ContiguousSpace::par_allocate(size_t size) {
675 return par_allocate_impl(size);
676 }
677
678 void ContiguousSpace::allocate_temporary_filler(int factor) {
679 // allocate temporary type array decreasing free size with factor 'factor'
680 assert(factor >= 0, "just checking");
681 size_t size = pointer_delta(end(), top());
682
683 // if space is full, return
684 if (size == 0) return;
685
686 if (factor > 0) {
687 size -= size/factor;
688 }
689 size = align_object_size(size);
690
691 const size_t array_header_size = typeArrayOopDesc::header_size(T_INT);
692 if (size >= align_object_size(array_header_size)) {
693 size_t length = (size - array_header_size) * (HeapWordSize / sizeof(jint));
694 // allocate uninitialized int array
695 typeArrayOop t = (typeArrayOop) allocate(size);
696 assert(t != NULL, "allocation should succeed");
697 t->set_mark(markOopDesc::prototype());
698 t->set_klass(Universe::intArrayKlassObj());
699 t->set_length((int)length);
700 } else {
701 assert(size == CollectedHeap::min_fill_size(),
702 "size for smallest fake object doesn't match");
703 instanceOop obj = (instanceOop) allocate(size);
704 obj->set_mark(markOopDesc::prototype());
705 obj->set_klass_gap(0);
706 obj->set_klass(SystemDictionary::Object_klass());
707 }
708 }
709
710 HeapWord* OffsetTableContigSpace::initialize_threshold() {
711 return _offsets.initialize_threshold();
712 }
713
714 HeapWord* OffsetTableContigSpace::cross_threshold(HeapWord* start, HeapWord* end) {
715 _offsets.alloc_block(start, end);
716 return _offsets.threshold();
717 }
718
719 OffsetTableContigSpace::OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
720 MemRegion mr) :
721 _offsets(sharedOffsetArray, mr),
722 _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true)
723 {
724 _offsets.set_contig_space(this);
725 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
726 }
727
728 #define OBJ_SAMPLE_INTERVAL 0
729 #define BLOCK_SAMPLE_INTERVAL 100
730
731 void OffsetTableContigSpace::verify() const {
732 HeapWord* p = bottom();
733 HeapWord* prev_p = NULL;
734 int objs = 0;
735 int blocks = 0;
736
737 if (VerifyObjectStartArray) {
738 _offsets.verify();
739 }
740
741 while (p < top()) {
742 size_t size = oop(p)->size();
743 // For a sampling of objects in the space, find it using the
744 // block offset table.
745 if (blocks == BLOCK_SAMPLE_INTERVAL) {
746 guarantee(p == block_start_const(p + (size/2)),
747 "check offset computation");
748 blocks = 0;
749 } else {
750 blocks++;
751 }
752
753 if (objs == OBJ_SAMPLE_INTERVAL) {
754 oop(p)->verify();
755 objs = 0;
756 } else {
757 objs++;
758 }
759 prev_p = p;
760 p += size;
761 }
762 guarantee(p == top(), "end of last object must match end of space");
763 }
764
765
766 size_t TenuredSpace::allowed_dead_ratio() const {
767 return MarkSweepDeadRatio;
768 }