1 /*
2 * Copyright (c) 2001, 2013, 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 AFLBinaryTreeDictionary(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 FreeBlockDictionary<FreeChunk>::atLeast);
127 // The small linAB initially has all the space and will allocate
128 // a chunk of any size.
129 HeapWord* addr = (HeapWord*) fc;
130 _smallLinearAllocBlock.set(addr, fc->size() ,
131 1024*SmallForLinearAlloc, fc->size());
132 // Note that _unallocated_block is not updated here.
133 // Allocations from the linear allocation block should
134 // update it.
135 } else {
136 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
137 SmallForLinearAlloc);
138 }
139 // CMSIndexedFreeListReplenish should be at least 1
140 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
141 _promoInfo.setSpace(this);
142 if (UseCMSBestFit) {
143 _fitStrategy = FreeBlockBestFitFirst;
144 } else {
145 _fitStrategy = FreeBlockStrategyNone;
146 }
147 check_free_list_consistency();
148
149 // Initialize locks for parallel case.
150
151 if (CollectedHeap::use_parallel_gc_threads()) {
152 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
153 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
154 "a freelist par lock",
155 true);
156 if (_indexedFreeListParLocks[i] == NULL)
157 vm_exit_during_initialization("Could not allocate a par lock");
158 DEBUG_ONLY(
159 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
160 )
161 }
162 _dictionary->set_par_lock(&_parDictionaryAllocLock);
163 }
164 }
165
166 // Like CompactibleSpace forward() but always calls cross_threshold() to
167 // update the block offset table. Removed initialize_threshold call because
168 // CFLS does not use a block offset array for contiguous spaces.
169 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
170 CompactPoint* cp, HeapWord* compact_top) {
171 // q is alive
172 // First check if we should switch compaction space
173 assert(this == cp->space, "'this' should be current compaction space.");
174 size_t compaction_max_size = pointer_delta(end(), compact_top);
175 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
176 "virtual adjustObjectSize_v() method is not correct");
177 size_t adjusted_size = adjustObjectSize(size);
178 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
179 "no small fragments allowed");
180 assert(minimum_free_block_size() == MinChunkSize,
181 "for de-virtualized reference below");
182 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
183 if (adjusted_size + MinChunkSize > compaction_max_size &&
184 adjusted_size != compaction_max_size) {
185 do {
186 // switch to next compaction space
187 cp->space->set_compaction_top(compact_top);
188 cp->space = cp->space->next_compaction_space();
189 if (cp->space == NULL) {
190 cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen);
191 assert(cp->gen != NULL, "compaction must succeed");
192 cp->space = cp->gen->first_compaction_space();
193 assert(cp->space != NULL, "generation must have a first compaction space");
194 }
195 compact_top = cp->space->bottom();
196 cp->space->set_compaction_top(compact_top);
197 // The correct adjusted_size may not be the same as that for this method
198 // (i.e., cp->space may no longer be "this" so adjust the size again.
199 // Use the virtual method which is not used above to save the virtual
200 // dispatch.
201 adjusted_size = cp->space->adjust_object_size_v(size);
202 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
203 assert(cp->space->minimum_free_block_size() == 0, "just checking");
204 } while (adjusted_size > compaction_max_size);
205 }
206
207 // store the forwarding pointer into the mark word
208 if ((HeapWord*)q != compact_top) {
209 q->forward_to(oop(compact_top));
210 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
211 } else {
212 // if the object isn't moving we can just set the mark to the default
213 // mark and handle it specially later on.
214 q->init_mark();
215 assert(q->forwardee() == NULL, "should be forwarded to NULL");
216 }
217
218 compact_top += adjusted_size;
219
220 // we need to update the offset table so that the beginnings of objects can be
221 // found during scavenge. Note that we are updating the offset table based on
222 // where the object will be once the compaction phase finishes.
223
224 // Always call cross_threshold(). A contiguous space can only call it when
225 // the compaction_top exceeds the current threshold but not for an
226 // non-contiguous space.
227 cp->threshold =
228 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
229 return compact_top;
230 }
231
232 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
233 // and use of single_block instead of alloc_block. The name here is not really
234 // appropriate - maybe a more general name could be invented for both the
235 // contiguous and noncontiguous spaces.
236
237 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
238 _bt.single_block(start, the_end);
239 return end();
240 }
241
242 // Initialize them to NULL.
243 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
244 for (size_t i = 0; i < IndexSetSize; i++) {
245 // Note that on platforms where objects are double word aligned,
246 // the odd array elements are not used. It is convenient, however,
247 // to map directly from the object size to the array element.
248 _indexedFreeList[i].reset(IndexSetSize);
249 _indexedFreeList[i].set_size(i);
250 assert(_indexedFreeList[i].count() == 0, "reset check failed");
251 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
252 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
253 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
254 }
255 }
256
257 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
258 for (size_t i = 1; i < IndexSetSize; i++) {
259 assert(_indexedFreeList[i].size() == (size_t) i,
260 "Indexed free list sizes are incorrect");
261 _indexedFreeList[i].reset(IndexSetSize);
262 assert(_indexedFreeList[i].count() == 0, "reset check failed");
263 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
264 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
265 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
266 }
267 }
268
269 void CompactibleFreeListSpace::reset(MemRegion mr) {
270 resetIndexedFreeListArray();
271 dictionary()->reset();
272 if (BlockOffsetArrayUseUnallocatedBlock) {
273 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
274 // Everything's allocated until proven otherwise.
275 _bt.set_unallocated_block(end());
276 }
277 if (!mr.is_empty()) {
278 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
279 _bt.single_block(mr.start(), mr.word_size());
280 FreeChunk* fc = (FreeChunk*) mr.start();
281 fc->set_size(mr.word_size());
282 if (mr.word_size() >= IndexSetSize ) {
283 returnChunkToDictionary(fc);
284 } else {
285 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
286 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc);
287 }
288 }
289 _promoInfo.reset();
290 _smallLinearAllocBlock._ptr = NULL;
291 _smallLinearAllocBlock._word_size = 0;
292 }
293
294 void CompactibleFreeListSpace::reset_after_compaction() {
295 // Reset the space to the new reality - one free chunk.
296 MemRegion mr(compaction_top(), end());
297 reset(mr);
298 // Now refill the linear allocation block(s) if possible.
299 if (_adaptive_freelists) {
300 refillLinearAllocBlocksIfNeeded();
301 } else {
302 // Place as much of mr in the linAB as we can get,
303 // provided it was big enough to go into the dictionary.
304 FreeChunk* fc = dictionary()->find_largest_dict();
305 if (fc != NULL) {
306 assert(fc->size() == mr.word_size(),
307 "Why was the chunk broken up?");
308 removeChunkFromDictionary(fc);
309 HeapWord* addr = (HeapWord*) fc;
310 _smallLinearAllocBlock.set(addr, fc->size() ,
311 1024*SmallForLinearAlloc, fc->size());
312 // Note that _unallocated_block is not updated here.
313 }
314 }
315 }
316
317 // Walks the entire dictionary, returning a coterminal
318 // chunk, if it exists. Use with caution since it involves
319 // a potentially complete walk of a potentially large tree.
320 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
321
322 assert_lock_strong(&_freelistLock);
323
324 return dictionary()->find_chunk_ends_at(end());
325 }
326
327
328 #ifndef PRODUCT
329 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
330 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
331 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
332 }
333 }
334
335 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
336 size_t sum = 0;
337 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
338 sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
339 }
340 return sum;
341 }
342
343 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
344 size_t count = 0;
345 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
346 debug_only(
347 ssize_t total_list_count = 0;
348 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
349 fc = fc->next()) {
350 total_list_count++;
351 }
352 assert(total_list_count == _indexedFreeList[i].count(),
353 "Count in list is incorrect");
354 )
355 count += _indexedFreeList[i].count();
356 }
357 return count;
358 }
359
360 size_t CompactibleFreeListSpace::totalCount() {
361 size_t num = totalCountInIndexedFreeLists();
362 num += dictionary()->total_count();
363 if (_smallLinearAllocBlock._word_size != 0) {
364 num++;
365 }
366 return num;
367 }
368 #endif
369
370 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
371 FreeChunk* fc = (FreeChunk*) p;
372 return fc->is_free();
373 }
374
375 size_t CompactibleFreeListSpace::used() const {
376 return capacity() - free();
377 }
378
379 size_t CompactibleFreeListSpace::free() const {
380 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
381 // if you do this while the structures are in flux you
382 // may get an approximate answer only; for instance
383 // because there is concurrent allocation either
384 // directly by mutators or for promotion during a GC.
385 // It's "MT-safe", however, in the sense that you are guaranteed
386 // not to crash and burn, for instance, because of walking
387 // pointers that could disappear as you were walking them.
388 // The approximation is because the various components
389 // that are read below are not read atomically (and
390 // further the computation of totalSizeInIndexedFreeLists()
391 // is itself a non-atomic computation. The normal use of
392 // this is during a resize operation at the end of GC
393 // and at that time you are guaranteed to get the
394 // correct actual value. However, for instance, this is
395 // also read completely asynchronously by the "perf-sampler"
396 // that supports jvmstat, and you are apt to see the values
397 // flicker in such cases.
398 assert(_dictionary != NULL, "No _dictionary?");
399 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
400 totalSizeInIndexedFreeLists() +
401 _smallLinearAllocBlock._word_size) * HeapWordSize;
402 }
403
404 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
405 assert(_dictionary != NULL, "No _dictionary?");
406 assert_locked();
407 size_t res = _dictionary->max_chunk_size();
408 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
409 (size_t) SmallForLinearAlloc - 1));
410 // XXX the following could potentially be pretty slow;
411 // should one, pesimally for the rare cases when res
412 // caclulated above is less than IndexSetSize,
413 // just return res calculated above? My reasoning was that
414 // those cases will be so rare that the extra time spent doesn't
415 // really matter....
416 // Note: do not change the loop test i >= res + IndexSetStride
417 // to i > res below, because i is unsigned and res may be zero.
418 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
419 i -= IndexSetStride) {
420 if (_indexedFreeList[i].head() != NULL) {
421 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
422 return i;
423 }
424 }
425 return res;
426 }
427
428 void LinearAllocBlock::print_on(outputStream* st) const {
429 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
430 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
431 _ptr, _word_size, _refillSize, _allocation_size_limit);
432 }
433
434 void CompactibleFreeListSpace::print_on(outputStream* st) const {
435 st->print_cr("COMPACTIBLE FREELIST SPACE");
436 st->print_cr(" Space:");
437 Space::print_on(st);
438
439 st->print_cr("promoInfo:");
440 _promoInfo.print_on(st);
441
442 st->print_cr("_smallLinearAllocBlock");
443 _smallLinearAllocBlock.print_on(st);
444
445 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
446
447 st->print_cr(" _fitStrategy = %s, _adaptive_freelists = %s",
448 _fitStrategy?"true":"false", _adaptive_freelists?"true":"false");
449 }
450
451 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
452 const {
453 reportIndexedFreeListStatistics();
454 gclog_or_tty->print_cr("Layout of Indexed Freelists");
455 gclog_or_tty->print_cr("---------------------------");
456 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
457 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
458 _indexedFreeList[i].print_on(gclog_or_tty);
459 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
460 fc = fc->next()) {
461 gclog_or_tty->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
462 fc, (HeapWord*)fc + i,
463 fc->cantCoalesce() ? "\t CC" : "");
464 }
465 }
466 }
467
468 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
469 const {
470 _promoInfo.print_on(st);
471 }
472
473 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
474 const {
475 _dictionary->report_statistics();
476 st->print_cr("Layout of Freelists in Tree");
477 st->print_cr("---------------------------");
478 _dictionary->print_free_lists(st);
479 }
480
481 class BlkPrintingClosure: public BlkClosure {
482 const CMSCollector* _collector;
483 const CompactibleFreeListSpace* _sp;
484 const CMSBitMap* _live_bit_map;
485 const bool _post_remark;
486 outputStream* _st;
487 public:
488 BlkPrintingClosure(const CMSCollector* collector,
489 const CompactibleFreeListSpace* sp,
490 const CMSBitMap* live_bit_map,
491 outputStream* st):
492 _collector(collector),
493 _sp(sp),
494 _live_bit_map(live_bit_map),
495 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
496 _st(st) { }
497 size_t do_blk(HeapWord* addr);
498 };
499
500 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
501 size_t sz = _sp->block_size_no_stall(addr, _collector);
502 assert(sz != 0, "Should always be able to compute a size");
503 if (_sp->block_is_obj(addr)) {
504 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
505 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
506 addr,
507 dead ? "dead" : "live",
508 sz,
509 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
510 if (CMSPrintObjectsInDump && !dead) {
511 oop(addr)->print_on(_st);
512 _st->print_cr("--------------------------------------");
513 }
514 } else { // free block
515 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
516 addr, sz, CMSPrintChunksInDump ? ":" : ".");
517 if (CMSPrintChunksInDump) {
518 ((FreeChunk*)addr)->print_on(_st);
519 _st->print_cr("--------------------------------------");
520 }
521 }
522 return sz;
523 }
524
525 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c,
526 outputStream* st) {
527 st->print_cr("\n=========================");
528 st->print_cr("Block layout in CMS Heap:");
529 st->print_cr("=========================");
530 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
531 blk_iterate(&bpcl);
532
533 st->print_cr("\n=======================================");
534 st->print_cr("Order & Layout of Promotion Info Blocks");
535 st->print_cr("=======================================");
536 print_promo_info_blocks(st);
537
538 st->print_cr("\n===========================");
539 st->print_cr("Order of Indexed Free Lists");
540 st->print_cr("=========================");
541 print_indexed_free_lists(st);
542
543 st->print_cr("\n=================================");
544 st->print_cr("Order of Free Lists in Dictionary");
545 st->print_cr("=================================");
546 print_dictionary_free_lists(st);
547 }
548
549
550 void CompactibleFreeListSpace::reportFreeListStatistics() const {
551 assert_lock_strong(&_freelistLock);
552 assert(PrintFLSStatistics != 0, "Reporting error");
553 _dictionary->report_statistics();
554 if (PrintFLSStatistics > 1) {
555 reportIndexedFreeListStatistics();
556 size_t total_size = totalSizeInIndexedFreeLists() +
557 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
558 gclog_or_tty->print(" free=" SIZE_FORMAT " frag=%1.4f\n", total_size, flsFrag());
559 }
560 }
561
562 void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const {
563 assert_lock_strong(&_freelistLock);
564 gclog_or_tty->print("Statistics for IndexedFreeLists:\n"
565 "--------------------------------\n");
566 size_t total_size = totalSizeInIndexedFreeLists();
567 size_t free_blocks = numFreeBlocksInIndexedFreeLists();
568 gclog_or_tty->print("Total Free Space: %d\n", total_size);
569 gclog_or_tty->print("Max Chunk Size: %d\n", maxChunkSizeInIndexedFreeLists());
570 gclog_or_tty->print("Number of Blocks: %d\n", free_blocks);
571 if (free_blocks != 0) {
572 gclog_or_tty->print("Av. Block Size: %d\n", total_size/free_blocks);
573 }
574 }
575
576 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
577 size_t res = 0;
578 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
579 debug_only(
580 ssize_t recount = 0;
581 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
582 fc = fc->next()) {
583 recount += 1;
584 }
585 assert(recount == _indexedFreeList[i].count(),
586 "Incorrect count in list");
587 )
588 res += _indexedFreeList[i].count();
589 }
590 return res;
591 }
592
593 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
594 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
595 if (_indexedFreeList[i].head() != NULL) {
596 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
597 return (size_t)i;
598 }
599 }
600 return 0;
601 }
602
603 void CompactibleFreeListSpace::set_end(HeapWord* value) {
604 HeapWord* prevEnd = end();
605 assert(prevEnd != value, "unnecessary set_end call");
606 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
607 "New end is below unallocated block");
608 _end = value;
609 if (prevEnd != NULL) {
610 // Resize the underlying block offset table.
611 _bt.resize(pointer_delta(value, bottom()));
612 if (value <= prevEnd) {
613 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
614 "New end is below unallocated block");
615 } else {
616 // Now, take this new chunk and add it to the free blocks.
617 // Note that the BOT has not yet been updated for this block.
618 size_t newFcSize = pointer_delta(value, prevEnd);
619 // XXX This is REALLY UGLY and should be fixed up. XXX
620 if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) {
621 // Mark the boundary of the new block in BOT
622 _bt.mark_block(prevEnd, value);
623 // put it all in the linAB
624 if (ParallelGCThreads == 0) {
625 _smallLinearAllocBlock._ptr = prevEnd;
626 _smallLinearAllocBlock._word_size = newFcSize;
627 repairLinearAllocBlock(&_smallLinearAllocBlock);
628 } else { // ParallelGCThreads > 0
629 MutexLockerEx x(parDictionaryAllocLock(),
630 Mutex::_no_safepoint_check_flag);
631 _smallLinearAllocBlock._ptr = prevEnd;
632 _smallLinearAllocBlock._word_size = newFcSize;
633 repairLinearAllocBlock(&_smallLinearAllocBlock);
634 }
635 // Births of chunks put into a LinAB are not recorded. Births
636 // of chunks as they are allocated out of a LinAB are.
637 } else {
638 // Add the block to the free lists, if possible coalescing it
639 // with the last free block, and update the BOT and census data.
640 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
641 }
642 }
643 }
644 }
645
646 class FreeListSpace_DCTOC : public Filtering_DCTOC {
647 CompactibleFreeListSpace* _cfls;
648 CMSCollector* _collector;
649 protected:
650 // Override.
651 #define walk_mem_region_with_cl_DECL(ClosureType) \
652 virtual void walk_mem_region_with_cl(MemRegion mr, \
653 HeapWord* bottom, HeapWord* top, \
654 ClosureType* cl); \
655 void walk_mem_region_with_cl_par(MemRegion mr, \
656 HeapWord* bottom, HeapWord* top, \
657 ClosureType* cl); \
658 void walk_mem_region_with_cl_nopar(MemRegion mr, \
659 HeapWord* bottom, HeapWord* top, \
660 ClosureType* cl)
661 walk_mem_region_with_cl_DECL(ExtendedOopClosure);
662 walk_mem_region_with_cl_DECL(FilteringClosure);
663
664 public:
665 FreeListSpace_DCTOC(CompactibleFreeListSpace* sp,
666 CMSCollector* collector,
667 ExtendedOopClosure* cl,
668 CardTableModRefBS::PrecisionStyle precision,
669 HeapWord* boundary) :
670 Filtering_DCTOC(sp, cl, precision, boundary),
671 _cfls(sp), _collector(collector) {}
672 };
673
674 // We de-virtualize the block-related calls below, since we know that our
675 // space is a CompactibleFreeListSpace.
676
677 #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
678 void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \
679 HeapWord* bottom, \
680 HeapWord* top, \
681 ClosureType* cl) { \
682 bool is_par = SharedHeap::heap()->n_par_threads() > 0; \
683 if (is_par) { \
684 assert(SharedHeap::heap()->n_par_threads() == \
685 SharedHeap::heap()->workers()->active_workers(), "Mismatch"); \
686 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
687 } else { \
688 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
689 } \
690 } \
691 void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
692 HeapWord* bottom, \
693 HeapWord* top, \
694 ClosureType* cl) { \
695 /* Skip parts that are before "mr", in case "block_start" sent us \
696 back too far. */ \
697 HeapWord* mr_start = mr.start(); \
698 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
699 HeapWord* next = bottom + bot_size; \
700 while (next < mr_start) { \
701 bottom = next; \
702 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
703 next = bottom + bot_size; \
704 } \
705 \
706 while (bottom < top) { \
707 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
708 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
709 oop(bottom)) && \
710 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
711 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
712 bottom += _cfls->adjustObjectSize(word_sz); \
713 } else { \
714 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
715 } \
716 } \
717 } \
718 void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
719 HeapWord* bottom, \
720 HeapWord* top, \
721 ClosureType* cl) { \
722 /* Skip parts that are before "mr", in case "block_start" sent us \
723 back too far. */ \
724 HeapWord* mr_start = mr.start(); \
725 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
726 HeapWord* next = bottom + bot_size; \
727 while (next < mr_start) { \
728 bottom = next; \
729 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
730 next = bottom + bot_size; \
731 } \
732 \
733 while (bottom < top) { \
734 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
735 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
736 oop(bottom)) && \
737 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
738 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
739 bottom += _cfls->adjustObjectSize(word_sz); \
740 } else { \
741 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
742 } \
743 } \
744 }
745
746 // (There are only two of these, rather than N, because the split is due
747 // only to the introduction of the FilteringClosure, a local part of the
748 // impl of this abstraction.)
749 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
750 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
751
752 DirtyCardToOopClosure*
753 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl,
754 CardTableModRefBS::PrecisionStyle precision,
755 HeapWord* boundary) {
756 return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary);
757 }
758
759
760 // Note on locking for the space iteration functions:
761 // since the collector's iteration activities are concurrent with
762 // allocation activities by mutators, absent a suitable mutual exclusion
763 // mechanism the iterators may go awry. For instace a block being iterated
764 // may suddenly be allocated or divided up and part of it allocated and
765 // so on.
766
767 // Apply the given closure to each block in the space.
768 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
769 assert_lock_strong(freelistLock());
770 HeapWord *cur, *limit;
771 for (cur = bottom(), limit = end(); cur < limit;
772 cur += cl->do_blk_careful(cur));
773 }
774
775 // Apply the given closure to each block in the space.
776 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
777 assert_lock_strong(freelistLock());
778 HeapWord *cur, *limit;
779 for (cur = bottom(), limit = end(); cur < limit;
780 cur += cl->do_blk(cur));
781 }
782
783 // Apply the given closure to each oop in the space.
784 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) {
785 assert_lock_strong(freelistLock());
786 HeapWord *cur, *limit;
787 size_t curSize;
788 for (cur = bottom(), limit = end(); cur < limit;
789 cur += curSize) {
790 curSize = block_size(cur);
791 if (block_is_obj(cur)) {
792 oop(cur)->oop_iterate(cl);
793 }
794 }
795 }
796
797 // Apply the given closure to each oop in the space \intersect memory region.
798 void CompactibleFreeListSpace::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
799 assert_lock_strong(freelistLock());
800 if (is_empty()) {
801 return;
802 }
803 MemRegion cur = MemRegion(bottom(), end());
804 mr = mr.intersection(cur);
805 if (mr.is_empty()) {
806 return;
807 }
808 if (mr.equals(cur)) {
809 oop_iterate(cl);
810 return;
811 }
812 assert(mr.end() <= end(), "just took an intersection above");
813 HeapWord* obj_addr = block_start(mr.start());
814 HeapWord* t = mr.end();
815
816 SpaceMemRegionOopsIterClosure smr_blk(cl, mr);
817 if (block_is_obj(obj_addr)) {
818 // Handle first object specially.
819 oop obj = oop(obj_addr);
820 obj_addr += adjustObjectSize(obj->oop_iterate(&smr_blk));
821 } else {
822 FreeChunk* fc = (FreeChunk*)obj_addr;
823 obj_addr += fc->size();
824 }
825 while (obj_addr < t) {
826 HeapWord* obj = obj_addr;
827 obj_addr += block_size(obj_addr);
828 // If "obj_addr" is not greater than top, then the
829 // entire object "obj" is within the region.
830 if (obj_addr <= t) {
831 if (block_is_obj(obj)) {
832 oop(obj)->oop_iterate(cl);
833 }
834 } else {
835 // "obj" extends beyond end of region
836 if (block_is_obj(obj)) {
837 oop(obj)->oop_iterate(&smr_blk);
838 }
839 break;
840 }
841 }
842 }
843
844 // NOTE: In the following methods, in order to safely be able to
845 // apply the closure to an object, we need to be sure that the
846 // object has been initialized. We are guaranteed that an object
847 // is initialized if we are holding the Heap_lock with the
848 // world stopped.
849 void CompactibleFreeListSpace::verify_objects_initialized() const {
850 if (is_init_completed()) {
851 assert_locked_or_safepoint(Heap_lock);
852 if (Universe::is_fully_initialized()) {
853 guarantee(SafepointSynchronize::is_at_safepoint(),
854 "Required for objects to be initialized");
855 }
856 } // else make a concession at vm start-up
857 }
858
859 // Apply the given closure to each object in the space
860 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
861 assert_lock_strong(freelistLock());
862 NOT_PRODUCT(verify_objects_initialized());
863 HeapWord *cur, *limit;
864 size_t curSize;
865 for (cur = bottom(), limit = end(); cur < limit;
866 cur += curSize) {
867 curSize = block_size(cur);
868 if (block_is_obj(cur)) {
869 blk->do_object(oop(cur));
870 }
871 }
872 }
873
874 // Apply the given closure to each live object in the space
875 // The usage of CompactibleFreeListSpace
876 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
877 // objects in the space with references to objects that are no longer
878 // valid. For example, an object may reference another object
879 // that has already been sweep up (collected). This method uses
880 // obj_is_alive() to determine whether it is safe to apply the closure to
881 // an object. See obj_is_alive() for details on how liveness of an
882 // object is decided.
883
884 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
885 assert_lock_strong(freelistLock());
886 NOT_PRODUCT(verify_objects_initialized());
887 HeapWord *cur, *limit;
888 size_t curSize;
889 for (cur = bottom(), limit = end(); cur < limit;
890 cur += curSize) {
891 curSize = block_size(cur);
892 if (block_is_obj(cur) && obj_is_alive(cur)) {
893 blk->do_object(oop(cur));
894 }
895 }
896 }
897
898 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
899 UpwardsObjectClosure* cl) {
900 assert_locked(freelistLock());
901 NOT_PRODUCT(verify_objects_initialized());
902 Space::object_iterate_mem(mr, cl);
903 }
904
905 // Callers of this iterator beware: The closure application should
906 // be robust in the face of uninitialized objects and should (always)
907 // return a correct size so that the next addr + size below gives us a
908 // valid block boundary. [See for instance,
909 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
910 // in ConcurrentMarkSweepGeneration.cpp.]
911 HeapWord*
912 CompactibleFreeListSpace::object_iterate_careful(ObjectClosureCareful* cl) {
913 assert_lock_strong(freelistLock());
914 HeapWord *addr, *last;
915 size_t size;
916 for (addr = bottom(), last = end();
917 addr < last; addr += size) {
918 FreeChunk* fc = (FreeChunk*)addr;
919 if (fc->is_free()) {
920 // Since we hold the free list lock, which protects direct
921 // allocation in this generation by mutators, a free object
922 // will remain free throughout this iteration code.
923 size = fc->size();
924 } else {
925 // Note that the object need not necessarily be initialized,
926 // because (for instance) the free list lock does NOT protect
927 // object initialization. The closure application below must
928 // therefore be correct in the face of uninitialized objects.
929 size = cl->do_object_careful(oop(addr));
930 if (size == 0) {
931 // An unparsable object found. Signal early termination.
932 return addr;
933 }
934 }
935 }
936 return NULL;
937 }
938
939 // Callers of this iterator beware: The closure application should
940 // be robust in the face of uninitialized objects and should (always)
941 // return a correct size so that the next addr + size below gives us a
942 // valid block boundary. [See for instance,
943 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
944 // in ConcurrentMarkSweepGeneration.cpp.]
945 HeapWord*
946 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
947 ObjectClosureCareful* cl) {
948 assert_lock_strong(freelistLock());
949 // Can't use used_region() below because it may not necessarily
950 // be the same as [bottom(),end()); although we could
951 // use [used_region().start(),round_to(used_region().end(),CardSize)),
952 // that appears too cumbersome, so we just do the simpler check
953 // in the assertion below.
954 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
955 "mr should be non-empty and within used space");
956 HeapWord *addr, *end;
957 size_t size;
958 for (addr = block_start_careful(mr.start()), end = mr.end();
959 addr < end; addr += size) {
960 FreeChunk* fc = (FreeChunk*)addr;
961 if (fc->is_free()) {
962 // Since we hold the free list lock, which protects direct
963 // allocation in this generation by mutators, a free object
964 // will remain free throughout this iteration code.
965 size = fc->size();
966 } else {
967 // Note that the object need not necessarily be initialized,
968 // because (for instance) the free list lock does NOT protect
969 // object initialization. The closure application below must
970 // therefore be correct in the face of uninitialized objects.
971 size = cl->do_object_careful_m(oop(addr), mr);
972 if (size == 0) {
973 // An unparsable object found. Signal early termination.
974 return addr;
975 }
976 }
977 }
978 return NULL;
979 }
980
981
982 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
983 NOT_PRODUCT(verify_objects_initialized());
984 return _bt.block_start(p);
985 }
986
987 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
988 return _bt.block_start_careful(p);
989 }
990
991 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
992 NOT_PRODUCT(verify_objects_initialized());
993 // This must be volatile, or else there is a danger that the compiler
994 // will compile the code below into a sometimes-infinite loop, by keeping
995 // the value read the first time in a register.
996 while (true) {
997 // We must do this until we get a consistent view of the object.
998 if (FreeChunk::indicatesFreeChunk(p)) {
999 volatile FreeChunk* fc = (volatile FreeChunk*)p;
1000 size_t res = fc->size();
1001 // If the object is still a free chunk, return the size, else it
1002 // has been allocated so try again.
1003 if (FreeChunk::indicatesFreeChunk(p)) {
1004 assert(res != 0, "Block size should not be 0");
1005 return res;
1006 }
1007 } else {
1008 // must read from what 'p' points to in each loop.
1009 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
1010 if (k != NULL) {
1011 assert(k->is_klass(), "Should really be klass oop.");
1012 oop o = (oop)p;
1013 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
1014 size_t res = o->size_given_klass(k);
1015 res = adjustObjectSize(res);
1016 assert(res != 0, "Block size should not be 0");
1017 return res;
1018 }
1019 }
1020 }
1021 }
1022
1023 // TODO: Now that is_parsable is gone, we should combine these two functions.
1024 // A variant of the above that uses the Printezis bits for
1025 // unparsable but allocated objects. This avoids any possible
1026 // stalls waiting for mutators to initialize objects, and is
1027 // thus potentially faster than the variant above. However,
1028 // this variant may return a zero size for a block that is
1029 // under mutation and for which a consistent size cannot be
1030 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
1031 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
1032 const CMSCollector* c)
1033 const {
1034 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1035 // This must be volatile, or else there is a danger that the compiler
1036 // will compile the code below into a sometimes-infinite loop, by keeping
1037 // the value read the first time in a register.
1038 DEBUG_ONLY(uint loops = 0;)
1039 while (true) {
1040 // We must do this until we get a consistent view of the object.
1041 if (FreeChunk::indicatesFreeChunk(p)) {
1042 volatile FreeChunk* fc = (volatile FreeChunk*)p;
1043 size_t res = fc->size();
1044 if (FreeChunk::indicatesFreeChunk(p)) {
1045 assert(res != 0, "Block size should not be 0");
1046 assert(loops == 0, "Should be 0");
1047 return res;
1048 }
1049 } else {
1050 // must read from what 'p' points to in each loop.
1051 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
1052 // We trust the size of any object that has a non-NULL
1053 // klass and (for those in the perm gen) is parsable
1054 // -- irrespective of its conc_safe-ty.
1055 if (k != NULL) {
1056 assert(k->is_klass(), "Should really be klass oop.");
1057 oop o = (oop)p;
1058 assert(o->is_oop(), "Should be an oop");
1059 size_t res = o->size_given_klass(k);
1060 res = adjustObjectSize(res);
1061 assert(res != 0, "Block size should not be 0");
1062 return res;
1063 } else {
1064 // May return 0 if P-bits not present.
1065 return c->block_size_if_printezis_bits(p);
1066 }
1067 }
1068 assert(loops == 0, "Can loop at most once");
1069 DEBUG_ONLY(loops++;)
1070 }
1071 }
1072
1073 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1074 NOT_PRODUCT(verify_objects_initialized());
1075 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1076 FreeChunk* fc = (FreeChunk*)p;
1077 if (fc->is_free()) {
1078 return fc->size();
1079 } else {
1080 // Ignore mark word because this may be a recently promoted
1081 // object whose mark word is used to chain together grey
1082 // objects (the last one would have a null value).
1083 assert(oop(p)->is_oop(true), "Should be an oop");
1084 return adjustObjectSize(oop(p)->size());
1085 }
1086 }
1087
1088 // This implementation assumes that the property of "being an object" is
1089 // stable. But being a free chunk may not be (because of parallel
1090 // promotion.)
1091 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1092 FreeChunk* fc = (FreeChunk*)p;
1093 assert(is_in_reserved(p), "Should be in space");
1094 // When doing a mark-sweep-compact of the CMS generation, this
1095 // assertion may fail because prepare_for_compaction() uses
1096 // space that is garbage to maintain information on ranges of
1097 // live objects so that these live ranges can be moved as a whole.
1098 // Comment out this assertion until that problem can be solved
1099 // (i.e., that the block start calculation may look at objects
1100 // at address below "p" in finding the object that contains "p"
1101 // and those objects (if garbage) may have been modified to hold
1102 // live range information.
1103 // assert(CollectedHeap::use_parallel_gc_threads() || _bt.block_start(p) == p,
1104 // "Should be a block boundary");
1105 if (FreeChunk::indicatesFreeChunk(p)) return false;
1106 Klass* k = oop(p)->klass_or_null();
1107 if (k != NULL) {
1108 // Ignore mark word because it may have been used to
1109 // chain together promoted objects (the last one
1110 // would have a null value).
1111 assert(oop(p)->is_oop(true), "Should be an oop");
1112 return true;
1113 } else {
1114 return false; // Was not an object at the start of collection.
1115 }
1116 }
1117
1118 // Check if the object is alive. This fact is checked either by consulting
1119 // the main marking bitmap in the sweeping phase or, if it's a permanent
1120 // generation and we're not in the sweeping phase, by checking the
1121 // perm_gen_verify_bit_map where we store the "deadness" information if
1122 // we did not sweep the perm gen in the most recent previous GC cycle.
1123 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1124 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1125 "Else races are possible");
1126 assert(block_is_obj(p), "The address should point to an object");
1127
1128 // If we're sweeping, we use object liveness information from the main bit map
1129 // for both perm gen and old gen.
1130 // We don't need to lock the bitmap (live_map or dead_map below), because
1131 // EITHER we are in the middle of the sweeping phase, and the
1132 // main marking bit map (live_map below) is locked,
1133 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1134 // is stable, because it's mutated only in the sweeping phase.
1135 // NOTE: This method is also used by jmap where, if class unloading is
1136 // off, the results can return "false" for legitimate perm objects,
1137 // when we are not in the midst of a sweeping phase, which can result
1138 // in jmap not reporting certain perm gen objects. This will be moot
1139 // if/when the perm gen goes away in the future.
1140 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1141 CMSBitMap* live_map = _collector->markBitMap();
1142 return live_map->par_isMarked((HeapWord*) p);
1143 }
1144 return true;
1145 }
1146
1147 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1148 FreeChunk* fc = (FreeChunk*)p;
1149 assert(is_in_reserved(p), "Should be in space");
1150 assert(_bt.block_start(p) == p, "Should be a block boundary");
1151 if (!fc->is_free()) {
1152 // Ignore mark word because it may have been used to
1153 // chain together promoted objects (the last one
1154 // would have a null value).
1155 assert(oop(p)->is_oop(true), "Should be an oop");
1156 return true;
1157 }
1158 return false;
1159 }
1160
1161 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1162 // approximate answer if you don't hold the freelistlock when you call this.
1163 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1164 size_t size = 0;
1165 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1166 debug_only(
1167 // We may be calling here without the lock in which case we
1168 // won't do this modest sanity check.
1169 if (freelistLock()->owned_by_self()) {
1170 size_t total_list_size = 0;
1171 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1172 fc = fc->next()) {
1173 total_list_size += i;
1174 }
1175 assert(total_list_size == i * _indexedFreeList[i].count(),
1176 "Count in list is incorrect");
1177 }
1178 )
1179 size += i * _indexedFreeList[i].count();
1180 }
1181 return size;
1182 }
1183
1184 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1185 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1186 return allocate(size);
1187 }
1188
1189 HeapWord*
1190 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1191 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1192 }
1193
1194 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1195 assert_lock_strong(freelistLock());
1196 HeapWord* res = NULL;
1197 assert(size == adjustObjectSize(size),
1198 "use adjustObjectSize() before calling into allocate()");
1199
1200 if (_adaptive_freelists) {
1201 res = allocate_adaptive_freelists(size);
1202 } else { // non-adaptive free lists
1203 res = allocate_non_adaptive_freelists(size);
1204 }
1205
1206 if (res != NULL) {
1207 // check that res does lie in this space!
1208 assert(is_in_reserved(res), "Not in this space!");
1209 assert(is_aligned((void*)res), "alignment check");
1210
1211 FreeChunk* fc = (FreeChunk*)res;
1212 fc->markNotFree();
1213 assert(!fc->is_free(), "shouldn't be marked free");
1214 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1215 // Verify that the block offset table shows this to
1216 // be a single block, but not one which is unallocated.
1217 _bt.verify_single_block(res, size);
1218 _bt.verify_not_unallocated(res, size);
1219 // mangle a just allocated object with a distinct pattern.
1220 debug_only(fc->mangleAllocated(size));
1221 }
1222
1223 return res;
1224 }
1225
1226 HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) {
1227 HeapWord* res = NULL;
1228 // try and use linear allocation for smaller blocks
1229 if (size < _smallLinearAllocBlock._allocation_size_limit) {
1230 // if successful, the following also adjusts block offset table
1231 res = getChunkFromSmallLinearAllocBlock(size);
1232 }
1233 // Else triage to indexed lists for smaller sizes
1234 if (res == NULL) {
1235 if (size < SmallForDictionary) {
1236 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1237 } else {
1238 // else get it from the big dictionary; if even this doesn't
1239 // work we are out of luck.
1240 res = (HeapWord*)getChunkFromDictionaryExact(size);
1241 }
1242 }
1243
1244 return res;
1245 }
1246
1247 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1248 assert_lock_strong(freelistLock());
1249 HeapWord* res = NULL;
1250 assert(size == adjustObjectSize(size),
1251 "use adjustObjectSize() before calling into allocate()");
1252
1253 // Strategy
1254 // if small
1255 // exact size from small object indexed list if small
1256 // small or large linear allocation block (linAB) as appropriate
1257 // take from lists of greater sized chunks
1258 // else
1259 // dictionary
1260 // small or large linear allocation block if it has the space
1261 // Try allocating exact size from indexTable first
1262 if (size < IndexSetSize) {
1263 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1264 if(res != NULL) {
1265 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1266 "Not removed from free list");
1267 // no block offset table adjustment is necessary on blocks in
1268 // the indexed lists.
1269
1270 // Try allocating from the small LinAB
1271 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1272 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1273 // if successful, the above also adjusts block offset table
1274 // Note that this call will refill the LinAB to
1275 // satisfy the request. This is different that
1276 // evm.
1277 // Don't record chunk off a LinAB? smallSplitBirth(size);
1278 } else {
1279 // Raid the exact free lists larger than size, even if they are not
1280 // overpopulated.
1281 res = (HeapWord*) getChunkFromGreater(size);
1282 }
1283 } else {
1284 // Big objects get allocated directly from the dictionary.
1285 res = (HeapWord*) getChunkFromDictionaryExact(size);
1286 if (res == NULL) {
1287 // Try hard not to fail since an allocation failure will likely
1288 // trigger a synchronous GC. Try to get the space from the
1289 // allocation blocks.
1290 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1291 }
1292 }
1293
1294 return res;
1295 }
1296
1297 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1298 // when promoting obj.
1299 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1300 // Depending on the object size, expansion may require refilling either a
1301 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1302 // is added because the dictionary may over-allocate to avoid fragmentation.
1303 size_t space = obj_size;
1304 if (!_adaptive_freelists) {
1305 space = MAX2(space, _smallLinearAllocBlock._refillSize);
1306 }
1307 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1308 return space;
1309 }
1310
1311 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1312 FreeChunk* ret;
1313
1314 assert(numWords >= MinChunkSize, "Size is less than minimum");
1315 assert(linearAllocationWouldFail() || bestFitFirst(),
1316 "Should not be here");
1317
1318 size_t i;
1319 size_t currSize = numWords + MinChunkSize;
1320 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1321 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1322 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
1323 if (fl->head()) {
1324 ret = getFromListGreater(fl, numWords);
1325 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1326 return ret;
1327 }
1328 }
1329
1330 currSize = MAX2((size_t)SmallForDictionary,
1331 (size_t)(numWords + MinChunkSize));
1332
1333 /* Try to get a chunk that satisfies request, while avoiding
1334 fragmentation that can't be handled. */
1335 {
1336 ret = dictionary()->get_chunk(currSize);
1337 if (ret != NULL) {
1338 assert(ret->size() - numWords >= MinChunkSize,
1339 "Chunk is too small");
1340 _bt.allocated((HeapWord*)ret, ret->size());
1341 /* Carve returned chunk. */
1342 (void) splitChunkAndReturnRemainder(ret, numWords);
1343 /* Label this as no longer a free chunk. */
1344 assert(ret->is_free(), "This chunk should be free");
1345 ret->link_prev(NULL);
1346 }
1347 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1348 return ret;
1349 }
1350 ShouldNotReachHere();
1351 }
1352
1353 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1354 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1355 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
1356 }
1357
1358 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1359 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1360 (_smallLinearAllocBlock._word_size == fc->size()),
1361 "Linear allocation block shows incorrect size");
1362 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1363 (_smallLinearAllocBlock._word_size == fc->size()));
1364 }
1365
1366 // Check if the purported free chunk is present either as a linear
1367 // allocation block, the size-indexed table of (smaller) free blocks,
1368 // or the larger free blocks kept in the binary tree dictionary.
1369 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
1370 if (verify_chunk_is_linear_alloc_block(fc)) {
1371 return true;
1372 } else if (fc->size() < IndexSetSize) {
1373 return verifyChunkInIndexedFreeLists(fc);
1374 } else {
1375 return dictionary()->verify_chunk_in_free_list(fc);
1376 }
1377 }
1378
1379 #ifndef PRODUCT
1380 void CompactibleFreeListSpace::assert_locked() const {
1381 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1382 }
1383
1384 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1385 CMSLockVerifier::assert_locked(lock);
1386 }
1387 #endif
1388
1389 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1390 // In the parallel case, the main thread holds the free list lock
1391 // on behalf the parallel threads.
1392 FreeChunk* fc;
1393 {
1394 // If GC is parallel, this might be called by several threads.
1395 // This should be rare enough that the locking overhead won't affect
1396 // the sequential code.
1397 MutexLockerEx x(parDictionaryAllocLock(),
1398 Mutex::_no_safepoint_check_flag);
1399 fc = getChunkFromDictionary(size);
1400 }
1401 if (fc != NULL) {
1402 fc->dontCoalesce();
1403 assert(fc->is_free(), "Should be free, but not coalescable");
1404 // Verify that the block offset table shows this to
1405 // be a single block, but not one which is unallocated.
1406 _bt.verify_single_block((HeapWord*)fc, fc->size());
1407 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1408 }
1409 return fc;
1410 }
1411
1412 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1413 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1414 assert_locked();
1415
1416 // if we are tracking promotions, then first ensure space for
1417 // promotion (including spooling space for saving header if necessary).
1418 // then allocate and copy, then track promoted info if needed.
1419 // When tracking (see PromotionInfo::track()), the mark word may
1420 // be displaced and in this case restoration of the mark word
1421 // occurs in the (oop_since_save_marks_)iterate phase.
1422 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1423 return NULL;
1424 }
1425 // Call the allocate(size_t, bool) form directly to avoid the
1426 // additional call through the allocate(size_t) form. Having
1427 // the compile inline the call is problematic because allocate(size_t)
1428 // is a virtual method.
1429 HeapWord* res = allocate(adjustObjectSize(obj_size));
1430 if (res != NULL) {
1431 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1432 // if we should be tracking promotions, do so.
1433 if (_promoInfo.tracking()) {
1434 _promoInfo.track((PromotedObject*)res);
1435 }
1436 }
1437 return oop(res);
1438 }
1439
1440 HeapWord*
1441 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1442 assert_locked();
1443 assert(size >= MinChunkSize, "minimum chunk size");
1444 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1445 "maximum from smallLinearAllocBlock");
1446 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1447 }
1448
1449 HeapWord*
1450 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1451 size_t size) {
1452 assert_locked();
1453 assert(size >= MinChunkSize, "too small");
1454 HeapWord* res = NULL;
1455 // Try to do linear allocation from blk, making sure that
1456 if (blk->_word_size == 0) {
1457 // We have probably been unable to fill this either in the prologue or
1458 // when it was exhausted at the last linear allocation. Bail out until
1459 // next time.
1460 assert(blk->_ptr == NULL, "consistency check");
1461 return NULL;
1462 }
1463 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1464 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1465 if (res != NULL) return res;
1466
1467 // about to exhaust this linear allocation block
1468 if (blk->_word_size == size) { // exactly satisfied
1469 res = blk->_ptr;
1470 _bt.allocated(res, blk->_word_size);
1471 } else if (size + MinChunkSize <= blk->_refillSize) {
1472 size_t sz = blk->_word_size;
1473 // Update _unallocated_block if the size is such that chunk would be
1474 // returned to the indexed free list. All other chunks in the indexed
1475 // free lists are allocated from the dictionary so that _unallocated_block
1476 // has already been adjusted for them. Do it here so that the cost
1477 // for all chunks added back to the indexed free lists.
1478 if (sz < SmallForDictionary) {
1479 _bt.allocated(blk->_ptr, sz);
1480 }
1481 // Return the chunk that isn't big enough, and then refill below.
1482 addChunkToFreeLists(blk->_ptr, sz);
1483 split_birth(sz);
1484 // Don't keep statistics on adding back chunk from a LinAB.
1485 } else {
1486 // A refilled block would not satisfy the request.
1487 return NULL;
1488 }
1489
1490 blk->_ptr = NULL; blk->_word_size = 0;
1491 refillLinearAllocBlock(blk);
1492 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1493 "block was replenished");
1494 if (res != NULL) {
1495 split_birth(size);
1496 repairLinearAllocBlock(blk);
1497 } else if (blk->_ptr != NULL) {
1498 res = blk->_ptr;
1499 size_t blk_size = blk->_word_size;
1500 blk->_word_size -= size;
1501 blk->_ptr += size;
1502 split_birth(size);
1503 repairLinearAllocBlock(blk);
1504 // Update BOT last so that other (parallel) GC threads see a consistent
1505 // view of the BOT and free blocks.
1506 // Above must occur before BOT is updated below.
1507 OrderAccess::storestore();
1508 _bt.split_block(res, blk_size, size); // adjust block offset table
1509 }
1510 return res;
1511 }
1512
1513 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1514 LinearAllocBlock* blk,
1515 size_t size) {
1516 assert_locked();
1517 assert(size >= MinChunkSize, "too small");
1518
1519 HeapWord* res = NULL;
1520 // This is the common case. Keep it simple.
1521 if (blk->_word_size >= size + MinChunkSize) {
1522 assert(blk->_ptr != NULL, "consistency check");
1523 res = blk->_ptr;
1524 // Note that the BOT is up-to-date for the linAB before allocation. It
1525 // indicates the start of the linAB. The split_block() updates the
1526 // BOT for the linAB after the allocation (indicates the start of the
1527 // next chunk to be allocated).
1528 size_t blk_size = blk->_word_size;
1529 blk->_word_size -= size;
1530 blk->_ptr += size;
1531 split_birth(size);
1532 repairLinearAllocBlock(blk);
1533 // Update BOT last so that other (parallel) GC threads see a consistent
1534 // view of the BOT and free blocks.
1535 // Above must occur before BOT is updated below.
1536 OrderAccess::storestore();
1537 _bt.split_block(res, blk_size, size); // adjust block offset table
1538 _bt.allocated(res, size);
1539 }
1540 return res;
1541 }
1542
1543 FreeChunk*
1544 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1545 assert_locked();
1546 assert(size < SmallForDictionary, "just checking");
1547 FreeChunk* res;
1548 res = _indexedFreeList[size].get_chunk_at_head();
1549 if (res == NULL) {
1550 res = getChunkFromIndexedFreeListHelper(size);
1551 }
1552 _bt.verify_not_unallocated((HeapWord*) res, size);
1553 assert(res == NULL || res->size() == size, "Incorrect block size");
1554 return res;
1555 }
1556
1557 FreeChunk*
1558 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1559 bool replenish) {
1560 assert_locked();
1561 FreeChunk* fc = NULL;
1562 if (size < SmallForDictionary) {
1563 assert(_indexedFreeList[size].head() == NULL ||
1564 _indexedFreeList[size].surplus() <= 0,
1565 "List for this size should be empty or under populated");
1566 // Try best fit in exact lists before replenishing the list
1567 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1568 // Replenish list.
1569 //
1570 // Things tried that failed.
1571 // Tried allocating out of the two LinAB's first before
1572 // replenishing lists.
1573 // Tried small linAB of size 256 (size in indexed list)
1574 // and replenishing indexed lists from the small linAB.
1575 //
1576 FreeChunk* newFc = NULL;
1577 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1578 if (replenish_size < SmallForDictionary) {
1579 // Do not replenish from an underpopulated size.
1580 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1581 _indexedFreeList[replenish_size].head() != NULL) {
1582 newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
1583 } else if (bestFitFirst()) {
1584 newFc = bestFitSmall(replenish_size);
1585 }
1586 }
1587 if (newFc == NULL && replenish_size > size) {
1588 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1589 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1590 }
1591 // Note: The stats update re split-death of block obtained above
1592 // will be recorded below precisely when we know we are going to
1593 // be actually splitting it into more than one pieces below.
1594 if (newFc != NULL) {
1595 if (replenish || CMSReplenishIntermediate) {
1596 // Replenish this list and return one block to caller.
1597 size_t i;
1598 FreeChunk *curFc, *nextFc;
1599 size_t num_blk = newFc->size() / size;
1600 assert(num_blk >= 1, "Smaller than requested?");
1601 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1602 if (num_blk > 1) {
1603 // we are sure we will be splitting the block just obtained
1604 // into multiple pieces; record the split-death of the original
1605 splitDeath(replenish_size);
1606 }
1607 // carve up and link blocks 0, ..., num_blk - 2
1608 // The last chunk is not added to the lists but is returned as the
1609 // free chunk.
1610 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1611 i = 0;
1612 i < (num_blk - 1);
1613 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1614 i++) {
1615 curFc->set_size(size);
1616 // Don't record this as a return in order to try and
1617 // determine the "returns" from a GC.
1618 _bt.verify_not_unallocated((HeapWord*) fc, size);
1619 _indexedFreeList[size].return_chunk_at_tail(curFc, false);
1620 _bt.mark_block((HeapWord*)curFc, size);
1621 split_birth(size);
1622 // Don't record the initial population of the indexed list
1623 // as a split birth.
1624 }
1625
1626 // check that the arithmetic was OK above
1627 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1628 "inconsistency in carving newFc");
1629 curFc->set_size(size);
1630 _bt.mark_block((HeapWord*)curFc, size);
1631 split_birth(size);
1632 fc = curFc;
1633 } else {
1634 // Return entire block to caller
1635 fc = newFc;
1636 }
1637 }
1638 }
1639 } else {
1640 // Get a free chunk from the free chunk dictionary to be returned to
1641 // replenish the indexed free list.
1642 fc = getChunkFromDictionaryExact(size);
1643 }
1644 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
1645 return fc;
1646 }
1647
1648 FreeChunk*
1649 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1650 assert_locked();
1651 FreeChunk* fc = _dictionary->get_chunk(size,
1652 FreeBlockDictionary<FreeChunk>::atLeast);
1653 if (fc == NULL) {
1654 return NULL;
1655 }
1656 _bt.allocated((HeapWord*)fc, fc->size());
1657 if (fc->size() >= size + MinChunkSize) {
1658 fc = splitChunkAndReturnRemainder(fc, size);
1659 }
1660 assert(fc->size() >= size, "chunk too small");
1661 assert(fc->size() < size + MinChunkSize, "chunk too big");
1662 _bt.verify_single_block((HeapWord*)fc, fc->size());
1663 return fc;
1664 }
1665
1666 FreeChunk*
1667 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1668 assert_locked();
1669 FreeChunk* fc = _dictionary->get_chunk(size,
1670 FreeBlockDictionary<FreeChunk>::atLeast);
1671 if (fc == NULL) {
1672 return fc;
1673 }
1674 _bt.allocated((HeapWord*)fc, fc->size());
1675 if (fc->size() == size) {
1676 _bt.verify_single_block((HeapWord*)fc, size);
1677 return fc;
1678 }
1679 assert(fc->size() > size, "get_chunk() guarantee");
1680 if (fc->size() < size + MinChunkSize) {
1681 // Return the chunk to the dictionary and go get a bigger one.
1682 returnChunkToDictionary(fc);
1683 fc = _dictionary->get_chunk(size + MinChunkSize,
1684 FreeBlockDictionary<FreeChunk>::atLeast);
1685 if (fc == NULL) {
1686 return NULL;
1687 }
1688 _bt.allocated((HeapWord*)fc, fc->size());
1689 }
1690 assert(fc->size() >= size + MinChunkSize, "tautology");
1691 fc = splitChunkAndReturnRemainder(fc, size);
1692 assert(fc->size() == size, "chunk is wrong size");
1693 _bt.verify_single_block((HeapWord*)fc, size);
1694 return fc;
1695 }
1696
1697 void
1698 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
1699 assert_locked();
1700
1701 size_t size = chunk->size();
1702 _bt.verify_single_block((HeapWord*)chunk, size);
1703 // adjust _unallocated_block downward, as necessary
1704 _bt.freed((HeapWord*)chunk, size);
1705 _dictionary->return_chunk(chunk);
1706 #ifndef PRODUCT
1707 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1708 TreeChunk<FreeChunk, AdaptiveFreeList>* tc = TreeChunk<FreeChunk, AdaptiveFreeList>::as_TreeChunk(chunk);
1709 TreeList<FreeChunk, AdaptiveFreeList>* tl = tc->list();
1710 tl->verify_stats();
1711 }
1712 #endif // PRODUCT
1713 }
1714
1715 void
1716 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
1717 assert_locked();
1718 size_t size = fc->size();
1719 _bt.verify_single_block((HeapWord*) fc, size);
1720 _bt.verify_not_unallocated((HeapWord*) fc, size);
1721 if (_adaptive_freelists) {
1722 _indexedFreeList[size].return_chunk_at_tail(fc);
1723 } else {
1724 _indexedFreeList[size].return_chunk_at_head(fc);
1725 }
1726 #ifndef PRODUCT
1727 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1728 _indexedFreeList[size].verify_stats();
1729 }
1730 #endif // PRODUCT
1731 }
1732
1733 // Add chunk to end of last block -- if it's the largest
1734 // block -- and update BOT and census data. We would
1735 // of course have preferred to coalesce it with the
1736 // last block, but it's currently less expensive to find the
1737 // largest block than it is to find the last.
1738 void
1739 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1740 HeapWord* chunk, size_t size) {
1741 // check that the chunk does lie in this space!
1742 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1743 // One of the parallel gc task threads may be here
1744 // whilst others are allocating.
1745 Mutex* lock = NULL;
1746 if (ParallelGCThreads != 0) {
1747 lock = &_parDictionaryAllocLock;
1748 }
1749 FreeChunk* ec;
1750 {
1751 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1752 ec = dictionary()->find_largest_dict(); // get largest block
1753 if (ec != NULL && ec->end() == (uintptr_t*) chunk) {
1754 // It's a coterminal block - we can coalesce.
1755 size_t old_size = ec->size();
1756 coalDeath(old_size);
1757 removeChunkFromDictionary(ec);
1758 size += old_size;
1759 } else {
1760 ec = (FreeChunk*)chunk;
1761 }
1762 }
1763 ec->set_size(size);
1764 debug_only(ec->mangleFreed(size));
1765 if (size < SmallForDictionary) {
1766 lock = _indexedFreeListParLocks[size];
1767 }
1768 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1769 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
1770 // record the birth under the lock since the recording involves
1771 // manipulation of the list on which the chunk lives and
1772 // if the chunk is allocated and is the last on the list,
1773 // the list can go away.
1774 coalBirth(size);
1775 }
1776
1777 void
1778 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1779 size_t size) {
1780 // check that the chunk does lie in this space!
1781 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1782 assert_locked();
1783 _bt.verify_single_block(chunk, size);
1784
1785 FreeChunk* fc = (FreeChunk*) chunk;
1786 fc->set_size(size);
1787 debug_only(fc->mangleFreed(size));
1788 if (size < SmallForDictionary) {
1789 returnChunkToFreeList(fc);
1790 } else {
1791 returnChunkToDictionary(fc);
1792 }
1793 }
1794
1795 void
1796 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1797 size_t size, bool coalesced) {
1798 assert_locked();
1799 assert(chunk != NULL, "null chunk");
1800 if (coalesced) {
1801 // repair BOT
1802 _bt.single_block(chunk, size);
1803 }
1804 addChunkToFreeLists(chunk, size);
1805 }
1806
1807 // We _must_ find the purported chunk on our free lists;
1808 // we assert if we don't.
1809 void
1810 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1811 size_t size = fc->size();
1812 assert_locked();
1813 debug_only(verifyFreeLists());
1814 if (size < SmallForDictionary) {
1815 removeChunkFromIndexedFreeList(fc);
1816 } else {
1817 removeChunkFromDictionary(fc);
1818 }
1819 _bt.verify_single_block((HeapWord*)fc, size);
1820 debug_only(verifyFreeLists());
1821 }
1822
1823 void
1824 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1825 size_t size = fc->size();
1826 assert_locked();
1827 assert(fc != NULL, "null chunk");
1828 _bt.verify_single_block((HeapWord*)fc, size);
1829 _dictionary->remove_chunk(fc);
1830 // adjust _unallocated_block upward, as necessary
1831 _bt.allocated((HeapWord*)fc, size);
1832 }
1833
1834 void
1835 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1836 assert_locked();
1837 size_t size = fc->size();
1838 _bt.verify_single_block((HeapWord*)fc, size);
1839 NOT_PRODUCT(
1840 if (FLSVerifyIndexTable) {
1841 verifyIndexedFreeList(size);
1842 }
1843 )
1844 _indexedFreeList[size].remove_chunk(fc);
1845 NOT_PRODUCT(
1846 if (FLSVerifyIndexTable) {
1847 verifyIndexedFreeList(size);
1848 }
1849 )
1850 }
1851
1852 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1853 /* A hint is the next larger size that has a surplus.
1854 Start search at a size large enough to guarantee that
1855 the excess is >= MIN_CHUNK. */
1856 size_t start = align_object_size(numWords + MinChunkSize);
1857 if (start < IndexSetSize) {
1858 AdaptiveFreeList<FreeChunk>* it = _indexedFreeList;
1859 size_t hint = _indexedFreeList[start].hint();
1860 while (hint < IndexSetSize) {
1861 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1862 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint];
1863 if (fl->surplus() > 0 && fl->head() != NULL) {
1864 // Found a list with surplus, reset original hint
1865 // and split out a free chunk which is returned.
1866 _indexedFreeList[start].set_hint(hint);
1867 FreeChunk* res = getFromListGreater(fl, numWords);
1868 assert(res == NULL || res->is_free(),
1869 "Should be returning a free chunk");
1870 return res;
1871 }
1872 hint = fl->hint(); /* keep looking */
1873 }
1874 /* None found. */
1875 it[start].set_hint(IndexSetSize);
1876 }
1877 return NULL;
1878 }
1879
1880 /* Requires fl->size >= numWords + MinChunkSize */
1881 FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl,
1882 size_t numWords) {
1883 FreeChunk *curr = fl->head();
1884 size_t oldNumWords = curr->size();
1885 assert(numWords >= MinChunkSize, "Word size is too small");
1886 assert(curr != NULL, "List is empty");
1887 assert(oldNumWords >= numWords + MinChunkSize,
1888 "Size of chunks in the list is too small");
1889
1890 fl->remove_chunk(curr);
1891 // recorded indirectly by splitChunkAndReturnRemainder -
1892 // smallSplit(oldNumWords, numWords);
1893 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1894 // Does anything have to be done for the remainder in terms of
1895 // fixing the card table?
1896 assert(new_chunk == NULL || new_chunk->is_free(),
1897 "Should be returning a free chunk");
1898 return new_chunk;
1899 }
1900
1901 FreeChunk*
1902 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1903 size_t new_size) {
1904 assert_locked();
1905 size_t size = chunk->size();
1906 assert(size > new_size, "Split from a smaller block?");
1907 assert(is_aligned(chunk), "alignment problem");
1908 assert(size == adjustObjectSize(size), "alignment problem");
1909 size_t rem_size = size - new_size;
1910 assert(rem_size == adjustObjectSize(rem_size), "alignment problem");
1911 assert(rem_size >= MinChunkSize, "Free chunk smaller than minimum");
1912 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1913 assert(is_aligned(ffc), "alignment problem");
1914 ffc->set_size(rem_size);
1915 ffc->link_next(NULL);
1916 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
1917 // Above must occur before BOT is updated below.
1918 // adjust block offset table
1919 OrderAccess::storestore();
1920 assert(chunk->is_free() && ffc->is_free(), "Error");
1921 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1922 if (rem_size < SmallForDictionary) {
1923 bool is_par = (SharedHeap::heap()->n_par_threads() > 0);
1924 if (is_par) _indexedFreeListParLocks[rem_size]->lock();
1925 assert(!is_par ||
1926 (SharedHeap::heap()->n_par_threads() ==
1927 SharedHeap::heap()->workers()->active_workers()), "Mismatch");
1928 returnChunkToFreeList(ffc);
1929 split(size, rem_size);
1930 if (is_par) _indexedFreeListParLocks[rem_size]->unlock();
1931 } else {
1932 returnChunkToDictionary(ffc);
1933 split(size ,rem_size);
1934 }
1935 chunk->set_size(new_size);
1936 return chunk;
1937 }
1938
1939 void
1940 CompactibleFreeListSpace::sweep_completed() {
1941 // Now that space is probably plentiful, refill linear
1942 // allocation blocks as needed.
1943 refillLinearAllocBlocksIfNeeded();
1944 }
1945
1946 void
1947 CompactibleFreeListSpace::gc_prologue() {
1948 assert_locked();
1949 if (PrintFLSStatistics != 0) {
1950 gclog_or_tty->print("Before GC:\n");
1951 reportFreeListStatistics();
1952 }
1953 refillLinearAllocBlocksIfNeeded();
1954 }
1955
1956 void
1957 CompactibleFreeListSpace::gc_epilogue() {
1958 assert_locked();
1959 if (PrintGCDetails && Verbose && !_adaptive_freelists) {
1960 if (_smallLinearAllocBlock._word_size == 0)
1961 warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure");
1962 }
1963 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1964 _promoInfo.stopTrackingPromotions();
1965 repairLinearAllocationBlocks();
1966 // Print Space's stats
1967 if (PrintFLSStatistics != 0) {
1968 gclog_or_tty->print("After GC:\n");
1969 reportFreeListStatistics();
1970 }
1971 }
1972
1973 // Iteration support, mostly delegated from a CMS generation
1974
1975 void CompactibleFreeListSpace::save_marks() {
1976 assert(Thread::current()->is_VM_thread(),
1977 "Global variable should only be set when single-threaded");
1978 // Mark the "end" of the used space at the time of this call;
1979 // note, however, that promoted objects from this point
1980 // on are tracked in the _promoInfo below.
1981 set_saved_mark_word(unallocated_block());
1982 #ifdef ASSERT
1983 // Check the sanity of save_marks() etc.
1984 MemRegion ur = used_region();
1985 MemRegion urasm = used_region_at_save_marks();
1986 assert(ur.contains(urasm),
1987 err_msg(" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
1988 " should contain [" PTR_FORMAT "," PTR_FORMAT ")",
1989 ur.start(), ur.end(), urasm.start(), urasm.end()));
1990 #endif
1991 // inform allocator that promotions should be tracked.
1992 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1993 _promoInfo.startTrackingPromotions();
1994 }
1995
1996 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
1997 assert(_promoInfo.tracking(), "No preceding save_marks?");
1998 assert(SharedHeap::heap()->n_par_threads() == 0,
1999 "Shouldn't be called if using parallel gc.");
2000 return _promoInfo.noPromotions();
2001 }
2002
2003 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
2004 \
2005 void CompactibleFreeListSpace:: \
2006 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
2007 assert(SharedHeap::heap()->n_par_threads() == 0, \
2008 "Shouldn't be called (yet) during parallel part of gc."); \
2009 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
2010 /* \
2011 * This also restores any displaced headers and removes the elements from \
2012 * the iteration set as they are processed, so that we have a clean slate \
2013 * at the end of the iteration. Note, thus, that if new objects are \
2014 * promoted as a result of the iteration they are iterated over as well. \
2015 */ \
2016 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
2017 }
2018
2019 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
2020
2021
2022 void CompactibleFreeListSpace::object_iterate_since_last_GC(ObjectClosure* cl) {
2023 // ugghh... how would one do this efficiently for a non-contiguous space?
2024 guarantee(false, "NYI");
2025 }
2026
2027 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
2028 return _smallLinearAllocBlock._word_size == 0;
2029 }
2030
2031 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
2032 // Fix up linear allocation blocks to look like free blocks
2033 repairLinearAllocBlock(&_smallLinearAllocBlock);
2034 }
2035
2036 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
2037 assert_locked();
2038 if (blk->_ptr != NULL) {
2039 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
2040 "Minimum block size requirement");
2041 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
2042 fc->set_size(blk->_word_size);
2043 fc->link_prev(NULL); // mark as free
2044 fc->dontCoalesce();
2045 assert(fc->is_free(), "just marked it free");
2046 assert(fc->cantCoalesce(), "just marked it uncoalescable");
2047 }
2048 }
2049
2050 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
2051 assert_locked();
2052 if (_smallLinearAllocBlock._ptr == NULL) {
2053 assert(_smallLinearAllocBlock._word_size == 0,
2054 "Size of linAB should be zero if the ptr is NULL");
2055 // Reset the linAB refill and allocation size limit.
2056 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
2057 }
2058 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
2059 }
2060
2061 void
2062 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
2063 assert_locked();
2064 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
2065 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
2066 "blk invariant");
2067 if (blk->_ptr == NULL) {
2068 refillLinearAllocBlock(blk);
2069 }
2070 if (PrintMiscellaneous && Verbose) {
2071 if (blk->_word_size == 0) {
2072 warning("CompactibleFreeListSpace(prologue):: Linear allocation failure");
2073 }
2074 }
2075 }
2076
2077 void
2078 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
2079 assert_locked();
2080 assert(blk->_word_size == 0 && blk->_ptr == NULL,
2081 "linear allocation block should be empty");
2082 FreeChunk* fc;
2083 if (blk->_refillSize < SmallForDictionary &&
2084 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
2085 // A linAB's strategy might be to use small sizes to reduce
2086 // fragmentation but still get the benefits of allocation from a
2087 // linAB.
2088 } else {
2089 fc = getChunkFromDictionary(blk->_refillSize);
2090 }
2091 if (fc != NULL) {
2092 blk->_ptr = (HeapWord*)fc;
2093 blk->_word_size = fc->size();
2094 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
2095 }
2096 }
2097
2098 // Support for concurrent collection policy decisions.
2099 bool CompactibleFreeListSpace::should_concurrent_collect() const {
2100 // In the future we might want to add in frgamentation stats --
2101 // including erosion of the "mountain" into this decision as well.
2102 return !adaptive_freelists() && linearAllocationWouldFail();
2103 }
2104
2105 // Support for compaction
2106
2107 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
2108 SCAN_AND_FORWARD(cp,end,block_is_obj,block_size);
2109 // prepare_for_compaction() uses the space between live objects
2110 // so that later phase can skip dead space quickly. So verification
2111 // of the free lists doesn't work after.
2112 }
2113
2114 #define obj_size(q) adjustObjectSize(oop(q)->size())
2115 #define adjust_obj_size(s) adjustObjectSize(s)
2116
2117 void CompactibleFreeListSpace::adjust_pointers() {
2118 // In other versions of adjust_pointers(), a bail out
2119 // based on the amount of live data in the generation
2120 // (i.e., if 0, bail out) may be used.
2121 // Cannot test used() == 0 here because the free lists have already
2122 // been mangled by the compaction.
2123
2124 SCAN_AND_ADJUST_POINTERS(adjust_obj_size);
2125 // See note about verification in prepare_for_compaction().
2126 }
2127
2128 void CompactibleFreeListSpace::compact() {
2129 SCAN_AND_COMPACT(obj_size);
2130 }
2131
2132 // fragmentation_metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
2133 // where fbs is free block sizes
2134 double CompactibleFreeListSpace::flsFrag() const {
2135 size_t itabFree = totalSizeInIndexedFreeLists();
2136 double frag = 0.0;
2137 size_t i;
2138
2139 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2140 double sz = i;
2141 frag += _indexedFreeList[i].count() * (sz * sz);
2142 }
2143
2144 double totFree = itabFree +
2145 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
2146 if (totFree > 0) {
2147 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
2148 (totFree * totFree));
2149 frag = (double)1.0 - frag;
2150 } else {
2151 assert(frag == 0.0, "Follows from totFree == 0");
2152 }
2153 return frag;
2154 }
2155
2156 void CompactibleFreeListSpace::beginSweepFLCensus(
2157 float inter_sweep_current,
2158 float inter_sweep_estimate,
2159 float intra_sweep_estimate) {
2160 assert_locked();
2161 size_t i;
2162 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2163 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
2164 if (PrintFLSStatistics > 1) {
2165 gclog_or_tty->print("size[%d] : ", i);
2166 }
2167 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2168 fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2169 fl->set_before_sweep(fl->count());
2170 fl->set_bfr_surp(fl->surplus());
2171 }
2172 _dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent,
2173 inter_sweep_current,
2174 inter_sweep_estimate,
2175 intra_sweep_estimate);
2176 }
2177
2178 void CompactibleFreeListSpace::setFLSurplus() {
2179 assert_locked();
2180 size_t i;
2181 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2182 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2183 fl->set_surplus(fl->count() -
2184 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2185 }
2186 }
2187
2188 void CompactibleFreeListSpace::setFLHints() {
2189 assert_locked();
2190 size_t i;
2191 size_t h = IndexSetSize;
2192 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2193 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2194 fl->set_hint(h);
2195 if (fl->surplus() > 0) {
2196 h = i;
2197 }
2198 }
2199 }
2200
2201 void CompactibleFreeListSpace::clearFLCensus() {
2202 assert_locked();
2203 size_t i;
2204 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2205 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2206 fl->set_prev_sweep(fl->count());
2207 fl->set_coal_births(0);
2208 fl->set_coal_deaths(0);
2209 fl->set_split_births(0);
2210 fl->set_split_deaths(0);
2211 }
2212 }
2213
2214 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2215 if (PrintFLSStatistics > 0) {
2216 HeapWord* largestAddr = (HeapWord*) dictionary()->find_largest_dict();
2217 gclog_or_tty->print_cr("CMS: Large block " PTR_FORMAT,
2218 largestAddr);
2219 }
2220 setFLSurplus();
2221 setFLHints();
2222 if (PrintGC && PrintFLSCensus > 0) {
2223 printFLCensus(sweep_count);
2224 }
2225 clearFLCensus();
2226 assert_locked();
2227 _dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent);
2228 }
2229
2230 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2231 if (size < SmallForDictionary) {
2232 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2233 return (fl->coal_desired() < 0) ||
2234 ((int)fl->count() > fl->coal_desired());
2235 } else {
2236 return dictionary()->coal_dict_over_populated(size);
2237 }
2238 }
2239
2240 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2241 assert(size < SmallForDictionary, "Size too large for indexed list");
2242 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2243 fl->increment_coal_births();
2244 fl->increment_surplus();
2245 }
2246
2247 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2248 assert(size < SmallForDictionary, "Size too large for indexed list");
2249 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2250 fl->increment_coal_deaths();
2251 fl->decrement_surplus();
2252 }
2253
2254 void CompactibleFreeListSpace::coalBirth(size_t size) {
2255 if (size < SmallForDictionary) {
2256 smallCoalBirth(size);
2257 } else {
2258 dictionary()->dict_census_update(size,
2259 false /* split */,
2260 true /* birth */);
2261 }
2262 }
2263
2264 void CompactibleFreeListSpace::coalDeath(size_t size) {
2265 if(size < SmallForDictionary) {
2266 smallCoalDeath(size);
2267 } else {
2268 dictionary()->dict_census_update(size,
2269 false /* split */,
2270 false /* birth */);
2271 }
2272 }
2273
2274 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2275 assert(size < SmallForDictionary, "Size too large for indexed list");
2276 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2277 fl->increment_split_births();
2278 fl->increment_surplus();
2279 }
2280
2281 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2282 assert(size < SmallForDictionary, "Size too large for indexed list");
2283 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2284 fl->increment_split_deaths();
2285 fl->decrement_surplus();
2286 }
2287
2288 void CompactibleFreeListSpace::split_birth(size_t size) {
2289 if (size < SmallForDictionary) {
2290 smallSplitBirth(size);
2291 } else {
2292 dictionary()->dict_census_update(size,
2293 true /* split */,
2294 true /* birth */);
2295 }
2296 }
2297
2298 void CompactibleFreeListSpace::splitDeath(size_t size) {
2299 if (size < SmallForDictionary) {
2300 smallSplitDeath(size);
2301 } else {
2302 dictionary()->dict_census_update(size,
2303 true /* split */,
2304 false /* birth */);
2305 }
2306 }
2307
2308 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2309 size_t to2 = from - to1;
2310 splitDeath(from);
2311 split_birth(to1);
2312 split_birth(to2);
2313 }
2314
2315 void CompactibleFreeListSpace::print() const {
2316 print_on(tty);
2317 }
2318
2319 void CompactibleFreeListSpace::prepare_for_verify() {
2320 assert_locked();
2321 repairLinearAllocationBlocks();
2322 // Verify that the SpoolBlocks look like free blocks of
2323 // appropriate sizes... To be done ...
2324 }
2325
2326 class VerifyAllBlksClosure: public BlkClosure {
2327 private:
2328 const CompactibleFreeListSpace* _sp;
2329 const MemRegion _span;
2330 HeapWord* _last_addr;
2331 size_t _last_size;
2332 bool _last_was_obj;
2333 bool _last_was_live;
2334
2335 public:
2336 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2337 MemRegion span) : _sp(sp), _span(span),
2338 _last_addr(NULL), _last_size(0),
2339 _last_was_obj(false), _last_was_live(false) { }
2340
2341 virtual size_t do_blk(HeapWord* addr) {
2342 size_t res;
2343 bool was_obj = false;
2344 bool was_live = false;
2345 if (_sp->block_is_obj(addr)) {
2346 was_obj = true;
2347 oop p = oop(addr);
2348 guarantee(p->is_oop(), "Should be an oop");
2349 res = _sp->adjustObjectSize(p->size());
2350 if (_sp->obj_is_alive(addr)) {
2351 was_live = true;
2352 p->verify();
2353 }
2354 } else {
2355 FreeChunk* fc = (FreeChunk*)addr;
2356 res = fc->size();
2357 if (FLSVerifyLists && !fc->cantCoalesce()) {
2358 guarantee(_sp->verify_chunk_in_free_list(fc),
2359 "Chunk should be on a free list");
2360 }
2361 }
2362 if (res == 0) {
2363 gclog_or_tty->print_cr("Livelock: no rank reduction!");
2364 gclog_or_tty->print_cr(
2365 " Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2366 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2367 addr, res, was_obj ?"true":"false", was_live ?"true":"false",
2368 _last_addr, _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2369 _sp->print_on(gclog_or_tty);
2370 guarantee(false, "Seppuku!");
2371 }
2372 _last_addr = addr;
2373 _last_size = res;
2374 _last_was_obj = was_obj;
2375 _last_was_live = was_live;
2376 return res;
2377 }
2378 };
2379
2380 class VerifyAllOopsClosure: public OopClosure {
2381 private:
2382 const CMSCollector* _collector;
2383 const CompactibleFreeListSpace* _sp;
2384 const MemRegion _span;
2385 const bool _past_remark;
2386 const CMSBitMap* _bit_map;
2387
2388 protected:
2389 void do_oop(void* p, oop obj) {
2390 if (_span.contains(obj)) { // the interior oop points into CMS heap
2391 if (!_span.contains(p)) { // reference from outside CMS heap
2392 // Should be a valid object; the first disjunct below allows
2393 // us to sidestep an assertion in block_is_obj() that insists
2394 // that p be in _sp. Note that several generations (and spaces)
2395 // are spanned by _span (CMS heap) above.
2396 guarantee(!_sp->is_in_reserved(obj) ||
2397 _sp->block_is_obj((HeapWord*)obj),
2398 "Should be an object");
2399 guarantee(obj->is_oop(), "Should be an oop");
2400 obj->verify();
2401 if (_past_remark) {
2402 // Remark has been completed, the object should be marked
2403 _bit_map->isMarked((HeapWord*)obj);
2404 }
2405 } else { // reference within CMS heap
2406 if (_past_remark) {
2407 // Remark has been completed -- so the referent should have
2408 // been marked, if referring object is.
2409 if (_bit_map->isMarked(_collector->block_start(p))) {
2410 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2411 }
2412 }
2413 }
2414 } else if (_sp->is_in_reserved(p)) {
2415 // the reference is from FLS, and points out of FLS
2416 guarantee(obj->is_oop(), "Should be an oop");
2417 obj->verify();
2418 }
2419 }
2420
2421 template <class T> void do_oop_work(T* p) {
2422 T heap_oop = oopDesc::load_heap_oop(p);
2423 if (!oopDesc::is_null(heap_oop)) {
2424 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2425 do_oop(p, obj);
2426 }
2427 }
2428
2429 public:
2430 VerifyAllOopsClosure(const CMSCollector* collector,
2431 const CompactibleFreeListSpace* sp, MemRegion span,
2432 bool past_remark, CMSBitMap* bit_map) :
2433 _collector(collector), _sp(sp), _span(span),
2434 _past_remark(past_remark), _bit_map(bit_map) { }
2435
2436 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2437 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2438 };
2439
2440 void CompactibleFreeListSpace::verify() const {
2441 assert_lock_strong(&_freelistLock);
2442 verify_objects_initialized();
2443 MemRegion span = _collector->_span;
2444 bool past_remark = (_collector->abstract_state() ==
2445 CMSCollector::Sweeping);
2446
2447 ResourceMark rm;
2448 HandleMark hm;
2449
2450 // Check integrity of CFL data structures
2451 _promoInfo.verify();
2452 _dictionary->verify();
2453 if (FLSVerifyIndexTable) {
2454 verifyIndexedFreeLists();
2455 }
2456 // Check integrity of all objects and free blocks in space
2457 {
2458 VerifyAllBlksClosure cl(this, span);
2459 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2460 }
2461 // Check that all references in the heap to FLS
2462 // are to valid objects in FLS or that references in
2463 // FLS are to valid objects elsewhere in the heap
2464 if (FLSVerifyAllHeapReferences)
2465 {
2466 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2467 _collector->markBitMap());
2468 CollectedHeap* ch = Universe::heap();
2469
2470 // Iterate over all oops in the heap. Uses the _no_header version
2471 // since we are not interested in following the klass pointers.
2472 ch->oop_iterate_no_header(&cl);
2473 }
2474
2475 if (VerifyObjectStartArray) {
2476 // Verify the block offset table
2477 _bt.verify();
2478 }
2479 }
2480
2481 #ifndef PRODUCT
2482 void CompactibleFreeListSpace::verifyFreeLists() const {
2483 if (FLSVerifyLists) {
2484 _dictionary->verify();
2485 verifyIndexedFreeLists();
2486 } else {
2487 if (FLSVerifyDictionary) {
2488 _dictionary->verify();
2489 }
2490 if (FLSVerifyIndexTable) {
2491 verifyIndexedFreeLists();
2492 }
2493 }
2494 }
2495 #endif
2496
2497 void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
2498 size_t i = 0;
2499 for (; i < IndexSetStart; i++) {
2500 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
2501 }
2502 for (; i < IndexSetSize; i++) {
2503 verifyIndexedFreeList(i);
2504 }
2505 }
2506
2507 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
2508 FreeChunk* fc = _indexedFreeList[size].head();
2509 FreeChunk* tail = _indexedFreeList[size].tail();
2510 size_t num = _indexedFreeList[size].count();
2511 size_t n = 0;
2512 guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL,
2513 "Slot should have been empty");
2514 for (; fc != NULL; fc = fc->next(), n++) {
2515 guarantee(fc->size() == size, "Size inconsistency");
2516 guarantee(fc->is_free(), "!free?");
2517 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
2518 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
2519 }
2520 guarantee(n == num, "Incorrect count");
2521 }
2522
2523 #ifndef PRODUCT
2524 void CompactibleFreeListSpace::check_free_list_consistency() const {
2525 assert((TreeChunk<FreeChunk, AdaptiveFreeList>::min_size() <= IndexSetSize),
2526 "Some sizes can't be allocated without recourse to"
2527 " linear allocation buffers");
2528 assert((TreeChunk<FreeChunk, AdaptiveFreeList>::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList>)),
2529 "else MIN_TREE_CHUNK_SIZE is wrong");
2530 assert(IndexSetStart != 0, "IndexSetStart not initialized");
2531 assert(IndexSetStride != 0, "IndexSetStride not initialized");
2532 }
2533 #endif
2534
2535 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2536 assert_lock_strong(&_freelistLock);
2537 AdaptiveFreeList<FreeChunk> total;
2538 gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count);
2539 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size");
2540 size_t total_free = 0;
2541 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2542 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2543 total_free += fl->count() * fl->size();
2544 if (i % (40*IndexSetStride) == 0) {
2545 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size");
2546 }
2547 fl->print_on(gclog_or_tty);
2548 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
2549 total.set_surplus( total.surplus() + fl->surplus() );
2550 total.set_desired( total.desired() + fl->desired() );
2551 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
2552 total.set_before_sweep(total.before_sweep() + fl->before_sweep());
2553 total.set_count( total.count() + fl->count() );
2554 total.set_coal_births( total.coal_births() + fl->coal_births() );
2555 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
2556 total.set_split_births(total.split_births() + fl->split_births());
2557 total.set_split_deaths(total.split_deaths() + fl->split_deaths());
2558 }
2559 total.print_on(gclog_or_tty, "TOTAL");
2560 gclog_or_tty->print_cr("Total free in indexed lists "
2561 SIZE_FORMAT " words", total_free);
2562 gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n",
2563 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
2564 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
2565 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2566 _dictionary->print_dict_census();
2567 }
2568
2569 ///////////////////////////////////////////////////////////////////////////
2570 // CFLS_LAB
2571 ///////////////////////////////////////////////////////////////////////////
2572
2573 #define VECTOR_257(x) \
2574 /* 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 */ \
2575 { 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, \
2576 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, \
2577 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, \
2578 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, \
2579 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, \
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 }
2584
2585 // Initialize with default setting of CMSParPromoteBlocksToClaim, _not_
2586 // OldPLABSize, whose static default is different; if overridden at the
2587 // command-line, this will get reinitialized via a call to
2588 // modify_initialization() below.
2589 AdaptiveWeightedAverage CFLS_LAB::_blocks_to_claim[] =
2590 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CMSParPromoteBlocksToClaim));
2591 size_t CFLS_LAB::_global_num_blocks[] = VECTOR_257(0);
2592 uint CFLS_LAB::_global_num_workers[] = VECTOR_257(0);
2593
2594 CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) :
2595 _cfls(cfls)
2596 {
2597 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2598 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2599 i < CompactibleFreeListSpace::IndexSetSize;
2600 i += CompactibleFreeListSpace::IndexSetStride) {
2601 _indexedFreeList[i].set_size(i);
2602 _num_blocks[i] = 0;
2603 }
2604 }
2605
2606 static bool _CFLS_LAB_modified = false;
2607
2608 void CFLS_LAB::modify_initialization(size_t n, unsigned wt) {
2609 assert(!_CFLS_LAB_modified, "Call only once");
2610 _CFLS_LAB_modified = true;
2611 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2612 i < CompactibleFreeListSpace::IndexSetSize;
2613 i += CompactibleFreeListSpace::IndexSetStride) {
2614 _blocks_to_claim[i].modify(n, wt, true /* force */);
2615 }
2616 }
2617
2618 HeapWord* CFLS_LAB::alloc(size_t word_sz) {
2619 FreeChunk* res;
2620 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2621 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2622 // This locking manages sync with other large object allocations.
2623 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2624 Mutex::_no_safepoint_check_flag);
2625 res = _cfls->getChunkFromDictionaryExact(word_sz);
2626 if (res == NULL) return NULL;
2627 } else {
2628 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
2629 if (fl->count() == 0) {
2630 // Attempt to refill this local free list.
2631 get_from_global_pool(word_sz, fl);
2632 // If it didn't work, give up.
2633 if (fl->count() == 0) return NULL;
2634 }
2635 res = fl->get_chunk_at_head();
2636 assert(res != NULL, "Why was count non-zero?");
2637 }
2638 res->markNotFree();
2639 assert(!res->is_free(), "shouldn't be marked free");
2640 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2641 // mangle a just allocated object with a distinct pattern.
2642 debug_only(res->mangleAllocated(word_sz));
2643 return (HeapWord*)res;
2644 }
2645
2646 // Get a chunk of blocks of the right size and update related
2647 // book-keeping stats
2648 void CFLS_LAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
2649 // Get the #blocks we want to claim
2650 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2651 assert(n_blks > 0, "Error");
2652 assert(ResizePLAB || n_blks == OldPLABSize, "Error");
2653 // In some cases, when the application has a phase change,
2654 // there may be a sudden and sharp shift in the object survival
2655 // profile, and updating the counts at the end of a scavenge
2656 // may not be quick enough, giving rise to large scavenge pauses
2657 // during these phase changes. It is beneficial to detect such
2658 // changes on-the-fly during a scavenge and avoid such a phase-change
2659 // pothole. The following code is a heuristic attempt to do that.
2660 // It is protected by a product flag until we have gained
2661 // enough experience with this heuristic and fine-tuned its behaviour.
2662 // WARNING: This might increase fragmentation if we overreact to
2663 // small spikes, so some kind of historical smoothing based on
2664 // previous experience with the greater reactivity might be useful.
2665 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2666 // default.
2667 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2668 size_t multiple = _num_blocks[word_sz]/(CMSOldPLABToleranceFactor*CMSOldPLABNumRefills*n_blks);
2669 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2670 n_blks = MIN2(n_blks, CMSOldPLABMax);
2671 }
2672 assert(n_blks > 0, "Error");
2673 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2674 // Update stats table entry for this block size
2675 _num_blocks[word_sz] += fl->count();
2676 }
2677
2678 void CFLS_LAB::compute_desired_plab_size() {
2679 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2680 i < CompactibleFreeListSpace::IndexSetSize;
2681 i += CompactibleFreeListSpace::IndexSetStride) {
2682 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2683 "Counter inconsistency");
2684 if (_global_num_workers[i] > 0) {
2685 // Need to smooth wrt historical average
2686 if (ResizeOldPLAB) {
2687 _blocks_to_claim[i].sample(
2688 MAX2((size_t)CMSOldPLABMin,
2689 MIN2((size_t)CMSOldPLABMax,
2690 _global_num_blocks[i]/(_global_num_workers[i]*CMSOldPLABNumRefills))));
2691 }
2692 // Reset counters for next round
2693 _global_num_workers[i] = 0;
2694 _global_num_blocks[i] = 0;
2695 if (PrintOldPLAB) {
2696 gclog_or_tty->print_cr("[%d]: %d", i, (size_t)_blocks_to_claim[i].average());
2697 }
2698 }
2699 }
2700 }
2701
2702 // If this is changed in the future to allow parallel
2703 // access, one would need to take the FL locks and,
2704 // depending on how it is used, stagger access from
2705 // parallel threads to reduce contention.
2706 void CFLS_LAB::retire(int tid) {
2707 // We run this single threaded with the world stopped;
2708 // so no need for locks and such.
2709 NOT_PRODUCT(Thread* t = Thread::current();)
2710 assert(Thread::current()->is_VM_thread(), "Error");
2711 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2712 i < CompactibleFreeListSpace::IndexSetSize;
2713 i += CompactibleFreeListSpace::IndexSetStride) {
2714 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2715 "Can't retire more than what we obtained");
2716 if (_num_blocks[i] > 0) {
2717 size_t num_retire = _indexedFreeList[i].count();
2718 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2719 {
2720 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2721 // Mutex::_no_safepoint_check_flag);
2722
2723 // Update globals stats for num_blocks used
2724 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2725 _global_num_workers[i]++;
2726 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2727 if (num_retire > 0) {
2728 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2729 // Reset this list.
2730 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
2731 _indexedFreeList[i].set_size(i);
2732 }
2733 }
2734 if (PrintOldPLAB) {
2735 gclog_or_tty->print_cr("%d[%d]: %d/%d/%d",
2736 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2737 }
2738 // Reset stats for next round
2739 _num_blocks[i] = 0;
2740 }
2741 }
2742 }
2743
2744 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2745 assert(fl->count() == 0, "Precondition.");
2746 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2747 "Precondition");
2748
2749 // We'll try all multiples of word_sz in the indexed set, starting with
2750 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2751 // then try getting a big chunk and splitting it.
2752 {
2753 bool found;
2754 int k;
2755 size_t cur_sz;
2756 for (k = 1, cur_sz = k * word_sz, found = false;
2757 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2758 (CMSSplitIndexedFreeListBlocks || k <= 1);
2759 k++, cur_sz = k * word_sz) {
2760 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
2761 fl_for_cur_sz.set_size(cur_sz);
2762 {
2763 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2764 Mutex::_no_safepoint_check_flag);
2765 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
2766 if (gfl->count() != 0) {
2767 // nn is the number of chunks of size cur_sz that
2768 // we'd need to split k-ways each, in order to create
2769 // "n" chunks of size word_sz each.
2770 const size_t nn = MAX2(n/k, (size_t)1);
2771 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2772 found = true;
2773 if (k > 1) {
2774 // Update split death stats for the cur_sz-size blocks list:
2775 // we increment the split death count by the number of blocks
2776 // we just took from the cur_sz-size blocks list and which
2777 // we will be splitting below.
2778 ssize_t deaths = gfl->split_deaths() +
2779 fl_for_cur_sz.count();
2780 gfl->set_split_deaths(deaths);
2781 }
2782 }
2783 }
2784 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2785 if (found) {
2786 if (k == 1) {
2787 fl->prepend(&fl_for_cur_sz);
2788 } else {
2789 // Divide each block on fl_for_cur_sz up k ways.
2790 FreeChunk* fc;
2791 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
2792 // Must do this in reverse order, so that anybody attempting to
2793 // access the main chunk sees it as a single free block until we
2794 // change it.
2795 size_t fc_size = fc->size();
2796 assert(fc->is_free(), "Error");
2797 for (int i = k-1; i >= 0; i--) {
2798 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2799 assert((i != 0) ||
2800 ((fc == ffc) && ffc->is_free() &&
2801 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2802 "Counting error");
2803 ffc->set_size(word_sz);
2804 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2805 ffc->link_next(NULL);
2806 // Above must occur before BOT is updated below.
2807 OrderAccess::storestore();
2808 // splitting from the right, fc_size == i * word_sz
2809 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2810 fc_size -= word_sz;
2811 assert(fc_size == i*word_sz, "Error");
2812 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2813 _bt.verify_single_block((HeapWord*)fc, fc_size);
2814 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2815 // Push this on "fl".
2816 fl->return_chunk_at_head(ffc);
2817 }
2818 // TRAP
2819 assert(fl->tail()->next() == NULL, "List invariant.");
2820 }
2821 }
2822 // Update birth stats for this block size.
2823 size_t num = fl->count();
2824 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2825 Mutex::_no_safepoint_check_flag);
2826 ssize_t births = _indexedFreeList[word_sz].split_births() + num;
2827 _indexedFreeList[word_sz].set_split_births(births);
2828 return;
2829 }
2830 }
2831 }
2832 // Otherwise, we'll split a block from the dictionary.
2833 FreeChunk* fc = NULL;
2834 FreeChunk* rem_fc = NULL;
2835 size_t rem;
2836 {
2837 MutexLockerEx x(parDictionaryAllocLock(),
2838 Mutex::_no_safepoint_check_flag);
2839 while (n > 0) {
2840 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()),
2841 FreeBlockDictionary<FreeChunk>::atLeast);
2842 if (fc != NULL) {
2843 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2844 dictionary()->dict_census_update(fc->size(),
2845 true /*split*/,
2846 false /*birth*/);
2847 break;
2848 } else {
2849 n--;
2850 }
2851 }
2852 if (fc == NULL) return;
2853 // Otherwise, split up that block.
2854 assert((ssize_t)n >= 1, "Control point invariant");
2855 assert(fc->is_free(), "Error: should be a free block");
2856 _bt.verify_single_block((HeapWord*)fc, fc->size());
2857 const size_t nn = fc->size() / word_sz;
2858 n = MIN2(nn, n);
2859 assert((ssize_t)n >= 1, "Control point invariant");
2860 rem = fc->size() - n * word_sz;
2861 // If there is a remainder, and it's too small, allocate one fewer.
2862 if (rem > 0 && rem < MinChunkSize) {
2863 n--; rem += word_sz;
2864 }
2865 // Note that at this point we may have n == 0.
2866 assert((ssize_t)n >= 0, "Control point invariant");
2867
2868 // If n is 0, the chunk fc that was found is not large
2869 // enough to leave a viable remainder. We are unable to
2870 // allocate even one block. Return fc to the
2871 // dictionary and return, leaving "fl" empty.
2872 if (n == 0) {
2873 returnChunkToDictionary(fc);
2874 assert(fl->count() == 0, "We never allocated any blocks");
2875 return;
2876 }
2877
2878 // First return the remainder, if any.
2879 // Note that we hold the lock until we decide if we're going to give
2880 // back the remainder to the dictionary, since a concurrent allocation
2881 // may otherwise see the heap as empty. (We're willing to take that
2882 // hit if the block is a small block.)
2883 if (rem > 0) {
2884 size_t prefix_size = n * word_sz;
2885 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2886 rem_fc->set_size(rem);
2887 rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2888 rem_fc->link_next(NULL);
2889 // Above must occur before BOT is updated below.
2890 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2891 OrderAccess::storestore();
2892 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2893 assert(fc->is_free(), "Error");
2894 fc->set_size(prefix_size);
2895 if (rem >= IndexSetSize) {
2896 returnChunkToDictionary(rem_fc);
2897 dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/);
2898 rem_fc = NULL;
2899 }
2900 // Otherwise, return it to the small list below.
2901 }
2902 }
2903 if (rem_fc != NULL) {
2904 MutexLockerEx x(_indexedFreeListParLocks[rem],
2905 Mutex::_no_safepoint_check_flag);
2906 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2907 _indexedFreeList[rem].return_chunk_at_head(rem_fc);
2908 smallSplitBirth(rem);
2909 }
2910 assert((ssize_t)n > 0 && fc != NULL, "Consistency");
2911 // Now do the splitting up.
2912 // Must do this in reverse order, so that anybody attempting to
2913 // access the main chunk sees it as a single free block until we
2914 // change it.
2915 size_t fc_size = n * word_sz;
2916 // All but first chunk in this loop
2917 for (ssize_t i = n-1; i > 0; i--) {
2918 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2919 ffc->set_size(word_sz);
2920 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2921 ffc->link_next(NULL);
2922 // Above must occur before BOT is updated below.
2923 OrderAccess::storestore();
2924 // splitting from the right, fc_size == (n - i + 1) * wordsize
2925 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2926 fc_size -= word_sz;
2927 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2928 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2929 _bt.verify_single_block((HeapWord*)fc, fc_size);
2930 // Push this on "fl".
2931 fl->return_chunk_at_head(ffc);
2932 }
2933 // First chunk
2934 assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block");
2935 // The blocks above should show their new sizes before the first block below
2936 fc->set_size(word_sz);
2937 fc->link_prev(NULL); // idempotent wrt free-ness, see assert above
2938 fc->link_next(NULL);
2939 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2940 _bt.verify_single_block((HeapWord*)fc, fc->size());
2941 fl->return_chunk_at_head(fc);
2942
2943 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2944 {
2945 // Update the stats for this block size.
2946 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2947 Mutex::_no_safepoint_check_flag);
2948 const ssize_t births = _indexedFreeList[word_sz].split_births() + n;
2949 _indexedFreeList[word_sz].set_split_births(births);
2950 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2951 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2952 }
2953
2954 // TRAP
2955 assert(fl->tail()->next() == NULL, "List invariant.");
2956 }
2957
2958 // Set up the space's par_seq_tasks structure for work claiming
2959 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2960 // XXX Need to suitably abstract and generalize this and the next
2961 // method into one.
2962 void
2963 CompactibleFreeListSpace::
2964 initialize_sequential_subtasks_for_rescan(int n_threads) {
2965 // The "size" of each task is fixed according to rescan_task_size.
2966 assert(n_threads > 0, "Unexpected n_threads argument");
2967 const size_t task_size = rescan_task_size();
2968 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2969 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2970 assert(n_tasks == 0 ||
2971 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2972 (used_region().start() + n_tasks*task_size >= used_region().end())),
2973 "n_tasks calculation incorrect");
2974 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2975 assert(!pst->valid(), "Clobbering existing data?");
2976 // Sets the condition for completion of the subtask (how many threads
2977 // need to finish in order to be done).
2978 pst->set_n_threads(n_threads);
2979 pst->set_n_tasks((int)n_tasks);
2980 }
2981
2982 // Set up the space's par_seq_tasks structure for work claiming
2983 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2984 void
2985 CompactibleFreeListSpace::
2986 initialize_sequential_subtasks_for_marking(int n_threads,
2987 HeapWord* low) {
2988 // The "size" of each task is fixed according to rescan_task_size.
2989 assert(n_threads > 0, "Unexpected n_threads argument");
2990 const size_t task_size = marking_task_size();
2991 assert(task_size > CardTableModRefBS::card_size_in_words &&
2992 (task_size % CardTableModRefBS::card_size_in_words == 0),
2993 "Otherwise arithmetic below would be incorrect");
2994 MemRegion span = _gen->reserved();
2995 if (low != NULL) {
2996 if (span.contains(low)) {
2997 // Align low down to a card boundary so that
2998 // we can use block_offset_careful() on span boundaries.
2999 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
3000 CardTableModRefBS::card_size);
3001 // Clip span prefix at aligned_low
3002 span = span.intersection(MemRegion(aligned_low, span.end()));
3003 } else if (low > span.end()) {
3004 span = MemRegion(low, low); // Null region
3005 } // else use entire span
3006 }
3007 assert(span.is_empty() ||
3008 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
3009 "span should start at a card boundary");
3010 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
3011 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
3012 assert(n_tasks == 0 ||
3013 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
3014 (span.start() + n_tasks*task_size >= span.end())),
3015 "n_tasks calculation incorrect");
3016 SequentialSubTasksDone* pst = conc_par_seq_tasks();
3017 assert(!pst->valid(), "Clobbering existing data?");
3018 // Sets the condition for completion of the subtask (how many threads
3019 // need to finish in order to be done).
3020 pst->set_n_threads(n_threads);
3021 pst->set_n_tasks((int)n_tasks);
3022 }