1 /*
2 * Copyright (c) 2001, 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.
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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
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc/cms/cmsLockVerifier.hpp"
27 #include "gc/cms/compactibleFreeListSpace.hpp"
28 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
29 #include "gc/cms/concurrentMarkSweepThread.hpp"
30 #include "gc/shared/blockOffsetTable.inline.hpp"
31 #include "gc/shared/collectedHeap.inline.hpp"
32 #include "gc/shared/genCollectedHeap.hpp"
33 #include "gc/shared/space.inline.hpp"
34 #include "gc/shared/spaceDecorator.hpp"
35 #include "logging/logStream.inline.hpp"
36 #include "memory/allocation.inline.hpp"
37 #include "memory/resourceArea.hpp"
38 #include "memory/universe.inline.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/globals.hpp"
41 #include "runtime/handles.inline.hpp"
42 #include "runtime/init.hpp"
43 #include "runtime/java.hpp"
44 #include "runtime/orderAccess.inline.hpp"
45 #include "runtime/vmThread.hpp"
46 #include "utilities/copy.hpp"
47
48 /////////////////////////////////////////////////////////////////////////
49 //// CompactibleFreeListSpace
50 /////////////////////////////////////////////////////////////////////////
51
52 // highest ranked free list lock rank
53 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
54
55 // Defaults are 0 so things will break badly if incorrectly initialized.
56 size_t CompactibleFreeListSpace::IndexSetStart = 0;
57 size_t CompactibleFreeListSpace::IndexSetStride = 0;
58
59 size_t MinChunkSize = 0;
60
61 void CompactibleFreeListSpace::set_cms_values() {
62 // Set CMS global values
63 assert(MinChunkSize == 0, "already set");
64
65 // MinChunkSize should be a multiple of MinObjAlignment and be large enough
66 // for chunks to contain a FreeChunk.
67 size_t min_chunk_size_in_bytes = align_size_up(sizeof(FreeChunk), MinObjAlignmentInBytes);
68 MinChunkSize = min_chunk_size_in_bytes / BytesPerWord;
69
70 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
71 IndexSetStart = MinChunkSize;
72 IndexSetStride = MinObjAlignment;
73 }
74
75 // Constructor
76 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr) :
77 _bt(bs, mr),
78 // free list locks are in the range of values taken by _lockRank
79 // This range currently is [_leaf+2, _leaf+3]
80 // Note: this requires that CFLspace c'tors
81 // are called serially in the order in which the locks are
82 // are acquired in the program text. This is true today.
83 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true,
84 Monitor::_safepoint_check_sometimes),
85 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
86 "CompactibleFreeListSpace._dict_par_lock", true,
87 Monitor::_safepoint_check_never),
88 _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
89 CMSRescanMultiple),
90 _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
91 CMSConcMarkMultiple),
92 _collector(NULL),
93 _preconsumptionDirtyCardClosure(NULL)
94 {
95 assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize,
96 "FreeChunk is larger than expected");
97 _bt.set_space(this);
98 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
99
100 _dictionary = new AFLBinaryTreeDictionary(mr);
101
102 assert(_dictionary != NULL, "CMS dictionary initialization");
103 // The indexed free lists are initially all empty and are lazily
104 // filled in on demand. Initialize the array elements to NULL.
105 initializeIndexedFreeListArray();
106
107 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
108 SmallForLinearAlloc);
109
110 // CMSIndexedFreeListReplenish should be at least 1
111 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
112 _promoInfo.setSpace(this);
113 if (UseCMSBestFit) {
114 _fitStrategy = FreeBlockBestFitFirst;
115 } else {
116 _fitStrategy = FreeBlockStrategyNone;
117 }
118 check_free_list_consistency();
119
120 // Initialize locks for parallel case.
121 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
122 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
123 "a freelist par lock", true, Mutex::_safepoint_check_sometimes);
124 DEBUG_ONLY(
125 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
126 )
127 }
128 _dictionary->set_par_lock(&_parDictionaryAllocLock);
129 }
130
131 // Like CompactibleSpace forward() but always calls cross_threshold() to
132 // update the block offset table. Removed initialize_threshold call because
133 // CFLS does not use a block offset array for contiguous spaces.
134 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
135 CompactPoint* cp, HeapWord* compact_top) {
136 // q is alive
137 // First check if we should switch compaction space
138 assert(this == cp->space, "'this' should be current compaction space.");
139 size_t compaction_max_size = pointer_delta(end(), compact_top);
140 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
141 "virtual adjustObjectSize_v() method is not correct");
142 size_t adjusted_size = adjustObjectSize(size);
143 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
144 "no small fragments allowed");
145 assert(minimum_free_block_size() == MinChunkSize,
146 "for de-virtualized reference below");
147 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
148 if (adjusted_size + MinChunkSize > compaction_max_size &&
149 adjusted_size != compaction_max_size) {
150 do {
151 // switch to next compaction space
152 cp->space->set_compaction_top(compact_top);
153 cp->space = cp->space->next_compaction_space();
154 if (cp->space == NULL) {
155 cp->gen = GenCollectedHeap::heap()->young_gen();
156 assert(cp->gen != NULL, "compaction must succeed");
157 cp->space = cp->gen->first_compaction_space();
158 assert(cp->space != NULL, "generation must have a first compaction space");
159 }
160 compact_top = cp->space->bottom();
161 cp->space->set_compaction_top(compact_top);
162 // The correct adjusted_size may not be the same as that for this method
163 // (i.e., cp->space may no longer be "this" so adjust the size again.
164 // Use the virtual method which is not used above to save the virtual
165 // dispatch.
166 adjusted_size = cp->space->adjust_object_size_v(size);
167 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
168 assert(cp->space->minimum_free_block_size() == 0, "just checking");
169 } while (adjusted_size > compaction_max_size);
170 }
171
172 // store the forwarding pointer into the mark word
173 if ((HeapWord*)q != compact_top) {
174 q->forward_to(oop(compact_top));
175 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
176 } else {
177 // if the object isn't moving we can just set the mark to the default
178 // mark and handle it specially later on.
179 q->init_mark();
180 assert(q->forwardee() == NULL, "should be forwarded to NULL");
181 }
182
183 compact_top += adjusted_size;
184
185 // we need to update the offset table so that the beginnings of objects can be
186 // found during scavenge. Note that we are updating the offset table based on
187 // where the object will be once the compaction phase finishes.
188
189 // Always call cross_threshold(). A contiguous space can only call it when
190 // the compaction_top exceeds the current threshold but not for an
191 // non-contiguous space.
192 cp->threshold =
193 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
194 return compact_top;
195 }
196
197 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
198 // and use of single_block instead of alloc_block. The name here is not really
199 // appropriate - maybe a more general name could be invented for both the
200 // contiguous and noncontiguous spaces.
201
202 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
203 _bt.single_block(start, the_end);
204 return end();
205 }
206
207 // Initialize them to NULL.
208 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
209 for (size_t i = 0; i < IndexSetSize; i++) {
210 // Note that on platforms where objects are double word aligned,
211 // the odd array elements are not used. It is convenient, however,
212 // to map directly from the object size to the array element.
213 _indexedFreeList[i].reset(IndexSetSize);
214 _indexedFreeList[i].set_size(i);
215 assert(_indexedFreeList[i].count() == 0, "reset check failed");
216 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
217 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
218 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
219 }
220 }
221
222 size_t CompactibleFreeListSpace::obj_size(const HeapWord* addr) const {
223 return adjustObjectSize(oop(addr)->size());
224 }
225
226 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
227 for (size_t i = 1; i < IndexSetSize; i++) {
228 assert(_indexedFreeList[i].size() == (size_t) i,
229 "Indexed free list sizes are incorrect");
230 _indexedFreeList[i].reset(IndexSetSize);
231 assert(_indexedFreeList[i].count() == 0, "reset check failed");
232 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
233 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
234 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
235 }
236 }
237
238 void CompactibleFreeListSpace::reset(MemRegion mr) {
239 resetIndexedFreeListArray();
240 dictionary()->reset();
241 if (BlockOffsetArrayUseUnallocatedBlock) {
242 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
243 // Everything's allocated until proven otherwise.
244 _bt.set_unallocated_block(end());
245 }
246 if (!mr.is_empty()) {
247 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
248 _bt.single_block(mr.start(), mr.word_size());
249 FreeChunk* fc = (FreeChunk*) mr.start();
250 fc->set_size(mr.word_size());
251 if (mr.word_size() >= IndexSetSize ) {
252 returnChunkToDictionary(fc);
253 } else {
254 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
255 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc);
256 }
257 coalBirth(mr.word_size());
258 }
259 _promoInfo.reset();
260 _smallLinearAllocBlock._ptr = NULL;
261 _smallLinearAllocBlock._word_size = 0;
262 }
263
264 void CompactibleFreeListSpace::reset_after_compaction() {
265 // Reset the space to the new reality - one free chunk.
266 MemRegion mr(compaction_top(), end());
267 reset(mr);
268 // Now refill the linear allocation block(s) if possible.
269 refillLinearAllocBlocksIfNeeded();
270 }
271
272 // Walks the entire dictionary, returning a coterminal
273 // chunk, if it exists. Use with caution since it involves
274 // a potentially complete walk of a potentially large tree.
275 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
276
277 assert_lock_strong(&_freelistLock);
278
279 return dictionary()->find_chunk_ends_at(end());
280 }
281
282
283 #ifndef PRODUCT
284 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
285 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
286 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
287 }
288 }
289
290 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
291 size_t sum = 0;
292 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
293 sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
294 }
295 return sum;
296 }
297
298 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
299 size_t count = 0;
300 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
301 debug_only(
302 ssize_t total_list_count = 0;
303 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
304 fc = fc->next()) {
305 total_list_count++;
306 }
307 assert(total_list_count == _indexedFreeList[i].count(),
308 "Count in list is incorrect");
309 )
310 count += _indexedFreeList[i].count();
311 }
312 return count;
313 }
314
315 size_t CompactibleFreeListSpace::totalCount() {
316 size_t num = totalCountInIndexedFreeLists();
317 num += dictionary()->total_count();
318 if (_smallLinearAllocBlock._word_size != 0) {
319 num++;
320 }
321 return num;
322 }
323 #endif
324
325 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
326 FreeChunk* fc = (FreeChunk*) p;
327 return fc->is_free();
328 }
329
330 size_t CompactibleFreeListSpace::used() const {
331 return capacity() - free();
332 }
333
334 size_t CompactibleFreeListSpace::free() const {
335 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
336 // if you do this while the structures are in flux you
337 // may get an approximate answer only; for instance
338 // because there is concurrent allocation either
339 // directly by mutators or for promotion during a GC.
340 // It's "MT-safe", however, in the sense that you are guaranteed
341 // not to crash and burn, for instance, because of walking
342 // pointers that could disappear as you were walking them.
343 // The approximation is because the various components
344 // that are read below are not read atomically (and
345 // further the computation of totalSizeInIndexedFreeLists()
346 // is itself a non-atomic computation. The normal use of
347 // this is during a resize operation at the end of GC
348 // and at that time you are guaranteed to get the
349 // correct actual value. However, for instance, this is
350 // also read completely asynchronously by the "perf-sampler"
351 // that supports jvmstat, and you are apt to see the values
352 // flicker in such cases.
353 assert(_dictionary != NULL, "No _dictionary?");
354 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
355 totalSizeInIndexedFreeLists() +
356 _smallLinearAllocBlock._word_size) * HeapWordSize;
357 }
358
359 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
360 assert(_dictionary != NULL, "No _dictionary?");
361 assert_locked();
362 size_t res = _dictionary->max_chunk_size();
363 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
364 (size_t) SmallForLinearAlloc - 1));
365 // XXX the following could potentially be pretty slow;
366 // should one, pessimistically for the rare cases when res
367 // calculated above is less than IndexSetSize,
368 // just return res calculated above? My reasoning was that
369 // those cases will be so rare that the extra time spent doesn't
370 // really matter....
371 // Note: do not change the loop test i >= res + IndexSetStride
372 // to i > res below, because i is unsigned and res may be zero.
373 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
374 i -= IndexSetStride) {
375 if (_indexedFreeList[i].head() != NULL) {
376 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
377 return i;
378 }
379 }
380 return res;
381 }
382
383 void LinearAllocBlock::print_on(outputStream* st) const {
384 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
385 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
386 p2i(_ptr), _word_size, _refillSize, _allocation_size_limit);
387 }
388
389 void CompactibleFreeListSpace::print_on(outputStream* st) const {
390 st->print_cr("COMPACTIBLE FREELIST SPACE");
391 st->print_cr(" Space:");
392 Space::print_on(st);
393
394 st->print_cr("promoInfo:");
395 _promoInfo.print_on(st);
396
397 st->print_cr("_smallLinearAllocBlock");
398 _smallLinearAllocBlock.print_on(st);
399
400 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
401
402 st->print_cr(" _fitStrategy = %s", BOOL_TO_STR(_fitStrategy));
403 }
404
405 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
406 const {
407 reportIndexedFreeListStatistics(st);
408 st->print_cr("Layout of Indexed Freelists");
409 st->print_cr("---------------------------");
410 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
411 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
412 _indexedFreeList[i].print_on(st);
413 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) {
414 st->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
415 p2i(fc), p2i((HeapWord*)fc + i),
416 fc->cantCoalesce() ? "\t CC" : "");
417 }
418 }
419 }
420
421 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
422 const {
423 _promoInfo.print_on(st);
424 }
425
426 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
427 const {
428 _dictionary->report_statistics(st);
429 st->print_cr("Layout of Freelists in Tree");
430 st->print_cr("---------------------------");
431 _dictionary->print_free_lists(st);
432 }
433
434 class BlkPrintingClosure: public BlkClosure {
435 const CMSCollector* _collector;
436 const CompactibleFreeListSpace* _sp;
437 const CMSBitMap* _live_bit_map;
438 const bool _post_remark;
439 outputStream* _st;
440 public:
441 BlkPrintingClosure(const CMSCollector* collector,
442 const CompactibleFreeListSpace* sp,
443 const CMSBitMap* live_bit_map,
444 outputStream* st):
445 _collector(collector),
446 _sp(sp),
447 _live_bit_map(live_bit_map),
448 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
449 _st(st) { }
450 size_t do_blk(HeapWord* addr);
451 };
452
453 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
454 size_t sz = _sp->block_size_no_stall(addr, _collector);
455 assert(sz != 0, "Should always be able to compute a size");
456 if (_sp->block_is_obj(addr)) {
457 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
458 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
459 p2i(addr),
460 dead ? "dead" : "live",
461 sz,
462 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
463 if (CMSPrintObjectsInDump && !dead) {
464 oop(addr)->print_on(_st);
465 _st->print_cr("--------------------------------------");
466 }
467 } else { // free block
468 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
469 p2i(addr), sz, CMSPrintChunksInDump ? ":" : ".");
470 if (CMSPrintChunksInDump) {
471 ((FreeChunk*)addr)->print_on(_st);
472 _st->print_cr("--------------------------------------");
473 }
474 }
475 return sz;
476 }
477
478 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st) {
479 st->print_cr("=========================");
480 st->print_cr("Block layout in CMS Heap:");
481 st->print_cr("=========================");
482 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
483 blk_iterate(&bpcl);
484
485 st->print_cr("=======================================");
486 st->print_cr("Order & Layout of Promotion Info Blocks");
487 st->print_cr("=======================================");
488 print_promo_info_blocks(st);
489
490 st->print_cr("===========================");
491 st->print_cr("Order of Indexed Free Lists");
492 st->print_cr("=========================");
493 print_indexed_free_lists(st);
494
495 st->print_cr("=================================");
496 st->print_cr("Order of Free Lists in Dictionary");
497 st->print_cr("=================================");
498 print_dictionary_free_lists(st);
499 }
500
501
502 void CompactibleFreeListSpace::reportFreeListStatistics(const char* title) const {
503 assert_lock_strong(&_freelistLock);
504 Log(gc, freelist, stats) log;
505 if (!log.is_debug()) {
506 return;
507 }
508 log.debug("%s", title);
509
510 LogStream out(log.debug());
511 _dictionary->report_statistics(&out);
512
513 if (log.is_trace()) {
514 ResourceMark rm;
515 reportIndexedFreeListStatistics(log.trace_stream());
516 size_t total_size = totalSizeInIndexedFreeLists() +
517 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
518 log.trace(" free=" SIZE_FORMAT " frag=%1.4f", total_size, flsFrag());
519 }
520 }
521
522 void CompactibleFreeListSpace::reportIndexedFreeListStatistics(outputStream* st) const {
523 assert_lock_strong(&_freelistLock);
524 st->print_cr("Statistics for IndexedFreeLists:");
525 st->print_cr("--------------------------------");
526 size_t total_size = totalSizeInIndexedFreeLists();
527 size_t free_blocks = numFreeBlocksInIndexedFreeLists();
528 st->print_cr("Total Free Space: " SIZE_FORMAT, total_size);
529 st->print_cr("Max Chunk Size: " SIZE_FORMAT, maxChunkSizeInIndexedFreeLists());
530 st->print_cr("Number of Blocks: " SIZE_FORMAT, free_blocks);
531 if (free_blocks != 0) {
532 st->print_cr("Av. Block Size: " SIZE_FORMAT, total_size/free_blocks);
533 }
534 }
535
536 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
537 size_t res = 0;
538 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
539 debug_only(
540 ssize_t recount = 0;
541 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
542 fc = fc->next()) {
543 recount += 1;
544 }
545 assert(recount == _indexedFreeList[i].count(),
546 "Incorrect count in list");
547 )
548 res += _indexedFreeList[i].count();
549 }
550 return res;
551 }
552
553 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
554 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
555 if (_indexedFreeList[i].head() != NULL) {
556 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
557 return (size_t)i;
558 }
559 }
560 return 0;
561 }
562
563 void CompactibleFreeListSpace::set_end(HeapWord* value) {
564 HeapWord* prevEnd = end();
565 assert(prevEnd != value, "unnecessary set_end call");
566 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
567 "New end is below unallocated block");
568 _end = value;
569 if (prevEnd != NULL) {
570 // Resize the underlying block offset table.
571 _bt.resize(pointer_delta(value, bottom()));
572 if (value <= prevEnd) {
573 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
574 "New end is below unallocated block");
575 } else {
576 // Now, take this new chunk and add it to the free blocks.
577 // Note that the BOT has not yet been updated for this block.
578 size_t newFcSize = pointer_delta(value, prevEnd);
579 // Add the block to the free lists, if possible coalescing it
580 // with the last free block, and update the BOT and census data.
581 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
582 }
583 }
584 }
585
586 class FreeListSpaceDCTOC : public FilteringDCTOC {
587 CompactibleFreeListSpace* _cfls;
588 CMSCollector* _collector;
589 bool _parallel;
590 protected:
591 // Override.
592 #define walk_mem_region_with_cl_DECL(ClosureType) \
593 virtual void walk_mem_region_with_cl(MemRegion mr, \
594 HeapWord* bottom, HeapWord* top, \
595 ClosureType* cl); \
596 void walk_mem_region_with_cl_par(MemRegion mr, \
597 HeapWord* bottom, HeapWord* top, \
598 ClosureType* cl); \
599 void walk_mem_region_with_cl_nopar(MemRegion mr, \
600 HeapWord* bottom, HeapWord* top, \
601 ClosureType* cl)
602 walk_mem_region_with_cl_DECL(ExtendedOopClosure);
603 walk_mem_region_with_cl_DECL(FilteringClosure);
604
605 public:
606 FreeListSpaceDCTOC(CompactibleFreeListSpace* sp,
607 CMSCollector* collector,
608 ExtendedOopClosure* cl,
609 CardTableModRefBS::PrecisionStyle precision,
610 HeapWord* boundary,
611 bool parallel) :
612 FilteringDCTOC(sp, cl, precision, boundary),
613 _cfls(sp), _collector(collector), _parallel(parallel) {}
614 };
615
616 // We de-virtualize the block-related calls below, since we know that our
617 // space is a CompactibleFreeListSpace.
618
619 #define FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
620 void FreeListSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr, \
621 HeapWord* bottom, \
622 HeapWord* top, \
623 ClosureType* cl) { \
624 if (_parallel) { \
625 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
626 } else { \
627 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
628 } \
629 } \
630 void FreeListSpaceDCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
631 HeapWord* bottom, \
632 HeapWord* top, \
633 ClosureType* cl) { \
634 /* Skip parts that are before "mr", in case "block_start" sent us \
635 back too far. */ \
636 HeapWord* mr_start = mr.start(); \
637 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
638 HeapWord* next = bottom + bot_size; \
639 while (next < mr_start) { \
640 bottom = next; \
641 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
642 next = bottom + bot_size; \
643 } \
644 \
645 while (bottom < top) { \
646 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
647 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
648 oop(bottom)) && \
649 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
650 size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
651 bottom += _cfls->adjustObjectSize(word_sz); \
652 } else { \
653 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
654 } \
655 } \
656 } \
657 void FreeListSpaceDCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
658 HeapWord* bottom, \
659 HeapWord* top, \
660 ClosureType* cl) { \
661 /* Skip parts that are before "mr", in case "block_start" sent us \
662 back too far. */ \
663 HeapWord* mr_start = mr.start(); \
664 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
665 HeapWord* next = bottom + bot_size; \
666 while (next < mr_start) { \
667 bottom = next; \
668 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
669 next = bottom + bot_size; \
670 } \
671 \
672 while (bottom < top) { \
673 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
674 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
675 oop(bottom)) && \
676 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
677 size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
678 bottom += _cfls->adjustObjectSize(word_sz); \
679 } else { \
680 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
681 } \
682 } \
683 }
684
685 // (There are only two of these, rather than N, because the split is due
686 // only to the introduction of the FilteringClosure, a local part of the
687 // impl of this abstraction.)
688 FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
689 FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
690
691 DirtyCardToOopClosure*
692 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl,
693 CardTableModRefBS::PrecisionStyle precision,
694 HeapWord* boundary,
695 bool parallel) {
696 return new FreeListSpaceDCTOC(this, _collector, cl, precision, boundary, parallel);
697 }
698
699
700 // Note on locking for the space iteration functions:
701 // since the collector's iteration activities are concurrent with
702 // allocation activities by mutators, absent a suitable mutual exclusion
703 // mechanism the iterators may go awry. For instance a block being iterated
704 // may suddenly be allocated or divided up and part of it allocated and
705 // so on.
706
707 // Apply the given closure to each block in the space.
708 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
709 assert_lock_strong(freelistLock());
710 HeapWord *cur, *limit;
711 for (cur = bottom(), limit = end(); cur < limit;
712 cur += cl->do_blk_careful(cur));
713 }
714
715 // Apply the given closure to each block in the space.
716 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
717 assert_lock_strong(freelistLock());
718 HeapWord *cur, *limit;
719 for (cur = bottom(), limit = end(); cur < limit;
720 cur += cl->do_blk(cur));
721 }
722
723 // Apply the given closure to each oop in the space.
724 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) {
725 assert_lock_strong(freelistLock());
726 HeapWord *cur, *limit;
727 size_t curSize;
728 for (cur = bottom(), limit = end(); cur < limit;
729 cur += curSize) {
730 curSize = block_size(cur);
731 if (block_is_obj(cur)) {
732 oop(cur)->oop_iterate(cl);
733 }
734 }
735 }
736
737 // NOTE: In the following methods, in order to safely be able to
738 // apply the closure to an object, we need to be sure that the
739 // object has been initialized. We are guaranteed that an object
740 // is initialized if we are holding the Heap_lock with the
741 // world stopped.
742 void CompactibleFreeListSpace::verify_objects_initialized() const {
743 if (is_init_completed()) {
744 assert_locked_or_safepoint(Heap_lock);
745 if (Universe::is_fully_initialized()) {
746 guarantee(SafepointSynchronize::is_at_safepoint(),
747 "Required for objects to be initialized");
748 }
749 } // else make a concession at vm start-up
750 }
751
752 // Apply the given closure to each object in the space
753 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
754 assert_lock_strong(freelistLock());
755 NOT_PRODUCT(verify_objects_initialized());
756 HeapWord *cur, *limit;
757 size_t curSize;
758 for (cur = bottom(), limit = end(); cur < limit;
759 cur += curSize) {
760 curSize = block_size(cur);
761 if (block_is_obj(cur)) {
762 blk->do_object(oop(cur));
763 }
764 }
765 }
766
767 // Apply the given closure to each live object in the space
768 // The usage of CompactibleFreeListSpace
769 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
770 // objects in the space with references to objects that are no longer
771 // valid. For example, an object may reference another object
772 // that has already been sweep up (collected). This method uses
773 // obj_is_alive() to determine whether it is safe to apply the closure to
774 // an object. See obj_is_alive() for details on how liveness of an
775 // object is decided.
776
777 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
778 assert_lock_strong(freelistLock());
779 NOT_PRODUCT(verify_objects_initialized());
780 HeapWord *cur, *limit;
781 size_t curSize;
782 for (cur = bottom(), limit = end(); cur < limit;
783 cur += curSize) {
784 curSize = block_size(cur);
785 if (block_is_obj(cur) && obj_is_alive(cur)) {
786 blk->do_object(oop(cur));
787 }
788 }
789 }
790
791 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
792 UpwardsObjectClosure* cl) {
793 assert_locked(freelistLock());
794 NOT_PRODUCT(verify_objects_initialized());
795 assert(!mr.is_empty(), "Should be non-empty");
796 // We use MemRegion(bottom(), end()) rather than used_region() below
797 // because the two are not necessarily equal for some kinds of
798 // spaces, in particular, certain kinds of free list spaces.
799 // We could use the more complicated but more precise:
800 // MemRegion(used_region().start(), round_to(used_region().end(), CardSize))
801 // but the slight imprecision seems acceptable in the assertion check.
802 assert(MemRegion(bottom(), end()).contains(mr),
803 "Should be within used space");
804 HeapWord* prev = cl->previous(); // max address from last time
805 if (prev >= mr.end()) { // nothing to do
806 return;
807 }
808 // This assert will not work when we go from cms space to perm
809 // space, and use same closure. Easy fix deferred for later. XXX YSR
810 // assert(prev == NULL || contains(prev), "Should be within space");
811
812 bool last_was_obj_array = false;
813 HeapWord *blk_start_addr, *region_start_addr;
814 if (prev > mr.start()) {
815 region_start_addr = prev;
816 blk_start_addr = prev;
817 // The previous invocation may have pushed "prev" beyond the
818 // last allocated block yet there may be still be blocks
819 // in this region due to a particular coalescing policy.
820 // Relax the assertion so that the case where the unallocated
821 // block is maintained and "prev" is beyond the unallocated
822 // block does not cause the assertion to fire.
823 assert((BlockOffsetArrayUseUnallocatedBlock &&
824 (!is_in(prev))) ||
825 (blk_start_addr == block_start(region_start_addr)), "invariant");
826 } else {
827 region_start_addr = mr.start();
828 blk_start_addr = block_start(region_start_addr);
829 }
830 HeapWord* region_end_addr = mr.end();
831 MemRegion derived_mr(region_start_addr, region_end_addr);
832 while (blk_start_addr < region_end_addr) {
833 const size_t size = block_size(blk_start_addr);
834 if (block_is_obj(blk_start_addr)) {
835 last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);
836 } else {
837 last_was_obj_array = false;
838 }
839 blk_start_addr += size;
840 }
841 if (!last_was_obj_array) {
842 assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),
843 "Should be within (closed) used space");
844 assert(blk_start_addr > prev, "Invariant");
845 cl->set_previous(blk_start_addr); // min address for next time
846 }
847 }
848
849 // Callers of this iterator beware: The closure application should
850 // be robust in the face of uninitialized objects and should (always)
851 // return a correct size so that the next addr + size below gives us a
852 // valid block boundary. [See for instance,
853 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
854 // in ConcurrentMarkSweepGeneration.cpp.]
855 HeapWord*
856 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
857 ObjectClosureCareful* cl) {
858 assert_lock_strong(freelistLock());
859 // Can't use used_region() below because it may not necessarily
860 // be the same as [bottom(),end()); although we could
861 // use [used_region().start(),round_to(used_region().end(),CardSize)),
862 // that appears too cumbersome, so we just do the simpler check
863 // in the assertion below.
864 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
865 "mr should be non-empty and within used space");
866 HeapWord *addr, *end;
867 size_t size;
868 for (addr = block_start_careful(mr.start()), end = mr.end();
869 addr < end; addr += size) {
870 FreeChunk* fc = (FreeChunk*)addr;
871 if (fc->is_free()) {
872 // Since we hold the free list lock, which protects direct
873 // allocation in this generation by mutators, a free object
874 // will remain free throughout this iteration code.
875 size = fc->size();
876 } else {
877 // Note that the object need not necessarily be initialized,
878 // because (for instance) the free list lock does NOT protect
879 // object initialization. The closure application below must
880 // therefore be correct in the face of uninitialized objects.
881 size = cl->do_object_careful_m(oop(addr), mr);
882 if (size == 0) {
883 // An unparsable object found. Signal early termination.
884 return addr;
885 }
886 }
887 }
888 return NULL;
889 }
890
891
892 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
893 NOT_PRODUCT(verify_objects_initialized());
894 return _bt.block_start(p);
895 }
896
897 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
898 return _bt.block_start_careful(p);
899 }
900
901 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
902 NOT_PRODUCT(verify_objects_initialized());
903 // This must be volatile, or else there is a danger that the compiler
904 // will compile the code below into a sometimes-infinite loop, by keeping
905 // the value read the first time in a register.
906 while (true) {
907 // We must do this until we get a consistent view of the object.
908 if (FreeChunk::indicatesFreeChunk(p)) {
909 volatile FreeChunk* fc = (volatile FreeChunk*)p;
910 size_t res = fc->size();
911
912 // Bugfix for systems with weak memory model (PPC64/IA64). The
913 // block's free bit was set and we have read the size of the
914 // block. Acquire and check the free bit again. If the block is
915 // still free, the read size is correct.
916 OrderAccess::acquire();
917
918 // If the object is still a free chunk, return the size, else it
919 // has been allocated so try again.
920 if (FreeChunk::indicatesFreeChunk(p)) {
921 assert(res != 0, "Block size should not be 0");
922 return res;
923 }
924 } else {
925 // must read from what 'p' points to in each loop.
926 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
927 if (k != NULL) {
928 assert(k->is_klass(), "Should really be klass oop.");
929 oop o = (oop)p;
930 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
931
932 // Bugfix for systems with weak memory model (PPC64/IA64).
933 // The object o may be an array. Acquire to make sure that the array
934 // size (third word) is consistent.
935 OrderAccess::acquire();
936
937 size_t res = o->size_given_klass(k);
938 res = adjustObjectSize(res);
939 assert(res != 0, "Block size should not be 0");
940 return res;
941 }
942 }
943 }
944 }
945
946 // TODO: Now that is_parsable is gone, we should combine these two functions.
947 // A variant of the above that uses the Printezis bits for
948 // unparsable but allocated objects. This avoids any possible
949 // stalls waiting for mutators to initialize objects, and is
950 // thus potentially faster than the variant above. However,
951 // this variant may return a zero size for a block that is
952 // under mutation and for which a consistent size cannot be
953 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
954 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
955 const CMSCollector* c)
956 const {
957 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
958 // This must be volatile, or else there is a danger that the compiler
959 // will compile the code below into a sometimes-infinite loop, by keeping
960 // the value read the first time in a register.
961 DEBUG_ONLY(uint loops = 0;)
962 while (true) {
963 // We must do this until we get a consistent view of the object.
964 if (FreeChunk::indicatesFreeChunk(p)) {
965 volatile FreeChunk* fc = (volatile FreeChunk*)p;
966 size_t res = fc->size();
967
968 // Bugfix for systems with weak memory model (PPC64/IA64). The
969 // free bit of the block was set and we have read the size of
970 // the block. Acquire and check the free bit again. If the
971 // block is still free, the read size is correct.
972 OrderAccess::acquire();
973
974 if (FreeChunk::indicatesFreeChunk(p)) {
975 assert(res != 0, "Block size should not be 0");
976 assert(loops == 0, "Should be 0");
977 return res;
978 }
979 } else {
980 // must read from what 'p' points to in each loop.
981 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
982 // We trust the size of any object that has a non-NULL
983 // klass and (for those in the perm gen) is parsable
984 // -- irrespective of its conc_safe-ty.
985 if (k != NULL) {
986 assert(k->is_klass(), "Should really be klass oop.");
987 oop o = (oop)p;
988 assert(o->is_oop(), "Should be an oop");
989
990 // Bugfix for systems with weak memory model (PPC64/IA64).
991 // The object o may be an array. Acquire to make sure that the array
992 // size (third word) is consistent.
993 OrderAccess::acquire();
994
995 size_t res = o->size_given_klass(k);
996 res = adjustObjectSize(res);
997 assert(res != 0, "Block size should not be 0");
998 return res;
999 } else {
1000 // May return 0 if P-bits not present.
1001 return c->block_size_if_printezis_bits(p);
1002 }
1003 }
1004 assert(loops == 0, "Can loop at most once");
1005 DEBUG_ONLY(loops++;)
1006 }
1007 }
1008
1009 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1010 NOT_PRODUCT(verify_objects_initialized());
1011 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1012 FreeChunk* fc = (FreeChunk*)p;
1013 if (fc->is_free()) {
1014 return fc->size();
1015 } else {
1016 // Ignore mark word because this may be a recently promoted
1017 // object whose mark word is used to chain together grey
1018 // objects (the last one would have a null value).
1019 assert(oop(p)->is_oop(true), "Should be an oop");
1020 return adjustObjectSize(oop(p)->size());
1021 }
1022 }
1023
1024 // This implementation assumes that the property of "being an object" is
1025 // stable. But being a free chunk may not be (because of parallel
1026 // promotion.)
1027 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1028 FreeChunk* fc = (FreeChunk*)p;
1029 assert(is_in_reserved(p), "Should be in space");
1030 if (FreeChunk::indicatesFreeChunk(p)) return false;
1031 Klass* k = oop(p)->klass_or_null();
1032 if (k != NULL) {
1033 // Ignore mark word because it may have been used to
1034 // chain together promoted objects (the last one
1035 // would have a null value).
1036 assert(oop(p)->is_oop(true), "Should be an oop");
1037 return true;
1038 } else {
1039 return false; // Was not an object at the start of collection.
1040 }
1041 }
1042
1043 // Check if the object is alive. This fact is checked either by consulting
1044 // the main marking bitmap in the sweeping phase or, if it's a permanent
1045 // generation and we're not in the sweeping phase, by checking the
1046 // perm_gen_verify_bit_map where we store the "deadness" information if
1047 // we did not sweep the perm gen in the most recent previous GC cycle.
1048 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1049 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1050 "Else races are possible");
1051 assert(block_is_obj(p), "The address should point to an object");
1052
1053 // If we're sweeping, we use object liveness information from the main bit map
1054 // for both perm gen and old gen.
1055 // We don't need to lock the bitmap (live_map or dead_map below), because
1056 // EITHER we are in the middle of the sweeping phase, and the
1057 // main marking bit map (live_map below) is locked,
1058 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1059 // is stable, because it's mutated only in the sweeping phase.
1060 // NOTE: This method is also used by jmap where, if class unloading is
1061 // off, the results can return "false" for legitimate perm objects,
1062 // when we are not in the midst of a sweeping phase, which can result
1063 // in jmap not reporting certain perm gen objects. This will be moot
1064 // if/when the perm gen goes away in the future.
1065 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1066 CMSBitMap* live_map = _collector->markBitMap();
1067 return live_map->par_isMarked((HeapWord*) p);
1068 }
1069 return true;
1070 }
1071
1072 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1073 FreeChunk* fc = (FreeChunk*)p;
1074 assert(is_in_reserved(p), "Should be in space");
1075 assert(_bt.block_start(p) == p, "Should be a block boundary");
1076 if (!fc->is_free()) {
1077 // Ignore mark word because it may have been used to
1078 // chain together promoted objects (the last one
1079 // would have a null value).
1080 assert(oop(p)->is_oop(true), "Should be an oop");
1081 return true;
1082 }
1083 return false;
1084 }
1085
1086 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1087 // approximate answer if you don't hold the freelistlock when you call this.
1088 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1089 size_t size = 0;
1090 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1091 debug_only(
1092 // We may be calling here without the lock in which case we
1093 // won't do this modest sanity check.
1094 if (freelistLock()->owned_by_self()) {
1095 size_t total_list_size = 0;
1096 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1097 fc = fc->next()) {
1098 total_list_size += i;
1099 }
1100 assert(total_list_size == i * _indexedFreeList[i].count(),
1101 "Count in list is incorrect");
1102 }
1103 )
1104 size += i * _indexedFreeList[i].count();
1105 }
1106 return size;
1107 }
1108
1109 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1110 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1111 return allocate(size);
1112 }
1113
1114 HeapWord*
1115 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1116 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1117 }
1118
1119 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1120 assert_lock_strong(freelistLock());
1121 HeapWord* res = NULL;
1122 assert(size == adjustObjectSize(size),
1123 "use adjustObjectSize() before calling into allocate()");
1124
1125 res = allocate_adaptive_freelists(size);
1126
1127 if (res != NULL) {
1128 // check that res does lie in this space!
1129 assert(is_in_reserved(res), "Not in this space!");
1130 assert(is_aligned((void*)res), "alignment check");
1131
1132 FreeChunk* fc = (FreeChunk*)res;
1133 fc->markNotFree();
1134 assert(!fc->is_free(), "shouldn't be marked free");
1135 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1136 // Verify that the block offset table shows this to
1137 // be a single block, but not one which is unallocated.
1138 _bt.verify_single_block(res, size);
1139 _bt.verify_not_unallocated(res, size);
1140 // mangle a just allocated object with a distinct pattern.
1141 debug_only(fc->mangleAllocated(size));
1142 }
1143
1144 return res;
1145 }
1146
1147 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1148 assert_lock_strong(freelistLock());
1149 HeapWord* res = NULL;
1150 assert(size == adjustObjectSize(size),
1151 "use adjustObjectSize() before calling into allocate()");
1152
1153 // Strategy
1154 // if small
1155 // exact size from small object indexed list if small
1156 // small or large linear allocation block (linAB) as appropriate
1157 // take from lists of greater sized chunks
1158 // else
1159 // dictionary
1160 // small or large linear allocation block if it has the space
1161 // Try allocating exact size from indexTable first
1162 if (size < IndexSetSize) {
1163 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1164 if(res != NULL) {
1165 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1166 "Not removed from free list");
1167 // no block offset table adjustment is necessary on blocks in
1168 // the indexed lists.
1169
1170 // Try allocating from the small LinAB
1171 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1172 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1173 // if successful, the above also adjusts block offset table
1174 // Note that this call will refill the LinAB to
1175 // satisfy the request. This is different that
1176 // evm.
1177 // Don't record chunk off a LinAB? smallSplitBirth(size);
1178 } else {
1179 // Raid the exact free lists larger than size, even if they are not
1180 // overpopulated.
1181 res = (HeapWord*) getChunkFromGreater(size);
1182 }
1183 } else {
1184 // Big objects get allocated directly from the dictionary.
1185 res = (HeapWord*) getChunkFromDictionaryExact(size);
1186 if (res == NULL) {
1187 // Try hard not to fail since an allocation failure will likely
1188 // trigger a synchronous GC. Try to get the space from the
1189 // allocation blocks.
1190 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1191 }
1192 }
1193
1194 return res;
1195 }
1196
1197 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1198 // when promoting obj.
1199 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1200 // Depending on the object size, expansion may require refilling either a
1201 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1202 // is added because the dictionary may over-allocate to avoid fragmentation.
1203 size_t space = obj_size;
1204 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1205 return space;
1206 }
1207
1208 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1209 FreeChunk* ret;
1210
1211 assert(numWords >= MinChunkSize, "Size is less than minimum");
1212 assert(linearAllocationWouldFail() || bestFitFirst(),
1213 "Should not be here");
1214
1215 size_t i;
1216 size_t currSize = numWords + MinChunkSize;
1217 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1218 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1219 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
1220 if (fl->head()) {
1221 ret = getFromListGreater(fl, numWords);
1222 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1223 return ret;
1224 }
1225 }
1226
1227 currSize = MAX2((size_t)SmallForDictionary,
1228 (size_t)(numWords + MinChunkSize));
1229
1230 /* Try to get a chunk that satisfies request, while avoiding
1231 fragmentation that can't be handled. */
1232 {
1233 ret = dictionary()->get_chunk(currSize);
1234 if (ret != NULL) {
1235 assert(ret->size() - numWords >= MinChunkSize,
1236 "Chunk is too small");
1237 _bt.allocated((HeapWord*)ret, ret->size());
1238 /* Carve returned chunk. */
1239 (void) splitChunkAndReturnRemainder(ret, numWords);
1240 /* Label this as no longer a free chunk. */
1241 assert(ret->is_free(), "This chunk should be free");
1242 ret->link_prev(NULL);
1243 }
1244 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1245 return ret;
1246 }
1247 ShouldNotReachHere();
1248 }
1249
1250 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1251 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1252 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
1253 }
1254
1255 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1256 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1257 (_smallLinearAllocBlock._word_size == fc->size()),
1258 "Linear allocation block shows incorrect size");
1259 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1260 (_smallLinearAllocBlock._word_size == fc->size()));
1261 }
1262
1263 // Check if the purported free chunk is present either as a linear
1264 // allocation block, the size-indexed table of (smaller) free blocks,
1265 // or the larger free blocks kept in the binary tree dictionary.
1266 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
1267 if (verify_chunk_is_linear_alloc_block(fc)) {
1268 return true;
1269 } else if (fc->size() < IndexSetSize) {
1270 return verifyChunkInIndexedFreeLists(fc);
1271 } else {
1272 return dictionary()->verify_chunk_in_free_list(fc);
1273 }
1274 }
1275
1276 #ifndef PRODUCT
1277 void CompactibleFreeListSpace::assert_locked() const {
1278 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1279 }
1280
1281 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1282 CMSLockVerifier::assert_locked(lock);
1283 }
1284 #endif
1285
1286 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1287 // In the parallel case, the main thread holds the free list lock
1288 // on behalf the parallel threads.
1289 FreeChunk* fc;
1290 {
1291 // If GC is parallel, this might be called by several threads.
1292 // This should be rare enough that the locking overhead won't affect
1293 // the sequential code.
1294 MutexLockerEx x(parDictionaryAllocLock(),
1295 Mutex::_no_safepoint_check_flag);
1296 fc = getChunkFromDictionary(size);
1297 }
1298 if (fc != NULL) {
1299 fc->dontCoalesce();
1300 assert(fc->is_free(), "Should be free, but not coalescable");
1301 // Verify that the block offset table shows this to
1302 // be a single block, but not one which is unallocated.
1303 _bt.verify_single_block((HeapWord*)fc, fc->size());
1304 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1305 }
1306 return fc;
1307 }
1308
1309 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1310 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1311 assert_locked();
1312
1313 // if we are tracking promotions, then first ensure space for
1314 // promotion (including spooling space for saving header if necessary).
1315 // then allocate and copy, then track promoted info if needed.
1316 // When tracking (see PromotionInfo::track()), the mark word may
1317 // be displaced and in this case restoration of the mark word
1318 // occurs in the (oop_since_save_marks_)iterate phase.
1319 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1320 return NULL;
1321 }
1322 // Call the allocate(size_t, bool) form directly to avoid the
1323 // additional call through the allocate(size_t) form. Having
1324 // the compile inline the call is problematic because allocate(size_t)
1325 // is a virtual method.
1326 HeapWord* res = allocate(adjustObjectSize(obj_size));
1327 if (res != NULL) {
1328 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1329 // if we should be tracking promotions, do so.
1330 if (_promoInfo.tracking()) {
1331 _promoInfo.track((PromotedObject*)res);
1332 }
1333 }
1334 return oop(res);
1335 }
1336
1337 HeapWord*
1338 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1339 assert_locked();
1340 assert(size >= MinChunkSize, "minimum chunk size");
1341 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1342 "maximum from smallLinearAllocBlock");
1343 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1344 }
1345
1346 HeapWord*
1347 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1348 size_t size) {
1349 assert_locked();
1350 assert(size >= MinChunkSize, "too small");
1351 HeapWord* res = NULL;
1352 // Try to do linear allocation from blk, making sure that
1353 if (blk->_word_size == 0) {
1354 // We have probably been unable to fill this either in the prologue or
1355 // when it was exhausted at the last linear allocation. Bail out until
1356 // next time.
1357 assert(blk->_ptr == NULL, "consistency check");
1358 return NULL;
1359 }
1360 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1361 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1362 if (res != NULL) return res;
1363
1364 // about to exhaust this linear allocation block
1365 if (blk->_word_size == size) { // exactly satisfied
1366 res = blk->_ptr;
1367 _bt.allocated(res, blk->_word_size);
1368 } else if (size + MinChunkSize <= blk->_refillSize) {
1369 size_t sz = blk->_word_size;
1370 // Update _unallocated_block if the size is such that chunk would be
1371 // returned to the indexed free list. All other chunks in the indexed
1372 // free lists are allocated from the dictionary so that _unallocated_block
1373 // has already been adjusted for them. Do it here so that the cost
1374 // for all chunks added back to the indexed free lists.
1375 if (sz < SmallForDictionary) {
1376 _bt.allocated(blk->_ptr, sz);
1377 }
1378 // Return the chunk that isn't big enough, and then refill below.
1379 addChunkToFreeLists(blk->_ptr, sz);
1380 split_birth(sz);
1381 // Don't keep statistics on adding back chunk from a LinAB.
1382 } else {
1383 // A refilled block would not satisfy the request.
1384 return NULL;
1385 }
1386
1387 blk->_ptr = NULL; blk->_word_size = 0;
1388 refillLinearAllocBlock(blk);
1389 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1390 "block was replenished");
1391 if (res != NULL) {
1392 split_birth(size);
1393 repairLinearAllocBlock(blk);
1394 } else if (blk->_ptr != NULL) {
1395 res = blk->_ptr;
1396 size_t blk_size = blk->_word_size;
1397 blk->_word_size -= size;
1398 blk->_ptr += size;
1399 split_birth(size);
1400 repairLinearAllocBlock(blk);
1401 // Update BOT last so that other (parallel) GC threads see a consistent
1402 // view of the BOT and free blocks.
1403 // Above must occur before BOT is updated below.
1404 OrderAccess::storestore();
1405 _bt.split_block(res, blk_size, size); // adjust block offset table
1406 }
1407 return res;
1408 }
1409
1410 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1411 LinearAllocBlock* blk,
1412 size_t size) {
1413 assert_locked();
1414 assert(size >= MinChunkSize, "too small");
1415
1416 HeapWord* res = NULL;
1417 // This is the common case. Keep it simple.
1418 if (blk->_word_size >= size + MinChunkSize) {
1419 assert(blk->_ptr != NULL, "consistency check");
1420 res = blk->_ptr;
1421 // Note that the BOT is up-to-date for the linAB before allocation. It
1422 // indicates the start of the linAB. The split_block() updates the
1423 // BOT for the linAB after the allocation (indicates the start of the
1424 // next chunk to be allocated).
1425 size_t blk_size = blk->_word_size;
1426 blk->_word_size -= size;
1427 blk->_ptr += size;
1428 split_birth(size);
1429 repairLinearAllocBlock(blk);
1430 // Update BOT last so that other (parallel) GC threads see a consistent
1431 // view of the BOT and free blocks.
1432 // Above must occur before BOT is updated below.
1433 OrderAccess::storestore();
1434 _bt.split_block(res, blk_size, size); // adjust block offset table
1435 _bt.allocated(res, size);
1436 }
1437 return res;
1438 }
1439
1440 FreeChunk*
1441 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1442 assert_locked();
1443 assert(size < SmallForDictionary, "just checking");
1444 FreeChunk* res;
1445 res = _indexedFreeList[size].get_chunk_at_head();
1446 if (res == NULL) {
1447 res = getChunkFromIndexedFreeListHelper(size);
1448 }
1449 _bt.verify_not_unallocated((HeapWord*) res, size);
1450 assert(res == NULL || res->size() == size, "Incorrect block size");
1451 return res;
1452 }
1453
1454 FreeChunk*
1455 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1456 bool replenish) {
1457 assert_locked();
1458 FreeChunk* fc = NULL;
1459 if (size < SmallForDictionary) {
1460 assert(_indexedFreeList[size].head() == NULL ||
1461 _indexedFreeList[size].surplus() <= 0,
1462 "List for this size should be empty or under populated");
1463 // Try best fit in exact lists before replenishing the list
1464 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1465 // Replenish list.
1466 //
1467 // Things tried that failed.
1468 // Tried allocating out of the two LinAB's first before
1469 // replenishing lists.
1470 // Tried small linAB of size 256 (size in indexed list)
1471 // and replenishing indexed lists from the small linAB.
1472 //
1473 FreeChunk* newFc = NULL;
1474 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1475 if (replenish_size < SmallForDictionary) {
1476 // Do not replenish from an underpopulated size.
1477 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1478 _indexedFreeList[replenish_size].head() != NULL) {
1479 newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
1480 } else if (bestFitFirst()) {
1481 newFc = bestFitSmall(replenish_size);
1482 }
1483 }
1484 if (newFc == NULL && replenish_size > size) {
1485 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1486 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1487 }
1488 // Note: The stats update re split-death of block obtained above
1489 // will be recorded below precisely when we know we are going to
1490 // be actually splitting it into more than one pieces below.
1491 if (newFc != NULL) {
1492 if (replenish || CMSReplenishIntermediate) {
1493 // Replenish this list and return one block to caller.
1494 size_t i;
1495 FreeChunk *curFc, *nextFc;
1496 size_t num_blk = newFc->size() / size;
1497 assert(num_blk >= 1, "Smaller than requested?");
1498 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1499 if (num_blk > 1) {
1500 // we are sure we will be splitting the block just obtained
1501 // into multiple pieces; record the split-death of the original
1502 splitDeath(replenish_size);
1503 }
1504 // carve up and link blocks 0, ..., num_blk - 2
1505 // The last chunk is not added to the lists but is returned as the
1506 // free chunk.
1507 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1508 i = 0;
1509 i < (num_blk - 1);
1510 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1511 i++) {
1512 curFc->set_size(size);
1513 // Don't record this as a return in order to try and
1514 // determine the "returns" from a GC.
1515 _bt.verify_not_unallocated((HeapWord*) fc, size);
1516 _indexedFreeList[size].return_chunk_at_tail(curFc, false);
1517 _bt.mark_block((HeapWord*)curFc, size);
1518 split_birth(size);
1519 // Don't record the initial population of the indexed list
1520 // as a split birth.
1521 }
1522
1523 // check that the arithmetic was OK above
1524 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1525 "inconsistency in carving newFc");
1526 curFc->set_size(size);
1527 _bt.mark_block((HeapWord*)curFc, size);
1528 split_birth(size);
1529 fc = curFc;
1530 } else {
1531 // Return entire block to caller
1532 fc = newFc;
1533 }
1534 }
1535 }
1536 } else {
1537 // Get a free chunk from the free chunk dictionary to be returned to
1538 // replenish the indexed free list.
1539 fc = getChunkFromDictionaryExact(size);
1540 }
1541 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
1542 return fc;
1543 }
1544
1545 FreeChunk*
1546 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1547 assert_locked();
1548 FreeChunk* fc = _dictionary->get_chunk(size,
1549 FreeBlockDictionary<FreeChunk>::atLeast);
1550 if (fc == NULL) {
1551 return NULL;
1552 }
1553 _bt.allocated((HeapWord*)fc, fc->size());
1554 if (fc->size() >= size + MinChunkSize) {
1555 fc = splitChunkAndReturnRemainder(fc, size);
1556 }
1557 assert(fc->size() >= size, "chunk too small");
1558 assert(fc->size() < size + MinChunkSize, "chunk too big");
1559 _bt.verify_single_block((HeapWord*)fc, fc->size());
1560 return fc;
1561 }
1562
1563 FreeChunk*
1564 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1565 assert_locked();
1566 FreeChunk* fc = _dictionary->get_chunk(size,
1567 FreeBlockDictionary<FreeChunk>::atLeast);
1568 if (fc == NULL) {
1569 return fc;
1570 }
1571 _bt.allocated((HeapWord*)fc, fc->size());
1572 if (fc->size() == size) {
1573 _bt.verify_single_block((HeapWord*)fc, size);
1574 return fc;
1575 }
1576 assert(fc->size() > size, "get_chunk() guarantee");
1577 if (fc->size() < size + MinChunkSize) {
1578 // Return the chunk to the dictionary and go get a bigger one.
1579 returnChunkToDictionary(fc);
1580 fc = _dictionary->get_chunk(size + MinChunkSize,
1581 FreeBlockDictionary<FreeChunk>::atLeast);
1582 if (fc == NULL) {
1583 return NULL;
1584 }
1585 _bt.allocated((HeapWord*)fc, fc->size());
1586 }
1587 assert(fc->size() >= size + MinChunkSize, "tautology");
1588 fc = splitChunkAndReturnRemainder(fc, size);
1589 assert(fc->size() == size, "chunk is wrong size");
1590 _bt.verify_single_block((HeapWord*)fc, size);
1591 return fc;
1592 }
1593
1594 void
1595 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
1596 assert_locked();
1597
1598 size_t size = chunk->size();
1599 _bt.verify_single_block((HeapWord*)chunk, size);
1600 // adjust _unallocated_block downward, as necessary
1601 _bt.freed((HeapWord*)chunk, size);
1602 _dictionary->return_chunk(chunk);
1603 #ifndef PRODUCT
1604 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1605 TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >* tc = TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::as_TreeChunk(chunk);
1606 TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* tl = tc->list();
1607 tl->verify_stats();
1608 }
1609 #endif // PRODUCT
1610 }
1611
1612 void
1613 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
1614 assert_locked();
1615 size_t size = fc->size();
1616 _bt.verify_single_block((HeapWord*) fc, size);
1617 _bt.verify_not_unallocated((HeapWord*) fc, size);
1618 _indexedFreeList[size].return_chunk_at_tail(fc);
1619 #ifndef PRODUCT
1620 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1621 _indexedFreeList[size].verify_stats();
1622 }
1623 #endif // PRODUCT
1624 }
1625
1626 // Add chunk to end of last block -- if it's the largest
1627 // block -- and update BOT and census data. We would
1628 // of course have preferred to coalesce it with the
1629 // last block, but it's currently less expensive to find the
1630 // largest block than it is to find the last.
1631 void
1632 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1633 HeapWord* chunk, size_t size) {
1634 // check that the chunk does lie in this space!
1635 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1636 // One of the parallel gc task threads may be here
1637 // whilst others are allocating.
1638 Mutex* lock = &_parDictionaryAllocLock;
1639 FreeChunk* ec;
1640 {
1641 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1642 ec = dictionary()->find_largest_dict(); // get largest block
1643 if (ec != NULL && ec->end() == (uintptr_t*) chunk) {
1644 // It's a coterminal block - we can coalesce.
1645 size_t old_size = ec->size();
1646 coalDeath(old_size);
1647 removeChunkFromDictionary(ec);
1648 size += old_size;
1649 } else {
1650 ec = (FreeChunk*)chunk;
1651 }
1652 }
1653 ec->set_size(size);
1654 debug_only(ec->mangleFreed(size));
1655 if (size < SmallForDictionary) {
1656 lock = _indexedFreeListParLocks[size];
1657 }
1658 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1659 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
1660 // record the birth under the lock since the recording involves
1661 // manipulation of the list on which the chunk lives and
1662 // if the chunk is allocated and is the last on the list,
1663 // the list can go away.
1664 coalBirth(size);
1665 }
1666
1667 void
1668 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1669 size_t size) {
1670 // check that the chunk does lie in this space!
1671 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1672 assert_locked();
1673 _bt.verify_single_block(chunk, size);
1674
1675 FreeChunk* fc = (FreeChunk*) chunk;
1676 fc->set_size(size);
1677 debug_only(fc->mangleFreed(size));
1678 if (size < SmallForDictionary) {
1679 returnChunkToFreeList(fc);
1680 } else {
1681 returnChunkToDictionary(fc);
1682 }
1683 }
1684
1685 void
1686 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1687 size_t size, bool coalesced) {
1688 assert_locked();
1689 assert(chunk != NULL, "null chunk");
1690 if (coalesced) {
1691 // repair BOT
1692 _bt.single_block(chunk, size);
1693 }
1694 addChunkToFreeLists(chunk, size);
1695 }
1696
1697 // We _must_ find the purported chunk on our free lists;
1698 // we assert if we don't.
1699 void
1700 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1701 size_t size = fc->size();
1702 assert_locked();
1703 debug_only(verifyFreeLists());
1704 if (size < SmallForDictionary) {
1705 removeChunkFromIndexedFreeList(fc);
1706 } else {
1707 removeChunkFromDictionary(fc);
1708 }
1709 _bt.verify_single_block((HeapWord*)fc, size);
1710 debug_only(verifyFreeLists());
1711 }
1712
1713 void
1714 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1715 size_t size = fc->size();
1716 assert_locked();
1717 assert(fc != NULL, "null chunk");
1718 _bt.verify_single_block((HeapWord*)fc, size);
1719 _dictionary->remove_chunk(fc);
1720 // adjust _unallocated_block upward, as necessary
1721 _bt.allocated((HeapWord*)fc, size);
1722 }
1723
1724 void
1725 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1726 assert_locked();
1727 size_t size = fc->size();
1728 _bt.verify_single_block((HeapWord*)fc, size);
1729 NOT_PRODUCT(
1730 if (FLSVerifyIndexTable) {
1731 verifyIndexedFreeList(size);
1732 }
1733 )
1734 _indexedFreeList[size].remove_chunk(fc);
1735 NOT_PRODUCT(
1736 if (FLSVerifyIndexTable) {
1737 verifyIndexedFreeList(size);
1738 }
1739 )
1740 }
1741
1742 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1743 /* A hint is the next larger size that has a surplus.
1744 Start search at a size large enough to guarantee that
1745 the excess is >= MIN_CHUNK. */
1746 size_t start = align_object_size(numWords + MinChunkSize);
1747 if (start < IndexSetSize) {
1748 AdaptiveFreeList<FreeChunk>* it = _indexedFreeList;
1749 size_t hint = _indexedFreeList[start].hint();
1750 while (hint < IndexSetSize) {
1751 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1752 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint];
1753 if (fl->surplus() > 0 && fl->head() != NULL) {
1754 // Found a list with surplus, reset original hint
1755 // and split out a free chunk which is returned.
1756 _indexedFreeList[start].set_hint(hint);
1757 FreeChunk* res = getFromListGreater(fl, numWords);
1758 assert(res == NULL || res->is_free(),
1759 "Should be returning a free chunk");
1760 return res;
1761 }
1762 hint = fl->hint(); /* keep looking */
1763 }
1764 /* None found. */
1765 it[start].set_hint(IndexSetSize);
1766 }
1767 return NULL;
1768 }
1769
1770 /* Requires fl->size >= numWords + MinChunkSize */
1771 FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl,
1772 size_t numWords) {
1773 FreeChunk *curr = fl->head();
1774 size_t oldNumWords = curr->size();
1775 assert(numWords >= MinChunkSize, "Word size is too small");
1776 assert(curr != NULL, "List is empty");
1777 assert(oldNumWords >= numWords + MinChunkSize,
1778 "Size of chunks in the list is too small");
1779
1780 fl->remove_chunk(curr);
1781 // recorded indirectly by splitChunkAndReturnRemainder -
1782 // smallSplit(oldNumWords, numWords);
1783 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1784 // Does anything have to be done for the remainder in terms of
1785 // fixing the card table?
1786 assert(new_chunk == NULL || new_chunk->is_free(),
1787 "Should be returning a free chunk");
1788 return new_chunk;
1789 }
1790
1791 FreeChunk*
1792 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1793 size_t new_size) {
1794 assert_locked();
1795 size_t size = chunk->size();
1796 assert(size > new_size, "Split from a smaller block?");
1797 assert(is_aligned(chunk), "alignment problem");
1798 assert(size == adjustObjectSize(size), "alignment problem");
1799 size_t rem_sz = size - new_size;
1800 assert(rem_sz == adjustObjectSize(rem_sz), "alignment problem");
1801 assert(rem_sz >= MinChunkSize, "Free chunk smaller than minimum");
1802 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1803 assert(is_aligned(ffc), "alignment problem");
1804 ffc->set_size(rem_sz);
1805 ffc->link_next(NULL);
1806 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
1807 // Above must occur before BOT is updated below.
1808 // adjust block offset table
1809 OrderAccess::storestore();
1810 assert(chunk->is_free() && ffc->is_free(), "Error");
1811 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1812 if (rem_sz < SmallForDictionary) {
1813 // The freeList lock is held, but multiple GC task threads might be executing in parallel.
1814 bool is_par = Thread::current()->is_GC_task_thread();
1815 if (is_par) _indexedFreeListParLocks[rem_sz]->lock();
1816 returnChunkToFreeList(ffc);
1817 split(size, rem_sz);
1818 if (is_par) _indexedFreeListParLocks[rem_sz]->unlock();
1819 } else {
1820 returnChunkToDictionary(ffc);
1821 split(size, rem_sz);
1822 }
1823 chunk->set_size(new_size);
1824 return chunk;
1825 }
1826
1827 void
1828 CompactibleFreeListSpace::sweep_completed() {
1829 // Now that space is probably plentiful, refill linear
1830 // allocation blocks as needed.
1831 refillLinearAllocBlocksIfNeeded();
1832 }
1833
1834 void
1835 CompactibleFreeListSpace::gc_prologue() {
1836 assert_locked();
1837 reportFreeListStatistics("Before GC:");
1838 refillLinearAllocBlocksIfNeeded();
1839 }
1840
1841 void
1842 CompactibleFreeListSpace::gc_epilogue() {
1843 assert_locked();
1844 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1845 _promoInfo.stopTrackingPromotions();
1846 repairLinearAllocationBlocks();
1847 reportFreeListStatistics("After GC:");
1848 }
1849
1850 // Iteration support, mostly delegated from a CMS generation
1851
1852 void CompactibleFreeListSpace::save_marks() {
1853 assert(Thread::current()->is_VM_thread(),
1854 "Global variable should only be set when single-threaded");
1855 // Mark the "end" of the used space at the time of this call;
1856 // note, however, that promoted objects from this point
1857 // on are tracked in the _promoInfo below.
1858 set_saved_mark_word(unallocated_block());
1859 #ifdef ASSERT
1860 // Check the sanity of save_marks() etc.
1861 MemRegion ur = used_region();
1862 MemRegion urasm = used_region_at_save_marks();
1863 assert(ur.contains(urasm),
1864 " Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
1865 " should contain [" PTR_FORMAT "," PTR_FORMAT ")",
1866 p2i(ur.start()), p2i(ur.end()), p2i(urasm.start()), p2i(urasm.end()));
1867 #endif
1868 // inform allocator that promotions should be tracked.
1869 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1870 _promoInfo.startTrackingPromotions();
1871 }
1872
1873 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
1874 assert(_promoInfo.tracking(), "No preceding save_marks?");
1875 return _promoInfo.noPromotions();
1876 }
1877
1878 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
1879 \
1880 void CompactibleFreeListSpace:: \
1881 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
1882 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
1883 /* \
1884 * This also restores any displaced headers and removes the elements from \
1885 * the iteration set as they are processed, so that we have a clean slate \
1886 * at the end of the iteration. Note, thus, that if new objects are \
1887 * promoted as a result of the iteration they are iterated over as well. \
1888 */ \
1889 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
1890 }
1891
1892 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
1893
1894 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
1895 return _smallLinearAllocBlock._word_size == 0;
1896 }
1897
1898 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
1899 // Fix up linear allocation blocks to look like free blocks
1900 repairLinearAllocBlock(&_smallLinearAllocBlock);
1901 }
1902
1903 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
1904 assert_locked();
1905 if (blk->_ptr != NULL) {
1906 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
1907 "Minimum block size requirement");
1908 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
1909 fc->set_size(blk->_word_size);
1910 fc->link_prev(NULL); // mark as free
1911 fc->dontCoalesce();
1912 assert(fc->is_free(), "just marked it free");
1913 assert(fc->cantCoalesce(), "just marked it uncoalescable");
1914 }
1915 }
1916
1917 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
1918 assert_locked();
1919 if (_smallLinearAllocBlock._ptr == NULL) {
1920 assert(_smallLinearAllocBlock._word_size == 0,
1921 "Size of linAB should be zero if the ptr is NULL");
1922 // Reset the linAB refill and allocation size limit.
1923 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
1924 }
1925 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
1926 }
1927
1928 void
1929 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
1930 assert_locked();
1931 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
1932 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
1933 "blk invariant");
1934 if (blk->_ptr == NULL) {
1935 refillLinearAllocBlock(blk);
1936 }
1937 }
1938
1939 void
1940 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
1941 assert_locked();
1942 assert(blk->_word_size == 0 && blk->_ptr == NULL,
1943 "linear allocation block should be empty");
1944 FreeChunk* fc;
1945 if (blk->_refillSize < SmallForDictionary &&
1946 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
1947 // A linAB's strategy might be to use small sizes to reduce
1948 // fragmentation but still get the benefits of allocation from a
1949 // linAB.
1950 } else {
1951 fc = getChunkFromDictionary(blk->_refillSize);
1952 }
1953 if (fc != NULL) {
1954 blk->_ptr = (HeapWord*)fc;
1955 blk->_word_size = fc->size();
1956 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
1957 }
1958 }
1959
1960 // Support for compaction
1961 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
1962 scan_and_forward(this, cp);
1963 // Prepare_for_compaction() uses the space between live objects
1964 // so that later phase can skip dead space quickly. So verification
1965 // of the free lists doesn't work after.
1966 }
1967
1968 void CompactibleFreeListSpace::adjust_pointers() {
1969 // In other versions of adjust_pointers(), a bail out
1970 // based on the amount of live data in the generation
1971 // (i.e., if 0, bail out) may be used.
1972 // Cannot test used() == 0 here because the free lists have already
1973 // been mangled by the compaction.
1974
1975 scan_and_adjust_pointers(this);
1976 // See note about verification in prepare_for_compaction().
1977 }
1978
1979 void CompactibleFreeListSpace::compact() {
1980 scan_and_compact(this);
1981 }
1982
1983 // Fragmentation metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
1984 // where fbs is free block sizes
1985 double CompactibleFreeListSpace::flsFrag() const {
1986 size_t itabFree = totalSizeInIndexedFreeLists();
1987 double frag = 0.0;
1988 size_t i;
1989
1990 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1991 double sz = i;
1992 frag += _indexedFreeList[i].count() * (sz * sz);
1993 }
1994
1995 double totFree = itabFree +
1996 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
1997 if (totFree > 0) {
1998 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
1999 (totFree * totFree));
2000 frag = (double)1.0 - frag;
2001 } else {
2002 assert(frag == 0.0, "Follows from totFree == 0");
2003 }
2004 return frag;
2005 }
2006
2007 void CompactibleFreeListSpace::beginSweepFLCensus(
2008 float inter_sweep_current,
2009 float inter_sweep_estimate,
2010 float intra_sweep_estimate) {
2011 assert_locked();
2012 size_t i;
2013 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2014 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
2015 log_trace(gc, freelist)("size[" SIZE_FORMAT "] : ", i);
2016 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2017 fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2018 fl->set_before_sweep(fl->count());
2019 fl->set_bfr_surp(fl->surplus());
2020 }
2021 _dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent,
2022 inter_sweep_current,
2023 inter_sweep_estimate,
2024 intra_sweep_estimate);
2025 }
2026
2027 void CompactibleFreeListSpace::setFLSurplus() {
2028 assert_locked();
2029 size_t i;
2030 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2031 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2032 fl->set_surplus(fl->count() -
2033 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2034 }
2035 }
2036
2037 void CompactibleFreeListSpace::setFLHints() {
2038 assert_locked();
2039 size_t i;
2040 size_t h = IndexSetSize;
2041 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2042 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2043 fl->set_hint(h);
2044 if (fl->surplus() > 0) {
2045 h = i;
2046 }
2047 }
2048 }
2049
2050 void CompactibleFreeListSpace::clearFLCensus() {
2051 assert_locked();
2052 size_t i;
2053 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2054 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2055 fl->set_prev_sweep(fl->count());
2056 fl->set_coal_births(0);
2057 fl->set_coal_deaths(0);
2058 fl->set_split_births(0);
2059 fl->set_split_deaths(0);
2060 }
2061 }
2062
2063 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2064 log_debug(gc, freelist)("CMS: Large block " PTR_FORMAT, p2i(dictionary()->find_largest_dict()));
2065 setFLSurplus();
2066 setFLHints();
2067 printFLCensus(sweep_count);
2068 clearFLCensus();
2069 assert_locked();
2070 _dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent);
2071 }
2072
2073 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2074 if (size < SmallForDictionary) {
2075 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2076 return (fl->coal_desired() < 0) ||
2077 ((int)fl->count() > fl->coal_desired());
2078 } else {
2079 return dictionary()->coal_dict_over_populated(size);
2080 }
2081 }
2082
2083 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2084 assert(size < SmallForDictionary, "Size too large for indexed list");
2085 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2086 fl->increment_coal_births();
2087 fl->increment_surplus();
2088 }
2089
2090 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2091 assert(size < SmallForDictionary, "Size too large for indexed list");
2092 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2093 fl->increment_coal_deaths();
2094 fl->decrement_surplus();
2095 }
2096
2097 void CompactibleFreeListSpace::coalBirth(size_t size) {
2098 if (size < SmallForDictionary) {
2099 smallCoalBirth(size);
2100 } else {
2101 dictionary()->dict_census_update(size,
2102 false /* split */,
2103 true /* birth */);
2104 }
2105 }
2106
2107 void CompactibleFreeListSpace::coalDeath(size_t size) {
2108 if(size < SmallForDictionary) {
2109 smallCoalDeath(size);
2110 } else {
2111 dictionary()->dict_census_update(size,
2112 false /* split */,
2113 false /* birth */);
2114 }
2115 }
2116
2117 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2118 assert(size < SmallForDictionary, "Size too large for indexed list");
2119 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2120 fl->increment_split_births();
2121 fl->increment_surplus();
2122 }
2123
2124 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2125 assert(size < SmallForDictionary, "Size too large for indexed list");
2126 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2127 fl->increment_split_deaths();
2128 fl->decrement_surplus();
2129 }
2130
2131 void CompactibleFreeListSpace::split_birth(size_t size) {
2132 if (size < SmallForDictionary) {
2133 smallSplitBirth(size);
2134 } else {
2135 dictionary()->dict_census_update(size,
2136 true /* split */,
2137 true /* birth */);
2138 }
2139 }
2140
2141 void CompactibleFreeListSpace::splitDeath(size_t size) {
2142 if (size < SmallForDictionary) {
2143 smallSplitDeath(size);
2144 } else {
2145 dictionary()->dict_census_update(size,
2146 true /* split */,
2147 false /* birth */);
2148 }
2149 }
2150
2151 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2152 size_t to2 = from - to1;
2153 splitDeath(from);
2154 split_birth(to1);
2155 split_birth(to2);
2156 }
2157
2158 void CompactibleFreeListSpace::print() const {
2159 print_on(tty);
2160 }
2161
2162 void CompactibleFreeListSpace::prepare_for_verify() {
2163 assert_locked();
2164 repairLinearAllocationBlocks();
2165 // Verify that the SpoolBlocks look like free blocks of
2166 // appropriate sizes... To be done ...
2167 }
2168
2169 class VerifyAllBlksClosure: public BlkClosure {
2170 private:
2171 const CompactibleFreeListSpace* _sp;
2172 const MemRegion _span;
2173 HeapWord* _last_addr;
2174 size_t _last_size;
2175 bool _last_was_obj;
2176 bool _last_was_live;
2177
2178 public:
2179 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2180 MemRegion span) : _sp(sp), _span(span),
2181 _last_addr(NULL), _last_size(0),
2182 _last_was_obj(false), _last_was_live(false) { }
2183
2184 virtual size_t do_blk(HeapWord* addr) {
2185 size_t res;
2186 bool was_obj = false;
2187 bool was_live = false;
2188 if (_sp->block_is_obj(addr)) {
2189 was_obj = true;
2190 oop p = oop(addr);
2191 guarantee(p->is_oop(), "Should be an oop");
2192 res = _sp->adjustObjectSize(p->size());
2193 if (_sp->obj_is_alive(addr)) {
2194 was_live = true;
2195 p->verify();
2196 }
2197 } else {
2198 FreeChunk* fc = (FreeChunk*)addr;
2199 res = fc->size();
2200 if (FLSVerifyLists && !fc->cantCoalesce()) {
2201 guarantee(_sp->verify_chunk_in_free_list(fc),
2202 "Chunk should be on a free list");
2203 }
2204 }
2205 if (res == 0) {
2206 Log(gc, verify) log;
2207 log.error("Livelock: no rank reduction!");
2208 log.error(" Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2209 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2210 p2i(addr), res, was_obj ?"true":"false", was_live ?"true":"false",
2211 p2i(_last_addr), _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2212 ResourceMark rm;
2213 _sp->print_on(log.error_stream());
2214 guarantee(false, "Verification failed.");
2215 }
2216 _last_addr = addr;
2217 _last_size = res;
2218 _last_was_obj = was_obj;
2219 _last_was_live = was_live;
2220 return res;
2221 }
2222 };
2223
2224 class VerifyAllOopsClosure: public OopClosure {
2225 private:
2226 const CMSCollector* _collector;
2227 const CompactibleFreeListSpace* _sp;
2228 const MemRegion _span;
2229 const bool _past_remark;
2230 const CMSBitMap* _bit_map;
2231
2232 protected:
2233 void do_oop(void* p, oop obj) {
2234 if (_span.contains(obj)) { // the interior oop points into CMS heap
2235 if (!_span.contains(p)) { // reference from outside CMS heap
2236 // Should be a valid object; the first disjunct below allows
2237 // us to sidestep an assertion in block_is_obj() that insists
2238 // that p be in _sp. Note that several generations (and spaces)
2239 // are spanned by _span (CMS heap) above.
2240 guarantee(!_sp->is_in_reserved(obj) ||
2241 _sp->block_is_obj((HeapWord*)obj),
2242 "Should be an object");
2243 guarantee(obj->is_oop(), "Should be an oop");
2244 obj->verify();
2245 if (_past_remark) {
2246 // Remark has been completed, the object should be marked
2247 _bit_map->isMarked((HeapWord*)obj);
2248 }
2249 } else { // reference within CMS heap
2250 if (_past_remark) {
2251 // Remark has been completed -- so the referent should have
2252 // been marked, if referring object is.
2253 if (_bit_map->isMarked(_collector->block_start(p))) {
2254 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2255 }
2256 }
2257 }
2258 } else if (_sp->is_in_reserved(p)) {
2259 // the reference is from FLS, and points out of FLS
2260 guarantee(obj->is_oop(), "Should be an oop");
2261 obj->verify();
2262 }
2263 }
2264
2265 template <class T> void do_oop_work(T* p) {
2266 T heap_oop = oopDesc::load_heap_oop(p);
2267 if (!oopDesc::is_null(heap_oop)) {
2268 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2269 do_oop(p, obj);
2270 }
2271 }
2272
2273 public:
2274 VerifyAllOopsClosure(const CMSCollector* collector,
2275 const CompactibleFreeListSpace* sp, MemRegion span,
2276 bool past_remark, CMSBitMap* bit_map) :
2277 _collector(collector), _sp(sp), _span(span),
2278 _past_remark(past_remark), _bit_map(bit_map) { }
2279
2280 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2281 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2282 };
2283
2284 void CompactibleFreeListSpace::verify() const {
2285 assert_lock_strong(&_freelistLock);
2286 verify_objects_initialized();
2287 MemRegion span = _collector->_span;
2288 bool past_remark = (_collector->abstract_state() ==
2289 CMSCollector::Sweeping);
2290
2291 ResourceMark rm;
2292 HandleMark hm;
2293
2294 // Check integrity of CFL data structures
2295 _promoInfo.verify();
2296 _dictionary->verify();
2297 if (FLSVerifyIndexTable) {
2298 verifyIndexedFreeLists();
2299 }
2300 // Check integrity of all objects and free blocks in space
2301 {
2302 VerifyAllBlksClosure cl(this, span);
2303 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2304 }
2305 // Check that all references in the heap to FLS
2306 // are to valid objects in FLS or that references in
2307 // FLS are to valid objects elsewhere in the heap
2308 if (FLSVerifyAllHeapReferences)
2309 {
2310 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2311 _collector->markBitMap());
2312
2313 // Iterate over all oops in the heap. Uses the _no_header version
2314 // since we are not interested in following the klass pointers.
2315 GenCollectedHeap::heap()->oop_iterate_no_header(&cl);
2316 }
2317
2318 if (VerifyObjectStartArray) {
2319 // Verify the block offset table
2320 _bt.verify();
2321 }
2322 }
2323
2324 #ifndef PRODUCT
2325 void CompactibleFreeListSpace::verifyFreeLists() const {
2326 if (FLSVerifyLists) {
2327 _dictionary->verify();
2328 verifyIndexedFreeLists();
2329 } else {
2330 if (FLSVerifyDictionary) {
2331 _dictionary->verify();
2332 }
2333 if (FLSVerifyIndexTable) {
2334 verifyIndexedFreeLists();
2335 }
2336 }
2337 }
2338 #endif
2339
2340 void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
2341 size_t i = 0;
2342 for (; i < IndexSetStart; i++) {
2343 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
2344 }
2345 for (; i < IndexSetSize; i++) {
2346 verifyIndexedFreeList(i);
2347 }
2348 }
2349
2350 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
2351 FreeChunk* fc = _indexedFreeList[size].head();
2352 FreeChunk* tail = _indexedFreeList[size].tail();
2353 size_t num = _indexedFreeList[size].count();
2354 size_t n = 0;
2355 guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL,
2356 "Slot should have been empty");
2357 for (; fc != NULL; fc = fc->next(), n++) {
2358 guarantee(fc->size() == size, "Size inconsistency");
2359 guarantee(fc->is_free(), "!free?");
2360 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
2361 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
2362 }
2363 guarantee(n == num, "Incorrect count");
2364 }
2365
2366 #ifndef PRODUCT
2367 void CompactibleFreeListSpace::check_free_list_consistency() const {
2368 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size() <= IndexSetSize),
2369 "Some sizes can't be allocated without recourse to"
2370 " linear allocation buffers");
2371 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >)),
2372 "else MIN_TREE_CHUNK_SIZE is wrong");
2373 assert(IndexSetStart != 0, "IndexSetStart not initialized");
2374 assert(IndexSetStride != 0, "IndexSetStride not initialized");
2375 }
2376 #endif
2377
2378 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2379 assert_lock_strong(&_freelistLock);
2380 LogTarget(Debug, gc, freelist, census) log;
2381 if (!log.is_enabled()) {
2382 return;
2383 }
2384 AdaptiveFreeList<FreeChunk> total;
2385 log.print("end sweep# " SIZE_FORMAT, sweep_count);
2386 ResourceMark rm;
2387 outputStream* out = log.stream();
2388 AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
2389 size_t total_free = 0;
2390 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2391 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2392 total_free += fl->count() * fl->size();
2393 if (i % (40*IndexSetStride) == 0) {
2394 AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
2395 }
2396 fl->print_on(out);
2397 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
2398 total.set_surplus( total.surplus() + fl->surplus() );
2399 total.set_desired( total.desired() + fl->desired() );
2400 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
2401 total.set_before_sweep(total.before_sweep() + fl->before_sweep());
2402 total.set_count( total.count() + fl->count() );
2403 total.set_coal_births( total.coal_births() + fl->coal_births() );
2404 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
2405 total.set_split_births(total.split_births() + fl->split_births());
2406 total.set_split_deaths(total.split_deaths() + fl->split_deaths());
2407 }
2408 total.print_on(out, "TOTAL");
2409 log.print("Total free in indexed lists " SIZE_FORMAT " words", total_free);
2410 log.print("growth: %8.5f deficit: %8.5f",
2411 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
2412 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
2413 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2414 _dictionary->print_dict_census(out);
2415 }
2416
2417 ///////////////////////////////////////////////////////////////////////////
2418 // CompactibleFreeListSpaceLAB
2419 ///////////////////////////////////////////////////////////////////////////
2420
2421 #define VECTOR_257(x) \
2422 /* 1 2 3 4 5 6 7 8 9 1x 11 12 13 14 15 16 17 18 19 2x 21 22 23 24 25 26 27 28 29 3x 31 32 */ \
2423 { x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2424 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2425 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2426 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2427 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2428 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2429 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2430 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2431 x }
2432
2433 // Initialize with default setting for CMS, _not_
2434 // generic OldPLABSize, whose static default is different; if overridden at the
2435 // command-line, this will get reinitialized via a call to
2436 // modify_initialization() below.
2437 AdaptiveWeightedAverage CompactibleFreeListSpaceLAB::_blocks_to_claim[] =
2438 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CompactibleFreeListSpaceLAB::_default_dynamic_old_plab_size));
2439 size_t CompactibleFreeListSpaceLAB::_global_num_blocks[] = VECTOR_257(0);
2440 uint CompactibleFreeListSpaceLAB::_global_num_workers[] = VECTOR_257(0);
2441
2442 CompactibleFreeListSpaceLAB::CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls) :
2443 _cfls(cfls)
2444 {
2445 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2446 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2447 i < CompactibleFreeListSpace::IndexSetSize;
2448 i += CompactibleFreeListSpace::IndexSetStride) {
2449 _indexedFreeList[i].set_size(i);
2450 _num_blocks[i] = 0;
2451 }
2452 }
2453
2454 static bool _CFLS_LAB_modified = false;
2455
2456 void CompactibleFreeListSpaceLAB::modify_initialization(size_t n, unsigned wt) {
2457 assert(!_CFLS_LAB_modified, "Call only once");
2458 _CFLS_LAB_modified = true;
2459 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2460 i < CompactibleFreeListSpace::IndexSetSize;
2461 i += CompactibleFreeListSpace::IndexSetStride) {
2462 _blocks_to_claim[i].modify(n, wt, true /* force */);
2463 }
2464 }
2465
2466 HeapWord* CompactibleFreeListSpaceLAB::alloc(size_t word_sz) {
2467 FreeChunk* res;
2468 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2469 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2470 // This locking manages sync with other large object allocations.
2471 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2472 Mutex::_no_safepoint_check_flag);
2473 res = _cfls->getChunkFromDictionaryExact(word_sz);
2474 if (res == NULL) return NULL;
2475 } else {
2476 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
2477 if (fl->count() == 0) {
2478 // Attempt to refill this local free list.
2479 get_from_global_pool(word_sz, fl);
2480 // If it didn't work, give up.
2481 if (fl->count() == 0) return NULL;
2482 }
2483 res = fl->get_chunk_at_head();
2484 assert(res != NULL, "Why was count non-zero?");
2485 }
2486 res->markNotFree();
2487 assert(!res->is_free(), "shouldn't be marked free");
2488 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2489 // mangle a just allocated object with a distinct pattern.
2490 debug_only(res->mangleAllocated(word_sz));
2491 return (HeapWord*)res;
2492 }
2493
2494 // Get a chunk of blocks of the right size and update related
2495 // book-keeping stats
2496 void CompactibleFreeListSpaceLAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
2497 // Get the #blocks we want to claim
2498 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2499 assert(n_blks > 0, "Error");
2500 assert(ResizeOldPLAB || n_blks == OldPLABSize, "Error");
2501 // In some cases, when the application has a phase change,
2502 // there may be a sudden and sharp shift in the object survival
2503 // profile, and updating the counts at the end of a scavenge
2504 // may not be quick enough, giving rise to large scavenge pauses
2505 // during these phase changes. It is beneficial to detect such
2506 // changes on-the-fly during a scavenge and avoid such a phase-change
2507 // pothole. The following code is a heuristic attempt to do that.
2508 // It is protected by a product flag until we have gained
2509 // enough experience with this heuristic and fine-tuned its behavior.
2510 // WARNING: This might increase fragmentation if we overreact to
2511 // small spikes, so some kind of historical smoothing based on
2512 // previous experience with the greater reactivity might be useful.
2513 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2514 // default.
2515 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2516 //
2517 // On a 32-bit VM, the denominator can become zero because of integer overflow,
2518 // which is why there is a cast to double.
2519 //
2520 size_t multiple = (size_t) (_num_blocks[word_sz]/(((double)CMSOldPLABToleranceFactor)*CMSOldPLABNumRefills*n_blks));
2521 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2522 n_blks = MIN2(n_blks, CMSOldPLABMax);
2523 }
2524 assert(n_blks > 0, "Error");
2525 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2526 // Update stats table entry for this block size
2527 _num_blocks[word_sz] += fl->count();
2528 }
2529
2530 void CompactibleFreeListSpaceLAB::compute_desired_plab_size() {
2531 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2532 i < CompactibleFreeListSpace::IndexSetSize;
2533 i += CompactibleFreeListSpace::IndexSetStride) {
2534 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2535 "Counter inconsistency");
2536 if (_global_num_workers[i] > 0) {
2537 // Need to smooth wrt historical average
2538 if (ResizeOldPLAB) {
2539 _blocks_to_claim[i].sample(
2540 MAX2(CMSOldPLABMin,
2541 MIN2(CMSOldPLABMax,
2542 _global_num_blocks[i]/_global_num_workers[i]/CMSOldPLABNumRefills)));
2543 }
2544 // Reset counters for next round
2545 _global_num_workers[i] = 0;
2546 _global_num_blocks[i] = 0;
2547 log_trace(gc, plab)("[" SIZE_FORMAT "]: " SIZE_FORMAT, i, (size_t)_blocks_to_claim[i].average());
2548 }
2549 }
2550 }
2551
2552 // If this is changed in the future to allow parallel
2553 // access, one would need to take the FL locks and,
2554 // depending on how it is used, stagger access from
2555 // parallel threads to reduce contention.
2556 void CompactibleFreeListSpaceLAB::retire(int tid) {
2557 // We run this single threaded with the world stopped;
2558 // so no need for locks and such.
2559 NOT_PRODUCT(Thread* t = Thread::current();)
2560 assert(Thread::current()->is_VM_thread(), "Error");
2561 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2562 i < CompactibleFreeListSpace::IndexSetSize;
2563 i += CompactibleFreeListSpace::IndexSetStride) {
2564 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2565 "Can't retire more than what we obtained");
2566 if (_num_blocks[i] > 0) {
2567 size_t num_retire = _indexedFreeList[i].count();
2568 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2569 {
2570 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2571 // Mutex::_no_safepoint_check_flag);
2572
2573 // Update globals stats for num_blocks used
2574 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2575 _global_num_workers[i]++;
2576 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2577 if (num_retire > 0) {
2578 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2579 // Reset this list.
2580 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
2581 _indexedFreeList[i].set_size(i);
2582 }
2583 }
2584 log_trace(gc, plab)("%d[" SIZE_FORMAT "]: " SIZE_FORMAT "/" SIZE_FORMAT "/" SIZE_FORMAT,
2585 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2586 // Reset stats for next round
2587 _num_blocks[i] = 0;
2588 }
2589 }
2590 }
2591
2592 // Used by par_get_chunk_of_blocks() for the chunks from the
2593 // indexed_free_lists. Looks for a chunk with size that is a multiple
2594 // of "word_sz" and if found, splits it into "word_sz" chunks and add
2595 // to the free list "fl". "n" is the maximum number of chunks to
2596 // be added to "fl".
2597 bool CompactibleFreeListSpace:: par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2598
2599 // We'll try all multiples of word_sz in the indexed set, starting with
2600 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2601 // then try getting a big chunk and splitting it.
2602 {
2603 bool found;
2604 int k;
2605 size_t cur_sz;
2606 for (k = 1, cur_sz = k * word_sz, found = false;
2607 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2608 (CMSSplitIndexedFreeListBlocks || k <= 1);
2609 k++, cur_sz = k * word_sz) {
2610 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
2611 fl_for_cur_sz.set_size(cur_sz);
2612 {
2613 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2614 Mutex::_no_safepoint_check_flag);
2615 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
2616 if (gfl->count() != 0) {
2617 // nn is the number of chunks of size cur_sz that
2618 // we'd need to split k-ways each, in order to create
2619 // "n" chunks of size word_sz each.
2620 const size_t nn = MAX2(n/k, (size_t)1);
2621 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2622 found = true;
2623 if (k > 1) {
2624 // Update split death stats for the cur_sz-size blocks list:
2625 // we increment the split death count by the number of blocks
2626 // we just took from the cur_sz-size blocks list and which
2627 // we will be splitting below.
2628 ssize_t deaths = gfl->split_deaths() +
2629 fl_for_cur_sz.count();
2630 gfl->set_split_deaths(deaths);
2631 }
2632 }
2633 }
2634 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2635 if (found) {
2636 if (k == 1) {
2637 fl->prepend(&fl_for_cur_sz);
2638 } else {
2639 // Divide each block on fl_for_cur_sz up k ways.
2640 FreeChunk* fc;
2641 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
2642 // Must do this in reverse order, so that anybody attempting to
2643 // access the main chunk sees it as a single free block until we
2644 // change it.
2645 size_t fc_size = fc->size();
2646 assert(fc->is_free(), "Error");
2647 for (int i = k-1; i >= 0; i--) {
2648 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2649 assert((i != 0) ||
2650 ((fc == ffc) && ffc->is_free() &&
2651 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2652 "Counting error");
2653 ffc->set_size(word_sz);
2654 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2655 ffc->link_next(NULL);
2656 // Above must occur before BOT is updated below.
2657 OrderAccess::storestore();
2658 // splitting from the right, fc_size == i * word_sz
2659 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2660 fc_size -= word_sz;
2661 assert(fc_size == i*word_sz, "Error");
2662 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2663 _bt.verify_single_block((HeapWord*)fc, fc_size);
2664 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2665 // Push this on "fl".
2666 fl->return_chunk_at_head(ffc);
2667 }
2668 // TRAP
2669 assert(fl->tail()->next() == NULL, "List invariant.");
2670 }
2671 }
2672 // Update birth stats for this block size.
2673 size_t num = fl->count();
2674 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2675 Mutex::_no_safepoint_check_flag);
2676 ssize_t births = _indexedFreeList[word_sz].split_births() + num;
2677 _indexedFreeList[word_sz].set_split_births(births);
2678 return true;
2679 }
2680 }
2681 return found;
2682 }
2683 }
2684
2685 FreeChunk* CompactibleFreeListSpace::get_n_way_chunk_to_split(size_t word_sz, size_t n) {
2686
2687 FreeChunk* fc = NULL;
2688 FreeChunk* rem_fc = NULL;
2689 size_t rem;
2690 {
2691 MutexLockerEx x(parDictionaryAllocLock(),
2692 Mutex::_no_safepoint_check_flag);
2693 while (n > 0) {
2694 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()),
2695 FreeBlockDictionary<FreeChunk>::atLeast);
2696 if (fc != NULL) {
2697 break;
2698 } else {
2699 n--;
2700 }
2701 }
2702 if (fc == NULL) return NULL;
2703 // Otherwise, split up that block.
2704 assert((ssize_t)n >= 1, "Control point invariant");
2705 assert(fc->is_free(), "Error: should be a free block");
2706 _bt.verify_single_block((HeapWord*)fc, fc->size());
2707 const size_t nn = fc->size() / word_sz;
2708 n = MIN2(nn, n);
2709 assert((ssize_t)n >= 1, "Control point invariant");
2710 rem = fc->size() - n * word_sz;
2711 // If there is a remainder, and it's too small, allocate one fewer.
2712 if (rem > 0 && rem < MinChunkSize) {
2713 n--; rem += word_sz;
2714 }
2715 // Note that at this point we may have n == 0.
2716 assert((ssize_t)n >= 0, "Control point invariant");
2717
2718 // If n is 0, the chunk fc that was found is not large
2719 // enough to leave a viable remainder. We are unable to
2720 // allocate even one block. Return fc to the
2721 // dictionary and return, leaving "fl" empty.
2722 if (n == 0) {
2723 returnChunkToDictionary(fc);
2724 return NULL;
2725 }
2726
2727 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2728 dictionary()->dict_census_update(fc->size(),
2729 true /*split*/,
2730 false /*birth*/);
2731
2732 // First return the remainder, if any.
2733 // Note that we hold the lock until we decide if we're going to give
2734 // back the remainder to the dictionary, since a concurrent allocation
2735 // may otherwise see the heap as empty. (We're willing to take that
2736 // hit if the block is a small block.)
2737 if (rem > 0) {
2738 size_t prefix_size = n * word_sz;
2739 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2740 rem_fc->set_size(rem);
2741 rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2742 rem_fc->link_next(NULL);
2743 // Above must occur before BOT is updated below.
2744 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2745 OrderAccess::storestore();
2746 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2747 assert(fc->is_free(), "Error");
2748 fc->set_size(prefix_size);
2749 if (rem >= IndexSetSize) {
2750 returnChunkToDictionary(rem_fc);
2751 dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/);
2752 rem_fc = NULL;
2753 }
2754 // Otherwise, return it to the small list below.
2755 }
2756 }
2757 if (rem_fc != NULL) {
2758 MutexLockerEx x(_indexedFreeListParLocks[rem],
2759 Mutex::_no_safepoint_check_flag);
2760 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2761 _indexedFreeList[rem].return_chunk_at_head(rem_fc);
2762 smallSplitBirth(rem);
2763 }
2764 assert(n * word_sz == fc->size(),
2765 "Chunk size " SIZE_FORMAT " is not exactly splittable by "
2766 SIZE_FORMAT " sized chunks of size " SIZE_FORMAT,
2767 fc->size(), n, word_sz);
2768 return fc;
2769 }
2770
2771 void CompactibleFreeListSpace:: par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t targetted_number_of_chunks, AdaptiveFreeList<FreeChunk>* fl) {
2772
2773 FreeChunk* fc = get_n_way_chunk_to_split(word_sz, targetted_number_of_chunks);
2774
2775 if (fc == NULL) {
2776 return;
2777 }
2778
2779 size_t n = fc->size() / word_sz;
2780
2781 assert((ssize_t)n > 0, "Consistency");
2782 // Now do the splitting up.
2783 // Must do this in reverse order, so that anybody attempting to
2784 // access the main chunk sees it as a single free block until we
2785 // change it.
2786 size_t fc_size = n * word_sz;
2787 // All but first chunk in this loop
2788 for (ssize_t i = n-1; i > 0; i--) {
2789 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2790 ffc->set_size(word_sz);
2791 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2792 ffc->link_next(NULL);
2793 // Above must occur before BOT is updated below.
2794 OrderAccess::storestore();
2795 // splitting from the right, fc_size == (n - i + 1) * wordsize
2796 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2797 fc_size -= word_sz;
2798 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2799 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2800 _bt.verify_single_block((HeapWord*)fc, fc_size);
2801 // Push this on "fl".
2802 fl->return_chunk_at_head(ffc);
2803 }
2804 // First chunk
2805 assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block");
2806 // The blocks above should show their new sizes before the first block below
2807 fc->set_size(word_sz);
2808 fc->link_prev(NULL); // idempotent wrt free-ness, see assert above
2809 fc->link_next(NULL);
2810 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2811 _bt.verify_single_block((HeapWord*)fc, fc->size());
2812 fl->return_chunk_at_head(fc);
2813
2814 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2815 {
2816 // Update the stats for this block size.
2817 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2818 Mutex::_no_safepoint_check_flag);
2819 const ssize_t births = _indexedFreeList[word_sz].split_births() + n;
2820 _indexedFreeList[word_sz].set_split_births(births);
2821 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2822 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2823 }
2824
2825 // TRAP
2826 assert(fl->tail()->next() == NULL, "List invariant.");
2827 }
2828
2829 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2830 assert(fl->count() == 0, "Precondition.");
2831 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2832 "Precondition");
2833
2834 if (par_get_chunk_of_blocks_IFL(word_sz, n, fl)) {
2835 // Got it
2836 return;
2837 }
2838
2839 // Otherwise, we'll split a block from the dictionary.
2840 par_get_chunk_of_blocks_dictionary(word_sz, n, fl);
2841 }
2842
2843 // Set up the space's par_seq_tasks structure for work claiming
2844 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2845 // XXX Need to suitably abstract and generalize this and the next
2846 // method into one.
2847 void
2848 CompactibleFreeListSpace::
2849 initialize_sequential_subtasks_for_rescan(int n_threads) {
2850 // The "size" of each task is fixed according to rescan_task_size.
2851 assert(n_threads > 0, "Unexpected n_threads argument");
2852 const size_t task_size = rescan_task_size();
2853 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2854 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2855 assert(n_tasks == 0 ||
2856 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2857 (used_region().start() + n_tasks*task_size >= used_region().end())),
2858 "n_tasks calculation incorrect");
2859 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2860 assert(!pst->valid(), "Clobbering existing data?");
2861 // Sets the condition for completion of the subtask (how many threads
2862 // need to finish in order to be done).
2863 pst->set_n_threads(n_threads);
2864 pst->set_n_tasks((int)n_tasks);
2865 }
2866
2867 // Set up the space's par_seq_tasks structure for work claiming
2868 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2869 void
2870 CompactibleFreeListSpace::
2871 initialize_sequential_subtasks_for_marking(int n_threads,
2872 HeapWord* low) {
2873 // The "size" of each task is fixed according to rescan_task_size.
2874 assert(n_threads > 0, "Unexpected n_threads argument");
2875 const size_t task_size = marking_task_size();
2876 assert(task_size > CardTableModRefBS::card_size_in_words &&
2877 (task_size % CardTableModRefBS::card_size_in_words == 0),
2878 "Otherwise arithmetic below would be incorrect");
2879 MemRegion span = _old_gen->reserved();
2880 if (low != NULL) {
2881 if (span.contains(low)) {
2882 // Align low down to a card boundary so that
2883 // we can use block_offset_careful() on span boundaries.
2884 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
2885 CardTableModRefBS::card_size);
2886 // Clip span prefix at aligned_low
2887 span = span.intersection(MemRegion(aligned_low, span.end()));
2888 } else if (low > span.end()) {
2889 span = MemRegion(low, low); // Null region
2890 } // else use entire span
2891 }
2892 assert(span.is_empty() ||
2893 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
2894 "span should start at a card boundary");
2895 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
2896 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
2897 assert(n_tasks == 0 ||
2898 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
2899 (span.start() + n_tasks*task_size >= span.end())),
2900 "n_tasks calculation incorrect");
2901 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2902 assert(!pst->valid(), "Clobbering existing data?");
2903 // Sets the condition for completion of the subtask (how many threads
2904 // need to finish in order to be done).
2905 pst->set_n_threads(n_threads);
2906 pst->set_n_tasks((int)n_tasks);
2907 }