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
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc_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.inline.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"
44
45 /////////////////////////////////////////////////////////////////////////
46 //// CompactibleFreeListSpace
47 /////////////////////////////////////////////////////////////////////////
48
49 // highest ranked free list lock rank
50 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
51
52 // Defaults are 0 so things will break badly if incorrectly initialized.
53 size_t CompactibleFreeListSpace::IndexSetStart = 0;
54 size_t CompactibleFreeListSpace::IndexSetStride = 0;
55
56 size_t MinChunkSize = 0;
57
58 void CompactibleFreeListSpace::set_cms_values() {
59 // Set CMS global values
60 assert(MinChunkSize == 0, "already set");
61
62 // MinChunkSize should be a multiple of MinObjAlignment and be large enough
63 // for chunks to contain a FreeChunk.
64 size_t min_chunk_size_in_bytes = align_size_up(sizeof(FreeChunk), MinObjAlignmentInBytes);
65 MinChunkSize = min_chunk_size_in_bytes / BytesPerWord;
66
67 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
68 IndexSetStart = MinChunkSize;
69 IndexSetStride = MinObjAlignment;
70 }
71
72 // Constructor
73 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs,
74 MemRegion mr, bool use_adaptive_freelists,
75 FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) :
76 _dictionaryChoice(dictionaryChoice),
77 _adaptive_freelists(use_adaptive_freelists),
78 _bt(bs, mr),
79 // free list locks are in the range of values taken by _lockRank
80 // This range currently is [_leaf+2, _leaf+3]
81 // Note: this requires that CFLspace c'tors
82 // are called serially in the order in which the locks are
83 // are acquired in the program text. This is true today.
84 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true),
85 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
86 "CompactibleFreeListSpace._dict_par_lock", true),
87 _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
88 CMSRescanMultiple),
89 _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
90 CMSConcMarkMultiple),
91 _collector(NULL)
92 {
93 assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize,
94 "FreeChunk is larger than expected");
95 _bt.set_space(this);
96 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
97 // We have all of "mr", all of which we place in the dictionary
98 // as one big chunk. We'll need to decide here which of several
99 // possible alternative dictionary implementations to use. For
100 // now the choice is easy, since we have only one working
101 // implementation, namely, the simple binary tree (splaying
102 // temporarily disabled).
103 switch (dictionaryChoice) {
104 case FreeBlockDictionary<FreeChunk>::dictionaryBinaryTree:
105 _dictionary = new BinaryTreeDictionary<FreeChunk, AdaptiveFreeList>(mr);
106 break;
107 case FreeBlockDictionary<FreeChunk>::dictionarySplayTree:
108 case FreeBlockDictionary<FreeChunk>::dictionarySkipList:
109 default:
110 warning("dictionaryChoice: selected option not understood; using"
111 " default BinaryTreeDictionary implementation instead.");
112 }
113 assert(_dictionary != NULL, "CMS dictionary initialization");
114 // The indexed free lists are initially all empty and are lazily
115 // filled in on demand. Initialize the array elements to NULL.
116 initializeIndexedFreeListArray();
117
118 // Not using adaptive free lists assumes that allocation is first
119 // from the linAB's. Also a cms perm gen which can be compacted
120 // has to have the klass's klassKlass allocated at a lower
121 // address in the heap than the klass so that the klassKlass is
122 // moved to its new location before the klass is moved.
123 // Set the _refillSize for the linear allocation blocks
124 if (!use_adaptive_freelists) {
125 FreeChunk* fc = _dictionary->get_chunk(mr.word_size());
126 // The small linAB initially has all the space and will allocate
127 // a chunk of any size.
128 HeapWord* addr = (HeapWord*) fc;
129 _smallLinearAllocBlock.set(addr, fc->size() ,
130 1024*SmallForLinearAlloc, fc->size());
131 // Note that _unallocated_block is not updated here.
132 // Allocations from the linear allocation block should
133 // update it.
134 } else {
135 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
136 SmallForLinearAlloc);
137 }
138 // CMSIndexedFreeListReplenish should be at least 1
139 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
140 _promoInfo.setSpace(this);
141 if (UseCMSBestFit) {
142 _fitStrategy = FreeBlockBestFitFirst;
143 } else {
144 _fitStrategy = FreeBlockStrategyNone;
145 }
146 check_free_list_consistency();
147
148 // Initialize locks for parallel case.
149
150 if (CollectedHeap::use_parallel_gc_threads()) {
151 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
152 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
153 "a freelist par lock",
154 true);
155 if (_indexedFreeListParLocks[i] == NULL)
156 vm_exit_during_initialization("Could not allocate a par lock");
157 DEBUG_ONLY(
158 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
159 )
160 }
161 _dictionary->set_par_lock(&_parDictionaryAllocLock);
162 }
163 }
164
165 // Like CompactibleSpace forward() but always calls cross_threshold() to
166 // update the block offset table. Removed initialize_threshold call because
167 // CFLS does not use a block offset array for contiguous spaces.
168 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
169 CompactPoint* cp, HeapWord* compact_top) {
170 // q is alive
171 // First check if we should switch compaction space
172 assert(this == cp->space, "'this' should be current compaction space.");
173 size_t compaction_max_size = pointer_delta(end(), compact_top);
174 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
175 "virtual adjustObjectSize_v() method is not correct");
176 size_t adjusted_size = adjustObjectSize(size);
177 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
178 "no small fragments allowed");
179 assert(minimum_free_block_size() == MinChunkSize,
180 "for de-virtualized reference below");
181 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
182 if (adjusted_size + MinChunkSize > compaction_max_size &&
183 adjusted_size != compaction_max_size) {
184 do {
185 // switch to next compaction space
186 cp->space->set_compaction_top(compact_top);
187 cp->space = cp->space->next_compaction_space();
188 if (cp->space == NULL) {
189 cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen);
190 assert(cp->gen != NULL, "compaction must succeed");
191 cp->space = cp->gen->first_compaction_space();
192 assert(cp->space != NULL, "generation must have a first compaction space");
193 }
194 compact_top = cp->space->bottom();
195 cp->space->set_compaction_top(compact_top);
196 // The correct adjusted_size may not be the same as that for this method
197 // (i.e., cp->space may no longer be "this" so adjust the size again.
198 // Use the virtual method which is not used above to save the virtual
199 // dispatch.
200 adjusted_size = cp->space->adjust_object_size_v(size);
201 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
202 assert(cp->space->minimum_free_block_size() == 0, "just checking");
203 } while (adjusted_size > compaction_max_size);
204 }
205
206 // store the forwarding pointer into the mark word
207 if ((HeapWord*)q != compact_top) {
208 q->forward_to(oop(compact_top));
209 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
210 } else {
211 // if the object isn't moving we can just set the mark to the default
212 // mark and handle it specially later on.
213 q->init_mark();
214 assert(q->forwardee() == NULL, "should be forwarded to NULL");
215 }
216
217 compact_top += adjusted_size;
218
219 // we need to update the offset table so that the beginnings of objects can be
220 // found during scavenge. Note that we are updating the offset table based on
221 // where the object will be once the compaction phase finishes.
222
223 // Always call cross_threshold(). A contiguous space can only call it when
224 // the compaction_top exceeds the current threshold but not for an
225 // non-contiguous space.
226 cp->threshold =
227 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
228 return compact_top;
229 }
230
231 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
232 // and use of single_block instead of alloc_block. The name here is not really
233 // appropriate - maybe a more general name could be invented for both the
234 // contiguous and noncontiguous spaces.
235
236 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
237 _bt.single_block(start, the_end);
238 return end();
239 }
240
241 // Initialize them to NULL.
242 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
243 for (size_t i = 0; i < IndexSetSize; i++) {
244 // Note that on platforms where objects are double word aligned,
245 // the odd array elements are not used. It is convenient, however,
246 // to map directly from the object size to the array element.
247 _indexedFreeList[i].reset(IndexSetSize);
248 _indexedFreeList[i].set_size(i);
249 assert(_indexedFreeList[i].count() == 0, "reset check failed");
250 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
251 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
252 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
253 }
254 }
255
256 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
257 for (size_t i = 1; i < IndexSetSize; i++) {
258 assert(_indexedFreeList[i].size() == (size_t) i,
259 "Indexed free list sizes are incorrect");
260 _indexedFreeList[i].reset(IndexSetSize);
261 assert(_indexedFreeList[i].count() == 0, "reset check failed");
262 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
263 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
264 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
265 }
266 }
267
268 void CompactibleFreeListSpace::reset(MemRegion mr) {
269 resetIndexedFreeListArray();
270 dictionary()->reset();
271 if (BlockOffsetArrayUseUnallocatedBlock) {
272 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
273 // Everything's allocated until proven otherwise.
274 _bt.set_unallocated_block(end());
275 }
276 if (!mr.is_empty()) {
277 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
278 _bt.single_block(mr.start(), mr.word_size());
279 FreeChunk* fc = (FreeChunk*) mr.start();
280 fc->set_size(mr.word_size());
281 if (mr.word_size() >= IndexSetSize ) {
282 returnChunkToDictionary(fc, true);
283 } else {
284 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
285 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc, true, true);
286 }
287 }
288 _promoInfo.reset();
289 _smallLinearAllocBlock._ptr = NULL;
290 _smallLinearAllocBlock._word_size = 0;
291 }
292
293 void CompactibleFreeListSpace::reset_after_compaction() {
294 // Reset the space to the new reality - one free chunk.
295 MemRegion mr(compaction_top(), end());
296 reset(mr);
297 // Now refill the linear allocation block(s) if possible.
298 if (_adaptive_freelists) {
299 refillLinearAllocBlocksIfNeeded();
300 } else {
301 // Place as much of mr in the linAB as we can get,
302 // provided it was big enough to go into the dictionary.
303 FreeChunk* fc = dictionary()->find_largest_dict();
304 if (fc != NULL) {
305 assert(fc->size() == mr.word_size(),
306 "Why was the chunk broken up?");
307 removeChunkFromDictionary(fc);
308 HeapWord* addr = (HeapWord*) fc;
309 _smallLinearAllocBlock.set(addr, fc->size() ,
310 1024*SmallForLinearAlloc, fc->size());
311 // Note that _unallocated_block is not updated here.
312 }
313 }
314 }
315
316 // Walks the entire dictionary, returning a coterminal
317 // chunk, if it exists. Use with caution since it involves
318 // a potentially complete walk of a potentially large tree.
319 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
320
321 assert_lock_strong(&_freelistLock);
322
323 return dictionary()->find_chunk_ends_at(end());
324 }
325
326
327 #ifndef PRODUCT
328 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
329 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
330 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
331 }
332 }
333
334 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
335 size_t sum = 0;
336 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
337 sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
338 }
339 return sum;
340 }
341
342 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
343 size_t count = 0;
344 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
345 debug_only(
346 ssize_t total_list_count = 0;
347 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
348 fc = fc->next()) {
349 total_list_count++;
350 }
351 assert(total_list_count == _indexedFreeList[i].count(),
352 "Count in list is incorrect");
353 )
354 count += _indexedFreeList[i].count();
355 }
356 return count;
357 }
358
359 size_t CompactibleFreeListSpace::totalCount() {
360 size_t num = totalCountInIndexedFreeLists();
361 num += dictionary()->total_count();
362 if (_smallLinearAllocBlock._word_size != 0) {
363 num++;
364 }
365 return num;
366 }
367 #endif
368
369 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
370 FreeChunk* fc = (FreeChunk*) p;
371 return fc->is_free();
372 }
373
374 size_t CompactibleFreeListSpace::used() const {
375 return capacity() - free();
376 }
377
378 size_t CompactibleFreeListSpace::free() const {
379 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
380 // if you do this while the structures are in flux you
381 // may get an approximate answer only; for instance
382 // because there is concurrent allocation either
383 // directly by mutators or for promotion during a GC.
384 // It's "MT-safe", however, in the sense that you are guaranteed
385 // not to crash and burn, for instance, because of walking
386 // pointers that could disappear as you were walking them.
387 // The approximation is because the various components
388 // that are read below are not read atomically (and
389 // further the computation of totalSizeInIndexedFreeLists()
390 // is itself a non-atomic computation. The normal use of
391 // this is during a resize operation at the end of GC
392 // and at that time you are guaranteed to get the
393 // correct actual value. However, for instance, this is
394 // also read completely asynchronously by the "perf-sampler"
395 // that supports jvmstat, and you are apt to see the values
396 // flicker in such cases.
397 assert(_dictionary != NULL, "No _dictionary?");
398 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
399 totalSizeInIndexedFreeLists() +
400 _smallLinearAllocBlock._word_size) * HeapWordSize;
401 }
402
403 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
404 assert(_dictionary != NULL, "No _dictionary?");
405 assert_locked();
406 size_t res = _dictionary->max_chunk_size();
407 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
408 (size_t) SmallForLinearAlloc - 1));
409 // XXX the following could potentially be pretty slow;
410 // should one, pesimally for the rare cases when res
411 // caclulated above is less than IndexSetSize,
412 // just return res calculated above? My reasoning was that
413 // those cases will be so rare that the extra time spent doesn't
414 // really matter....
415 // Note: do not change the loop test i >= res + IndexSetStride
416 // to i > res below, because i is unsigned and res may be zero.
417 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
418 i -= IndexSetStride) {
419 if (_indexedFreeList[i].head() != NULL) {
420 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
421 return i;
422 }
423 }
424 return res;
425 }
426
427 void LinearAllocBlock::print_on(outputStream* st) const {
428 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
429 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
430 _ptr, _word_size, _refillSize, _allocation_size_limit);
431 }
432
433 void CompactibleFreeListSpace::print_on(outputStream* st) const {
434 st->print_cr("COMPACTIBLE FREELIST SPACE");
435 st->print_cr(" Space:");
436 Space::print_on(st);
437
438 st->print_cr("promoInfo:");
439 _promoInfo.print_on(st);
440
441 st->print_cr("_smallLinearAllocBlock");
442 _smallLinearAllocBlock.print_on(st);
443
444 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
445
446 st->print_cr(" _fitStrategy = %s, _adaptive_freelists = %s",
447 _fitStrategy?"true":"false", _adaptive_freelists?"true":"false");
448 }
449
450 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
451 const {
452 reportIndexedFreeListStatistics();
453 gclog_or_tty->print_cr("Layout of Indexed Freelists");
454 gclog_or_tty->print_cr("---------------------------");
455 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
456 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
457 _indexedFreeList[i].print_on(gclog_or_tty);
458 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
459 fc = fc->next()) {
460 gclog_or_tty->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
461 fc, (HeapWord*)fc + i,
462 fc->cantCoalesce() ? "\t CC" : "");
463 }
464 }
465 }
466
467 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
468 const {
469 _promoInfo.print_on(st);
470 }
471
472 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
473 const {
474 _dictionary->report_statistics();
475 st->print_cr("Layout of Freelists in Tree");
476 st->print_cr("---------------------------");
477 _dictionary->print_free_lists(st);
478 }
479
480 class BlkPrintingClosure: public BlkClosure {
481 const CMSCollector* _collector;
482 const CompactibleFreeListSpace* _sp;
483 const CMSBitMap* _live_bit_map;
484 const bool _post_remark;
485 outputStream* _st;
486 public:
487 BlkPrintingClosure(const CMSCollector* collector,
488 const CompactibleFreeListSpace* sp,
489 const CMSBitMap* live_bit_map,
490 outputStream* st):
491 _collector(collector),
492 _sp(sp),
493 _live_bit_map(live_bit_map),
494 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
495 _st(st) { }
496 size_t do_blk(HeapWord* addr);
497 };
498
499 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
500 size_t sz = _sp->block_size_no_stall(addr, _collector);
501 assert(sz != 0, "Should always be able to compute a size");
502 if (_sp->block_is_obj(addr)) {
503 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
504 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
505 addr,
506 dead ? "dead" : "live",
507 sz,
508 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
509 if (CMSPrintObjectsInDump && !dead) {
510 oop(addr)->print_on(_st);
511 _st->print_cr("--------------------------------------");
512 }
513 } else { // free block
514 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
515 addr, sz, CMSPrintChunksInDump ? ":" : ".");
516 if (CMSPrintChunksInDump) {
517 ((FreeChunk*)addr)->print_on(_st);
518 _st->print_cr("--------------------------------------");
519 }
520 }
521 return sz;
522 }
523
524 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c,
525 outputStream* st) {
526 st->print_cr("\n=========================");
527 st->print_cr("Block layout in CMS Heap:");
528 st->print_cr("=========================");
529 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
530 blk_iterate(&bpcl);
531
532 st->print_cr("\n=======================================");
533 st->print_cr("Order & Layout of Promotion Info Blocks");
534 st->print_cr("=======================================");
535 print_promo_info_blocks(st);
536
537 st->print_cr("\n===========================");
538 st->print_cr("Order of Indexed Free Lists");
539 st->print_cr("=========================");
540 print_indexed_free_lists(st);
541
542 st->print_cr("\n=================================");
543 st->print_cr("Order of Free Lists in Dictionary");
544 st->print_cr("=================================");
545 print_dictionary_free_lists(st);
546 }
547
548
549 void CompactibleFreeListSpace::reportFreeListStatistics() const {
550 assert_lock_strong(&_freelistLock);
551 assert(PrintFLSStatistics != 0, "Reporting error");
552 _dictionary->report_statistics();
553 if (PrintFLSStatistics > 1) {
554 reportIndexedFreeListStatistics();
555 size_t total_size = totalSizeInIndexedFreeLists() +
556 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
557 gclog_or_tty->print(" free=%ld frag=%1.4f\n", total_size, flsFrag());
558 }
559 }
560
561 void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const {
562 assert_lock_strong(&_freelistLock);
563 gclog_or_tty->print("Statistics for IndexedFreeLists:\n"
564 "--------------------------------\n");
565 size_t total_size = totalSizeInIndexedFreeLists();
566 size_t free_blocks = numFreeBlocksInIndexedFreeLists();
567 gclog_or_tty->print("Total Free Space: %d\n", total_size);
568 gclog_or_tty->print("Max Chunk Size: %d\n", maxChunkSizeInIndexedFreeLists());
569 gclog_or_tty->print("Number of Blocks: %d\n", free_blocks);
570 if (free_blocks != 0) {
571 gclog_or_tty->print("Av. Block Size: %d\n", total_size/free_blocks);
572 }
573 }
574
575 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
576 size_t res = 0;
577 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
578 debug_only(
579 ssize_t recount = 0;
580 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
581 fc = fc->next()) {
582 recount += 1;
583 }
584 assert(recount == _indexedFreeList[i].count(),
585 "Incorrect count in list");
586 )
587 res += _indexedFreeList[i].count();
588 }
589 return res;
590 }
591
592 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
593 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
594 if (_indexedFreeList[i].head() != NULL) {
595 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
596 return (size_t)i;
597 }
598 }
599 return 0;
600 }
601
602 void CompactibleFreeListSpace::set_end(HeapWord* value) {
603 HeapWord* prevEnd = end();
604 assert(prevEnd != value, "unnecessary set_end call");
605 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
606 "New end is below unallocated block");
607 _end = value;
608 if (prevEnd != NULL) {
609 // Resize the underlying block offset table.
610 _bt.resize(pointer_delta(value, bottom()));
611 if (value <= prevEnd) {
612 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
613 "New end is below unallocated block");
614 } else {
615 // Now, take this new chunk and add it to the free blocks.
616 // Note that the BOT has not yet been updated for this block.
617 size_t newFcSize = pointer_delta(value, prevEnd);
618 // XXX This is REALLY UGLY and should be fixed up. XXX
619 if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) {
620 // Mark the boundary of the new block in BOT
621 _bt.mark_block(prevEnd, value);
622 // put it all in the linAB
623 if (ParallelGCThreads == 0) {
624 _smallLinearAllocBlock._ptr = prevEnd;
625 _smallLinearAllocBlock._word_size = newFcSize;
626 repairLinearAllocBlock(&_smallLinearAllocBlock);
627 } else { // ParallelGCThreads > 0
628 MutexLockerEx x(parDictionaryAllocLock(),
629 Mutex::_no_safepoint_check_flag);
630 _smallLinearAllocBlock._ptr = prevEnd;
631 _smallLinearAllocBlock._word_size = newFcSize;
632 repairLinearAllocBlock(&_smallLinearAllocBlock);
633 }
634 // Births of chunks put into a LinAB are not recorded. Births
635 // of chunks as they are allocated out of a LinAB are.
636 } else {
637 // Add the block to the free lists, if possible coalescing it
638 // with the last free block, and update the BOT and census data.
639 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
640 }
641 }
642 }
643 }
644
645 class FreeListSpace_DCTOC : public Filtering_DCTOC {
646 CompactibleFreeListSpace* _cfls;
647 CMSCollector* _collector;
648 protected:
649 // Override.
650 #define walk_mem_region_with_cl_DECL(ClosureType) \
651 virtual void walk_mem_region_with_cl(MemRegion mr, \
652 HeapWord* bottom, HeapWord* top, \
653 ClosureType* cl); \
654 void walk_mem_region_with_cl_par(MemRegion mr, \
655 HeapWord* bottom, HeapWord* top, \
656 ClosureType* cl); \
657 void walk_mem_region_with_cl_nopar(MemRegion mr, \
658 HeapWord* bottom, HeapWord* top, \
659 ClosureType* cl)
660 walk_mem_region_with_cl_DECL(ExtendedOopClosure);
661 walk_mem_region_with_cl_DECL(FilteringClosure);
662
663 public:
664 FreeListSpace_DCTOC(CompactibleFreeListSpace* sp,
665 CMSCollector* collector,
666 ExtendedOopClosure* cl,
667 CardTableModRefBS::PrecisionStyle precision,
668 HeapWord* boundary) :
669 Filtering_DCTOC(sp, cl, precision, boundary),
670 _cfls(sp), _collector(collector) {}
671 };
672
673 // We de-virtualize the block-related calls below, since we know that our
674 // space is a CompactibleFreeListSpace.
675
676 #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
677 void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \
678 HeapWord* bottom, \
679 HeapWord* top, \
680 ClosureType* cl) { \
681 bool is_par = SharedHeap::heap()->n_par_threads() > 0; \
682 if (is_par) { \
683 assert(SharedHeap::heap()->n_par_threads() == \
684 SharedHeap::heap()->workers()->active_workers(), "Mismatch"); \
685 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
686 } else { \
687 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
688 } \
689 } \
690 void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
691 HeapWord* bottom, \
692 HeapWord* top, \
693 ClosureType* cl) { \
694 /* Skip parts that are before "mr", in case "block_start" sent us \
695 back too far. */ \
696 HeapWord* mr_start = mr.start(); \
697 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
698 HeapWord* next = bottom + bot_size; \
699 while (next < mr_start) { \
700 bottom = next; \
701 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
702 next = bottom + bot_size; \
703 } \
704 \
705 while (bottom < top) { \
706 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
707 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
708 oop(bottom)) && \
709 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
710 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
711 bottom += _cfls->adjustObjectSize(word_sz); \
712 } else { \
713 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
714 } \
715 } \
716 } \
717 void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
718 HeapWord* bottom, \
719 HeapWord* top, \
720 ClosureType* cl) { \
721 /* Skip parts that are before "mr", in case "block_start" sent us \
722 back too far. */ \
723 HeapWord* mr_start = mr.start(); \
724 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
725 HeapWord* next = bottom + bot_size; \
726 while (next < mr_start) { \
727 bottom = next; \
728 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
729 next = bottom + bot_size; \
730 } \
731 \
732 while (bottom < top) { \
733 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
734 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
735 oop(bottom)) && \
736 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
737 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
738 bottom += _cfls->adjustObjectSize(word_sz); \
739 } else { \
740 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
741 } \
742 } \
743 }
744
745 // (There are only two of these, rather than N, because the split is due
746 // only to the introduction of the FilteringClosure, a local part of the
747 // impl of this abstraction.)
748 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
749 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
750
751 DirtyCardToOopClosure*
752 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl,
753 CardTableModRefBS::PrecisionStyle precision,
754 HeapWord* boundary) {
755 return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary);
756 }
757
758
759 // Note on locking for the space iteration functions:
760 // since the collector's iteration activities are concurrent with
761 // allocation activities by mutators, absent a suitable mutual exclusion
762 // mechanism the iterators may go awry. For instace a block being iterated
763 // may suddenly be allocated or divided up and part of it allocated and
764 // so on.
765
766 // Apply the given closure to each block in the space.
767 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
768 assert_lock_strong(freelistLock());
769 HeapWord *cur, *limit;
770 for (cur = bottom(), limit = end(); cur < limit;
771 cur += cl->do_blk_careful(cur));
772 }
773
774 // Apply the given closure to each block in the space.
775 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
776 assert_lock_strong(freelistLock());
777 HeapWord *cur, *limit;
778 for (cur = bottom(), limit = end(); cur < limit;
779 cur += cl->do_blk(cur));
780 }
781
782 // Apply the given closure to each oop in the space.
783 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) {
784 assert_lock_strong(freelistLock());
785 HeapWord *cur, *limit;
786 size_t curSize;
787 for (cur = bottom(), limit = end(); cur < limit;
788 cur += curSize) {
789 curSize = block_size(cur);
790 if (block_is_obj(cur)) {
791 oop(cur)->oop_iterate(cl);
792 }
793 }
794 }
795
796 // Apply the given closure to each oop in the space \intersect memory region.
797 void CompactibleFreeListSpace::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
798 assert_lock_strong(freelistLock());
799 if (is_empty()) {
800 return;
801 }
802 MemRegion cur = MemRegion(bottom(), end());
803 mr = mr.intersection(cur);
804 if (mr.is_empty()) {
805 return;
806 }
807 if (mr.equals(cur)) {
808 oop_iterate(cl);
809 return;
810 }
811 assert(mr.end() <= end(), "just took an intersection above");
812 HeapWord* obj_addr = block_start(mr.start());
813 HeapWord* t = mr.end();
814
815 SpaceMemRegionOopsIterClosure smr_blk(cl, mr);
816 if (block_is_obj(obj_addr)) {
817 // Handle first object specially.
818 oop obj = oop(obj_addr);
819 obj_addr += adjustObjectSize(obj->oop_iterate(&smr_blk));
820 } else {
821 FreeChunk* fc = (FreeChunk*)obj_addr;
822 obj_addr += fc->size();
823 }
824 while (obj_addr < t) {
825 HeapWord* obj = obj_addr;
826 obj_addr += block_size(obj_addr);
827 // If "obj_addr" is not greater than top, then the
828 // entire object "obj" is within the region.
829 if (obj_addr <= t) {
830 if (block_is_obj(obj)) {
831 oop(obj)->oop_iterate(cl);
832 }
833 } else {
834 // "obj" extends beyond end of region
835 if (block_is_obj(obj)) {
836 oop(obj)->oop_iterate(&smr_blk);
837 }
838 break;
839 }
840 }
841 }
842
843 // NOTE: In the following methods, in order to safely be able to
844 // apply the closure to an object, we need to be sure that the
845 // object has been initialized. We are guaranteed that an object
846 // is initialized if we are holding the Heap_lock with the
847 // world stopped.
848 void CompactibleFreeListSpace::verify_objects_initialized() const {
849 if (is_init_completed()) {
850 assert_locked_or_safepoint(Heap_lock);
851 if (Universe::is_fully_initialized()) {
852 guarantee(SafepointSynchronize::is_at_safepoint(),
853 "Required for objects to be initialized");
854 }
855 } // else make a concession at vm start-up
856 }
857
858 // Apply the given closure to each object in the space
859 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
860 assert_lock_strong(freelistLock());
861 NOT_PRODUCT(verify_objects_initialized());
862 HeapWord *cur, *limit;
863 size_t curSize;
864 for (cur = bottom(), limit = end(); cur < limit;
865 cur += curSize) {
866 curSize = block_size(cur);
867 if (block_is_obj(cur)) {
868 blk->do_object(oop(cur));
869 }
870 }
871 }
872
873 // Apply the given closure to each live object in the space
874 // The usage of CompactibleFreeListSpace
875 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
876 // objects in the space with references to objects that are no longer
877 // valid. For example, an object may reference another object
878 // that has already been sweep up (collected). This method uses
879 // obj_is_alive() to determine whether it is safe to apply the closure to
880 // an object. See obj_is_alive() for details on how liveness of an
881 // object is decided.
882
883 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
884 assert_lock_strong(freelistLock());
885 NOT_PRODUCT(verify_objects_initialized());
886 HeapWord *cur, *limit;
887 size_t curSize;
888 for (cur = bottom(), limit = end(); cur < limit;
889 cur += curSize) {
890 curSize = block_size(cur);
891 if (block_is_obj(cur) && obj_is_alive(cur)) {
892 blk->do_object(oop(cur));
893 }
894 }
895 }
896
897 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
898 UpwardsObjectClosure* cl) {
899 assert_locked(freelistLock());
900 NOT_PRODUCT(verify_objects_initialized());
901 Space::object_iterate_mem(mr, cl);
902 }
903
904 // Callers of this iterator beware: The closure application should
905 // be robust in the face of uninitialized objects and should (always)
906 // return a correct size so that the next addr + size below gives us a
907 // valid block boundary. [See for instance,
908 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
909 // in ConcurrentMarkSweepGeneration.cpp.]
910 HeapWord*
911 CompactibleFreeListSpace::object_iterate_careful(ObjectClosureCareful* cl) {
912 assert_lock_strong(freelistLock());
913 HeapWord *addr, *last;
914 size_t size;
915 for (addr = bottom(), last = end();
916 addr < last; addr += size) {
917 FreeChunk* fc = (FreeChunk*)addr;
918 if (fc->is_free()) {
919 // Since we hold the free list lock, which protects direct
920 // allocation in this generation by mutators, a free object
921 // will remain free throughout this iteration code.
922 size = fc->size();
923 } else {
924 // Note that the object need not necessarily be initialized,
925 // because (for instance) the free list lock does NOT protect
926 // object initialization. The closure application below must
927 // therefore be correct in the face of uninitialized objects.
928 size = cl->do_object_careful(oop(addr));
929 if (size == 0) {
930 // An unparsable object found. Signal early termination.
931 return addr;
932 }
933 }
934 }
935 return NULL;
936 }
937
938 // Callers of this iterator beware: The closure application should
939 // be robust in the face of uninitialized objects and should (always)
940 // return a correct size so that the next addr + size below gives us a
941 // valid block boundary. [See for instance,
942 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
943 // in ConcurrentMarkSweepGeneration.cpp.]
944 HeapWord*
945 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
946 ObjectClosureCareful* cl) {
947 assert_lock_strong(freelistLock());
948 // Can't use used_region() below because it may not necessarily
949 // be the same as [bottom(),end()); although we could
950 // use [used_region().start(),round_to(used_region().end(),CardSize)),
951 // that appears too cumbersome, so we just do the simpler check
952 // in the assertion below.
953 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
954 "mr should be non-empty and within used space");
955 HeapWord *addr, *end;
956 size_t size;
957 for (addr = block_start_careful(mr.start()), end = mr.end();
958 addr < end; addr += size) {
959 FreeChunk* fc = (FreeChunk*)addr;
960 if (fc->is_free()) {
961 // Since we hold the free list lock, which protects direct
962 // allocation in this generation by mutators, a free object
963 // will remain free throughout this iteration code.
964 size = fc->size();
965 } else {
966 // Note that the object need not necessarily be initialized,
967 // because (for instance) the free list lock does NOT protect
968 // object initialization. The closure application below must
969 // therefore be correct in the face of uninitialized objects.
970 size = cl->do_object_careful_m(oop(addr), mr);
971 if (size == 0) {
972 // An unparsable object found. Signal early termination.
973 return addr;
974 }
975 }
976 }
977 return NULL;
978 }
979
980
981 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
982 NOT_PRODUCT(verify_objects_initialized());
983 return _bt.block_start(p);
984 }
985
986 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
987 return _bt.block_start_careful(p);
988 }
989
990 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
991 NOT_PRODUCT(verify_objects_initialized());
992 // This must be volatile, or else there is a danger that the compiler
993 // will compile the code below into a sometimes-infinite loop, by keeping
994 // the value read the first time in a register.
995 while (true) {
996 // We must do this until we get a consistent view of the object.
997 if (FreeChunk::indicatesFreeChunk(p)) {
998 volatile FreeChunk* fc = (volatile FreeChunk*)p;
999 size_t res = fc->size();
1000 // If the object is still a free chunk, return the size, else it
1001 // has been allocated so try again.
1002 if (FreeChunk::indicatesFreeChunk(p)) {
1003 assert(res != 0, "Block size should not be 0");
1004 return res;
1005 }
1006 } else {
1007 // must read from what 'p' points to in each loop.
1008 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
1009 if (k != NULL) {
1010 assert(k->is_klass(), "Should really be klass oop.");
1011 oop o = (oop)p;
1012 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
1013 size_t res = o->size_given_klass(k);
1014 res = adjustObjectSize(res);
1015 assert(res != 0, "Block size should not be 0");
1016 return res;
1017 }
1018 }
1019 }
1020 }
1021
1022 // TODO: Now that is_parsable is gone, we should combine these two functions.
1023 // A variant of the above that uses the Printezis bits for
1024 // unparsable but allocated objects. This avoids any possible
1025 // stalls waiting for mutators to initialize objects, and is
1026 // thus potentially faster than the variant above. However,
1027 // this variant may return a zero size for a block that is
1028 // under mutation and for which a consistent size cannot be
1029 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
1030 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
1031 const CMSCollector* c)
1032 const {
1033 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1034 // This must be volatile, or else there is a danger that the compiler
1035 // will compile the code below into a sometimes-infinite loop, by keeping
1036 // the value read the first time in a register.
1037 DEBUG_ONLY(uint loops = 0;)
1038 while (true) {
1039 // We must do this until we get a consistent view of the object.
1040 if (FreeChunk::indicatesFreeChunk(p)) {
1041 volatile FreeChunk* fc = (volatile FreeChunk*)p;
1042 size_t res = fc->size();
1043 if (FreeChunk::indicatesFreeChunk(p)) {
1044 assert(res != 0, "Block size should not be 0");
1045 assert(loops == 0, "Should be 0");
1046 return res;
1047 }
1048 } else {
1049 // must read from what 'p' points to in each loop.
1050 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
1051 // We trust the size of any object that has a non-NULL
1052 // klass and (for those in the perm gen) is parsable
1053 // -- irrespective of its conc_safe-ty.
1054 if (k != NULL) {
1055 assert(k->is_klass(), "Should really be klass oop.");
1056 oop o = (oop)p;
1057 assert(o->is_oop(), "Should be an oop");
1058 size_t res = o->size_given_klass(k);
1059 res = adjustObjectSize(res);
1060 assert(res != 0, "Block size should not be 0");
1061 return res;
1062 } else {
1063 // May return 0 if P-bits not present.
1064 return c->block_size_if_printezis_bits(p);
1065 }
1066 }
1067 assert(loops == 0, "Can loop at most once");
1068 DEBUG_ONLY(loops++;)
1069 }
1070 }
1071
1072 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1073 NOT_PRODUCT(verify_objects_initialized());
1074 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1075 FreeChunk* fc = (FreeChunk*)p;
1076 if (fc->is_free()) {
1077 return fc->size();
1078 } else {
1079 // Ignore mark word because this may be a recently promoted
1080 // object whose mark word is used to chain together grey
1081 // objects (the last one would have a null value).
1082 assert(oop(p)->is_oop(true), "Should be an oop");
1083 return adjustObjectSize(oop(p)->size());
1084 }
1085 }
1086
1087 // This implementation assumes that the property of "being an object" is
1088 // stable. But being a free chunk may not be (because of parallel
1089 // promotion.)
1090 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1091 FreeChunk* fc = (FreeChunk*)p;
1092 assert(is_in_reserved(p), "Should be in space");
1093 // When doing a mark-sweep-compact of the CMS generation, this
1094 // assertion may fail because prepare_for_compaction() uses
1095 // space that is garbage to maintain information on ranges of
1096 // live objects so that these live ranges can be moved as a whole.
1097 // Comment out this assertion until that problem can be solved
1098 // (i.e., that the block start calculation may look at objects
1099 // at address below "p" in finding the object that contains "p"
1100 // and those objects (if garbage) may have been modified to hold
1101 // live range information.
1102 // assert(CollectedHeap::use_parallel_gc_threads() || _bt.block_start(p) == p,
1103 // "Should be a block boundary");
1104 if (FreeChunk::indicatesFreeChunk(p)) return false;
1105 Klass* k = oop(p)->klass_or_null();
1106 if (k != NULL) {
1107 // Ignore mark word because it may have been used to
1108 // chain together promoted objects (the last one
1109 // would have a null value).
1110 assert(oop(p)->is_oop(true), "Should be an oop");
1111 return true;
1112 } else {
1113 return false; // Was not an object at the start of collection.
1114 }
1115 }
1116
1117 // Check if the object is alive. This fact is checked either by consulting
1118 // the main marking bitmap in the sweeping phase or, if it's a permanent
1119 // generation and we're not in the sweeping phase, by checking the
1120 // perm_gen_verify_bit_map where we store the "deadness" information if
1121 // we did not sweep the perm gen in the most recent previous GC cycle.
1122 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1123 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1124 "Else races are possible");
1125 assert(block_is_obj(p), "The address should point to an object");
1126
1127 // If we're sweeping, we use object liveness information from the main bit map
1128 // for both perm gen and old gen.
1129 // We don't need to lock the bitmap (live_map or dead_map below), because
1130 // EITHER we are in the middle of the sweeping phase, and the
1131 // main marking bit map (live_map below) is locked,
1132 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1133 // is stable, because it's mutated only in the sweeping phase.
1134 // NOTE: This method is also used by jmap where, if class unloading is
1135 // off, the results can return "false" for legitimate perm objects,
1136 // when we are not in the midst of a sweeping phase, which can result
1137 // in jmap not reporting certain perm gen objects. This will be moot
1138 // if/when the perm gen goes away in the future.
1139 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1140 CMSBitMap* live_map = _collector->markBitMap();
1141 return live_map->par_isMarked((HeapWord*) p);
1142 }
1143 return true;
1144 }
1145
1146 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1147 FreeChunk* fc = (FreeChunk*)p;
1148 assert(is_in_reserved(p), "Should be in space");
1149 assert(_bt.block_start(p) == p, "Should be a block boundary");
1150 if (!fc->is_free()) {
1151 // Ignore mark word because it may have been used to
1152 // chain together promoted objects (the last one
1153 // would have a null value).
1154 assert(oop(p)->is_oop(true), "Should be an oop");
1155 return true;
1156 }
1157 return false;
1158 }
1159
1160 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1161 // approximate answer if you don't hold the freelistlock when you call this.
1162 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1163 size_t size = 0;
1164 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1165 debug_only(
1166 // We may be calling here without the lock in which case we
1167 // won't do this modest sanity check.
1168 if (freelistLock()->owned_by_self()) {
1169 size_t total_list_size = 0;
1170 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1171 fc = fc->next()) {
1172 total_list_size += i;
1173 }
1174 assert(total_list_size == i * _indexedFreeList[i].count(),
1175 "Count in list is incorrect");
1176 }
1177 )
1178 size += i * _indexedFreeList[i].count();
1179 }
1180 return size;
1181 }
1182
1183 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1184 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1185 return allocate(size);
1186 }
1187
1188 HeapWord*
1189 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1190 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1191 }
1192
1193 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1194 assert_lock_strong(freelistLock());
1195 HeapWord* res = NULL;
1196 assert(size == adjustObjectSize(size),
1197 "use adjustObjectSize() before calling into allocate()");
1198
1199 if (_adaptive_freelists) {
1200 res = allocate_adaptive_freelists(size);
1201 } else { // non-adaptive free lists
1202 res = allocate_non_adaptive_freelists(size);
1203 }
1204
1205 if (res != NULL) {
1206 // check that res does lie in this space!
1207 assert(is_in_reserved(res), "Not in this space!");
1208 assert(is_aligned((void*)res), "alignment check");
1209
1210 FreeChunk* fc = (FreeChunk*)res;
1211 fc->markNotFree();
1212 assert(!fc->is_free(), "shouldn't be marked free");
1213 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1214 // Verify that the block offset table shows this to
1215 // be a single block, but not one which is unallocated.
1216 _bt.verify_single_block(res, size);
1217 _bt.verify_not_unallocated(res, size);
1218 // mangle a just allocated object with a distinct pattern.
1219 debug_only(fc->mangleAllocated(size));
1220 }
1221
1222 return res;
1223 }
1224
1225 HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) {
1226 HeapWord* res = NULL;
1227 // try and use linear allocation for smaller blocks
1228 if (size < _smallLinearAllocBlock._allocation_size_limit) {
1229 // if successful, the following also adjusts block offset table
1230 res = getChunkFromSmallLinearAllocBlock(size);
1231 }
1232 // Else triage to indexed lists for smaller sizes
1233 if (res == NULL) {
1234 if (size < SmallForDictionary) {
1235 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1236 } else {
1237 // else get it from the big dictionary; if even this doesn't
1238 // work we are out of luck.
1239 res = (HeapWord*)getChunkFromDictionaryExact(size);
1240 }
1241 }
1242
1243 return res;
1244 }
1245
1246 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1247 assert_lock_strong(freelistLock());
1248 HeapWord* res = NULL;
1249 assert(size == adjustObjectSize(size),
1250 "use adjustObjectSize() before calling into allocate()");
1251
1252 // Strategy
1253 // if small
1254 // exact size from small object indexed list if small
1255 // small or large linear allocation block (linAB) as appropriate
1256 // take from lists of greater sized chunks
1257 // else
1258 // dictionary
1259 // small or large linear allocation block if it has the space
1260 // Try allocating exact size from indexTable first
1261 if (size < IndexSetSize) {
1262 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1263 if(res != NULL) {
1264 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1265 "Not removed from free list");
1266 // no block offset table adjustment is necessary on blocks in
1267 // the indexed lists.
1268
1269 // Try allocating from the small LinAB
1270 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1271 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1272 // if successful, the above also adjusts block offset table
1273 // Note that this call will refill the LinAB to
1274 // satisfy the request. This is different that
1275 // evm.
1276 // Don't record chunk off a LinAB? smallSplitBirth(size);
1277 } else {
1278 // Raid the exact free lists larger than size, even if they are not
1279 // overpopulated.
1280 res = (HeapWord*) getChunkFromGreater(size);
1281 }
1282 } else {
1283 // Big objects get allocated directly from the dictionary.
1284 res = (HeapWord*) getChunkFromDictionaryExact(size);
1285 if (res == NULL) {
1286 // Try hard not to fail since an allocation failure will likely
1287 // trigger a synchronous GC. Try to get the space from the
1288 // allocation blocks.
1289 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1290 }
1291 }
1292
1293 return res;
1294 }
1295
1296 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1297 // when promoting obj.
1298 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1299 // Depending on the object size, expansion may require refilling either a
1300 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1301 // is added because the dictionary may over-allocate to avoid fragmentation.
1302 size_t space = obj_size;
1303 if (!_adaptive_freelists) {
1304 space = MAX2(space, _smallLinearAllocBlock._refillSize);
1305 }
1306 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1307 return space;
1308 }
1309
1310 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1311 FreeChunk* ret;
1312
1313 assert(numWords >= MinChunkSize, "Size is less than minimum");
1314 assert(linearAllocationWouldFail() || bestFitFirst(),
1315 "Should not be here");
1316
1317 size_t i;
1318 size_t currSize = numWords + MinChunkSize;
1319 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1320 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1321 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
1322 if (fl->head()) {
1323 ret = getFromListGreater(fl, numWords);
1324 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1325 return ret;
1326 }
1327 }
1328
1329 currSize = MAX2((size_t)SmallForDictionary,
1330 (size_t)(numWords + MinChunkSize));
1331
1332 /* Try to get a chunk that satisfies request, while avoiding
1333 fragmentation that can't be handled. */
1334 {
1335 ret = dictionary()->get_chunk(currSize);
1336 if (ret != NULL) {
1337 assert(ret->size() - numWords >= MinChunkSize,
1338 "Chunk is too small");
1339 _bt.allocated((HeapWord*)ret, ret->size());
1340 /* Carve returned chunk. */
1341 (void) splitChunkAndReturnRemainder(ret, numWords);
1342 /* Label this as no longer a free chunk. */
1343 assert(ret->is_free(), "This chunk should be free");
1344 ret->link_prev(NULL);
1345 }
1346 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1347 return ret;
1348 }
1349 ShouldNotReachHere();
1350 }
1351
1352 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1353 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1354 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
1355 }
1356
1357 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1358 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1359 (_smallLinearAllocBlock._word_size == fc->size()),
1360 "Linear allocation block shows incorrect size");
1361 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1362 (_smallLinearAllocBlock._word_size == fc->size()));
1363 }
1364
1365 // Check if the purported free chunk is present either as a linear
1366 // allocation block, the size-indexed table of (smaller) free blocks,
1367 // or the larger free blocks kept in the binary tree dictionary.
1368 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
1369 if (verify_chunk_is_linear_alloc_block(fc)) {
1370 return true;
1371 } else if (fc->size() < IndexSetSize) {
1372 return verifyChunkInIndexedFreeLists(fc);
1373 } else {
1374 return dictionary()->verify_chunk_in_free_list(fc);
1375 }
1376 }
1377
1378 #ifndef PRODUCT
1379 void CompactibleFreeListSpace::assert_locked() const {
1380 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1381 }
1382
1383 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1384 CMSLockVerifier::assert_locked(lock);
1385 }
1386 #endif
1387
1388 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1389 // In the parallel case, the main thread holds the free list lock
1390 // on behalf the parallel threads.
1391 FreeChunk* fc;
1392 {
1393 // If GC is parallel, this might be called by several threads.
1394 // This should be rare enough that the locking overhead won't affect
1395 // the sequential code.
1396 MutexLockerEx x(parDictionaryAllocLock(),
1397 Mutex::_no_safepoint_check_flag);
1398 fc = getChunkFromDictionary(size);
1399 }
1400 if (fc != NULL) {
1401 fc->dontCoalesce();
1402 assert(fc->is_free(), "Should be free, but not coalescable");
1403 // Verify that the block offset table shows this to
1404 // be a single block, but not one which is unallocated.
1405 _bt.verify_single_block((HeapWord*)fc, fc->size());
1406 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1407 }
1408 return fc;
1409 }
1410
1411 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1412 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1413 assert_locked();
1414
1415 // if we are tracking promotions, then first ensure space for
1416 // promotion (including spooling space for saving header if necessary).
1417 // then allocate and copy, then track promoted info if needed.
1418 // When tracking (see PromotionInfo::track()), the mark word may
1419 // be displaced and in this case restoration of the mark word
1420 // occurs in the (oop_since_save_marks_)iterate phase.
1421 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1422 return NULL;
1423 }
1424 // Call the allocate(size_t, bool) form directly to avoid the
1425 // additional call through the allocate(size_t) form. Having
1426 // the compile inline the call is problematic because allocate(size_t)
1427 // is a virtual method.
1428 HeapWord* res = allocate(adjustObjectSize(obj_size));
1429 if (res != NULL) {
1430 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1431 // if we should be tracking promotions, do so.
1432 if (_promoInfo.tracking()) {
1433 _promoInfo.track((PromotedObject*)res);
1434 }
1435 }
1436 return oop(res);
1437 }
1438
1439 HeapWord*
1440 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1441 assert_locked();
1442 assert(size >= MinChunkSize, "minimum chunk size");
1443 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1444 "maximum from smallLinearAllocBlock");
1445 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1446 }
1447
1448 HeapWord*
1449 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1450 size_t size) {
1451 assert_locked();
1452 assert(size >= MinChunkSize, "too small");
1453 HeapWord* res = NULL;
1454 // Try to do linear allocation from blk, making sure that
1455 if (blk->_word_size == 0) {
1456 // We have probably been unable to fill this either in the prologue or
1457 // when it was exhausted at the last linear allocation. Bail out until
1458 // next time.
1459 assert(blk->_ptr == NULL, "consistency check");
1460 return NULL;
1461 }
1462 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1463 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1464 if (res != NULL) return res;
1465
1466 // about to exhaust this linear allocation block
1467 if (blk->_word_size == size) { // exactly satisfied
1468 res = blk->_ptr;
1469 _bt.allocated(res, blk->_word_size);
1470 } else if (size + MinChunkSize <= blk->_refillSize) {
1471 size_t sz = blk->_word_size;
1472 // Update _unallocated_block if the size is such that chunk would be
1473 // returned to the indexed free list. All other chunks in the indexed
1474 // free lists are allocated from the dictionary so that _unallocated_block
1475 // has already been adjusted for them. Do it here so that the cost
1476 // for all chunks added back to the indexed free lists.
1477 if (sz < SmallForDictionary) {
1478 _bt.allocated(blk->_ptr, sz);
1479 }
1480 // Return the chunk that isn't big enough, and then refill below.
1481 addChunkToFreeLists(blk->_ptr, sz, true);
1482 split_birth(sz);
1483 // Don't keep statistics on adding back chunk from a LinAB.
1484 } else {
1485 // A refilled block would not satisfy the request.
1486 return NULL;
1487 }
1488
1489 blk->_ptr = NULL; blk->_word_size = 0;
1490 refillLinearAllocBlock(blk);
1491 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1492 "block was replenished");
1493 if (res != NULL) {
1494 split_birth(size);
1495 repairLinearAllocBlock(blk);
1496 } else if (blk->_ptr != NULL) {
1497 res = blk->_ptr;
1498 size_t blk_size = blk->_word_size;
1499 blk->_word_size -= size;
1500 blk->_ptr += size;
1501 split_birth(size);
1502 repairLinearAllocBlock(blk);
1503 // Update BOT last so that other (parallel) GC threads see a consistent
1504 // view of the BOT and free blocks.
1505 // Above must occur before BOT is updated below.
1506 OrderAccess::storestore();
1507 _bt.split_block(res, blk_size, size); // adjust block offset table
1508 }
1509 return res;
1510 }
1511
1512 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1513 LinearAllocBlock* blk,
1514 size_t size) {
1515 assert_locked();
1516 assert(size >= MinChunkSize, "too small");
1517
1518 HeapWord* res = NULL;
1519 // This is the common case. Keep it simple.
1520 if (blk->_word_size >= size + MinChunkSize) {
1521 assert(blk->_ptr != NULL, "consistency check");
1522 res = blk->_ptr;
1523 // Note that the BOT is up-to-date for the linAB before allocation. It
1524 // indicates the start of the linAB. The split_block() updates the
1525 // BOT for the linAB after the allocation (indicates the start of the
1526 // next chunk to be allocated).
1527 size_t blk_size = blk->_word_size;
1528 blk->_word_size -= size;
1529 blk->_ptr += size;
1530 split_birth(size);
1531 repairLinearAllocBlock(blk);
1532 // Update BOT last so that other (parallel) GC threads see a consistent
1533 // view of the BOT and free blocks.
1534 // Above must occur before BOT is updated below.
1535 OrderAccess::storestore();
1536 _bt.split_block(res, blk_size, size); // adjust block offset table
1537 _bt.allocated(res, size);
1538 }
1539 return res;
1540 }
1541
1542 FreeChunk*
1543 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1544 assert_locked();
1545 assert(size < SmallForDictionary, "just checking");
1546 FreeChunk* res;
1547 res = _indexedFreeList[size].get_chunk_at_head();
1548 if (res == NULL) {
1549 res = getChunkFromIndexedFreeListHelper(size);
1550 }
1551 _bt.verify_not_unallocated((HeapWord*) res, size);
1552 assert(res == NULL || res->size() == size, "Incorrect block size");
1553 return res;
1554 }
1555
1556 FreeChunk*
1557 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1558 bool replenish) {
1559 assert_locked();
1560 FreeChunk* fc = NULL;
1561 if (size < SmallForDictionary) {
1562 assert(_indexedFreeList[size].head() == NULL ||
1563 _indexedFreeList[size].surplus() <= 0,
1564 "List for this size should be empty or under populated");
1565 // Try best fit in exact lists before replenishing the list
1566 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1567 // Replenish list.
1568 //
1569 // Things tried that failed.
1570 // Tried allocating out of the two LinAB's first before
1571 // replenishing lists.
1572 // Tried small linAB of size 256 (size in indexed list)
1573 // and replenishing indexed lists from the small linAB.
1574 //
1575 FreeChunk* newFc = NULL;
1576 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1577 if (replenish_size < SmallForDictionary) {
1578 // Do not replenish from an underpopulated size.
1579 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1580 _indexedFreeList[replenish_size].head() != NULL) {
1581 newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
1582 } else if (bestFitFirst()) {
1583 newFc = bestFitSmall(replenish_size);
1584 }
1585 }
1586 if (newFc == NULL && replenish_size > size) {
1587 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1588 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1589 }
1590 // Note: The stats update re split-death of block obtained above
1591 // will be recorded below precisely when we know we are going to
1592 // be actually splitting it into more than one pieces below.
1593 if (newFc != NULL) {
1594 if (replenish || CMSReplenishIntermediate) {
1595 // Replenish this list and return one block to caller.
1596 size_t i;
1597 FreeChunk *curFc, *nextFc;
1598 size_t num_blk = newFc->size() / size;
1599 assert(num_blk >= 1, "Smaller than requested?");
1600 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1601 if (num_blk > 1) {
1602 // we are sure we will be splitting the block just obtained
1603 // into multiple pieces; record the split-death of the original
1604 splitDeath(replenish_size);
1605 }
1606 // carve up and link blocks 0, ..., num_blk - 2
1607 // The last chunk is not added to the lists but is returned as the
1608 // free chunk.
1609 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1610 i = 0;
1611 i < (num_blk - 1);
1612 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1613 i++) {
1614 curFc->set_size(size);
1615 // Don't record this as a return in order to try and
1616 // determine the "returns" from a GC.
1617 _bt.verify_not_unallocated((HeapWord*) fc, size);
1618 _indexedFreeList[size].return_chunk_at_tail(curFc, false, true);
1619 _bt.mark_block((HeapWord*)curFc, size);
1620 split_birth(size);
1621 // Don't record the initial population of the indexed list
1622 // as a split birth.
1623 }
1624
1625 // check that the arithmetic was OK above
1626 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1627 "inconsistency in carving newFc");
1628 curFc->set_size(size);
1629 _bt.mark_block((HeapWord*)curFc, size);
1630 split_birth(size);
1631 fc = curFc;
1632 } else {
1633 // Return entire block to caller
1634 fc = newFc;
1635 }
1636 }
1637 }
1638 } else {
1639 // Get a free chunk from the free chunk dictionary to be returned to
1640 // replenish the indexed free list.
1641 fc = getChunkFromDictionaryExact(size);
1642 }
1643 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
1644 return fc;
1645 }
1646
1647 FreeChunk*
1648 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1649 assert_locked();
1650 FreeChunk* fc = _dictionary->get_chunk(size);
1651 if (fc == NULL) {
1652 return NULL;
1653 }
1654 _bt.allocated((HeapWord*)fc, fc->size());
1655 if (fc->size() >= size + MinChunkSize) {
1656 fc = splitChunkAndReturnRemainder(fc, size);
1657 }
1658 assert(fc->size() >= size, "chunk too small");
1659 assert(fc->size() < size + MinChunkSize, "chunk too big");
1660 _bt.verify_single_block((HeapWord*)fc, fc->size());
1661 return fc;
1662 }
1663
1664 FreeChunk*
1665 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1666 assert_locked();
1667 FreeChunk* fc = _dictionary->get_chunk(size);
1668 if (fc == NULL) {
1669 return fc;
1670 }
1671 _bt.allocated((HeapWord*)fc, fc->size());
1672 if (fc->size() == size) {
1673 _bt.verify_single_block((HeapWord*)fc, size);
1674 return fc;
1675 }
1676 assert(fc->size() > size, "get_chunk() guarantee");
1677 if (fc->size() < size + MinChunkSize) {
1678 // Return the chunk to the dictionary and go get a bigger one.
1679 returnChunkToDictionary(fc, true);
1680 fc = _dictionary->get_chunk(size + MinChunkSize);
1681 if (fc == NULL) {
1682 return NULL;
1683 }
1684 _bt.allocated((HeapWord*)fc, fc->size());
1685 }
1686 assert(fc->size() >= size + MinChunkSize, "tautology");
1687 fc = splitChunkAndReturnRemainder(fc, size);
1688 assert(fc->size() == size, "chunk is wrong size");
1689 _bt.verify_single_block((HeapWord*)fc, size);
1690 return fc;
1691 }
1692
1693 void
1694 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk, bool deallocate_pages) {
1695 assert_locked();
1696
1697 size_t size = chunk->size();
1698 _bt.verify_single_block((HeapWord*)chunk, size);
1699 // adjust _unallocated_block downward, as necessary
1700 _bt.freed((HeapWord*)chunk, size);
1701 _dictionary->return_chunk(chunk, deallocate_pages);
1702 #ifndef PRODUCT
1703 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1704 TreeChunk<FreeChunk, AdaptiveFreeList>* tc = TreeChunk<FreeChunk, AdaptiveFreeList>::as_TreeChunk(chunk);
1705 TreeList<FreeChunk, AdaptiveFreeList>* tl = tc->list();
1706 tl->verify_stats();
1707 }
1708 #endif // PRODUCT
1709 }
1710
1711 void
1712 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc, bool deallocate_pages) {
1713 assert_locked();
1714 size_t size = fc->size();
1715 _bt.verify_single_block((HeapWord*) fc, size);
1716 _bt.verify_not_unallocated((HeapWord*) fc, size);
1717 if (_adaptive_freelists) {
1718 _indexedFreeList[size].return_chunk_at_tail(fc, true, deallocate_pages);
1719 } else {
1720 _indexedFreeList[size].return_chunk_at_head(fc, true, deallocate_pages);
1721 }
1722 #ifndef PRODUCT
1723 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1724 _indexedFreeList[size].verify_stats();
1725 }
1726 #endif // PRODUCT
1727 }
1728
1729 // Add chunk to end of last block -- if it's the largest
1730 // block -- and update BOT and census data. We would
1731 // of course have preferred to coalesce it with the
1732 // last block, but it's currently less expensive to find the
1733 // largest block than it is to find the last.
1734 void
1735 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1736 HeapWord* chunk, size_t size) {
1737 // check that the chunk does lie in this space!
1738 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1739 // One of the parallel gc task threads may be here
1740 // whilst others are allocating.
1741 Mutex* lock = NULL;
1742 if (ParallelGCThreads != 0) {
1743 lock = &_parDictionaryAllocLock;
1744 }
1745 FreeChunk* ec;
1746 {
1747 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1748 ec = dictionary()->find_largest_dict(); // get largest block
1749 if (ec != NULL && ec->end() == (uintptr_t*) chunk) {
1750 // It's a coterminal block - we can coalesce.
1751 size_t old_size = ec->size();
1752 coalDeath(old_size);
1753 removeChunkFromDictionary(ec);
1754 size += old_size;
1755 } else {
1756 ec = (FreeChunk*)chunk;
1757 }
1758 }
1759 ec->set_size(size);
1760 debug_only(ec->mangleFreed(size));
1761 if (size < SmallForDictionary) {
1762 lock = _indexedFreeListParLocks[size];
1763 }
1764 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1765 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true, true);
1766 // record the birth under the lock since the recording involves
1767 // manipulation of the list on which the chunk lives and
1768 // if the chunk is allocated and is the last on the list,
1769 // the list can go away.
1770 coalBirth(size);
1771 }
1772
1773 void
1774 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1775 size_t size,
1776 bool deallocate_pages) {
1777 // check that the chunk does lie in this space!
1778 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1779 assert_locked();
1780 _bt.verify_single_block(chunk, size);
1781
1782 FreeChunk* fc = (FreeChunk*) chunk;
1783 fc->set_size(size);
1784 debug_only(fc->mangleFreed(size));
1785 if (size < SmallForDictionary) {
1786 returnChunkToFreeList(fc, deallocate_pages);
1787 } else {
1788 returnChunkToDictionary(fc, deallocate_pages);
1789 }
1790 }
1791
1792 void
1793 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1794 size_t size, bool coalesced, bool deallocate_pages) {
1795 assert_locked();
1796 assert(chunk != NULL, "null chunk");
1797 if (coalesced) {
1798 // repair BOT
1799 _bt.single_block(chunk, size);
1800 }
1801 addChunkToFreeLists(chunk, size, deallocate_pages);
1802 }
1803
1804 // We _must_ find the purported chunk on our free lists;
1805 // we assert if we don't.
1806 void
1807 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1808 size_t size = fc->size();
1809 assert_locked();
1810 debug_only(verifyFreeLists());
1811 if (size < SmallForDictionary) {
1812 removeChunkFromIndexedFreeList(fc);
1813 } else {
1814 removeChunkFromDictionary(fc);
1815 }
1816 _bt.verify_single_block((HeapWord*)fc, size);
1817 debug_only(verifyFreeLists());
1818 }
1819
1820 void
1821 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1822 size_t size = fc->size();
1823 assert_locked();
1824 assert(fc != NULL, "null chunk");
1825 _bt.verify_single_block((HeapWord*)fc, size);
1826 _dictionary->remove_chunk(fc);
1827 // adjust _unallocated_block upward, as necessary
1828 _bt.allocated((HeapWord*)fc, size);
1829 }
1830
1831 void
1832 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1833 assert_locked();
1834 size_t size = fc->size();
1835 _bt.verify_single_block((HeapWord*)fc, size);
1836 NOT_PRODUCT(
1837 if (FLSVerifyIndexTable) {
1838 verifyIndexedFreeList(size);
1839 }
1840 )
1841 _indexedFreeList[size].remove_chunk(fc);
1842 NOT_PRODUCT(
1843 if (FLSVerifyIndexTable) {
1844 verifyIndexedFreeList(size);
1845 }
1846 )
1847 }
1848
1849 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1850 /* A hint is the next larger size that has a surplus.
1851 Start search at a size large enough to guarantee that
1852 the excess is >= MIN_CHUNK. */
1853 size_t start = align_object_size(numWords + MinChunkSize);
1854 if (start < IndexSetSize) {
1855 AdaptiveFreeList<FreeChunk>* it = _indexedFreeList;
1856 size_t hint = _indexedFreeList[start].hint();
1857 while (hint < IndexSetSize) {
1858 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1859 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint];
1860 if (fl->surplus() > 0 && fl->head() != NULL) {
1861 // Found a list with surplus, reset original hint
1862 // and split out a free chunk which is returned.
1863 _indexedFreeList[start].set_hint(hint);
1864 FreeChunk* res = getFromListGreater(fl, numWords);
1865 assert(res == NULL || res->is_free(),
1866 "Should be returning a free chunk");
1867 return res;
1868 }
1869 hint = fl->hint(); /* keep looking */
1870 }
1871 /* None found. */
1872 it[start].set_hint(IndexSetSize);
1873 }
1874 return NULL;
1875 }
1876
1877 /* Requires fl->size >= numWords + MinChunkSize */
1878 FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl,
1879 size_t numWords) {
1880 FreeChunk *curr = fl->head();
1881 size_t oldNumWords = curr->size();
1882 assert(numWords >= MinChunkSize, "Word size is too small");
1883 assert(curr != NULL, "List is empty");
1884 assert(oldNumWords >= numWords + MinChunkSize,
1885 "Size of chunks in the list is too small");
1886
1887 fl->remove_chunk(curr);
1888 // recorded indirectly by splitChunkAndReturnRemainder -
1889 // smallSplit(oldNumWords, numWords);
1890 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1891 // Does anything have to be done for the remainder in terms of
1892 // fixing the card table?
1893 assert(new_chunk == NULL || new_chunk->is_free(),
1894 "Should be returning a free chunk");
1895 return new_chunk;
1896 }
1897
1898 FreeChunk*
1899 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1900 size_t new_size) {
1901 assert_locked();
1902 size_t size = chunk->size();
1903 assert(size > new_size, "Split from a smaller block?");
1904 assert(is_aligned(chunk), "alignment problem");
1905 assert(size == adjustObjectSize(size), "alignment problem");
1906 size_t rem_size = size - new_size;
1907 assert(rem_size == adjustObjectSize(rem_size), "alignment problem");
1908 assert(rem_size >= MinChunkSize, "Free chunk smaller than minimum");
1909 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1910 assert(is_aligned(ffc), "alignment problem");
1911 ffc->set_size(rem_size);
1912 ffc->link_next(NULL);
1913 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
1914 // Above must occur before BOT is updated below.
1915 // adjust block offset table
1916 OrderAccess::storestore();
1917 assert(chunk->is_free() && ffc->is_free(), "Error");
1918 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1919 if (rem_size < SmallForDictionary) {
1920 bool is_par = (SharedHeap::heap()->n_par_threads() > 0);
1921 if (is_par) _indexedFreeListParLocks[rem_size]->lock();
1922 assert(!is_par ||
1923 (SharedHeap::heap()->n_par_threads() ==
1924 SharedHeap::heap()->workers()->active_workers()), "Mismatch");
1925 // We don't need to deallocate pages here because a chunk is split
1926 // and its pages are already deallocated at this point. Otherwise,
1927 // we would be wastefully calling a system call to deallocate
1928 // pages especially at every OG allocation after a compacting GC.
1929 returnChunkToFreeList(ffc, false);
1930 split(size, rem_size);
1931 if (is_par) _indexedFreeListParLocks[rem_size]->unlock();
1932 } else {
1933 // We don't need to deallocate pages here because a chunk is split
1934 // and its pages are already deallocated at this point. Otherwise,
1935 // we would be wastefully calling a system call to deallocate
1936 // pages especially at every OG allocation after a compacting GC.
1937 returnChunkToDictionary(ffc, false);
1938 split(size ,rem_size);
1939 }
1940 chunk->set_size(new_size);
1941 return chunk;
1942 }
1943
1944 void
1945 CompactibleFreeListSpace::sweep_completed() {
1946 // Now that space is probably plentiful, refill linear
1947 // allocation blocks as needed.
1948 refillLinearAllocBlocksIfNeeded();
1949 }
1950
1951 void
1952 CompactibleFreeListSpace::gc_prologue() {
1953 assert_locked();
1954 if (PrintFLSStatistics != 0) {
1955 gclog_or_tty->print("Before GC:\n");
1956 reportFreeListStatistics();
1957 }
1958 refillLinearAllocBlocksIfNeeded();
1959 }
1960
1961 void
1962 CompactibleFreeListSpace::gc_epilogue() {
1963 assert_locked();
1964 if (PrintGCDetails && Verbose && !_adaptive_freelists) {
1965 if (_smallLinearAllocBlock._word_size == 0)
1966 warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure");
1967 }
1968 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1969 _promoInfo.stopTrackingPromotions();
1970 repairLinearAllocationBlocks();
1971 // Print Space's stats
1972 if (PrintFLSStatistics != 0) {
1973 gclog_or_tty->print("After GC:\n");
1974 reportFreeListStatistics();
1975 }
1976 }
1977
1978 // Iteration support, mostly delegated from a CMS generation
1979
1980 void CompactibleFreeListSpace::save_marks() {
1981 assert(Thread::current()->is_VM_thread(),
1982 "Global variable should only be set when single-threaded");
1983 // Mark the "end" of the used space at the time of this call;
1984 // note, however, that promoted objects from this point
1985 // on are tracked in the _promoInfo below.
1986 set_saved_mark_word(unallocated_block());
1987 #ifdef ASSERT
1988 // Check the sanity of save_marks() etc.
1989 MemRegion ur = used_region();
1990 MemRegion urasm = used_region_at_save_marks();
1991 assert(ur.contains(urasm),
1992 err_msg(" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
1993 " should contain [" PTR_FORMAT "," PTR_FORMAT ")",
1994 ur.start(), ur.end(), urasm.start(), urasm.end()));
1995 #endif
1996 // inform allocator that promotions should be tracked.
1997 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1998 _promoInfo.startTrackingPromotions();
1999 }
2000
2001 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
2002 assert(_promoInfo.tracking(), "No preceding save_marks?");
2003 assert(SharedHeap::heap()->n_par_threads() == 0,
2004 "Shouldn't be called if using parallel gc.");
2005 return _promoInfo.noPromotions();
2006 }
2007
2008 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
2009 \
2010 void CompactibleFreeListSpace:: \
2011 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
2012 assert(SharedHeap::heap()->n_par_threads() == 0, \
2013 "Shouldn't be called (yet) during parallel part of gc."); \
2014 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
2015 /* \
2016 * This also restores any displaced headers and removes the elements from \
2017 * the iteration set as they are processed, so that we have a clean slate \
2018 * at the end of the iteration. Note, thus, that if new objects are \
2019 * promoted as a result of the iteration they are iterated over as well. \
2020 */ \
2021 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
2022 }
2023
2024 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
2025
2026
2027 void CompactibleFreeListSpace::object_iterate_since_last_GC(ObjectClosure* cl) {
2028 // ugghh... how would one do this efficiently for a non-contiguous space?
2029 guarantee(false, "NYI");
2030 }
2031
2032 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
2033 return _smallLinearAllocBlock._word_size == 0;
2034 }
2035
2036 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
2037 // Fix up linear allocation blocks to look like free blocks
2038 repairLinearAllocBlock(&_smallLinearAllocBlock);
2039 }
2040
2041 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
2042 assert_locked();
2043 if (blk->_ptr != NULL) {
2044 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
2045 "Minimum block size requirement");
2046 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
2047 fc->set_size(blk->_word_size);
2048 fc->link_prev(NULL); // mark as free
2049 fc->dontCoalesce();
2050 assert(fc->is_free(), "just marked it free");
2051 assert(fc->cantCoalesce(), "just marked it uncoalescable");
2052 }
2053 }
2054
2055 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
2056 assert_locked();
2057 if (_smallLinearAllocBlock._ptr == NULL) {
2058 assert(_smallLinearAllocBlock._word_size == 0,
2059 "Size of linAB should be zero if the ptr is NULL");
2060 // Reset the linAB refill and allocation size limit.
2061 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
2062 }
2063 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
2064 }
2065
2066 void
2067 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
2068 assert_locked();
2069 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
2070 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
2071 "blk invariant");
2072 if (blk->_ptr == NULL) {
2073 refillLinearAllocBlock(blk);
2074 }
2075 if (PrintMiscellaneous && Verbose) {
2076 if (blk->_word_size == 0) {
2077 warning("CompactibleFreeListSpace(prologue):: Linear allocation failure");
2078 }
2079 }
2080 }
2081
2082 void
2083 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
2084 assert_locked();
2085 assert(blk->_word_size == 0 && blk->_ptr == NULL,
2086 "linear allocation block should be empty");
2087 FreeChunk* fc;
2088 if (blk->_refillSize < SmallForDictionary &&
2089 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
2090 // A linAB's strategy might be to use small sizes to reduce
2091 // fragmentation but still get the benefits of allocation from a
2092 // linAB.
2093 } else {
2094 fc = getChunkFromDictionary(blk->_refillSize);
2095 }
2096 if (fc != NULL) {
2097 blk->_ptr = (HeapWord*)fc;
2098 blk->_word_size = fc->size();
2099 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
2100 }
2101 }
2102
2103 // Support for concurrent collection policy decisions.
2104 bool CompactibleFreeListSpace::should_concurrent_collect() const {
2105 // In the future we might want to add in frgamentation stats --
2106 // including erosion of the "mountain" into this decision as well.
2107 return !adaptive_freelists() && linearAllocationWouldFail();
2108 }
2109
2110 // Support for compaction
2111
2112 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
2113 SCAN_AND_FORWARD(cp,end,block_is_obj,block_size);
2114 // prepare_for_compaction() uses the space between live objects
2115 // so that later phase can skip dead space quickly. So verification
2116 // of the free lists doesn't work after.
2117 }
2118
2119 #define obj_size(q) adjustObjectSize(oop(q)->size())
2120 #define adjust_obj_size(s) adjustObjectSize(s)
2121
2122 void CompactibleFreeListSpace::adjust_pointers() {
2123 // In other versions of adjust_pointers(), a bail out
2124 // based on the amount of live data in the generation
2125 // (i.e., if 0, bail out) may be used.
2126 // Cannot test used() == 0 here because the free lists have already
2127 // been mangled by the compaction.
2128
2129 SCAN_AND_ADJUST_POINTERS(adjust_obj_size);
2130 // See note about verification in prepare_for_compaction().
2131 }
2132
2133 void CompactibleFreeListSpace::compact() {
2134 SCAN_AND_COMPACT(obj_size);
2135 }
2136
2137 // fragmentation_metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
2138 // where fbs is free block sizes
2139 double CompactibleFreeListSpace::flsFrag() const {
2140 size_t itabFree = totalSizeInIndexedFreeLists();
2141 double frag = 0.0;
2142 size_t i;
2143
2144 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2145 double sz = i;
2146 frag += _indexedFreeList[i].count() * (sz * sz);
2147 }
2148
2149 double totFree = itabFree +
2150 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
2151 if (totFree > 0) {
2152 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
2153 (totFree * totFree));
2154 frag = (double)1.0 - frag;
2155 } else {
2156 assert(frag == 0.0, "Follows from totFree == 0");
2157 }
2158 return frag;
2159 }
2160
2161 void CompactibleFreeListSpace::beginSweepFLCensus(
2162 float inter_sweep_current,
2163 float inter_sweep_estimate,
2164 float intra_sweep_estimate) {
2165 assert_locked();
2166 size_t i;
2167 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2168 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
2169 if (PrintFLSStatistics > 1) {
2170 gclog_or_tty->print("size[%d] : ", i);
2171 }
2172 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2173 fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2174 fl->set_before_sweep(fl->count());
2175 fl->set_bfr_surp(fl->surplus());
2176 }
2177 _dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent,
2178 inter_sweep_current,
2179 inter_sweep_estimate,
2180 intra_sweep_estimate);
2181 }
2182
2183 void CompactibleFreeListSpace::setFLSurplus() {
2184 assert_locked();
2185 size_t i;
2186 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2187 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2188 fl->set_surplus(fl->count() -
2189 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2190 }
2191 }
2192
2193 void CompactibleFreeListSpace::setFLHints() {
2194 assert_locked();
2195 size_t i;
2196 size_t h = IndexSetSize;
2197 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2198 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2199 fl->set_hint(h);
2200 if (fl->surplus() > 0) {
2201 h = i;
2202 }
2203 }
2204 }
2205
2206 void CompactibleFreeListSpace::clearFLCensus() {
2207 assert_locked();
2208 size_t i;
2209 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2210 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2211 fl->set_prev_sweep(fl->count());
2212 fl->set_coal_births(0);
2213 fl->set_coal_deaths(0);
2214 fl->set_split_births(0);
2215 fl->set_split_deaths(0);
2216 }
2217 }
2218
2219 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2220 if (PrintFLSStatistics > 0) {
2221 HeapWord* largestAddr = (HeapWord*) dictionary()->find_largest_dict();
2222 gclog_or_tty->print_cr("CMS: Large block " PTR_FORMAT,
2223 largestAddr);
2224 }
2225 setFLSurplus();
2226 setFLHints();
2227 if (PrintGC && PrintFLSCensus > 0) {
2228 printFLCensus(sweep_count);
2229 }
2230 clearFLCensus();
2231 assert_locked();
2232 _dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent);
2233 }
2234
2235 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2236 if (size < SmallForDictionary) {
2237 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2238 return (fl->coal_desired() < 0) ||
2239 ((int)fl->count() > fl->coal_desired());
2240 } else {
2241 return dictionary()->coal_dict_over_populated(size);
2242 }
2243 }
2244
2245 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2246 assert(size < SmallForDictionary, "Size too large for indexed list");
2247 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2248 fl->increment_coal_births();
2249 fl->increment_surplus();
2250 }
2251
2252 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2253 assert(size < SmallForDictionary, "Size too large for indexed list");
2254 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2255 fl->increment_coal_deaths();
2256 fl->decrement_surplus();
2257 }
2258
2259 void CompactibleFreeListSpace::coalBirth(size_t size) {
2260 if (size < SmallForDictionary) {
2261 smallCoalBirth(size);
2262 } else {
2263 dictionary()->dict_census_update(size,
2264 false /* split */,
2265 true /* birth */);
2266 }
2267 }
2268
2269 void CompactibleFreeListSpace::coalDeath(size_t size) {
2270 if(size < SmallForDictionary) {
2271 smallCoalDeath(size);
2272 } else {
2273 dictionary()->dict_census_update(size,
2274 false /* split */,
2275 false /* birth */);
2276 }
2277 }
2278
2279 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2280 assert(size < SmallForDictionary, "Size too large for indexed list");
2281 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2282 fl->increment_split_births();
2283 fl->increment_surplus();
2284 }
2285
2286 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2287 assert(size < SmallForDictionary, "Size too large for indexed list");
2288 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2289 fl->increment_split_deaths();
2290 fl->decrement_surplus();
2291 }
2292
2293 void CompactibleFreeListSpace::split_birth(size_t size) {
2294 if (size < SmallForDictionary) {
2295 smallSplitBirth(size);
2296 } else {
2297 dictionary()->dict_census_update(size,
2298 true /* split */,
2299 true /* birth */);
2300 }
2301 }
2302
2303 void CompactibleFreeListSpace::splitDeath(size_t size) {
2304 if (size < SmallForDictionary) {
2305 smallSplitDeath(size);
2306 } else {
2307 dictionary()->dict_census_update(size,
2308 true /* split */,
2309 false /* birth */);
2310 }
2311 }
2312
2313 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2314 size_t to2 = from - to1;
2315 splitDeath(from);
2316 split_birth(to1);
2317 split_birth(to2);
2318 }
2319
2320 void CompactibleFreeListSpace::print() const {
2321 print_on(tty);
2322 }
2323
2324 void CompactibleFreeListSpace::prepare_for_verify() {
2325 assert_locked();
2326 repairLinearAllocationBlocks();
2327 // Verify that the SpoolBlocks look like free blocks of
2328 // appropriate sizes... To be done ...
2329 }
2330
2331 class VerifyAllBlksClosure: public BlkClosure {
2332 private:
2333 const CompactibleFreeListSpace* _sp;
2334 const MemRegion _span;
2335 HeapWord* _last_addr;
2336 size_t _last_size;
2337 bool _last_was_obj;
2338 bool _last_was_live;
2339
2340 public:
2341 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2342 MemRegion span) : _sp(sp), _span(span),
2343 _last_addr(NULL), _last_size(0),
2344 _last_was_obj(false), _last_was_live(false) { }
2345
2346 virtual size_t do_blk(HeapWord* addr) {
2347 size_t res;
2348 bool was_obj = false;
2349 bool was_live = false;
2350 if (_sp->block_is_obj(addr)) {
2351 was_obj = true;
2352 oop p = oop(addr);
2353 guarantee(p->is_oop(), "Should be an oop");
2354 res = _sp->adjustObjectSize(p->size());
2355 if (_sp->obj_is_alive(addr)) {
2356 was_live = true;
2357 p->verify();
2358 }
2359 } else {
2360 FreeChunk* fc = (FreeChunk*)addr;
2361 res = fc->size();
2362 if (FLSVerifyLists && !fc->cantCoalesce()) {
2363 guarantee(_sp->verify_chunk_in_free_list(fc),
2364 "Chunk should be on a free list");
2365 }
2366 }
2367 if (res == 0) {
2368 gclog_or_tty->print_cr("Livelock: no rank reduction!");
2369 gclog_or_tty->print_cr(
2370 " Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2371 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2372 addr, res, was_obj ?"true":"false", was_live ?"true":"false",
2373 _last_addr, _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2374 _sp->print_on(gclog_or_tty);
2375 guarantee(false, "Seppuku!");
2376 }
2377 _last_addr = addr;
2378 _last_size = res;
2379 _last_was_obj = was_obj;
2380 _last_was_live = was_live;
2381 return res;
2382 }
2383 };
2384
2385 class VerifyAllOopsClosure: public OopClosure {
2386 private:
2387 const CMSCollector* _collector;
2388 const CompactibleFreeListSpace* _sp;
2389 const MemRegion _span;
2390 const bool _past_remark;
2391 const CMSBitMap* _bit_map;
2392
2393 protected:
2394 void do_oop(void* p, oop obj) {
2395 if (_span.contains(obj)) { // the interior oop points into CMS heap
2396 if (!_span.contains(p)) { // reference from outside CMS heap
2397 // Should be a valid object; the first disjunct below allows
2398 // us to sidestep an assertion in block_is_obj() that insists
2399 // that p be in _sp. Note that several generations (and spaces)
2400 // are spanned by _span (CMS heap) above.
2401 guarantee(!_sp->is_in_reserved(obj) ||
2402 _sp->block_is_obj((HeapWord*)obj),
2403 "Should be an object");
2404 guarantee(obj->is_oop(), "Should be an oop");
2405 obj->verify();
2406 if (_past_remark) {
2407 // Remark has been completed, the object should be marked
2408 _bit_map->isMarked((HeapWord*)obj);
2409 }
2410 } else { // reference within CMS heap
2411 if (_past_remark) {
2412 // Remark has been completed -- so the referent should have
2413 // been marked, if referring object is.
2414 if (_bit_map->isMarked(_collector->block_start(p))) {
2415 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2416 }
2417 }
2418 }
2419 } else if (_sp->is_in_reserved(p)) {
2420 // the reference is from FLS, and points out of FLS
2421 guarantee(obj->is_oop(), "Should be an oop");
2422 obj->verify();
2423 }
2424 }
2425
2426 template <class T> void do_oop_work(T* p) {
2427 T heap_oop = oopDesc::load_heap_oop(p);
2428 if (!oopDesc::is_null(heap_oop)) {
2429 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2430 do_oop(p, obj);
2431 }
2432 }
2433
2434 public:
2435 VerifyAllOopsClosure(const CMSCollector* collector,
2436 const CompactibleFreeListSpace* sp, MemRegion span,
2437 bool past_remark, CMSBitMap* bit_map) :
2438 _collector(collector), _sp(sp), _span(span),
2439 _past_remark(past_remark), _bit_map(bit_map) { }
2440
2441 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2442 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2443 };
2444
2445 void CompactibleFreeListSpace::verify() const {
2446 assert_lock_strong(&_freelistLock);
2447 verify_objects_initialized();
2448 MemRegion span = _collector->_span;
2449 bool past_remark = (_collector->abstract_state() ==
2450 CMSCollector::Sweeping);
2451
2452 ResourceMark rm;
2453 HandleMark hm;
2454
2455 // Check integrity of CFL data structures
2456 _promoInfo.verify();
2457 _dictionary->verify();
2458 if (FLSVerifyIndexTable) {
2459 verifyIndexedFreeLists();
2460 }
2461 // Check integrity of all objects and free blocks in space
2462 {
2463 VerifyAllBlksClosure cl(this, span);
2464 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2465 }
2466 // Check that all references in the heap to FLS
2467 // are to valid objects in FLS or that references in
2468 // FLS are to valid objects elsewhere in the heap
2469 if (FLSVerifyAllHeapReferences)
2470 {
2471 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2472 _collector->markBitMap());
2473 CollectedHeap* ch = Universe::heap();
2474
2475 // Iterate over all oops in the heap. Uses the _no_header version
2476 // since we are not interested in following the klass pointers.
2477 ch->oop_iterate_no_header(&cl);
2478 }
2479
2480 if (VerifyObjectStartArray) {
2481 // Verify the block offset table
2482 _bt.verify();
2483 }
2484 }
2485
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
2501
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 }
2511
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->is_free(), "!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 }
2527
2528 #ifndef PRODUCT
2529 void CompactibleFreeListSpace::check_free_list_consistency() const {
2530 assert((TreeChunk<FreeChunk, AdaptiveFreeList>::min_size() <= IndexSetSize),
2531 "Some sizes can't be allocated without recourse to"
2532 " linear allocation buffers");
2533 assert((TreeChunk<FreeChunk, AdaptiveFreeList>::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList>)),
2534 "else MIN_TREE_CHUNK_SIZE is wrong");
2535 assert(IndexSetStart != 0, "IndexSetStart not initialized");
2536 assert(IndexSetStride != 0, "IndexSetStride not initialized");
2537 }
2538 #endif
2539
2540 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2541 assert_lock_strong(&_freelistLock);
2542 AdaptiveFreeList<FreeChunk> total;
2543 gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count);
2544 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size");
2545 size_t total_free = 0;
2546 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2547 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2548 total_free += fl->count() * fl->size();
2549 if (i % (40*IndexSetStride) == 0) {
2550 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size");
2551 }
2552 fl->print_on(gclog_or_tty);
2553 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
2554 total.set_surplus( total.surplus() + fl->surplus() );
2555 total.set_desired( total.desired() + fl->desired() );
2556 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
2557 total.set_before_sweep(total.before_sweep() + fl->before_sweep());
2558 total.set_count( total.count() + fl->count() );
2559 total.set_coal_births( total.coal_births() + fl->coal_births() );
2560 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
2561 total.set_split_births(total.split_births() + fl->split_births());
2562 total.set_split_deaths(total.split_deaths() + fl->split_deaths());
2563 }
2564 total.print_on(gclog_or_tty, "TOTAL");
2565 gclog_or_tty->print_cr("Total free in indexed lists "
2566 SIZE_FORMAT " words", total_free);
2567 gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n",
2568 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
2569 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
2570 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2571 _dictionary->print_dict_census();
2572 }
2573
2574 ///////////////////////////////////////////////////////////////////////////
2575 // CFLS_LAB
2576 ///////////////////////////////////////////////////////////////////////////
2577
2578 #define VECTOR_257(x) \
2579 /* 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 */ \
2580 { 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, \
2581 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, \
2582 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, \
2583 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, \
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 }
2589
2590 // Initialize with default setting of CMSParPromoteBlocksToClaim, _not_
2591 // OldPLABSize, whose static default is different; if overridden at the
2592 // command-line, this will get reinitialized via a call to
2593 // modify_initialization() below.
2594 AdaptiveWeightedAverage CFLS_LAB::_blocks_to_claim[] =
2595 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CMSParPromoteBlocksToClaim));
2596 size_t CFLS_LAB::_global_num_blocks[] = VECTOR_257(0);
2597 uint CFLS_LAB::_global_num_workers[] = VECTOR_257(0);
2598
2599 CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) :
2600 _cfls(cfls)
2601 {
2602 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2603 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2604 i < CompactibleFreeListSpace::IndexSetSize;
2605 i += CompactibleFreeListSpace::IndexSetStride) {
2606 _indexedFreeList[i].set_size(i);
2607 _num_blocks[i] = 0;
2608 }
2609 }
2610
2611 static bool _CFLS_LAB_modified = false;
2612
2613 void CFLS_LAB::modify_initialization(size_t n, unsigned wt) {
2614 assert(!_CFLS_LAB_modified, "Call only once");
2615 _CFLS_LAB_modified = true;
2616 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2617 i < CompactibleFreeListSpace::IndexSetSize;
2618 i += CompactibleFreeListSpace::IndexSetStride) {
2619 _blocks_to_claim[i].modify(n, wt, true /* force */);
2620 }
2621 }
2622
2623 HeapWord* CFLS_LAB::alloc(size_t word_sz) {
2624 FreeChunk* res;
2625 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2626 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2627 // This locking manages sync with other large object allocations.
2628 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2629 Mutex::_no_safepoint_check_flag);
2630 res = _cfls->getChunkFromDictionaryExact(word_sz);
2631 if (res == NULL) return NULL;
2632 } else {
2633 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
2634 if (fl->count() == 0) {
2635 // Attempt to refill this local free list.
2636 get_from_global_pool(word_sz, fl);
2637 // If it didn't work, give up.
2638 if (fl->count() == 0) return NULL;
2639 }
2640 res = fl->get_chunk_at_head();
2641 assert(res != NULL, "Why was count non-zero?");
2642 }
2643 res->markNotFree();
2644 assert(!res->is_free(), "shouldn't be marked free");
2645 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2646 // mangle a just allocated object with a distinct pattern.
2647 debug_only(res->mangleAllocated(word_sz));
2648 return (HeapWord*)res;
2649 }
2650
2651 // Get a chunk of blocks of the right size and update related
2652 // book-keeping stats
2653 void CFLS_LAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
2654 // Get the #blocks we want to claim
2655 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2656 assert(n_blks > 0, "Error");
2657 assert(ResizePLAB || n_blks == OldPLABSize, "Error");
2658 // In some cases, when the application has a phase change,
2659 // there may be a sudden and sharp shift in the object survival
2660 // profile, and updating the counts at the end of a scavenge
2661 // may not be quick enough, giving rise to large scavenge pauses
2662 // during these phase changes. It is beneficial to detect such
2663 // changes on-the-fly during a scavenge and avoid such a phase-change
2664 // pothole. The following code is a heuristic attempt to do that.
2665 // It is protected by a product flag until we have gained
2666 // enough experience with this heuristic and fine-tuned its behaviour.
2667 // WARNING: This might increase fragmentation if we overreact to
2668 // small spikes, so some kind of historical smoothing based on
2669 // previous experience with the greater reactivity might be useful.
2670 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2671 // default.
2672 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2673 size_t multiple = _num_blocks[word_sz]/(CMSOldPLABToleranceFactor*CMSOldPLABNumRefills*n_blks);
2674 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2675 n_blks = MIN2(n_blks, CMSOldPLABMax);
2676 }
2677 assert(n_blks > 0, "Error");
2678 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2679 // Update stats table entry for this block size
2680 _num_blocks[word_sz] += fl->count();
2681 }
2682
2683 void CFLS_LAB::compute_desired_plab_size() {
2684 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2685 i < CompactibleFreeListSpace::IndexSetSize;
2686 i += CompactibleFreeListSpace::IndexSetStride) {
2687 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2688 "Counter inconsistency");
2689 if (_global_num_workers[i] > 0) {
2690 // Need to smooth wrt historical average
2691 if (ResizeOldPLAB) {
2692 _blocks_to_claim[i].sample(
2693 MAX2((size_t)CMSOldPLABMin,
2694 MIN2((size_t)CMSOldPLABMax,
2695 _global_num_blocks[i]/(_global_num_workers[i]*CMSOldPLABNumRefills))));
2696 }
2697 // Reset counters for next round
2698 _global_num_workers[i] = 0;
2699 _global_num_blocks[i] = 0;
2700 if (PrintOldPLAB) {
2701 gclog_or_tty->print_cr("[%d]: %d", i, (size_t)_blocks_to_claim[i].average());
2702 }
2703 }
2704 }
2705 }
2706
2707 // If this is changed in the future to allow parallel
2708 // access, one would need to take the FL locks and,
2709 // depending on how it is used, stagger access from
2710 // parallel threads to reduce contention.
2711 void CFLS_LAB::retire(int tid) {
2712 // We run this single threaded with the world stopped;
2713 // so no need for locks and such.
2714 NOT_PRODUCT(Thread* t = Thread::current();)
2715 assert(Thread::current()->is_VM_thread(), "Error");
2716 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2717 i < CompactibleFreeListSpace::IndexSetSize;
2718 i += CompactibleFreeListSpace::IndexSetStride) {
2719 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2720 "Can't retire more than what we obtained");
2721 if (_num_blocks[i] > 0) {
2722 size_t num_retire = _indexedFreeList[i].count();
2723 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2724 {
2725 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2726 // Mutex::_no_safepoint_check_flag);
2727
2728 // Update globals stats for num_blocks used
2729 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2730 _global_num_workers[i]++;
2731 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2732 if (num_retire > 0) {
2733 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2734 // Reset this list.
2735 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
2736 _indexedFreeList[i].set_size(i);
2737 }
2738 }
2739 if (PrintOldPLAB) {
2740 gclog_or_tty->print_cr("%d[%d]: %d/%d/%d",
2741 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2742 }
2743 // Reset stats for next round
2744 _num_blocks[i] = 0;
2745 }
2746 }
2747 }
2748
2749 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2750 assert(fl->count() == 0, "Precondition.");
2751 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2752 "Precondition");
2753
2754 // We'll try all multiples of word_sz in the indexed set, starting with
2755 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2756 // then try getting a big chunk and splitting it.
2757 {
2758 bool found;
2759 int k;
2760 size_t cur_sz;
2761 for (k = 1, cur_sz = k * word_sz, found = false;
2762 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2763 (CMSSplitIndexedFreeListBlocks || k <= 1);
2764 k++, cur_sz = k * word_sz) {
2765 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
2766 fl_for_cur_sz.set_size(cur_sz);
2767 {
2768 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2769 Mutex::_no_safepoint_check_flag);
2770 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
2771 if (gfl->count() != 0) {
2772 // nn is the number of chunks of size cur_sz that
2773 // we'd need to split k-ways each, in order to create
2774 // "n" chunks of size word_sz each.
2775 const size_t nn = MAX2(n/k, (size_t)1);
2776 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2777 found = true;
2778 if (k > 1) {
2779 // Update split death stats for the cur_sz-size blocks list:
2780 // we increment the split death count by the number of blocks
2781 // we just took from the cur_sz-size blocks list and which
2782 // we will be splitting below.
2783 ssize_t deaths = gfl->split_deaths() +
2784 fl_for_cur_sz.count();
2785 gfl->set_split_deaths(deaths);
2786 }
2787 }
2788 }
2789 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2790 if (found) {
2791 if (k == 1) {
2792 fl->prepend(&fl_for_cur_sz);
2793 } else {
2794 // Divide each block on fl_for_cur_sz up k ways.
2795 FreeChunk* fc;
2796 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
2797 // Must do this in reverse order, so that anybody attempting to
2798 // access the main chunk sees it as a single free block until we
2799 // change it.
2800 size_t fc_size = fc->size();
2801 assert(fc->is_free(), "Error");
2802 for (int i = k-1; i >= 0; i--) {
2803 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2804 assert((i != 0) ||
2805 ((fc == ffc) && ffc->is_free() &&
2806 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2807 "Counting error");
2808 ffc->set_size(word_sz);
2809 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2810 ffc->link_next(NULL);
2811 // Above must occur before BOT is updated below.
2812 OrderAccess::storestore();
2813 // splitting from the right, fc_size == i * word_sz
2814 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2815 fc_size -= word_sz;
2816 assert(fc_size == i*word_sz, "Error");
2817 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2818 _bt.verify_single_block((HeapWord*)fc, fc_size);
2819 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2820 // Push this on "fl".
2821 //
2822 // Note: deallocate_pages=false (3rd arg). No need to
2823 // deallocate pages for the free chunk when it's returned
2824 // back to the free lists because the original free chunk
2825 // comes from the free lists and pages are already
2826 // deallocated. Since this function is called frequently
2827 // for each promotion of an object, this helps in speed by
2828 // avoiding unnecessary system calls
2829 // (os::deallocate_pages()). This applies to the other
2830 // returnChunk... calls in this function as well.
2831 fl->return_chunk_at_head(ffc, true, false);
2832 }
2833 // TRAP
2834 assert(fl->tail()->next() == NULL, "List invariant.");
2835 }
2836 }
2837 // Update birth stats for this block size.
2838 size_t num = fl->count();
2839 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2840 Mutex::_no_safepoint_check_flag);
2841 ssize_t births = _indexedFreeList[word_sz].split_births() + num;
2842 _indexedFreeList[word_sz].set_split_births(births);
2843 return;
2844 }
2845 }
2846 }
2847 // Otherwise, we'll split a block from the dictionary.
2848 FreeChunk* fc = NULL;
2849 FreeChunk* rem_fc = NULL;
2850 size_t rem;
2851 {
2852 MutexLockerEx x(parDictionaryAllocLock(),
2853 Mutex::_no_safepoint_check_flag);
2854 while (n > 0) {
2855 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()),
2856 FreeBlockDictionary<FreeChunk>::atLeast);
2857 if (fc != NULL) {
2858 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2859 dictionary()->dict_census_update(fc->size(),
2860 true /*split*/,
2861 false /*birth*/);
2862 break;
2863 } else {
2864 n--;
2865 }
2866 }
2867 if (fc == NULL) return;
2868 // Otherwise, split up that block.
2869 assert((ssize_t)n >= 1, "Control point invariant");
2870 assert(fc->is_free(), "Error: should be a free block");
2871 _bt.verify_single_block((HeapWord*)fc, fc->size());
2872 const size_t nn = fc->size() / word_sz;
2873 n = MIN2(nn, n);
2874 assert((ssize_t)n >= 1, "Control point invariant");
2875 rem = fc->size() - n * word_sz;
2876 // If there is a remainder, and it's too small, allocate one fewer.
2877 if (rem > 0 && rem < MinChunkSize) {
2878 n--; rem += word_sz;
2879 }
2880 // Note that at this point we may have n == 0.
2881 assert((ssize_t)n >= 0, "Control point invariant");
2882
2883 // If n is 0, the chunk fc that was found is not large
2884 // enough to leave a viable remainder. We are unable to
2885 // allocate even one block. Return fc to the
2886 // dictionary and return, leaving "fl" empty.
2887 if (n == 0) {
2888 returnChunkToDictionary(fc, false);
2889 assert(fl->count() == 0, "We never allocated any blocks");
2890 return;
2891 }
2892
2893 // First return the remainder, if any.
2894 // Note that we hold the lock until we decide if we're going to give
2895 // back the remainder to the dictionary, since a concurrent allocation
2896 // may otherwise see the heap as empty. (We're willing to take that
2897 // hit if the block is a small block.)
2898 if (rem > 0) {
2899 size_t prefix_size = n * word_sz;
2900 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2901 rem_fc->set_size(rem);
2902 rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2903 rem_fc->link_next(NULL);
2904 // Above must occur before BOT is updated below.
2905 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2906 OrderAccess::storestore();
2907 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2908 assert(fc->is_free(), "Error");
2909 fc->set_size(prefix_size);
2910 if (rem >= IndexSetSize) {
2911 returnChunkToDictionary(rem_fc, false);
2912 dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/);
2913 rem_fc = NULL;
2914 }
2915 // Otherwise, return it to the small list below.
2916 }
2917 }
2918 if (rem_fc != NULL) {
2919 MutexLockerEx x(_indexedFreeListParLocks[rem],
2920 Mutex::_no_safepoint_check_flag);
2921 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2922 _indexedFreeList[rem].return_chunk_at_head(rem_fc, true, false);
2923 smallSplitBirth(rem);
2924 }
2925 assert((ssize_t)n > 0 && fc != NULL, "Consistency");
2926 // Now do the splitting up.
2927 // Must do this in reverse order, so that anybody attempting to
2928 // access the main chunk sees it as a single free block until we
2929 // change it.
2930 size_t fc_size = n * word_sz;
2931 // All but first chunk in this loop
2932 for (ssize_t i = n-1; i > 0; i--) {
2933 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2934 ffc->set_size(word_sz);
2935 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2936 ffc->link_next(NULL);
2937 // Above must occur before BOT is updated below.
2938 OrderAccess::storestore();
2939 // splitting from the right, fc_size == (n - i + 1) * wordsize
2940 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2941 fc_size -= word_sz;
2942 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2943 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2944 _bt.verify_single_block((HeapWord*)fc, fc_size);
2945 // Push this on "fl".
2946 fl->return_chunk_at_head(ffc, true, false);
2947 }
2948 // First chunk
2949 assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block");
2950 // The blocks above should show their new sizes before the first block below
2951 fc->set_size(word_sz);
2952 fc->link_prev(NULL); // idempotent wrt free-ness, see assert above
2953 fc->link_next(NULL);
2954 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2955 _bt.verify_single_block((HeapWord*)fc, fc->size());
2956 fl->return_chunk_at_head(fc, true, false);
2957
2958 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2959 {
2960 // Update the stats for this block size.
2961 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2962 Mutex::_no_safepoint_check_flag);
2963 const ssize_t births = _indexedFreeList[word_sz].split_births() + n;
2964 _indexedFreeList[word_sz].set_split_births(births);
2965 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2966 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2967 }
2968
2969 // TRAP
2970 assert(fl->tail()->next() == NULL, "List invariant.");
2971 }
2972
2973 // Set up the space's par_seq_tasks structure for work claiming
2974 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2975 // XXX Need to suitably abstract and generalize this and the next
2976 // method into one.
2977 void
2978 CompactibleFreeListSpace::
2979 initialize_sequential_subtasks_for_rescan(int n_threads) {
2980 // The "size" of each task is fixed according to rescan_task_size.
2981 assert(n_threads > 0, "Unexpected n_threads argument");
2982 const size_t task_size = rescan_task_size();
2983 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2984 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2985 assert(n_tasks == 0 ||
2986 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2987 (used_region().start() + n_tasks*task_size >= used_region().end())),
2988 "n_tasks calculation incorrect");
2989 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2990 assert(!pst->valid(), "Clobbering existing data?");
2991 // Sets the condition for completion of the subtask (how many threads
2992 // need to finish in order to be done).
2993 pst->set_n_threads(n_threads);
2994 pst->set_n_tasks((int)n_tasks);
2995 }
2996
2997 // Set up the space's par_seq_tasks structure for work claiming
2998 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2999 void
3000 CompactibleFreeListSpace::
3001 initialize_sequential_subtasks_for_marking(int n_threads,
3002 HeapWord* low) {
3003 // The "size" of each task is fixed according to rescan_task_size.
3004 assert(n_threads > 0, "Unexpected n_threads argument");
3005 const size_t task_size = marking_task_size();
3006 assert(task_size > CardTableModRefBS::card_size_in_words &&
3007 (task_size % CardTableModRefBS::card_size_in_words == 0),
3008 "Otherwise arithmetic below would be incorrect");
3009 MemRegion span = _gen->reserved();
3010 if (low != NULL) {
3011 if (span.contains(low)) {
3012 // Align low down to a card boundary so that
3013 // we can use block_offset_careful() on span boundaries.
3014 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
3015 CardTableModRefBS::card_size);
3016 // Clip span prefix at aligned_low
3017 span = span.intersection(MemRegion(aligned_low, span.end()));
3018 } else if (low > span.end()) {
3019 span = MemRegion(low, low); // Null region
3020 } // else use entire span
3021 }
3022 assert(span.is_empty() ||
3023 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
3024 "span should start at a card boundary");
3025 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
3026 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
3027 assert(n_tasks == 0 ||
3028 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
3029 (span.start() + n_tasks*task_size >= span.end())),
3030 "n_tasks calculation incorrect");
3031 SequentialSubTasksDone* pst = conc_par_seq_tasks();
3032 assert(!pst->valid(), "Clobbering existing data?");
3033 // Sets the condition for completion of the subtask (how many threads
3034 // need to finish in order to be done).
3035 pst->set_n_threads(n_threads);
3036 pst->set_n_tasks((int)n_tasks);
3037 }