Mon, 16 Apr 2012 08:57:18 +0200
4988100: oop_verify_old_oop appears to be dead
Summary: removed oop_verify_old_oop and allow_dirty. Also reviewed by: alexlamsl@gmail.com
Reviewed-by: jmasa, jwilhelm
1 /*
2 * Copyright (c) 2001, 2012, 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
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7 * published by the Free Software Foundation.
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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).
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15 * You should have received a copy of the GNU General Public License version
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/concurrentMarkSweep/cmsLockVerifier.hpp"
27 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp"
28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
29 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
30 #include "gc_implementation/shared/liveRange.hpp"
31 #include "gc_implementation/shared/spaceDecorator.hpp"
32 #include "gc_interface/collectedHeap.hpp"
33 #include "memory/allocation.inline.hpp"
34 #include "memory/blockOffsetTable.inline.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/globals.hpp"
39 #include "runtime/handles.inline.hpp"
40 #include "runtime/init.hpp"
41 #include "runtime/java.hpp"
42 #include "runtime/vmThread.hpp"
43 #include "utilities/copy.hpp"
45 /////////////////////////////////////////////////////////////////////////
46 //// CompactibleFreeListSpace
47 /////////////////////////////////////////////////////////////////////////
49 // highest ranked free list lock rank
50 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
52 // Defaults are 0 so things will break badly if incorrectly initialized.
53 size_t CompactibleFreeListSpace::IndexSetStart = 0;
54 size_t CompactibleFreeListSpace::IndexSetStride = 0;
56 size_t MinChunkSize = 0;
58 void CompactibleFreeListSpace::set_cms_values() {
59 // Set CMS global values
60 assert(MinChunkSize == 0, "already set");
61 #define numQuanta(x,y) ((x+y-1)/y)
62 MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment;
64 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
65 IndexSetStart = MinChunkSize;
66 IndexSetStride = MinObjAlignment;
67 }
69 // Constructor
70 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs,
71 MemRegion mr, bool use_adaptive_freelists,
72 FreeBlockDictionary::DictionaryChoice dictionaryChoice) :
73 _dictionaryChoice(dictionaryChoice),
74 _adaptive_freelists(use_adaptive_freelists),
75 _bt(bs, mr),
76 // free list locks are in the range of values taken by _lockRank
77 // This range currently is [_leaf+2, _leaf+3]
78 // Note: this requires that CFLspace c'tors
79 // are called serially in the order in which the locks are
80 // are acquired in the program text. This is true today.
81 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true),
82 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
83 "CompactibleFreeListSpace._dict_par_lock", true),
84 _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
85 CMSRescanMultiple),
86 _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
87 CMSConcMarkMultiple),
88 _collector(NULL)
89 {
90 _bt.set_space(this);
91 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
92 // We have all of "mr", all of which we place in the dictionary
93 // as one big chunk. We'll need to decide here which of several
94 // possible alternative dictionary implementations to use. For
95 // now the choice is easy, since we have only one working
96 // implementation, namely, the simple binary tree (splaying
97 // temporarily disabled).
98 switch (dictionaryChoice) {
99 case FreeBlockDictionary::dictionarySplayTree:
100 case FreeBlockDictionary::dictionarySkipList:
101 default:
102 warning("dictionaryChoice: selected option not understood; using"
103 " default BinaryTreeDictionary implementation instead.");
104 case FreeBlockDictionary::dictionaryBinaryTree:
105 _dictionary = new BinaryTreeDictionary(mr);
106 break;
107 }
108 assert(_dictionary != NULL, "CMS dictionary initialization");
109 // The indexed free lists are initially all empty and are lazily
110 // filled in on demand. Initialize the array elements to NULL.
111 initializeIndexedFreeListArray();
113 // Not using adaptive free lists assumes that allocation is first
114 // from the linAB's. Also a cms perm gen which can be compacted
115 // has to have the klass's klassKlass allocated at a lower
116 // address in the heap than the klass so that the klassKlass is
117 // moved to its new location before the klass is moved.
118 // Set the _refillSize for the linear allocation blocks
119 if (!use_adaptive_freelists) {
120 FreeChunk* fc = _dictionary->getChunk(mr.word_size());
121 // The small linAB initially has all the space and will allocate
122 // a chunk of any size.
123 HeapWord* addr = (HeapWord*) fc;
124 _smallLinearAllocBlock.set(addr, fc->size() ,
125 1024*SmallForLinearAlloc, fc->size());
126 // Note that _unallocated_block is not updated here.
127 // Allocations from the linear allocation block should
128 // update it.
129 } else {
130 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
131 SmallForLinearAlloc);
132 }
133 // CMSIndexedFreeListReplenish should be at least 1
134 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
135 _promoInfo.setSpace(this);
136 if (UseCMSBestFit) {
137 _fitStrategy = FreeBlockBestFitFirst;
138 } else {
139 _fitStrategy = FreeBlockStrategyNone;
140 }
141 check_free_list_consistency();
143 // Initialize locks for parallel case.
145 if (CollectedHeap::use_parallel_gc_threads()) {
146 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
147 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
148 "a freelist par lock",
149 true);
150 if (_indexedFreeListParLocks[i] == NULL)
151 vm_exit_during_initialization("Could not allocate a par lock");
152 DEBUG_ONLY(
153 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
154 )
155 }
156 _dictionary->set_par_lock(&_parDictionaryAllocLock);
157 }
158 }
160 // Like CompactibleSpace forward() but always calls cross_threshold() to
161 // update the block offset table. Removed initialize_threshold call because
162 // CFLS does not use a block offset array for contiguous spaces.
163 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
164 CompactPoint* cp, HeapWord* compact_top) {
165 // q is alive
166 // First check if we should switch compaction space
167 assert(this == cp->space, "'this' should be current compaction space.");
168 size_t compaction_max_size = pointer_delta(end(), compact_top);
169 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
170 "virtual adjustObjectSize_v() method is not correct");
171 size_t adjusted_size = adjustObjectSize(size);
172 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
173 "no small fragments allowed");
174 assert(minimum_free_block_size() == MinChunkSize,
175 "for de-virtualized reference below");
176 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
177 if (adjusted_size + MinChunkSize > compaction_max_size &&
178 adjusted_size != compaction_max_size) {
179 do {
180 // switch to next compaction space
181 cp->space->set_compaction_top(compact_top);
182 cp->space = cp->space->next_compaction_space();
183 if (cp->space == NULL) {
184 cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen);
185 assert(cp->gen != NULL, "compaction must succeed");
186 cp->space = cp->gen->first_compaction_space();
187 assert(cp->space != NULL, "generation must have a first compaction space");
188 }
189 compact_top = cp->space->bottom();
190 cp->space->set_compaction_top(compact_top);
191 // The correct adjusted_size may not be the same as that for this method
192 // (i.e., cp->space may no longer be "this" so adjust the size again.
193 // Use the virtual method which is not used above to save the virtual
194 // dispatch.
195 adjusted_size = cp->space->adjust_object_size_v(size);
196 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
197 assert(cp->space->minimum_free_block_size() == 0, "just checking");
198 } while (adjusted_size > compaction_max_size);
199 }
201 // store the forwarding pointer into the mark word
202 if ((HeapWord*)q != compact_top) {
203 q->forward_to(oop(compact_top));
204 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
205 } else {
206 // if the object isn't moving we can just set the mark to the default
207 // mark and handle it specially later on.
208 q->init_mark();
209 assert(q->forwardee() == NULL, "should be forwarded to NULL");
210 }
212 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(q, adjusted_size));
213 compact_top += adjusted_size;
215 // we need to update the offset table so that the beginnings of objects can be
216 // found during scavenge. Note that we are updating the offset table based on
217 // where the object will be once the compaction phase finishes.
219 // Always call cross_threshold(). A contiguous space can only call it when
220 // the compaction_top exceeds the current threshold but not for an
221 // non-contiguous space.
222 cp->threshold =
223 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
224 return compact_top;
225 }
227 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
228 // and use of single_block instead of alloc_block. The name here is not really
229 // appropriate - maybe a more general name could be invented for both the
230 // contiguous and noncontiguous spaces.
232 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
233 _bt.single_block(start, the_end);
234 return end();
235 }
237 // Initialize them to NULL.
238 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
239 for (size_t i = 0; i < IndexSetSize; i++) {
240 // Note that on platforms where objects are double word aligned,
241 // the odd array elements are not used. It is convenient, however,
242 // to map directly from the object size to the array element.
243 _indexedFreeList[i].reset(IndexSetSize);
244 _indexedFreeList[i].set_size(i);
245 assert(_indexedFreeList[i].count() == 0, "reset check failed");
246 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
247 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
248 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
249 }
250 }
252 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
253 for (size_t i = 1; i < IndexSetSize; i++) {
254 assert(_indexedFreeList[i].size() == (size_t) i,
255 "Indexed free list sizes are incorrect");
256 _indexedFreeList[i].reset(IndexSetSize);
257 assert(_indexedFreeList[i].count() == 0, "reset check failed");
258 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
259 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
260 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
261 }
262 }
264 void CompactibleFreeListSpace::reset(MemRegion mr) {
265 resetIndexedFreeListArray();
266 dictionary()->reset();
267 if (BlockOffsetArrayUseUnallocatedBlock) {
268 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
269 // Everything's allocated until proven otherwise.
270 _bt.set_unallocated_block(end());
271 }
272 if (!mr.is_empty()) {
273 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
274 _bt.single_block(mr.start(), mr.word_size());
275 FreeChunk* fc = (FreeChunk*) mr.start();
276 fc->setSize(mr.word_size());
277 if (mr.word_size() >= IndexSetSize ) {
278 returnChunkToDictionary(fc);
279 } else {
280 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
281 _indexedFreeList[mr.word_size()].returnChunkAtHead(fc);
282 }
283 }
284 _promoInfo.reset();
285 _smallLinearAllocBlock._ptr = NULL;
286 _smallLinearAllocBlock._word_size = 0;
287 }
289 void CompactibleFreeListSpace::reset_after_compaction() {
290 // Reset the space to the new reality - one free chunk.
291 MemRegion mr(compaction_top(), end());
292 reset(mr);
293 // Now refill the linear allocation block(s) if possible.
294 if (_adaptive_freelists) {
295 refillLinearAllocBlocksIfNeeded();
296 } else {
297 // Place as much of mr in the linAB as we can get,
298 // provided it was big enough to go into the dictionary.
299 FreeChunk* fc = dictionary()->findLargestDict();
300 if (fc != NULL) {
301 assert(fc->size() == mr.word_size(),
302 "Why was the chunk broken up?");
303 removeChunkFromDictionary(fc);
304 HeapWord* addr = (HeapWord*) fc;
305 _smallLinearAllocBlock.set(addr, fc->size() ,
306 1024*SmallForLinearAlloc, fc->size());
307 // Note that _unallocated_block is not updated here.
308 }
309 }
310 }
312 // Walks the entire dictionary, returning a coterminal
313 // chunk, if it exists. Use with caution since it involves
314 // a potentially complete walk of a potentially large tree.
315 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
317 assert_lock_strong(&_freelistLock);
319 return dictionary()->find_chunk_ends_at(end());
320 }
323 #ifndef PRODUCT
324 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
325 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
326 _indexedFreeList[i].allocation_stats()->set_returnedBytes(0);
327 }
328 }
330 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
331 size_t sum = 0;
332 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
333 sum += _indexedFreeList[i].allocation_stats()->returnedBytes();
334 }
335 return sum;
336 }
338 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
339 size_t count = 0;
340 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
341 debug_only(
342 ssize_t total_list_count = 0;
343 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
344 fc = fc->next()) {
345 total_list_count++;
346 }
347 assert(total_list_count == _indexedFreeList[i].count(),
348 "Count in list is incorrect");
349 )
350 count += _indexedFreeList[i].count();
351 }
352 return count;
353 }
355 size_t CompactibleFreeListSpace::totalCount() {
356 size_t num = totalCountInIndexedFreeLists();
357 num += dictionary()->totalCount();
358 if (_smallLinearAllocBlock._word_size != 0) {
359 num++;
360 }
361 return num;
362 }
363 #endif
365 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
366 FreeChunk* fc = (FreeChunk*) p;
367 return fc->isFree();
368 }
370 size_t CompactibleFreeListSpace::used() const {
371 return capacity() - free();
372 }
374 size_t CompactibleFreeListSpace::free() const {
375 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
376 // if you do this while the structures are in flux you
377 // may get an approximate answer only; for instance
378 // because there is concurrent allocation either
379 // directly by mutators or for promotion during a GC.
380 // It's "MT-safe", however, in the sense that you are guaranteed
381 // not to crash and burn, for instance, because of walking
382 // pointers that could disappear as you were walking them.
383 // The approximation is because the various components
384 // that are read below are not read atomically (and
385 // further the computation of totalSizeInIndexedFreeLists()
386 // is itself a non-atomic computation. The normal use of
387 // this is during a resize operation at the end of GC
388 // and at that time you are guaranteed to get the
389 // correct actual value. However, for instance, this is
390 // also read completely asynchronously by the "perf-sampler"
391 // that supports jvmstat, and you are apt to see the values
392 // flicker in such cases.
393 assert(_dictionary != NULL, "No _dictionary?");
394 return (_dictionary->totalChunkSize(DEBUG_ONLY(freelistLock())) +
395 totalSizeInIndexedFreeLists() +
396 _smallLinearAllocBlock._word_size) * HeapWordSize;
397 }
399 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
400 assert(_dictionary != NULL, "No _dictionary?");
401 assert_locked();
402 size_t res = _dictionary->maxChunkSize();
403 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
404 (size_t) SmallForLinearAlloc - 1));
405 // XXX the following could potentially be pretty slow;
406 // should one, pesimally for the rare cases when res
407 // caclulated above is less than IndexSetSize,
408 // just return res calculated above? My reasoning was that
409 // those cases will be so rare that the extra time spent doesn't
410 // really matter....
411 // Note: do not change the loop test i >= res + IndexSetStride
412 // to i > res below, because i is unsigned and res may be zero.
413 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
414 i -= IndexSetStride) {
415 if (_indexedFreeList[i].head() != NULL) {
416 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
417 return i;
418 }
419 }
420 return res;
421 }
423 void LinearAllocBlock::print_on(outputStream* st) const {
424 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
425 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
426 _ptr, _word_size, _refillSize, _allocation_size_limit);
427 }
429 void CompactibleFreeListSpace::print_on(outputStream* st) const {
430 st->print_cr("COMPACTIBLE FREELIST SPACE");
431 st->print_cr(" Space:");
432 Space::print_on(st);
434 st->print_cr("promoInfo:");
435 _promoInfo.print_on(st);
437 st->print_cr("_smallLinearAllocBlock");
438 _smallLinearAllocBlock.print_on(st);
440 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
442 st->print_cr(" _fitStrategy = %s, _adaptive_freelists = %s",
443 _fitStrategy?"true":"false", _adaptive_freelists?"true":"false");
444 }
446 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
447 const {
448 reportIndexedFreeListStatistics();
449 gclog_or_tty->print_cr("Layout of Indexed Freelists");
450 gclog_or_tty->print_cr("---------------------------");
451 FreeList::print_labels_on(st, "size");
452 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
453 _indexedFreeList[i].print_on(gclog_or_tty);
454 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
455 fc = fc->next()) {
456 gclog_or_tty->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
457 fc, (HeapWord*)fc + i,
458 fc->cantCoalesce() ? "\t CC" : "");
459 }
460 }
461 }
463 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
464 const {
465 _promoInfo.print_on(st);
466 }
468 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
469 const {
470 _dictionary->reportStatistics();
471 st->print_cr("Layout of Freelists in Tree");
472 st->print_cr("---------------------------");
473 _dictionary->print_free_lists(st);
474 }
476 class BlkPrintingClosure: public BlkClosure {
477 const CMSCollector* _collector;
478 const CompactibleFreeListSpace* _sp;
479 const CMSBitMap* _live_bit_map;
480 const bool _post_remark;
481 outputStream* _st;
482 public:
483 BlkPrintingClosure(const CMSCollector* collector,
484 const CompactibleFreeListSpace* sp,
485 const CMSBitMap* live_bit_map,
486 outputStream* st):
487 _collector(collector),
488 _sp(sp),
489 _live_bit_map(live_bit_map),
490 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
491 _st(st) { }
492 size_t do_blk(HeapWord* addr);
493 };
495 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
496 size_t sz = _sp->block_size_no_stall(addr, _collector);
497 assert(sz != 0, "Should always be able to compute a size");
498 if (_sp->block_is_obj(addr)) {
499 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
500 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
501 addr,
502 dead ? "dead" : "live",
503 sz,
504 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
505 if (CMSPrintObjectsInDump && !dead) {
506 oop(addr)->print_on(_st);
507 _st->print_cr("--------------------------------------");
508 }
509 } else { // free block
510 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
511 addr, sz, CMSPrintChunksInDump ? ":" : ".");
512 if (CMSPrintChunksInDump) {
513 ((FreeChunk*)addr)->print_on(_st);
514 _st->print_cr("--------------------------------------");
515 }
516 }
517 return sz;
518 }
520 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c,
521 outputStream* st) {
522 st->print_cr("\n=========================");
523 st->print_cr("Block layout in CMS Heap:");
524 st->print_cr("=========================");
525 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
526 blk_iterate(&bpcl);
528 st->print_cr("\n=======================================");
529 st->print_cr("Order & Layout of Promotion Info Blocks");
530 st->print_cr("=======================================");
531 print_promo_info_blocks(st);
533 st->print_cr("\n===========================");
534 st->print_cr("Order of Indexed Free Lists");
535 st->print_cr("=========================");
536 print_indexed_free_lists(st);
538 st->print_cr("\n=================================");
539 st->print_cr("Order of Free Lists in Dictionary");
540 st->print_cr("=================================");
541 print_dictionary_free_lists(st);
542 }
545 void CompactibleFreeListSpace::reportFreeListStatistics() const {
546 assert_lock_strong(&_freelistLock);
547 assert(PrintFLSStatistics != 0, "Reporting error");
548 _dictionary->reportStatistics();
549 if (PrintFLSStatistics > 1) {
550 reportIndexedFreeListStatistics();
551 size_t totalSize = totalSizeInIndexedFreeLists() +
552 _dictionary->totalChunkSize(DEBUG_ONLY(freelistLock()));
553 gclog_or_tty->print(" free=%ld frag=%1.4f\n", totalSize, flsFrag());
554 }
555 }
557 void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const {
558 assert_lock_strong(&_freelistLock);
559 gclog_or_tty->print("Statistics for IndexedFreeLists:\n"
560 "--------------------------------\n");
561 size_t totalSize = totalSizeInIndexedFreeLists();
562 size_t freeBlocks = numFreeBlocksInIndexedFreeLists();
563 gclog_or_tty->print("Total Free Space: %d\n", totalSize);
564 gclog_or_tty->print("Max Chunk Size: %d\n", maxChunkSizeInIndexedFreeLists());
565 gclog_or_tty->print("Number of Blocks: %d\n", freeBlocks);
566 if (freeBlocks != 0) {
567 gclog_or_tty->print("Av. Block Size: %d\n", totalSize/freeBlocks);
568 }
569 }
571 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
572 size_t res = 0;
573 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
574 debug_only(
575 ssize_t recount = 0;
576 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
577 fc = fc->next()) {
578 recount += 1;
579 }
580 assert(recount == _indexedFreeList[i].count(),
581 "Incorrect count in list");
582 )
583 res += _indexedFreeList[i].count();
584 }
585 return res;
586 }
588 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
589 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
590 if (_indexedFreeList[i].head() != NULL) {
591 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
592 return (size_t)i;
593 }
594 }
595 return 0;
596 }
598 void CompactibleFreeListSpace::set_end(HeapWord* value) {
599 HeapWord* prevEnd = end();
600 assert(prevEnd != value, "unnecessary set_end call");
601 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
602 "New end is below unallocated block");
603 _end = value;
604 if (prevEnd != NULL) {
605 // Resize the underlying block offset table.
606 _bt.resize(pointer_delta(value, bottom()));
607 if (value <= prevEnd) {
608 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
609 "New end is below unallocated block");
610 } else {
611 // Now, take this new chunk and add it to the free blocks.
612 // Note that the BOT has not yet been updated for this block.
613 size_t newFcSize = pointer_delta(value, prevEnd);
614 // XXX This is REALLY UGLY and should be fixed up. XXX
615 if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) {
616 // Mark the boundary of the new block in BOT
617 _bt.mark_block(prevEnd, value);
618 // put it all in the linAB
619 if (ParallelGCThreads == 0) {
620 _smallLinearAllocBlock._ptr = prevEnd;
621 _smallLinearAllocBlock._word_size = newFcSize;
622 repairLinearAllocBlock(&_smallLinearAllocBlock);
623 } else { // ParallelGCThreads > 0
624 MutexLockerEx x(parDictionaryAllocLock(),
625 Mutex::_no_safepoint_check_flag);
626 _smallLinearAllocBlock._ptr = prevEnd;
627 _smallLinearAllocBlock._word_size = newFcSize;
628 repairLinearAllocBlock(&_smallLinearAllocBlock);
629 }
630 // Births of chunks put into a LinAB are not recorded. Births
631 // of chunks as they are allocated out of a LinAB are.
632 } else {
633 // Add the block to the free lists, if possible coalescing it
634 // with the last free block, and update the BOT and census data.
635 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
636 }
637 }
638 }
639 }
641 class FreeListSpace_DCTOC : public Filtering_DCTOC {
642 CompactibleFreeListSpace* _cfls;
643 CMSCollector* _collector;
644 protected:
645 // Override.
646 #define walk_mem_region_with_cl_DECL(ClosureType) \
647 virtual void walk_mem_region_with_cl(MemRegion mr, \
648 HeapWord* bottom, HeapWord* top, \
649 ClosureType* cl); \
650 void walk_mem_region_with_cl_par(MemRegion mr, \
651 HeapWord* bottom, HeapWord* top, \
652 ClosureType* cl); \
653 void walk_mem_region_with_cl_nopar(MemRegion mr, \
654 HeapWord* bottom, HeapWord* top, \
655 ClosureType* cl)
656 walk_mem_region_with_cl_DECL(OopClosure);
657 walk_mem_region_with_cl_DECL(FilteringClosure);
659 public:
660 FreeListSpace_DCTOC(CompactibleFreeListSpace* sp,
661 CMSCollector* collector,
662 OopClosure* cl,
663 CardTableModRefBS::PrecisionStyle precision,
664 HeapWord* boundary) :
665 Filtering_DCTOC(sp, cl, precision, boundary),
666 _cfls(sp), _collector(collector) {}
667 };
669 // We de-virtualize the block-related calls below, since we know that our
670 // space is a CompactibleFreeListSpace.
672 #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
673 void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \
674 HeapWord* bottom, \
675 HeapWord* top, \
676 ClosureType* cl) { \
677 bool is_par = SharedHeap::heap()->n_par_threads() > 0; \
678 if (is_par) { \
679 assert(SharedHeap::heap()->n_par_threads() == \
680 SharedHeap::heap()->workers()->active_workers(), "Mismatch"); \
681 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
682 } else { \
683 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
684 } \
685 } \
686 void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
687 HeapWord* bottom, \
688 HeapWord* top, \
689 ClosureType* cl) { \
690 /* Skip parts that are before "mr", in case "block_start" sent us \
691 back too far. */ \
692 HeapWord* mr_start = mr.start(); \
693 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
694 HeapWord* next = bottom + bot_size; \
695 while (next < mr_start) { \
696 bottom = next; \
697 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
698 next = bottom + bot_size; \
699 } \
700 \
701 while (bottom < top) { \
702 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
703 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
704 oop(bottom)) && \
705 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
706 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
707 bottom += _cfls->adjustObjectSize(word_sz); \
708 } else { \
709 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
710 } \
711 } \
712 } \
713 void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
714 HeapWord* bottom, \
715 HeapWord* top, \
716 ClosureType* cl) { \
717 /* Skip parts that are before "mr", in case "block_start" sent us \
718 back too far. */ \
719 HeapWord* mr_start = mr.start(); \
720 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
721 HeapWord* next = bottom + bot_size; \
722 while (next < mr_start) { \
723 bottom = next; \
724 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
725 next = bottom + bot_size; \
726 } \
727 \
728 while (bottom < top) { \
729 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
730 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
731 oop(bottom)) && \
732 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
733 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
734 bottom += _cfls->adjustObjectSize(word_sz); \
735 } else { \
736 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
737 } \
738 } \
739 }
741 // (There are only two of these, rather than N, because the split is due
742 // only to the introduction of the FilteringClosure, a local part of the
743 // impl of this abstraction.)
744 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(OopClosure)
745 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
747 DirtyCardToOopClosure*
748 CompactibleFreeListSpace::new_dcto_cl(OopClosure* cl,
749 CardTableModRefBS::PrecisionStyle precision,
750 HeapWord* boundary) {
751 return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary);
752 }
755 // Note on locking for the space iteration functions:
756 // since the collector's iteration activities are concurrent with
757 // allocation activities by mutators, absent a suitable mutual exclusion
758 // mechanism the iterators may go awry. For instace a block being iterated
759 // may suddenly be allocated or divided up and part of it allocated and
760 // so on.
762 // Apply the given closure to each block in the space.
763 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
764 assert_lock_strong(freelistLock());
765 HeapWord *cur, *limit;
766 for (cur = bottom(), limit = end(); cur < limit;
767 cur += cl->do_blk_careful(cur));
768 }
770 // Apply the given closure to each block in the space.
771 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
772 assert_lock_strong(freelistLock());
773 HeapWord *cur, *limit;
774 for (cur = bottom(), limit = end(); cur < limit;
775 cur += cl->do_blk(cur));
776 }
778 // Apply the given closure to each oop in the space.
779 void CompactibleFreeListSpace::oop_iterate(OopClosure* cl) {
780 assert_lock_strong(freelistLock());
781 HeapWord *cur, *limit;
782 size_t curSize;
783 for (cur = bottom(), limit = end(); cur < limit;
784 cur += curSize) {
785 curSize = block_size(cur);
786 if (block_is_obj(cur)) {
787 oop(cur)->oop_iterate(cl);
788 }
789 }
790 }
792 // Apply the given closure to each oop in the space \intersect memory region.
793 void CompactibleFreeListSpace::oop_iterate(MemRegion mr, OopClosure* cl) {
794 assert_lock_strong(freelistLock());
795 if (is_empty()) {
796 return;
797 }
798 MemRegion cur = MemRegion(bottom(), end());
799 mr = mr.intersection(cur);
800 if (mr.is_empty()) {
801 return;
802 }
803 if (mr.equals(cur)) {
804 oop_iterate(cl);
805 return;
806 }
807 assert(mr.end() <= end(), "just took an intersection above");
808 HeapWord* obj_addr = block_start(mr.start());
809 HeapWord* t = mr.end();
811 SpaceMemRegionOopsIterClosure smr_blk(cl, mr);
812 if (block_is_obj(obj_addr)) {
813 // Handle first object specially.
814 oop obj = oop(obj_addr);
815 obj_addr += adjustObjectSize(obj->oop_iterate(&smr_blk));
816 } else {
817 FreeChunk* fc = (FreeChunk*)obj_addr;
818 obj_addr += fc->size();
819 }
820 while (obj_addr < t) {
821 HeapWord* obj = obj_addr;
822 obj_addr += block_size(obj_addr);
823 // If "obj_addr" is not greater than top, then the
824 // entire object "obj" is within the region.
825 if (obj_addr <= t) {
826 if (block_is_obj(obj)) {
827 oop(obj)->oop_iterate(cl);
828 }
829 } else {
830 // "obj" extends beyond end of region
831 if (block_is_obj(obj)) {
832 oop(obj)->oop_iterate(&smr_blk);
833 }
834 break;
835 }
836 }
837 }
839 // NOTE: In the following methods, in order to safely be able to
840 // apply the closure to an object, we need to be sure that the
841 // object has been initialized. We are guaranteed that an object
842 // is initialized if we are holding the Heap_lock with the
843 // world stopped.
844 void CompactibleFreeListSpace::verify_objects_initialized() const {
845 if (is_init_completed()) {
846 assert_locked_or_safepoint(Heap_lock);
847 if (Universe::is_fully_initialized()) {
848 guarantee(SafepointSynchronize::is_at_safepoint(),
849 "Required for objects to be initialized");
850 }
851 } // else make a concession at vm start-up
852 }
854 // Apply the given closure to each object in the space
855 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
856 assert_lock_strong(freelistLock());
857 NOT_PRODUCT(verify_objects_initialized());
858 HeapWord *cur, *limit;
859 size_t curSize;
860 for (cur = bottom(), limit = end(); cur < limit;
861 cur += curSize) {
862 curSize = block_size(cur);
863 if (block_is_obj(cur)) {
864 blk->do_object(oop(cur));
865 }
866 }
867 }
869 // Apply the given closure to each live object in the space
870 // The usage of CompactibleFreeListSpace
871 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
872 // objects in the space with references to objects that are no longer
873 // valid. For example, an object may reference another object
874 // that has already been sweep up (collected). This method uses
875 // obj_is_alive() to determine whether it is safe to apply the closure to
876 // an object. See obj_is_alive() for details on how liveness of an
877 // object is decided.
879 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
880 assert_lock_strong(freelistLock());
881 NOT_PRODUCT(verify_objects_initialized());
882 HeapWord *cur, *limit;
883 size_t curSize;
884 for (cur = bottom(), limit = end(); cur < limit;
885 cur += curSize) {
886 curSize = block_size(cur);
887 if (block_is_obj(cur) && obj_is_alive(cur)) {
888 blk->do_object(oop(cur));
889 }
890 }
891 }
893 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
894 UpwardsObjectClosure* cl) {
895 assert_locked(freelistLock());
896 NOT_PRODUCT(verify_objects_initialized());
897 Space::object_iterate_mem(mr, cl);
898 }
900 // Callers of this iterator beware: The closure application should
901 // be robust in the face of uninitialized objects and should (always)
902 // return a correct size so that the next addr + size below gives us a
903 // valid block boundary. [See for instance,
904 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
905 // in ConcurrentMarkSweepGeneration.cpp.]
906 HeapWord*
907 CompactibleFreeListSpace::object_iterate_careful(ObjectClosureCareful* cl) {
908 assert_lock_strong(freelistLock());
909 HeapWord *addr, *last;
910 size_t size;
911 for (addr = bottom(), last = end();
912 addr < last; addr += size) {
913 FreeChunk* fc = (FreeChunk*)addr;
914 if (fc->isFree()) {
915 // Since we hold the free list lock, which protects direct
916 // allocation in this generation by mutators, a free object
917 // will remain free throughout this iteration code.
918 size = fc->size();
919 } else {
920 // Note that the object need not necessarily be initialized,
921 // because (for instance) the free list lock does NOT protect
922 // object initialization. The closure application below must
923 // therefore be correct in the face of uninitialized objects.
924 size = cl->do_object_careful(oop(addr));
925 if (size == 0) {
926 // An unparsable object found. Signal early termination.
927 return addr;
928 }
929 }
930 }
931 return NULL;
932 }
934 // Callers of this iterator beware: The closure application should
935 // be robust in the face of uninitialized objects and should (always)
936 // return a correct size so that the next addr + size below gives us a
937 // valid block boundary. [See for instance,
938 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
939 // in ConcurrentMarkSweepGeneration.cpp.]
940 HeapWord*
941 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
942 ObjectClosureCareful* cl) {
943 assert_lock_strong(freelistLock());
944 // Can't use used_region() below because it may not necessarily
945 // be the same as [bottom(),end()); although we could
946 // use [used_region().start(),round_to(used_region().end(),CardSize)),
947 // that appears too cumbersome, so we just do the simpler check
948 // in the assertion below.
949 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
950 "mr should be non-empty and within used space");
951 HeapWord *addr, *end;
952 size_t size;
953 for (addr = block_start_careful(mr.start()), end = mr.end();
954 addr < end; addr += size) {
955 FreeChunk* fc = (FreeChunk*)addr;
956 if (fc->isFree()) {
957 // Since we hold the free list lock, which protects direct
958 // allocation in this generation by mutators, a free object
959 // will remain free throughout this iteration code.
960 size = fc->size();
961 } else {
962 // Note that the object need not necessarily be initialized,
963 // because (for instance) the free list lock does NOT protect
964 // object initialization. The closure application below must
965 // therefore be correct in the face of uninitialized objects.
966 size = cl->do_object_careful_m(oop(addr), mr);
967 if (size == 0) {
968 // An unparsable object found. Signal early termination.
969 return addr;
970 }
971 }
972 }
973 return NULL;
974 }
977 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
978 NOT_PRODUCT(verify_objects_initialized());
979 return _bt.block_start(p);
980 }
982 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
983 return _bt.block_start_careful(p);
984 }
986 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
987 NOT_PRODUCT(verify_objects_initialized());
988 // This must be volatile, or else there is a danger that the compiler
989 // will compile the code below into a sometimes-infinite loop, by keeping
990 // the value read the first time in a register.
991 while (true) {
992 // We must do this until we get a consistent view of the object.
993 if (FreeChunk::indicatesFreeChunk(p)) {
994 volatile FreeChunk* fc = (volatile FreeChunk*)p;
995 size_t res = fc->size();
996 // If the object is still a free chunk, return the size, else it
997 // has been allocated so try again.
998 if (FreeChunk::indicatesFreeChunk(p)) {
999 assert(res != 0, "Block size should not be 0");
1000 return res;
1001 }
1002 } else {
1003 // must read from what 'p' points to in each loop.
1004 klassOop k = ((volatile oopDesc*)p)->klass_or_null();
1005 if (k != NULL) {
1006 assert(k->is_oop(true /* ignore mark word */), "Should be klass oop");
1007 oop o = (oop)p;
1008 assert(o->is_parsable(), "Should be parsable");
1009 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
1010 size_t res = o->size_given_klass(k->klass_part());
1011 res = adjustObjectSize(res);
1012 assert(res != 0, "Block size should not be 0");
1013 return res;
1014 }
1015 }
1016 }
1017 }
1019 // A variant of the above that uses the Printezis bits for
1020 // unparsable but allocated objects. This avoids any possible
1021 // stalls waiting for mutators to initialize objects, and is
1022 // thus potentially faster than the variant above. However,
1023 // this variant may return a zero size for a block that is
1024 // under mutation and for which a consistent size cannot be
1025 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
1026 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
1027 const CMSCollector* c)
1028 const {
1029 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1030 // This must be volatile, or else there is a danger that the compiler
1031 // will compile the code below into a sometimes-infinite loop, by keeping
1032 // the value read the first time in a register.
1033 DEBUG_ONLY(uint loops = 0;)
1034 while (true) {
1035 // We must do this until we get a consistent view of the object.
1036 if (FreeChunk::indicatesFreeChunk(p)) {
1037 volatile FreeChunk* fc = (volatile FreeChunk*)p;
1038 size_t res = fc->size();
1039 if (FreeChunk::indicatesFreeChunk(p)) {
1040 assert(res != 0, "Block size should not be 0");
1041 assert(loops == 0, "Should be 0");
1042 return res;
1043 }
1044 } else {
1045 // must read from what 'p' points to in each loop.
1046 klassOop k = ((volatile oopDesc*)p)->klass_or_null();
1047 // We trust the size of any object that has a non-NULL
1048 // klass and (for those in the perm gen) is parsable
1049 // -- irrespective of its conc_safe-ty.
1050 if (k != NULL && ((oopDesc*)p)->is_parsable()) {
1051 assert(k->is_oop(), "Should really be klass oop.");
1052 oop o = (oop)p;
1053 assert(o->is_oop(), "Should be an oop");
1054 size_t res = o->size_given_klass(k->klass_part());
1055 res = adjustObjectSize(res);
1056 assert(res != 0, "Block size should not be 0");
1057 return res;
1058 } else {
1059 // May return 0 if P-bits not present.
1060 return c->block_size_if_printezis_bits(p);
1061 }
1062 }
1063 assert(loops == 0, "Can loop at most once");
1064 DEBUG_ONLY(loops++;)
1065 }
1066 }
1068 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1069 NOT_PRODUCT(verify_objects_initialized());
1070 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1071 FreeChunk* fc = (FreeChunk*)p;
1072 if (fc->isFree()) {
1073 return fc->size();
1074 } else {
1075 // Ignore mark word because this may be a recently promoted
1076 // object whose mark word is used to chain together grey
1077 // objects (the last one would have a null value).
1078 assert(oop(p)->is_oop(true), "Should be an oop");
1079 return adjustObjectSize(oop(p)->size());
1080 }
1081 }
1083 // This implementation assumes that the property of "being an object" is
1084 // stable. But being a free chunk may not be (because of parallel
1085 // promotion.)
1086 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1087 FreeChunk* fc = (FreeChunk*)p;
1088 assert(is_in_reserved(p), "Should be in space");
1089 // When doing a mark-sweep-compact of the CMS generation, this
1090 // assertion may fail because prepare_for_compaction() uses
1091 // space that is garbage to maintain information on ranges of
1092 // live objects so that these live ranges can be moved as a whole.
1093 // Comment out this assertion until that problem can be solved
1094 // (i.e., that the block start calculation may look at objects
1095 // at address below "p" in finding the object that contains "p"
1096 // and those objects (if garbage) may have been modified to hold
1097 // live range information.
1098 // assert(CollectedHeap::use_parallel_gc_threads() || _bt.block_start(p) == p,
1099 // "Should be a block boundary");
1100 if (FreeChunk::indicatesFreeChunk(p)) return false;
1101 klassOop k = oop(p)->klass_or_null();
1102 if (k != NULL) {
1103 // Ignore mark word because it may have been used to
1104 // chain together promoted objects (the last one
1105 // would have a null value).
1106 assert(oop(p)->is_oop(true), "Should be an oop");
1107 return true;
1108 } else {
1109 return false; // Was not an object at the start of collection.
1110 }
1111 }
1113 // Check if the object is alive. This fact is checked either by consulting
1114 // the main marking bitmap in the sweeping phase or, if it's a permanent
1115 // generation and we're not in the sweeping phase, by checking the
1116 // perm_gen_verify_bit_map where we store the "deadness" information if
1117 // we did not sweep the perm gen in the most recent previous GC cycle.
1118 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1119 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1120 "Else races are possible");
1121 assert(block_is_obj(p), "The address should point to an object");
1123 // If we're sweeping, we use object liveness information from the main bit map
1124 // for both perm gen and old gen.
1125 // We don't need to lock the bitmap (live_map or dead_map below), because
1126 // EITHER we are in the middle of the sweeping phase, and the
1127 // main marking bit map (live_map below) is locked,
1128 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1129 // is stable, because it's mutated only in the sweeping phase.
1130 // NOTE: This method is also used by jmap where, if class unloading is
1131 // off, the results can return "false" for legitimate perm objects,
1132 // when we are not in the midst of a sweeping phase, which can result
1133 // in jmap not reporting certain perm gen objects. This will be moot
1134 // if/when the perm gen goes away in the future.
1135 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1136 CMSBitMap* live_map = _collector->markBitMap();
1137 return live_map->par_isMarked((HeapWord*) p);
1138 } else {
1139 // If we're not currently sweeping and we haven't swept the perm gen in
1140 // the previous concurrent cycle then we may have dead but unswept objects
1141 // in the perm gen. In this case, we use the "deadness" information
1142 // that we had saved in perm_gen_verify_bit_map at the last sweep.
1143 if (!CMSClassUnloadingEnabled && _collector->_permGen->reserved().contains(p)) {
1144 if (_collector->verifying()) {
1145 CMSBitMap* dead_map = _collector->perm_gen_verify_bit_map();
1146 // Object is marked in the dead_map bitmap at the previous sweep
1147 // when we know that it's dead; if the bitmap is not allocated then
1148 // the object is alive.
1149 return (dead_map->sizeInBits() == 0) // bit_map has been allocated
1150 || !dead_map->par_isMarked((HeapWord*) p);
1151 } else {
1152 return false; // We can't say for sure if it's live, so we say that it's dead.
1153 }
1154 }
1155 }
1156 return true;
1157 }
1159 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1160 FreeChunk* fc = (FreeChunk*)p;
1161 assert(is_in_reserved(p), "Should be in space");
1162 assert(_bt.block_start(p) == p, "Should be a block boundary");
1163 if (!fc->isFree()) {
1164 // Ignore mark word because it may have been used to
1165 // chain together promoted objects (the last one
1166 // would have a null value).
1167 assert(oop(p)->is_oop(true), "Should be an oop");
1168 return true;
1169 }
1170 return false;
1171 }
1173 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1174 // approximate answer if you don't hold the freelistlock when you call this.
1175 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1176 size_t size = 0;
1177 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1178 debug_only(
1179 // We may be calling here without the lock in which case we
1180 // won't do this modest sanity check.
1181 if (freelistLock()->owned_by_self()) {
1182 size_t total_list_size = 0;
1183 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1184 fc = fc->next()) {
1185 total_list_size += i;
1186 }
1187 assert(total_list_size == i * _indexedFreeList[i].count(),
1188 "Count in list is incorrect");
1189 }
1190 )
1191 size += i * _indexedFreeList[i].count();
1192 }
1193 return size;
1194 }
1196 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1197 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1198 return allocate(size);
1199 }
1201 HeapWord*
1202 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1203 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1204 }
1206 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1207 assert_lock_strong(freelistLock());
1208 HeapWord* res = NULL;
1209 assert(size == adjustObjectSize(size),
1210 "use adjustObjectSize() before calling into allocate()");
1212 if (_adaptive_freelists) {
1213 res = allocate_adaptive_freelists(size);
1214 } else { // non-adaptive free lists
1215 res = allocate_non_adaptive_freelists(size);
1216 }
1218 if (res != NULL) {
1219 // check that res does lie in this space!
1220 assert(is_in_reserved(res), "Not in this space!");
1221 assert(is_aligned((void*)res), "alignment check");
1223 FreeChunk* fc = (FreeChunk*)res;
1224 fc->markNotFree();
1225 assert(!fc->isFree(), "shouldn't be marked free");
1226 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1227 // Verify that the block offset table shows this to
1228 // be a single block, but not one which is unallocated.
1229 _bt.verify_single_block(res, size);
1230 _bt.verify_not_unallocated(res, size);
1231 // mangle a just allocated object with a distinct pattern.
1232 debug_only(fc->mangleAllocated(size));
1233 }
1235 return res;
1236 }
1238 HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) {
1239 HeapWord* res = NULL;
1240 // try and use linear allocation for smaller blocks
1241 if (size < _smallLinearAllocBlock._allocation_size_limit) {
1242 // if successful, the following also adjusts block offset table
1243 res = getChunkFromSmallLinearAllocBlock(size);
1244 }
1245 // Else triage to indexed lists for smaller sizes
1246 if (res == NULL) {
1247 if (size < SmallForDictionary) {
1248 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1249 } else {
1250 // else get it from the big dictionary; if even this doesn't
1251 // work we are out of luck.
1252 res = (HeapWord*)getChunkFromDictionaryExact(size);
1253 }
1254 }
1256 return res;
1257 }
1259 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1260 assert_lock_strong(freelistLock());
1261 HeapWord* res = NULL;
1262 assert(size == adjustObjectSize(size),
1263 "use adjustObjectSize() before calling into allocate()");
1265 // Strategy
1266 // if small
1267 // exact size from small object indexed list if small
1268 // small or large linear allocation block (linAB) as appropriate
1269 // take from lists of greater sized chunks
1270 // else
1271 // dictionary
1272 // small or large linear allocation block if it has the space
1273 // Try allocating exact size from indexTable first
1274 if (size < IndexSetSize) {
1275 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1276 if(res != NULL) {
1277 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1278 "Not removed from free list");
1279 // no block offset table adjustment is necessary on blocks in
1280 // the indexed lists.
1282 // Try allocating from the small LinAB
1283 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1284 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1285 // if successful, the above also adjusts block offset table
1286 // Note that this call will refill the LinAB to
1287 // satisfy the request. This is different that
1288 // evm.
1289 // Don't record chunk off a LinAB? smallSplitBirth(size);
1290 } else {
1291 // Raid the exact free lists larger than size, even if they are not
1292 // overpopulated.
1293 res = (HeapWord*) getChunkFromGreater(size);
1294 }
1295 } else {
1296 // Big objects get allocated directly from the dictionary.
1297 res = (HeapWord*) getChunkFromDictionaryExact(size);
1298 if (res == NULL) {
1299 // Try hard not to fail since an allocation failure will likely
1300 // trigger a synchronous GC. Try to get the space from the
1301 // allocation blocks.
1302 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1303 }
1304 }
1306 return res;
1307 }
1309 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1310 // when promoting obj.
1311 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1312 // Depending on the object size, expansion may require refilling either a
1313 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1314 // is added because the dictionary may over-allocate to avoid fragmentation.
1315 size_t space = obj_size;
1316 if (!_adaptive_freelists) {
1317 space = MAX2(space, _smallLinearAllocBlock._refillSize);
1318 }
1319 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1320 return space;
1321 }
1323 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1324 FreeChunk* ret;
1326 assert(numWords >= MinChunkSize, "Size is less than minimum");
1327 assert(linearAllocationWouldFail() || bestFitFirst(),
1328 "Should not be here");
1330 size_t i;
1331 size_t currSize = numWords + MinChunkSize;
1332 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1333 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1334 FreeList* fl = &_indexedFreeList[i];
1335 if (fl->head()) {
1336 ret = getFromListGreater(fl, numWords);
1337 assert(ret == NULL || ret->isFree(), "Should be returning a free chunk");
1338 return ret;
1339 }
1340 }
1342 currSize = MAX2((size_t)SmallForDictionary,
1343 (size_t)(numWords + MinChunkSize));
1345 /* Try to get a chunk that satisfies request, while avoiding
1346 fragmentation that can't be handled. */
1347 {
1348 ret = dictionary()->getChunk(currSize);
1349 if (ret != NULL) {
1350 assert(ret->size() - numWords >= MinChunkSize,
1351 "Chunk is too small");
1352 _bt.allocated((HeapWord*)ret, ret->size());
1353 /* Carve returned chunk. */
1354 (void) splitChunkAndReturnRemainder(ret, numWords);
1355 /* Label this as no longer a free chunk. */
1356 assert(ret->isFree(), "This chunk should be free");
1357 ret->linkPrev(NULL);
1358 }
1359 assert(ret == NULL || ret->isFree(), "Should be returning a free chunk");
1360 return ret;
1361 }
1362 ShouldNotReachHere();
1363 }
1365 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1366 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1367 return _indexedFreeList[fc->size()].verifyChunkInFreeLists(fc);
1368 }
1370 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1371 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1372 (_smallLinearAllocBlock._word_size == fc->size()),
1373 "Linear allocation block shows incorrect size");
1374 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1375 (_smallLinearAllocBlock._word_size == fc->size()));
1376 }
1378 // Check if the purported free chunk is present either as a linear
1379 // allocation block, the size-indexed table of (smaller) free blocks,
1380 // or the larger free blocks kept in the binary tree dictionary.
1381 bool CompactibleFreeListSpace::verifyChunkInFreeLists(FreeChunk* fc) const {
1382 if (verify_chunk_is_linear_alloc_block(fc)) {
1383 return true;
1384 } else if (fc->size() < IndexSetSize) {
1385 return verifyChunkInIndexedFreeLists(fc);
1386 } else {
1387 return dictionary()->verifyChunkInFreeLists(fc);
1388 }
1389 }
1391 #ifndef PRODUCT
1392 void CompactibleFreeListSpace::assert_locked() const {
1393 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1394 }
1396 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1397 CMSLockVerifier::assert_locked(lock);
1398 }
1399 #endif
1401 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1402 // In the parallel case, the main thread holds the free list lock
1403 // on behalf the parallel threads.
1404 FreeChunk* fc;
1405 {
1406 // If GC is parallel, this might be called by several threads.
1407 // This should be rare enough that the locking overhead won't affect
1408 // the sequential code.
1409 MutexLockerEx x(parDictionaryAllocLock(),
1410 Mutex::_no_safepoint_check_flag);
1411 fc = getChunkFromDictionary(size);
1412 }
1413 if (fc != NULL) {
1414 fc->dontCoalesce();
1415 assert(fc->isFree(), "Should be free, but not coalescable");
1416 // Verify that the block offset table shows this to
1417 // be a single block, but not one which is unallocated.
1418 _bt.verify_single_block((HeapWord*)fc, fc->size());
1419 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1420 }
1421 return fc;
1422 }
1424 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1425 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1426 assert_locked();
1428 // if we are tracking promotions, then first ensure space for
1429 // promotion (including spooling space for saving header if necessary).
1430 // then allocate and copy, then track promoted info if needed.
1431 // When tracking (see PromotionInfo::track()), the mark word may
1432 // be displaced and in this case restoration of the mark word
1433 // occurs in the (oop_since_save_marks_)iterate phase.
1434 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1435 return NULL;
1436 }
1437 // Call the allocate(size_t, bool) form directly to avoid the
1438 // additional call through the allocate(size_t) form. Having
1439 // the compile inline the call is problematic because allocate(size_t)
1440 // is a virtual method.
1441 HeapWord* res = allocate(adjustObjectSize(obj_size));
1442 if (res != NULL) {
1443 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1444 // if we should be tracking promotions, do so.
1445 if (_promoInfo.tracking()) {
1446 _promoInfo.track((PromotedObject*)res);
1447 }
1448 }
1449 return oop(res);
1450 }
1452 HeapWord*
1453 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1454 assert_locked();
1455 assert(size >= MinChunkSize, "minimum chunk size");
1456 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1457 "maximum from smallLinearAllocBlock");
1458 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1459 }
1461 HeapWord*
1462 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1463 size_t size) {
1464 assert_locked();
1465 assert(size >= MinChunkSize, "too small");
1466 HeapWord* res = NULL;
1467 // Try to do linear allocation from blk, making sure that
1468 if (blk->_word_size == 0) {
1469 // We have probably been unable to fill this either in the prologue or
1470 // when it was exhausted at the last linear allocation. Bail out until
1471 // next time.
1472 assert(blk->_ptr == NULL, "consistency check");
1473 return NULL;
1474 }
1475 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1476 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1477 if (res != NULL) return res;
1479 // about to exhaust this linear allocation block
1480 if (blk->_word_size == size) { // exactly satisfied
1481 res = blk->_ptr;
1482 _bt.allocated(res, blk->_word_size);
1483 } else if (size + MinChunkSize <= blk->_refillSize) {
1484 size_t sz = blk->_word_size;
1485 // Update _unallocated_block if the size is such that chunk would be
1486 // returned to the indexed free list. All other chunks in the indexed
1487 // free lists are allocated from the dictionary so that _unallocated_block
1488 // has already been adjusted for them. Do it here so that the cost
1489 // for all chunks added back to the indexed free lists.
1490 if (sz < SmallForDictionary) {
1491 _bt.allocated(blk->_ptr, sz);
1492 }
1493 // Return the chunk that isn't big enough, and then refill below.
1494 addChunkToFreeLists(blk->_ptr, sz);
1495 splitBirth(sz);
1496 // Don't keep statistics on adding back chunk from a LinAB.
1497 } else {
1498 // A refilled block would not satisfy the request.
1499 return NULL;
1500 }
1502 blk->_ptr = NULL; blk->_word_size = 0;
1503 refillLinearAllocBlock(blk);
1504 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1505 "block was replenished");
1506 if (res != NULL) {
1507 splitBirth(size);
1508 repairLinearAllocBlock(blk);
1509 } else if (blk->_ptr != NULL) {
1510 res = blk->_ptr;
1511 size_t blk_size = blk->_word_size;
1512 blk->_word_size -= size;
1513 blk->_ptr += size;
1514 splitBirth(size);
1515 repairLinearAllocBlock(blk);
1516 // Update BOT last so that other (parallel) GC threads see a consistent
1517 // view of the BOT and free blocks.
1518 // Above must occur before BOT is updated below.
1519 OrderAccess::storestore();
1520 _bt.split_block(res, blk_size, size); // adjust block offset table
1521 }
1522 return res;
1523 }
1525 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1526 LinearAllocBlock* blk,
1527 size_t size) {
1528 assert_locked();
1529 assert(size >= MinChunkSize, "too small");
1531 HeapWord* res = NULL;
1532 // This is the common case. Keep it simple.
1533 if (blk->_word_size >= size + MinChunkSize) {
1534 assert(blk->_ptr != NULL, "consistency check");
1535 res = blk->_ptr;
1536 // Note that the BOT is up-to-date for the linAB before allocation. It
1537 // indicates the start of the linAB. The split_block() updates the
1538 // BOT for the linAB after the allocation (indicates the start of the
1539 // next chunk to be allocated).
1540 size_t blk_size = blk->_word_size;
1541 blk->_word_size -= size;
1542 blk->_ptr += size;
1543 splitBirth(size);
1544 repairLinearAllocBlock(blk);
1545 // Update BOT last so that other (parallel) GC threads see a consistent
1546 // view of the BOT and free blocks.
1547 // Above must occur before BOT is updated below.
1548 OrderAccess::storestore();
1549 _bt.split_block(res, blk_size, size); // adjust block offset table
1550 _bt.allocated(res, size);
1551 }
1552 return res;
1553 }
1555 FreeChunk*
1556 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1557 assert_locked();
1558 assert(size < SmallForDictionary, "just checking");
1559 FreeChunk* res;
1560 res = _indexedFreeList[size].getChunkAtHead();
1561 if (res == NULL) {
1562 res = getChunkFromIndexedFreeListHelper(size);
1563 }
1564 _bt.verify_not_unallocated((HeapWord*) res, size);
1565 assert(res == NULL || res->size() == size, "Incorrect block size");
1566 return res;
1567 }
1569 FreeChunk*
1570 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1571 bool replenish) {
1572 assert_locked();
1573 FreeChunk* fc = NULL;
1574 if (size < SmallForDictionary) {
1575 assert(_indexedFreeList[size].head() == NULL ||
1576 _indexedFreeList[size].surplus() <= 0,
1577 "List for this size should be empty or under populated");
1578 // Try best fit in exact lists before replenishing the list
1579 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1580 // Replenish list.
1581 //
1582 // Things tried that failed.
1583 // Tried allocating out of the two LinAB's first before
1584 // replenishing lists.
1585 // Tried small linAB of size 256 (size in indexed list)
1586 // and replenishing indexed lists from the small linAB.
1587 //
1588 FreeChunk* newFc = NULL;
1589 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1590 if (replenish_size < SmallForDictionary) {
1591 // Do not replenish from an underpopulated size.
1592 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1593 _indexedFreeList[replenish_size].head() != NULL) {
1594 newFc = _indexedFreeList[replenish_size].getChunkAtHead();
1595 } else if (bestFitFirst()) {
1596 newFc = bestFitSmall(replenish_size);
1597 }
1598 }
1599 if (newFc == NULL && replenish_size > size) {
1600 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1601 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1602 }
1603 // Note: The stats update re split-death of block obtained above
1604 // will be recorded below precisely when we know we are going to
1605 // be actually splitting it into more than one pieces below.
1606 if (newFc != NULL) {
1607 if (replenish || CMSReplenishIntermediate) {
1608 // Replenish this list and return one block to caller.
1609 size_t i;
1610 FreeChunk *curFc, *nextFc;
1611 size_t num_blk = newFc->size() / size;
1612 assert(num_blk >= 1, "Smaller than requested?");
1613 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1614 if (num_blk > 1) {
1615 // we are sure we will be splitting the block just obtained
1616 // into multiple pieces; record the split-death of the original
1617 splitDeath(replenish_size);
1618 }
1619 // carve up and link blocks 0, ..., num_blk - 2
1620 // The last chunk is not added to the lists but is returned as the
1621 // free chunk.
1622 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1623 i = 0;
1624 i < (num_blk - 1);
1625 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1626 i++) {
1627 curFc->setSize(size);
1628 // Don't record this as a return in order to try and
1629 // determine the "returns" from a GC.
1630 _bt.verify_not_unallocated((HeapWord*) fc, size);
1631 _indexedFreeList[size].returnChunkAtTail(curFc, false);
1632 _bt.mark_block((HeapWord*)curFc, size);
1633 splitBirth(size);
1634 // Don't record the initial population of the indexed list
1635 // as a split birth.
1636 }
1638 // check that the arithmetic was OK above
1639 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1640 "inconsistency in carving newFc");
1641 curFc->setSize(size);
1642 _bt.mark_block((HeapWord*)curFc, size);
1643 splitBirth(size);
1644 fc = curFc;
1645 } else {
1646 // Return entire block to caller
1647 fc = newFc;
1648 }
1649 }
1650 }
1651 } else {
1652 // Get a free chunk from the free chunk dictionary to be returned to
1653 // replenish the indexed free list.
1654 fc = getChunkFromDictionaryExact(size);
1655 }
1656 // assert(fc == NULL || fc->isFree(), "Should be returning a free chunk");
1657 return fc;
1658 }
1660 FreeChunk*
1661 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1662 assert_locked();
1663 FreeChunk* fc = _dictionary->getChunk(size);
1664 if (fc == NULL) {
1665 return NULL;
1666 }
1667 _bt.allocated((HeapWord*)fc, fc->size());
1668 if (fc->size() >= size + MinChunkSize) {
1669 fc = splitChunkAndReturnRemainder(fc, size);
1670 }
1671 assert(fc->size() >= size, "chunk too small");
1672 assert(fc->size() < size + MinChunkSize, "chunk too big");
1673 _bt.verify_single_block((HeapWord*)fc, fc->size());
1674 return fc;
1675 }
1677 FreeChunk*
1678 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1679 assert_locked();
1680 FreeChunk* fc = _dictionary->getChunk(size);
1681 if (fc == NULL) {
1682 return fc;
1683 }
1684 _bt.allocated((HeapWord*)fc, fc->size());
1685 if (fc->size() == size) {
1686 _bt.verify_single_block((HeapWord*)fc, size);
1687 return fc;
1688 }
1689 assert(fc->size() > size, "getChunk() guarantee");
1690 if (fc->size() < size + MinChunkSize) {
1691 // Return the chunk to the dictionary and go get a bigger one.
1692 returnChunkToDictionary(fc);
1693 fc = _dictionary->getChunk(size + MinChunkSize);
1694 if (fc == NULL) {
1695 return NULL;
1696 }
1697 _bt.allocated((HeapWord*)fc, fc->size());
1698 }
1699 assert(fc->size() >= size + MinChunkSize, "tautology");
1700 fc = splitChunkAndReturnRemainder(fc, size);
1701 assert(fc->size() == size, "chunk is wrong size");
1702 _bt.verify_single_block((HeapWord*)fc, size);
1703 return fc;
1704 }
1706 void
1707 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
1708 assert_locked();
1710 size_t size = chunk->size();
1711 _bt.verify_single_block((HeapWord*)chunk, size);
1712 // adjust _unallocated_block downward, as necessary
1713 _bt.freed((HeapWord*)chunk, size);
1714 _dictionary->returnChunk(chunk);
1715 #ifndef PRODUCT
1716 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1717 TreeChunk::as_TreeChunk(chunk)->list()->verify_stats();
1718 }
1719 #endif // PRODUCT
1720 }
1722 void
1723 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
1724 assert_locked();
1725 size_t size = fc->size();
1726 _bt.verify_single_block((HeapWord*) fc, size);
1727 _bt.verify_not_unallocated((HeapWord*) fc, size);
1728 if (_adaptive_freelists) {
1729 _indexedFreeList[size].returnChunkAtTail(fc);
1730 } else {
1731 _indexedFreeList[size].returnChunkAtHead(fc);
1732 }
1733 #ifndef PRODUCT
1734 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1735 _indexedFreeList[size].verify_stats();
1736 }
1737 #endif // PRODUCT
1738 }
1740 // Add chunk to end of last block -- if it's the largest
1741 // block -- and update BOT and census data. We would
1742 // of course have preferred to coalesce it with the
1743 // last block, but it's currently less expensive to find the
1744 // largest block than it is to find the last.
1745 void
1746 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1747 HeapWord* chunk, size_t size) {
1748 // check that the chunk does lie in this space!
1749 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1750 // One of the parallel gc task threads may be here
1751 // whilst others are allocating.
1752 Mutex* lock = NULL;
1753 if (ParallelGCThreads != 0) {
1754 lock = &_parDictionaryAllocLock;
1755 }
1756 FreeChunk* ec;
1757 {
1758 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1759 ec = dictionary()->findLargestDict(); // get largest block
1760 if (ec != NULL && ec->end() == chunk) {
1761 // It's a coterminal block - we can coalesce.
1762 size_t old_size = ec->size();
1763 coalDeath(old_size);
1764 removeChunkFromDictionary(ec);
1765 size += old_size;
1766 } else {
1767 ec = (FreeChunk*)chunk;
1768 }
1769 }
1770 ec->setSize(size);
1771 debug_only(ec->mangleFreed(size));
1772 if (size < SmallForDictionary) {
1773 lock = _indexedFreeListParLocks[size];
1774 }
1775 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1776 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
1777 // record the birth under the lock since the recording involves
1778 // manipulation of the list on which the chunk lives and
1779 // if the chunk is allocated and is the last on the list,
1780 // the list can go away.
1781 coalBirth(size);
1782 }
1784 void
1785 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1786 size_t size) {
1787 // check that the chunk does lie in this space!
1788 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1789 assert_locked();
1790 _bt.verify_single_block(chunk, size);
1792 FreeChunk* fc = (FreeChunk*) chunk;
1793 fc->setSize(size);
1794 debug_only(fc->mangleFreed(size));
1795 if (size < SmallForDictionary) {
1796 returnChunkToFreeList(fc);
1797 } else {
1798 returnChunkToDictionary(fc);
1799 }
1800 }
1802 void
1803 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1804 size_t size, bool coalesced) {
1805 assert_locked();
1806 assert(chunk != NULL, "null chunk");
1807 if (coalesced) {
1808 // repair BOT
1809 _bt.single_block(chunk, size);
1810 }
1811 addChunkToFreeLists(chunk, size);
1812 }
1814 // We _must_ find the purported chunk on our free lists;
1815 // we assert if we don't.
1816 void
1817 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1818 size_t size = fc->size();
1819 assert_locked();
1820 debug_only(verifyFreeLists());
1821 if (size < SmallForDictionary) {
1822 removeChunkFromIndexedFreeList(fc);
1823 } else {
1824 removeChunkFromDictionary(fc);
1825 }
1826 _bt.verify_single_block((HeapWord*)fc, size);
1827 debug_only(verifyFreeLists());
1828 }
1830 void
1831 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1832 size_t size = fc->size();
1833 assert_locked();
1834 assert(fc != NULL, "null chunk");
1835 _bt.verify_single_block((HeapWord*)fc, size);
1836 _dictionary->removeChunk(fc);
1837 // adjust _unallocated_block upward, as necessary
1838 _bt.allocated((HeapWord*)fc, size);
1839 }
1841 void
1842 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1843 assert_locked();
1844 size_t size = fc->size();
1845 _bt.verify_single_block((HeapWord*)fc, size);
1846 NOT_PRODUCT(
1847 if (FLSVerifyIndexTable) {
1848 verifyIndexedFreeList(size);
1849 }
1850 )
1851 _indexedFreeList[size].removeChunk(fc);
1852 NOT_PRODUCT(
1853 if (FLSVerifyIndexTable) {
1854 verifyIndexedFreeList(size);
1855 }
1856 )
1857 }
1859 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1860 /* A hint is the next larger size that has a surplus.
1861 Start search at a size large enough to guarantee that
1862 the excess is >= MIN_CHUNK. */
1863 size_t start = align_object_size(numWords + MinChunkSize);
1864 if (start < IndexSetSize) {
1865 FreeList* it = _indexedFreeList;
1866 size_t hint = _indexedFreeList[start].hint();
1867 while (hint < IndexSetSize) {
1868 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1869 FreeList *fl = &_indexedFreeList[hint];
1870 if (fl->surplus() > 0 && fl->head() != NULL) {
1871 // Found a list with surplus, reset original hint
1872 // and split out a free chunk which is returned.
1873 _indexedFreeList[start].set_hint(hint);
1874 FreeChunk* res = getFromListGreater(fl, numWords);
1875 assert(res == NULL || res->isFree(),
1876 "Should be returning a free chunk");
1877 return res;
1878 }
1879 hint = fl->hint(); /* keep looking */
1880 }
1881 /* None found. */
1882 it[start].set_hint(IndexSetSize);
1883 }
1884 return NULL;
1885 }
1887 /* Requires fl->size >= numWords + MinChunkSize */
1888 FreeChunk* CompactibleFreeListSpace::getFromListGreater(FreeList* fl,
1889 size_t numWords) {
1890 FreeChunk *curr = fl->head();
1891 size_t oldNumWords = curr->size();
1892 assert(numWords >= MinChunkSize, "Word size is too small");
1893 assert(curr != NULL, "List is empty");
1894 assert(oldNumWords >= numWords + MinChunkSize,
1895 "Size of chunks in the list is too small");
1897 fl->removeChunk(curr);
1898 // recorded indirectly by splitChunkAndReturnRemainder -
1899 // smallSplit(oldNumWords, numWords);
1900 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1901 // Does anything have to be done for the remainder in terms of
1902 // fixing the card table?
1903 assert(new_chunk == NULL || new_chunk->isFree(),
1904 "Should be returning a free chunk");
1905 return new_chunk;
1906 }
1908 FreeChunk*
1909 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1910 size_t new_size) {
1911 assert_locked();
1912 size_t size = chunk->size();
1913 assert(size > new_size, "Split from a smaller block?");
1914 assert(is_aligned(chunk), "alignment problem");
1915 assert(size == adjustObjectSize(size), "alignment problem");
1916 size_t rem_size = size - new_size;
1917 assert(rem_size == adjustObjectSize(rem_size), "alignment problem");
1918 assert(rem_size >= MinChunkSize, "Free chunk smaller than minimum");
1919 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1920 assert(is_aligned(ffc), "alignment problem");
1921 ffc->setSize(rem_size);
1922 ffc->linkNext(NULL);
1923 ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
1924 // Above must occur before BOT is updated below.
1925 // adjust block offset table
1926 OrderAccess::storestore();
1927 assert(chunk->isFree() && ffc->isFree(), "Error");
1928 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1929 if (rem_size < SmallForDictionary) {
1930 bool is_par = (SharedHeap::heap()->n_par_threads() > 0);
1931 if (is_par) _indexedFreeListParLocks[rem_size]->lock();
1932 assert(!is_par ||
1933 (SharedHeap::heap()->n_par_threads() ==
1934 SharedHeap::heap()->workers()->active_workers()), "Mismatch");
1935 returnChunkToFreeList(ffc);
1936 split(size, rem_size);
1937 if (is_par) _indexedFreeListParLocks[rem_size]->unlock();
1938 } else {
1939 returnChunkToDictionary(ffc);
1940 split(size ,rem_size);
1941 }
1942 chunk->setSize(new_size);
1943 return chunk;
1944 }
1946 void
1947 CompactibleFreeListSpace::sweep_completed() {
1948 // Now that space is probably plentiful, refill linear
1949 // allocation blocks as needed.
1950 refillLinearAllocBlocksIfNeeded();
1951 }
1953 void
1954 CompactibleFreeListSpace::gc_prologue() {
1955 assert_locked();
1956 if (PrintFLSStatistics != 0) {
1957 gclog_or_tty->print("Before GC:\n");
1958 reportFreeListStatistics();
1959 }
1960 refillLinearAllocBlocksIfNeeded();
1961 }
1963 void
1964 CompactibleFreeListSpace::gc_epilogue() {
1965 assert_locked();
1966 if (PrintGCDetails && Verbose && !_adaptive_freelists) {
1967 if (_smallLinearAllocBlock._word_size == 0)
1968 warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure");
1969 }
1970 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1971 _promoInfo.stopTrackingPromotions();
1972 repairLinearAllocationBlocks();
1973 // Print Space's stats
1974 if (PrintFLSStatistics != 0) {
1975 gclog_or_tty->print("After GC:\n");
1976 reportFreeListStatistics();
1977 }
1978 }
1980 // Iteration support, mostly delegated from a CMS generation
1982 void CompactibleFreeListSpace::save_marks() {
1983 assert(Thread::current()->is_VM_thread(),
1984 "Global variable should only be set when single-threaded");
1985 // Mark the "end" of the used space at the time of this call;
1986 // note, however, that promoted objects from this point
1987 // on are tracked in the _promoInfo below.
1988 set_saved_mark_word(unallocated_block());
1989 #ifdef ASSERT
1990 // Check the sanity of save_marks() etc.
1991 MemRegion ur = used_region();
1992 MemRegion urasm = used_region_at_save_marks();
1993 assert(ur.contains(urasm),
1994 err_msg(" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
1995 " should contain [" PTR_FORMAT "," PTR_FORMAT ")",
1996 ur.start(), ur.end(), urasm.start(), urasm.end()));
1997 #endif
1998 // inform allocator that promotions should be tracked.
1999 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
2000 _promoInfo.startTrackingPromotions();
2001 }
2003 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
2004 assert(_promoInfo.tracking(), "No preceding save_marks?");
2005 assert(SharedHeap::heap()->n_par_threads() == 0,
2006 "Shouldn't be called if using parallel gc.");
2007 return _promoInfo.noPromotions();
2008 }
2010 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
2011 \
2012 void CompactibleFreeListSpace:: \
2013 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
2014 assert(SharedHeap::heap()->n_par_threads() == 0, \
2015 "Shouldn't be called (yet) during parallel part of gc."); \
2016 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
2017 /* \
2018 * This also restores any displaced headers and removes the elements from \
2019 * the iteration set as they are processed, so that we have a clean slate \
2020 * at the end of the iteration. Note, thus, that if new objects are \
2021 * promoted as a result of the iteration they are iterated over as well. \
2022 */ \
2023 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
2024 }
2026 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
2029 void CompactibleFreeListSpace::object_iterate_since_last_GC(ObjectClosure* cl) {
2030 // ugghh... how would one do this efficiently for a non-contiguous space?
2031 guarantee(false, "NYI");
2032 }
2034 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
2035 return _smallLinearAllocBlock._word_size == 0;
2036 }
2038 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
2039 // Fix up linear allocation blocks to look like free blocks
2040 repairLinearAllocBlock(&_smallLinearAllocBlock);
2041 }
2043 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
2044 assert_locked();
2045 if (blk->_ptr != NULL) {
2046 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
2047 "Minimum block size requirement");
2048 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
2049 fc->setSize(blk->_word_size);
2050 fc->linkPrev(NULL); // mark as free
2051 fc->dontCoalesce();
2052 assert(fc->isFree(), "just marked it free");
2053 assert(fc->cantCoalesce(), "just marked it uncoalescable");
2054 }
2055 }
2057 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
2058 assert_locked();
2059 if (_smallLinearAllocBlock._ptr == NULL) {
2060 assert(_smallLinearAllocBlock._word_size == 0,
2061 "Size of linAB should be zero if the ptr is NULL");
2062 // Reset the linAB refill and allocation size limit.
2063 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
2064 }
2065 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
2066 }
2068 void
2069 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
2070 assert_locked();
2071 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
2072 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
2073 "blk invariant");
2074 if (blk->_ptr == NULL) {
2075 refillLinearAllocBlock(blk);
2076 }
2077 if (PrintMiscellaneous && Verbose) {
2078 if (blk->_word_size == 0) {
2079 warning("CompactibleFreeListSpace(prologue):: Linear allocation failure");
2080 }
2081 }
2082 }
2084 void
2085 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
2086 assert_locked();
2087 assert(blk->_word_size == 0 && blk->_ptr == NULL,
2088 "linear allocation block should be empty");
2089 FreeChunk* fc;
2090 if (blk->_refillSize < SmallForDictionary &&
2091 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
2092 // A linAB's strategy might be to use small sizes to reduce
2093 // fragmentation but still get the benefits of allocation from a
2094 // linAB.
2095 } else {
2096 fc = getChunkFromDictionary(blk->_refillSize);
2097 }
2098 if (fc != NULL) {
2099 blk->_ptr = (HeapWord*)fc;
2100 blk->_word_size = fc->size();
2101 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
2102 }
2103 }
2105 // Support for concurrent collection policy decisions.
2106 bool CompactibleFreeListSpace::should_concurrent_collect() const {
2107 // In the future we might want to add in frgamentation stats --
2108 // including erosion of the "mountain" into this decision as well.
2109 return !adaptive_freelists() && linearAllocationWouldFail();
2110 }
2112 // Support for compaction
2114 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
2115 SCAN_AND_FORWARD(cp,end,block_is_obj,block_size);
2116 // prepare_for_compaction() uses the space between live objects
2117 // so that later phase can skip dead space quickly. So verification
2118 // of the free lists doesn't work after.
2119 }
2121 #define obj_size(q) adjustObjectSize(oop(q)->size())
2122 #define adjust_obj_size(s) adjustObjectSize(s)
2124 void CompactibleFreeListSpace::adjust_pointers() {
2125 // In other versions of adjust_pointers(), a bail out
2126 // based on the amount of live data in the generation
2127 // (i.e., if 0, bail out) may be used.
2128 // Cannot test used() == 0 here because the free lists have already
2129 // been mangled by the compaction.
2131 SCAN_AND_ADJUST_POINTERS(adjust_obj_size);
2132 // See note about verification in prepare_for_compaction().
2133 }
2135 void CompactibleFreeListSpace::compact() {
2136 SCAN_AND_COMPACT(obj_size);
2137 }
2139 // fragmentation_metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
2140 // where fbs is free block sizes
2141 double CompactibleFreeListSpace::flsFrag() const {
2142 size_t itabFree = totalSizeInIndexedFreeLists();
2143 double frag = 0.0;
2144 size_t i;
2146 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2147 double sz = i;
2148 frag += _indexedFreeList[i].count() * (sz * sz);
2149 }
2151 double totFree = itabFree +
2152 _dictionary->totalChunkSize(DEBUG_ONLY(freelistLock()));
2153 if (totFree > 0) {
2154 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
2155 (totFree * totFree));
2156 frag = (double)1.0 - frag;
2157 } else {
2158 assert(frag == 0.0, "Follows from totFree == 0");
2159 }
2160 return frag;
2161 }
2163 void CompactibleFreeListSpace::beginSweepFLCensus(
2164 float inter_sweep_current,
2165 float inter_sweep_estimate,
2166 float intra_sweep_estimate) {
2167 assert_locked();
2168 size_t i;
2169 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2170 FreeList* fl = &_indexedFreeList[i];
2171 if (PrintFLSStatistics > 1) {
2172 gclog_or_tty->print("size[%d] : ", i);
2173 }
2174 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2175 fl->set_coalDesired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2176 fl->set_beforeSweep(fl->count());
2177 fl->set_bfrSurp(fl->surplus());
2178 }
2179 _dictionary->beginSweepDictCensus(CMSLargeCoalSurplusPercent,
2180 inter_sweep_current,
2181 inter_sweep_estimate,
2182 intra_sweep_estimate);
2183 }
2185 void CompactibleFreeListSpace::setFLSurplus() {
2186 assert_locked();
2187 size_t i;
2188 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2189 FreeList *fl = &_indexedFreeList[i];
2190 fl->set_surplus(fl->count() -
2191 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2192 }
2193 }
2195 void CompactibleFreeListSpace::setFLHints() {
2196 assert_locked();
2197 size_t i;
2198 size_t h = IndexSetSize;
2199 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2200 FreeList *fl = &_indexedFreeList[i];
2201 fl->set_hint(h);
2202 if (fl->surplus() > 0) {
2203 h = i;
2204 }
2205 }
2206 }
2208 void CompactibleFreeListSpace::clearFLCensus() {
2209 assert_locked();
2210 size_t i;
2211 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2212 FreeList *fl = &_indexedFreeList[i];
2213 fl->set_prevSweep(fl->count());
2214 fl->set_coalBirths(0);
2215 fl->set_coalDeaths(0);
2216 fl->set_splitBirths(0);
2217 fl->set_splitDeaths(0);
2218 }
2219 }
2221 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2222 if (PrintFLSStatistics > 0) {
2223 HeapWord* largestAddr = (HeapWord*) dictionary()->findLargestDict();
2224 gclog_or_tty->print_cr("CMS: Large block " PTR_FORMAT,
2225 largestAddr);
2226 }
2227 setFLSurplus();
2228 setFLHints();
2229 if (PrintGC && PrintFLSCensus > 0) {
2230 printFLCensus(sweep_count);
2231 }
2232 clearFLCensus();
2233 assert_locked();
2234 _dictionary->endSweepDictCensus(CMSLargeSplitSurplusPercent);
2235 }
2237 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2238 if (size < SmallForDictionary) {
2239 FreeList *fl = &_indexedFreeList[size];
2240 return (fl->coalDesired() < 0) ||
2241 ((int)fl->count() > fl->coalDesired());
2242 } else {
2243 return dictionary()->coalDictOverPopulated(size);
2244 }
2245 }
2247 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2248 assert(size < SmallForDictionary, "Size too large for indexed list");
2249 FreeList *fl = &_indexedFreeList[size];
2250 fl->increment_coalBirths();
2251 fl->increment_surplus();
2252 }
2254 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2255 assert(size < SmallForDictionary, "Size too large for indexed list");
2256 FreeList *fl = &_indexedFreeList[size];
2257 fl->increment_coalDeaths();
2258 fl->decrement_surplus();
2259 }
2261 void CompactibleFreeListSpace::coalBirth(size_t size) {
2262 if (size < SmallForDictionary) {
2263 smallCoalBirth(size);
2264 } else {
2265 dictionary()->dictCensusUpdate(size,
2266 false /* split */,
2267 true /* birth */);
2268 }
2269 }
2271 void CompactibleFreeListSpace::coalDeath(size_t size) {
2272 if(size < SmallForDictionary) {
2273 smallCoalDeath(size);
2274 } else {
2275 dictionary()->dictCensusUpdate(size,
2276 false /* split */,
2277 false /* birth */);
2278 }
2279 }
2281 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2282 assert(size < SmallForDictionary, "Size too large for indexed list");
2283 FreeList *fl = &_indexedFreeList[size];
2284 fl->increment_splitBirths();
2285 fl->increment_surplus();
2286 }
2288 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2289 assert(size < SmallForDictionary, "Size too large for indexed list");
2290 FreeList *fl = &_indexedFreeList[size];
2291 fl->increment_splitDeaths();
2292 fl->decrement_surplus();
2293 }
2295 void CompactibleFreeListSpace::splitBirth(size_t size) {
2296 if (size < SmallForDictionary) {
2297 smallSplitBirth(size);
2298 } else {
2299 dictionary()->dictCensusUpdate(size,
2300 true /* split */,
2301 true /* birth */);
2302 }
2303 }
2305 void CompactibleFreeListSpace::splitDeath(size_t size) {
2306 if (size < SmallForDictionary) {
2307 smallSplitDeath(size);
2308 } else {
2309 dictionary()->dictCensusUpdate(size,
2310 true /* split */,
2311 false /* birth */);
2312 }
2313 }
2315 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2316 size_t to2 = from - to1;
2317 splitDeath(from);
2318 splitBirth(to1);
2319 splitBirth(to2);
2320 }
2322 void CompactibleFreeListSpace::print() const {
2323 print_on(tty);
2324 }
2326 void CompactibleFreeListSpace::prepare_for_verify() {
2327 assert_locked();
2328 repairLinearAllocationBlocks();
2329 // Verify that the SpoolBlocks look like free blocks of
2330 // appropriate sizes... To be done ...
2331 }
2333 class VerifyAllBlksClosure: public BlkClosure {
2334 private:
2335 const CompactibleFreeListSpace* _sp;
2336 const MemRegion _span;
2337 HeapWord* _last_addr;
2338 size_t _last_size;
2339 bool _last_was_obj;
2340 bool _last_was_live;
2342 public:
2343 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2344 MemRegion span) : _sp(sp), _span(span),
2345 _last_addr(NULL), _last_size(0),
2346 _last_was_obj(false), _last_was_live(false) { }
2348 virtual size_t do_blk(HeapWord* addr) {
2349 size_t res;
2350 bool was_obj = false;
2351 bool was_live = false;
2352 if (_sp->block_is_obj(addr)) {
2353 was_obj = true;
2354 oop p = oop(addr);
2355 guarantee(p->is_oop(), "Should be an oop");
2356 res = _sp->adjustObjectSize(p->size());
2357 if (_sp->obj_is_alive(addr)) {
2358 was_live = true;
2359 p->verify();
2360 }
2361 } else {
2362 FreeChunk* fc = (FreeChunk*)addr;
2363 res = fc->size();
2364 if (FLSVerifyLists && !fc->cantCoalesce()) {
2365 guarantee(_sp->verifyChunkInFreeLists(fc),
2366 "Chunk should be on a free list");
2367 }
2368 }
2369 if (res == 0) {
2370 gclog_or_tty->print_cr("Livelock: no rank reduction!");
2371 gclog_or_tty->print_cr(
2372 " Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2373 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2374 addr, res, was_obj ?"true":"false", was_live ?"true":"false",
2375 _last_addr, _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2376 _sp->print_on(gclog_or_tty);
2377 guarantee(false, "Seppuku!");
2378 }
2379 _last_addr = addr;
2380 _last_size = res;
2381 _last_was_obj = was_obj;
2382 _last_was_live = was_live;
2383 return res;
2384 }
2385 };
2387 class VerifyAllOopsClosure: public OopClosure {
2388 private:
2389 const CMSCollector* _collector;
2390 const CompactibleFreeListSpace* _sp;
2391 const MemRegion _span;
2392 const bool _past_remark;
2393 const CMSBitMap* _bit_map;
2395 protected:
2396 void do_oop(void* p, oop obj) {
2397 if (_span.contains(obj)) { // the interior oop points into CMS heap
2398 if (!_span.contains(p)) { // reference from outside CMS heap
2399 // Should be a valid object; the first disjunct below allows
2400 // us to sidestep an assertion in block_is_obj() that insists
2401 // that p be in _sp. Note that several generations (and spaces)
2402 // are spanned by _span (CMS heap) above.
2403 guarantee(!_sp->is_in_reserved(obj) ||
2404 _sp->block_is_obj((HeapWord*)obj),
2405 "Should be an object");
2406 guarantee(obj->is_oop(), "Should be an oop");
2407 obj->verify();
2408 if (_past_remark) {
2409 // Remark has been completed, the object should be marked
2410 _bit_map->isMarked((HeapWord*)obj);
2411 }
2412 } else { // reference within CMS heap
2413 if (_past_remark) {
2414 // Remark has been completed -- so the referent should have
2415 // been marked, if referring object is.
2416 if (_bit_map->isMarked(_collector->block_start(p))) {
2417 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2418 }
2419 }
2420 }
2421 } else if (_sp->is_in_reserved(p)) {
2422 // the reference is from FLS, and points out of FLS
2423 guarantee(obj->is_oop(), "Should be an oop");
2424 obj->verify();
2425 }
2426 }
2428 template <class T> void do_oop_work(T* p) {
2429 T heap_oop = oopDesc::load_heap_oop(p);
2430 if (!oopDesc::is_null(heap_oop)) {
2431 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2432 do_oop(p, obj);
2433 }
2434 }
2436 public:
2437 VerifyAllOopsClosure(const CMSCollector* collector,
2438 const CompactibleFreeListSpace* sp, MemRegion span,
2439 bool past_remark, CMSBitMap* bit_map) :
2440 OopClosure(), _collector(collector), _sp(sp), _span(span),
2441 _past_remark(past_remark), _bit_map(bit_map) { }
2443 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2444 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2445 };
2447 void CompactibleFreeListSpace::verify() const {
2448 assert_lock_strong(&_freelistLock);
2449 verify_objects_initialized();
2450 MemRegion span = _collector->_span;
2451 bool past_remark = (_collector->abstract_state() ==
2452 CMSCollector::Sweeping);
2454 ResourceMark rm;
2455 HandleMark hm;
2457 // Check integrity of CFL data structures
2458 _promoInfo.verify();
2459 _dictionary->verify();
2460 if (FLSVerifyIndexTable) {
2461 verifyIndexedFreeLists();
2462 }
2463 // Check integrity of all objects and free blocks in space
2464 {
2465 VerifyAllBlksClosure cl(this, span);
2466 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2467 }
2468 // Check that all references in the heap to FLS
2469 // are to valid objects in FLS or that references in
2470 // FLS are to valid objects elsewhere in the heap
2471 if (FLSVerifyAllHeapReferences)
2472 {
2473 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2474 _collector->markBitMap());
2475 CollectedHeap* ch = Universe::heap();
2476 ch->oop_iterate(&cl); // all oops in generations
2477 ch->permanent_oop_iterate(&cl); // all oops in perm gen
2478 }
2480 if (VerifyObjectStartArray) {
2481 // Verify the block offset table
2482 _bt.verify();
2483 }
2484 }
2486 #ifndef PRODUCT
2487 void CompactibleFreeListSpace::verifyFreeLists() const {
2488 if (FLSVerifyLists) {
2489 _dictionary->verify();
2490 verifyIndexedFreeLists();
2491 } else {
2492 if (FLSVerifyDictionary) {
2493 _dictionary->verify();
2494 }
2495 if (FLSVerifyIndexTable) {
2496 verifyIndexedFreeLists();
2497 }
2498 }
2499 }
2500 #endif
2502 void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
2503 size_t i = 0;
2504 for (; i < IndexSetStart; i++) {
2505 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
2506 }
2507 for (; i < IndexSetSize; i++) {
2508 verifyIndexedFreeList(i);
2509 }
2510 }
2512 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
2513 FreeChunk* fc = _indexedFreeList[size].head();
2514 FreeChunk* tail = _indexedFreeList[size].tail();
2515 size_t num = _indexedFreeList[size].count();
2516 size_t n = 0;
2517 guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL,
2518 "Slot should have been empty");
2519 for (; fc != NULL; fc = fc->next(), n++) {
2520 guarantee(fc->size() == size, "Size inconsistency");
2521 guarantee(fc->isFree(), "!free?");
2522 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
2523 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
2524 }
2525 guarantee(n == num, "Incorrect count");
2526 }
2528 #ifndef PRODUCT
2529 void CompactibleFreeListSpace::check_free_list_consistency() const {
2530 assert(_dictionary->minSize() <= IndexSetSize,
2531 "Some sizes can't be allocated without recourse to"
2532 " linear allocation buffers");
2533 assert(MIN_TREE_CHUNK_SIZE*HeapWordSize == sizeof(TreeChunk),
2534 "else MIN_TREE_CHUNK_SIZE is wrong");
2535 assert((IndexSetStride == 2 && IndexSetStart == 4) || // 32-bit
2536 (IndexSetStride == 1 && IndexSetStart == 3), "just checking"); // 64-bit
2537 assert((IndexSetStride != 2) || (IndexSetStart % 2 == 0),
2538 "Some for-loops may be incorrectly initialized");
2539 assert((IndexSetStride != 2) || (IndexSetSize % 2 == 1),
2540 "For-loops that iterate over IndexSet with stride 2 may be wrong");
2541 }
2542 #endif
2544 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2545 assert_lock_strong(&_freelistLock);
2546 FreeList total;
2547 gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count);
2548 FreeList::print_labels_on(gclog_or_tty, "size");
2549 size_t totalFree = 0;
2550 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2551 const FreeList *fl = &_indexedFreeList[i];
2552 totalFree += fl->count() * fl->size();
2553 if (i % (40*IndexSetStride) == 0) {
2554 FreeList::print_labels_on(gclog_or_tty, "size");
2555 }
2556 fl->print_on(gclog_or_tty);
2557 total.set_bfrSurp( total.bfrSurp() + fl->bfrSurp() );
2558 total.set_surplus( total.surplus() + fl->surplus() );
2559 total.set_desired( total.desired() + fl->desired() );
2560 total.set_prevSweep( total.prevSweep() + fl->prevSweep() );
2561 total.set_beforeSweep(total.beforeSweep() + fl->beforeSweep());
2562 total.set_count( total.count() + fl->count() );
2563 total.set_coalBirths( total.coalBirths() + fl->coalBirths() );
2564 total.set_coalDeaths( total.coalDeaths() + fl->coalDeaths() );
2565 total.set_splitBirths(total.splitBirths() + fl->splitBirths());
2566 total.set_splitDeaths(total.splitDeaths() + fl->splitDeaths());
2567 }
2568 total.print_on(gclog_or_tty, "TOTAL");
2569 gclog_or_tty->print_cr("Total free in indexed lists "
2570 SIZE_FORMAT " words", totalFree);
2571 gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n",
2572 (double)(total.splitBirths()+total.coalBirths()-total.splitDeaths()-total.coalDeaths())/
2573 (total.prevSweep() != 0 ? (double)total.prevSweep() : 1.0),
2574 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2575 _dictionary->printDictCensus();
2576 }
2578 ///////////////////////////////////////////////////////////////////////////
2579 // CFLS_LAB
2580 ///////////////////////////////////////////////////////////////////////////
2582 #define VECTOR_257(x) \
2583 /* 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 */ \
2584 { 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, \
2585 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, \
2586 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, \
2587 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, \
2588 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, \
2589 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, \
2590 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, \
2591 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, \
2592 x }
2594 // Initialize with default setting of CMSParPromoteBlocksToClaim, _not_
2595 // OldPLABSize, whose static default is different; if overridden at the
2596 // command-line, this will get reinitialized via a call to
2597 // modify_initialization() below.
2598 AdaptiveWeightedAverage CFLS_LAB::_blocks_to_claim[] =
2599 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CMSParPromoteBlocksToClaim));
2600 size_t CFLS_LAB::_global_num_blocks[] = VECTOR_257(0);
2601 uint CFLS_LAB::_global_num_workers[] = VECTOR_257(0);
2603 CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) :
2604 _cfls(cfls)
2605 {
2606 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2607 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2608 i < CompactibleFreeListSpace::IndexSetSize;
2609 i += CompactibleFreeListSpace::IndexSetStride) {
2610 _indexedFreeList[i].set_size(i);
2611 _num_blocks[i] = 0;
2612 }
2613 }
2615 static bool _CFLS_LAB_modified = false;
2617 void CFLS_LAB::modify_initialization(size_t n, unsigned wt) {
2618 assert(!_CFLS_LAB_modified, "Call only once");
2619 _CFLS_LAB_modified = true;
2620 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2621 i < CompactibleFreeListSpace::IndexSetSize;
2622 i += CompactibleFreeListSpace::IndexSetStride) {
2623 _blocks_to_claim[i].modify(n, wt, true /* force */);
2624 }
2625 }
2627 HeapWord* CFLS_LAB::alloc(size_t word_sz) {
2628 FreeChunk* res;
2629 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2630 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2631 // This locking manages sync with other large object allocations.
2632 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2633 Mutex::_no_safepoint_check_flag);
2634 res = _cfls->getChunkFromDictionaryExact(word_sz);
2635 if (res == NULL) return NULL;
2636 } else {
2637 FreeList* fl = &_indexedFreeList[word_sz];
2638 if (fl->count() == 0) {
2639 // Attempt to refill this local free list.
2640 get_from_global_pool(word_sz, fl);
2641 // If it didn't work, give up.
2642 if (fl->count() == 0) return NULL;
2643 }
2644 res = fl->getChunkAtHead();
2645 assert(res != NULL, "Why was count non-zero?");
2646 }
2647 res->markNotFree();
2648 assert(!res->isFree(), "shouldn't be marked free");
2649 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2650 // mangle a just allocated object with a distinct pattern.
2651 debug_only(res->mangleAllocated(word_sz));
2652 return (HeapWord*)res;
2653 }
2655 // Get a chunk of blocks of the right size and update related
2656 // book-keeping stats
2657 void CFLS_LAB::get_from_global_pool(size_t word_sz, FreeList* fl) {
2658 // Get the #blocks we want to claim
2659 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2660 assert(n_blks > 0, "Error");
2661 assert(ResizePLAB || n_blks == OldPLABSize, "Error");
2662 // In some cases, when the application has a phase change,
2663 // there may be a sudden and sharp shift in the object survival
2664 // profile, and updating the counts at the end of a scavenge
2665 // may not be quick enough, giving rise to large scavenge pauses
2666 // during these phase changes. It is beneficial to detect such
2667 // changes on-the-fly during a scavenge and avoid such a phase-change
2668 // pothole. The following code is a heuristic attempt to do that.
2669 // It is protected by a product flag until we have gained
2670 // enough experience with this heuristic and fine-tuned its behaviour.
2671 // WARNING: This might increase fragmentation if we overreact to
2672 // small spikes, so some kind of historical smoothing based on
2673 // previous experience with the greater reactivity might be useful.
2674 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2675 // default.
2676 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2677 size_t multiple = _num_blocks[word_sz]/(CMSOldPLABToleranceFactor*CMSOldPLABNumRefills*n_blks);
2678 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2679 n_blks = MIN2(n_blks, CMSOldPLABMax);
2680 }
2681 assert(n_blks > 0, "Error");
2682 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2683 // Update stats table entry for this block size
2684 _num_blocks[word_sz] += fl->count();
2685 }
2687 void CFLS_LAB::compute_desired_plab_size() {
2688 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2689 i < CompactibleFreeListSpace::IndexSetSize;
2690 i += CompactibleFreeListSpace::IndexSetStride) {
2691 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2692 "Counter inconsistency");
2693 if (_global_num_workers[i] > 0) {
2694 // Need to smooth wrt historical average
2695 if (ResizeOldPLAB) {
2696 _blocks_to_claim[i].sample(
2697 MAX2((size_t)CMSOldPLABMin,
2698 MIN2((size_t)CMSOldPLABMax,
2699 _global_num_blocks[i]/(_global_num_workers[i]*CMSOldPLABNumRefills))));
2700 }
2701 // Reset counters for next round
2702 _global_num_workers[i] = 0;
2703 _global_num_blocks[i] = 0;
2704 if (PrintOldPLAB) {
2705 gclog_or_tty->print_cr("[%d]: %d", i, (size_t)_blocks_to_claim[i].average());
2706 }
2707 }
2708 }
2709 }
2711 // If this is changed in the future to allow parallel
2712 // access, one would need to take the FL locks and,
2713 // depending on how it is used, stagger access from
2714 // parallel threads to reduce contention.
2715 void CFLS_LAB::retire(int tid) {
2716 // We run this single threaded with the world stopped;
2717 // so no need for locks and such.
2718 NOT_PRODUCT(Thread* t = Thread::current();)
2719 assert(Thread::current()->is_VM_thread(), "Error");
2720 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2721 i < CompactibleFreeListSpace::IndexSetSize;
2722 i += CompactibleFreeListSpace::IndexSetStride) {
2723 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2724 "Can't retire more than what we obtained");
2725 if (_num_blocks[i] > 0) {
2726 size_t num_retire = _indexedFreeList[i].count();
2727 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2728 {
2729 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2730 // Mutex::_no_safepoint_check_flag);
2732 // Update globals stats for num_blocks used
2733 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2734 _global_num_workers[i]++;
2735 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2736 if (num_retire > 0) {
2737 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2738 // Reset this list.
2739 _indexedFreeList[i] = FreeList();
2740 _indexedFreeList[i].set_size(i);
2741 }
2742 }
2743 if (PrintOldPLAB) {
2744 gclog_or_tty->print_cr("%d[%d]: %d/%d/%d",
2745 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2746 }
2747 // Reset stats for next round
2748 _num_blocks[i] = 0;
2749 }
2750 }
2751 }
2753 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl) {
2754 assert(fl->count() == 0, "Precondition.");
2755 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2756 "Precondition");
2758 // We'll try all multiples of word_sz in the indexed set, starting with
2759 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2760 // then try getting a big chunk and splitting it.
2761 {
2762 bool found;
2763 int k;
2764 size_t cur_sz;
2765 for (k = 1, cur_sz = k * word_sz, found = false;
2766 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2767 (CMSSplitIndexedFreeListBlocks || k <= 1);
2768 k++, cur_sz = k * word_sz) {
2769 FreeList fl_for_cur_sz; // Empty.
2770 fl_for_cur_sz.set_size(cur_sz);
2771 {
2772 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2773 Mutex::_no_safepoint_check_flag);
2774 FreeList* gfl = &_indexedFreeList[cur_sz];
2775 if (gfl->count() != 0) {
2776 // nn is the number of chunks of size cur_sz that
2777 // we'd need to split k-ways each, in order to create
2778 // "n" chunks of size word_sz each.
2779 const size_t nn = MAX2(n/k, (size_t)1);
2780 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2781 found = true;
2782 if (k > 1) {
2783 // Update split death stats for the cur_sz-size blocks list:
2784 // we increment the split death count by the number of blocks
2785 // we just took from the cur_sz-size blocks list and which
2786 // we will be splitting below.
2787 ssize_t deaths = gfl->splitDeaths() +
2788 fl_for_cur_sz.count();
2789 gfl->set_splitDeaths(deaths);
2790 }
2791 }
2792 }
2793 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2794 if (found) {
2795 if (k == 1) {
2796 fl->prepend(&fl_for_cur_sz);
2797 } else {
2798 // Divide each block on fl_for_cur_sz up k ways.
2799 FreeChunk* fc;
2800 while ((fc = fl_for_cur_sz.getChunkAtHead()) != NULL) {
2801 // Must do this in reverse order, so that anybody attempting to
2802 // access the main chunk sees it as a single free block until we
2803 // change it.
2804 size_t fc_size = fc->size();
2805 assert(fc->isFree(), "Error");
2806 for (int i = k-1; i >= 0; i--) {
2807 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2808 assert((i != 0) ||
2809 ((fc == ffc) && ffc->isFree() &&
2810 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2811 "Counting error");
2812 ffc->setSize(word_sz);
2813 ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
2814 ffc->linkNext(NULL);
2815 // Above must occur before BOT is updated below.
2816 OrderAccess::storestore();
2817 // splitting from the right, fc_size == i * word_sz
2818 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2819 fc_size -= word_sz;
2820 assert(fc_size == i*word_sz, "Error");
2821 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2822 _bt.verify_single_block((HeapWord*)fc, fc_size);
2823 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2824 // Push this on "fl".
2825 fl->returnChunkAtHead(ffc);
2826 }
2827 // TRAP
2828 assert(fl->tail()->next() == NULL, "List invariant.");
2829 }
2830 }
2831 // Update birth stats for this block size.
2832 size_t num = fl->count();
2833 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2834 Mutex::_no_safepoint_check_flag);
2835 ssize_t births = _indexedFreeList[word_sz].splitBirths() + num;
2836 _indexedFreeList[word_sz].set_splitBirths(births);
2837 return;
2838 }
2839 }
2840 }
2841 // Otherwise, we'll split a block from the dictionary.
2842 FreeChunk* fc = NULL;
2843 FreeChunk* rem_fc = NULL;
2844 size_t rem;
2845 {
2846 MutexLockerEx x(parDictionaryAllocLock(),
2847 Mutex::_no_safepoint_check_flag);
2848 while (n > 0) {
2849 fc = dictionary()->getChunk(MAX2(n * word_sz,
2850 _dictionary->minSize()),
2851 FreeBlockDictionary::atLeast);
2852 if (fc != NULL) {
2853 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2854 dictionary()->dictCensusUpdate(fc->size(),
2855 true /*split*/,
2856 false /*birth*/);
2857 break;
2858 } else {
2859 n--;
2860 }
2861 }
2862 if (fc == NULL) return;
2863 // Otherwise, split up that block.
2864 assert((ssize_t)n >= 1, "Control point invariant");
2865 assert(fc->isFree(), "Error: should be a free block");
2866 _bt.verify_single_block((HeapWord*)fc, fc->size());
2867 const size_t nn = fc->size() / word_sz;
2868 n = MIN2(nn, n);
2869 assert((ssize_t)n >= 1, "Control point invariant");
2870 rem = fc->size() - n * word_sz;
2871 // If there is a remainder, and it's too small, allocate one fewer.
2872 if (rem > 0 && rem < MinChunkSize) {
2873 n--; rem += word_sz;
2874 }
2875 // Note that at this point we may have n == 0.
2876 assert((ssize_t)n >= 0, "Control point invariant");
2878 // If n is 0, the chunk fc that was found is not large
2879 // enough to leave a viable remainder. We are unable to
2880 // allocate even one block. Return fc to the
2881 // dictionary and return, leaving "fl" empty.
2882 if (n == 0) {
2883 returnChunkToDictionary(fc);
2884 assert(fl->count() == 0, "We never allocated any blocks");
2885 return;
2886 }
2888 // First return the remainder, if any.
2889 // Note that we hold the lock until we decide if we're going to give
2890 // back the remainder to the dictionary, since a concurrent allocation
2891 // may otherwise see the heap as empty. (We're willing to take that
2892 // hit if the block is a small block.)
2893 if (rem > 0) {
2894 size_t prefix_size = n * word_sz;
2895 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2896 rem_fc->setSize(rem);
2897 rem_fc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
2898 rem_fc->linkNext(NULL);
2899 // Above must occur before BOT is updated below.
2900 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2901 OrderAccess::storestore();
2902 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2903 assert(fc->isFree(), "Error");
2904 fc->setSize(prefix_size);
2905 if (rem >= IndexSetSize) {
2906 returnChunkToDictionary(rem_fc);
2907 dictionary()->dictCensusUpdate(rem, true /*split*/, true /*birth*/);
2908 rem_fc = NULL;
2909 }
2910 // Otherwise, return it to the small list below.
2911 }
2912 }
2913 if (rem_fc != NULL) {
2914 MutexLockerEx x(_indexedFreeListParLocks[rem],
2915 Mutex::_no_safepoint_check_flag);
2916 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2917 _indexedFreeList[rem].returnChunkAtHead(rem_fc);
2918 smallSplitBirth(rem);
2919 }
2920 assert((ssize_t)n > 0 && fc != NULL, "Consistency");
2921 // Now do the splitting up.
2922 // Must do this in reverse order, so that anybody attempting to
2923 // access the main chunk sees it as a single free block until we
2924 // change it.
2925 size_t fc_size = n * word_sz;
2926 // All but first chunk in this loop
2927 for (ssize_t i = n-1; i > 0; i--) {
2928 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2929 ffc->setSize(word_sz);
2930 ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
2931 ffc->linkNext(NULL);
2932 // Above must occur before BOT is updated below.
2933 OrderAccess::storestore();
2934 // splitting from the right, fc_size == (n - i + 1) * wordsize
2935 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2936 fc_size -= word_sz;
2937 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2938 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2939 _bt.verify_single_block((HeapWord*)fc, fc_size);
2940 // Push this on "fl".
2941 fl->returnChunkAtHead(ffc);
2942 }
2943 // First chunk
2944 assert(fc->isFree() && fc->size() == n*word_sz, "Error: should still be a free block");
2945 // The blocks above should show their new sizes before the first block below
2946 fc->setSize(word_sz);
2947 fc->linkPrev(NULL); // idempotent wrt free-ness, see assert above
2948 fc->linkNext(NULL);
2949 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2950 _bt.verify_single_block((HeapWord*)fc, fc->size());
2951 fl->returnChunkAtHead(fc);
2953 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2954 {
2955 // Update the stats for this block size.
2956 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2957 Mutex::_no_safepoint_check_flag);
2958 const ssize_t births = _indexedFreeList[word_sz].splitBirths() + n;
2959 _indexedFreeList[word_sz].set_splitBirths(births);
2960 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2961 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2962 }
2964 // TRAP
2965 assert(fl->tail()->next() == NULL, "List invariant.");
2966 }
2968 // Set up the space's par_seq_tasks structure for work claiming
2969 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2970 // XXX Need to suitably abstract and generalize this and the next
2971 // method into one.
2972 void
2973 CompactibleFreeListSpace::
2974 initialize_sequential_subtasks_for_rescan(int n_threads) {
2975 // The "size" of each task is fixed according to rescan_task_size.
2976 assert(n_threads > 0, "Unexpected n_threads argument");
2977 const size_t task_size = rescan_task_size();
2978 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2979 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2980 assert(n_tasks == 0 ||
2981 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2982 (used_region().start() + n_tasks*task_size >= used_region().end())),
2983 "n_tasks calculation incorrect");
2984 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2985 assert(!pst->valid(), "Clobbering existing data?");
2986 // Sets the condition for completion of the subtask (how many threads
2987 // need to finish in order to be done).
2988 pst->set_n_threads(n_threads);
2989 pst->set_n_tasks((int)n_tasks);
2990 }
2992 // Set up the space's par_seq_tasks structure for work claiming
2993 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2994 void
2995 CompactibleFreeListSpace::
2996 initialize_sequential_subtasks_for_marking(int n_threads,
2997 HeapWord* low) {
2998 // The "size" of each task is fixed according to rescan_task_size.
2999 assert(n_threads > 0, "Unexpected n_threads argument");
3000 const size_t task_size = marking_task_size();
3001 assert(task_size > CardTableModRefBS::card_size_in_words &&
3002 (task_size % CardTableModRefBS::card_size_in_words == 0),
3003 "Otherwise arithmetic below would be incorrect");
3004 MemRegion span = _gen->reserved();
3005 if (low != NULL) {
3006 if (span.contains(low)) {
3007 // Align low down to a card boundary so that
3008 // we can use block_offset_careful() on span boundaries.
3009 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
3010 CardTableModRefBS::card_size);
3011 // Clip span prefix at aligned_low
3012 span = span.intersection(MemRegion(aligned_low, span.end()));
3013 } else if (low > span.end()) {
3014 span = MemRegion(low, low); // Null region
3015 } // else use entire span
3016 }
3017 assert(span.is_empty() ||
3018 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
3019 "span should start at a card boundary");
3020 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
3021 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
3022 assert(n_tasks == 0 ||
3023 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
3024 (span.start() + n_tasks*task_size >= span.end())),
3025 "n_tasks calculation incorrect");
3026 SequentialSubTasksDone* pst = conc_par_seq_tasks();
3027 assert(!pst->valid(), "Clobbering existing data?");
3028 // Sets the condition for completion of the subtask (how many threads
3029 // need to finish in order to be done).
3030 pst->set_n_threads(n_threads);
3031 pst->set_n_tasks((int)n_tasks);
3032 }