1 /*
2 * Copyright (c) 2001, 2015, 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).
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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,
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20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc/cms/cmsLockVerifier.hpp"
27 #include "gc/cms/compactibleFreeListSpace.hpp"
28 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
29 #include "gc/cms/concurrentMarkSweepThread.hpp"
30 #include "gc/shared/blockOffsetTable.inline.hpp"
31 #include "gc/shared/collectedHeap.inline.hpp"
32 #include "gc/shared/gcTraceTime.hpp"
33 #include "gc/shared/genCollectedHeap.hpp"
34 #include "gc/shared/liveRange.hpp"
35 #include "gc/shared/space.inline.hpp"
36 #include "gc/shared/spaceDecorator.hpp"
37 #include "memory/allocation.inline.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "runtime/globals.hpp"
42 #include "runtime/handles.inline.hpp"
43 #include "runtime/init.hpp"
44 #include "runtime/java.hpp"
45 #include "runtime/orderAccess.inline.hpp"
46 #include "runtime/vmThread.hpp"
47 #include "utilities/copy.hpp"
48
49 /////////////////////////////////////////////////////////////////////////
50 //// CompactibleFreeListSpace
51 /////////////////////////////////////////////////////////////////////////
52
53 // highest ranked free list lock rank
54 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
55
56 // Defaults are 0 so things will break badly if incorrectly initialized.
57 size_t CompactibleFreeListSpace::IndexSetStart = 0;
58 size_t CompactibleFreeListSpace::IndexSetStride = 0;
59
60 size_t MinChunkSize = 0;
61
62 void CompactibleFreeListSpace::set_cms_values() {
63 // Set CMS global values
64 assert(MinChunkSize == 0, "already set");
65
66 // MinChunkSize should be a multiple of MinObjAlignment and be large enough
67 // for chunks to contain a FreeChunk.
68 size_t min_chunk_size_in_bytes = align_size_up(sizeof(FreeChunk), MinObjAlignmentInBytes);
69 MinChunkSize = min_chunk_size_in_bytes / BytesPerWord;
70
71 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
72 IndexSetStart = MinChunkSize;
73 IndexSetStride = MinObjAlignment;
74 }
75
76 // Constructor
77 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs,
78 MemRegion mr, bool use_adaptive_freelists,
79 FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) :
80 _dictionaryChoice(dictionaryChoice),
81 _adaptive_freelists(use_adaptive_freelists),
82 _bt(bs, mr),
83 // free list locks are in the range of values taken by _lockRank
84 // This range currently is [_leaf+2, _leaf+3]
85 // Note: this requires that CFLspace c'tors
86 // are called serially in the order in which the locks are
87 // are acquired in the program text. This is true today.
88 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true,
89 Monitor::_safepoint_check_sometimes),
90 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
91 "CompactibleFreeListSpace._dict_par_lock", true,
92 Monitor::_safepoint_check_never),
93 _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
94 CMSRescanMultiple),
95 _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
96 CMSConcMarkMultiple),
97 _collector(NULL),
98 _preconsumptionDirtyCardClosure(NULL)
99 {
100 assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize,
101 "FreeChunk is larger than expected");
102 _bt.set_space(this);
103 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
104 // We have all of "mr", all of which we place in the dictionary
105 // as one big chunk. We'll need to decide here which of several
106 // possible alternative dictionary implementations to use. For
107 // now the choice is easy, since we have only one working
108 // implementation, namely, the simple binary tree (splaying
109 // temporarily disabled).
110 switch (dictionaryChoice) {
111 case FreeBlockDictionary<FreeChunk>::dictionaryBinaryTree:
112 _dictionary = new AFLBinaryTreeDictionary(mr);
113 break;
114 case FreeBlockDictionary<FreeChunk>::dictionarySplayTree:
115 case FreeBlockDictionary<FreeChunk>::dictionarySkipList:
116 default:
117 warning("dictionaryChoice: selected option not understood; using"
118 " default BinaryTreeDictionary implementation instead.");
119 }
120 assert(_dictionary != NULL, "CMS dictionary initialization");
121 // The indexed free lists are initially all empty and are lazily
122 // filled in on demand. Initialize the array elements to NULL.
123 initializeIndexedFreeListArray();
124
125 // Not using adaptive free lists assumes that allocation is first
126 // from the linAB's. Also a cms perm gen which can be compacted
127 // has to have the klass's klassKlass allocated at a lower
128 // address in the heap than the klass so that the klassKlass is
129 // moved to its new location before the klass is moved.
130 // Set the _refillSize for the linear allocation blocks
131 if (!use_adaptive_freelists) {
132 FreeChunk* fc = _dictionary->get_chunk(mr.word_size(),
133 FreeBlockDictionary<FreeChunk>::atLeast);
134 // The small linAB initially has all the space and will allocate
135 // a chunk of any size.
136 HeapWord* addr = (HeapWord*) fc;
137 _smallLinearAllocBlock.set(addr, fc->size() ,
138 1024*SmallForLinearAlloc, fc->size());
139 // Note that _unallocated_block is not updated here.
140 // Allocations from the linear allocation block should
141 // update it.
142 } else {
143 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
144 SmallForLinearAlloc);
145 }
146 // CMSIndexedFreeListReplenish should be at least 1
147 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
148 _promoInfo.setSpace(this);
149 if (UseCMSBestFit) {
150 _fitStrategy = FreeBlockBestFitFirst;
151 } else {
152 _fitStrategy = FreeBlockStrategyNone;
153 }
154 check_free_list_consistency();
155
156 // Initialize locks for parallel case.
157 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
158 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
159 "a freelist par lock", true, Mutex::_safepoint_check_sometimes);
160 DEBUG_ONLY(
161 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
162 )
163 }
164 _dictionary->set_par_lock(&_parDictionaryAllocLock);
165 }
166
167 // Like CompactibleSpace forward() but always calls cross_threshold() to
168 // update the block offset table. Removed initialize_threshold call because
169 // CFLS does not use a block offset array for contiguous spaces.
170 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
171 CompactPoint* cp, HeapWord* compact_top) {
172 // q is alive
173 // First check if we should switch compaction space
174 assert(this == cp->space, "'this' should be current compaction space.");
175 size_t compaction_max_size = pointer_delta(end(), compact_top);
176 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
177 "virtual adjustObjectSize_v() method is not correct");
178 size_t adjusted_size = adjustObjectSize(size);
179 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
180 "no small fragments allowed");
181 assert(minimum_free_block_size() == MinChunkSize,
182 "for de-virtualized reference below");
183 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
184 if (adjusted_size + MinChunkSize > compaction_max_size &&
185 adjusted_size != compaction_max_size) {
186 do {
187 // switch to next compaction space
188 cp->space->set_compaction_top(compact_top);
189 cp->space = cp->space->next_compaction_space();
190 if (cp->space == NULL) {
191 cp->gen = GenCollectedHeap::heap()->young_gen();
192 assert(cp->gen != NULL, "compaction must succeed");
193 cp->space = cp->gen->first_compaction_space();
194 assert(cp->space != NULL, "generation must have a first compaction space");
195 }
196 compact_top = cp->space->bottom();
197 cp->space->set_compaction_top(compact_top);
198 // The correct adjusted_size may not be the same as that for this method
199 // (i.e., cp->space may no longer be "this" so adjust the size again.
200 // Use the virtual method which is not used above to save the virtual
201 // dispatch.
202 adjusted_size = cp->space->adjust_object_size_v(size);
203 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
204 assert(cp->space->minimum_free_block_size() == 0, "just checking");
205 } while (adjusted_size > compaction_max_size);
206 }
207
208 // store the forwarding pointer into the mark word
209 if ((HeapWord*)q != compact_top) {
210 q->forward_to(oop(compact_top));
211 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
212 } else {
213 // if the object isn't moving we can just set the mark to the default
214 // mark and handle it specially later on.
215 q->init_mark();
216 assert(q->forwardee() == NULL, "should be forwarded to NULL");
217 }
218
219 compact_top += adjusted_size;
220
221 // we need to update the offset table so that the beginnings of objects can be
222 // found during scavenge. Note that we are updating the offset table based on
223 // where the object will be once the compaction phase finishes.
224
225 // Always call cross_threshold(). A contiguous space can only call it when
226 // the compaction_top exceeds the current threshold but not for an
227 // non-contiguous space.
228 cp->threshold =
229 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
230 return compact_top;
231 }
232
233 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
234 // and use of single_block instead of alloc_block. The name here is not really
235 // appropriate - maybe a more general name could be invented for both the
236 // contiguous and noncontiguous spaces.
237
238 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
239 _bt.single_block(start, the_end);
240 return end();
241 }
242
243 // Initialize them to NULL.
244 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
245 for (size_t i = 0; i < IndexSetSize; i++) {
246 // Note that on platforms where objects are double word aligned,
247 // the odd array elements are not used. It is convenient, however,
248 // to map directly from the object size to the array element.
249 _indexedFreeList[i].reset(IndexSetSize);
250 _indexedFreeList[i].set_size(i);
251 assert(_indexedFreeList[i].count() == 0, "reset check failed");
252 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
253 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
254 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
255 }
256 }
257
258 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
259 for (size_t i = 1; i < IndexSetSize; i++) {
260 assert(_indexedFreeList[i].size() == (size_t) i,
261 "Indexed free list sizes are incorrect");
262 _indexedFreeList[i].reset(IndexSetSize);
263 assert(_indexedFreeList[i].count() == 0, "reset check failed");
264 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
265 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
266 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
267 }
268 }
269
270 void CompactibleFreeListSpace::reset(MemRegion mr) {
271 resetIndexedFreeListArray();
272 dictionary()->reset();
273 if (BlockOffsetArrayUseUnallocatedBlock) {
274 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
275 // Everything's allocated until proven otherwise.
276 _bt.set_unallocated_block(end());
277 }
278 if (!mr.is_empty()) {
279 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
280 _bt.single_block(mr.start(), mr.word_size());
281 FreeChunk* fc = (FreeChunk*) mr.start();
282 fc->set_size(mr.word_size());
283 if (mr.word_size() >= IndexSetSize ) {
284 returnChunkToDictionary(fc);
285 } else {
286 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
287 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc);
288 }
289 coalBirth(mr.word_size());
290 }
291 _promoInfo.reset();
292 _smallLinearAllocBlock._ptr = NULL;
293 _smallLinearAllocBlock._word_size = 0;
294 }
295
296 void CompactibleFreeListSpace::reset_after_compaction() {
297 // Reset the space to the new reality - one free chunk.
298 MemRegion mr(compaction_top(), end());
299 reset(mr);
300 // Now refill the linear allocation block(s) if possible.
301 if (_adaptive_freelists) {
302 refillLinearAllocBlocksIfNeeded();
303 } else {
304 // Place as much of mr in the linAB as we can get,
305 // provided it was big enough to go into the dictionary.
306 FreeChunk* fc = dictionary()->find_largest_dict();
307 if (fc != NULL) {
308 assert(fc->size() == mr.word_size(),
309 "Why was the chunk broken up?");
310 removeChunkFromDictionary(fc);
311 HeapWord* addr = (HeapWord*) fc;
312 _smallLinearAllocBlock.set(addr, fc->size() ,
313 1024*SmallForLinearAlloc, fc->size());
314 // Note that _unallocated_block is not updated here.
315 }
316 }
317 }
318
319 // Walks the entire dictionary, returning a coterminal
320 // chunk, if it exists. Use with caution since it involves
321 // a potentially complete walk of a potentially large tree.
322 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
323
324 assert_lock_strong(&_freelistLock);
325
326 return dictionary()->find_chunk_ends_at(end());
327 }
328
329
330 #ifndef PRODUCT
331 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
332 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
333 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
334 }
335 }
336
337 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
338 size_t sum = 0;
339 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
340 sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
341 }
342 return sum;
343 }
344
345 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
346 size_t count = 0;
347 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
348 debug_only(
349 ssize_t total_list_count = 0;
350 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
351 fc = fc->next()) {
352 total_list_count++;
353 }
354 assert(total_list_count == _indexedFreeList[i].count(),
355 "Count in list is incorrect");
356 )
357 count += _indexedFreeList[i].count();
358 }
359 return count;
360 }
361
362 size_t CompactibleFreeListSpace::totalCount() {
363 size_t num = totalCountInIndexedFreeLists();
364 num += dictionary()->total_count();
365 if (_smallLinearAllocBlock._word_size != 0) {
366 num++;
367 }
368 return num;
369 }
370 #endif
371
372 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
373 FreeChunk* fc = (FreeChunk*) p;
374 return fc->is_free();
375 }
376
377 size_t CompactibleFreeListSpace::used() const {
378 return capacity() - free();
379 }
380
381 size_t CompactibleFreeListSpace::free() const {
382 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
383 // if you do this while the structures are in flux you
384 // may get an approximate answer only; for instance
385 // because there is concurrent allocation either
386 // directly by mutators or for promotion during a GC.
387 // It's "MT-safe", however, in the sense that you are guaranteed
388 // not to crash and burn, for instance, because of walking
389 // pointers that could disappear as you were walking them.
390 // The approximation is because the various components
391 // that are read below are not read atomically (and
392 // further the computation of totalSizeInIndexedFreeLists()
393 // is itself a non-atomic computation. The normal use of
394 // this is during a resize operation at the end of GC
395 // and at that time you are guaranteed to get the
396 // correct actual value. However, for instance, this is
397 // also read completely asynchronously by the "perf-sampler"
398 // that supports jvmstat, and you are apt to see the values
399 // flicker in such cases.
400 assert(_dictionary != NULL, "No _dictionary?");
401 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
402 totalSizeInIndexedFreeLists() +
403 _smallLinearAllocBlock._word_size) * HeapWordSize;
404 }
405
406 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
407 assert(_dictionary != NULL, "No _dictionary?");
408 assert_locked();
409 size_t res = _dictionary->max_chunk_size();
410 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
411 (size_t) SmallForLinearAlloc - 1));
412 // XXX the following could potentially be pretty slow;
413 // should one, pessimistically for the rare cases when res
414 // calculated above is less than IndexSetSize,
415 // just return res calculated above? My reasoning was that
416 // those cases will be so rare that the extra time spent doesn't
417 // really matter....
418 // Note: do not change the loop test i >= res + IndexSetStride
419 // to i > res below, because i is unsigned and res may be zero.
420 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
421 i -= IndexSetStride) {
422 if (_indexedFreeList[i].head() != NULL) {
423 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
424 return i;
425 }
426 }
427 return res;
428 }
429
430 void LinearAllocBlock::print_on(outputStream* st) const {
431 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
432 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
433 p2i(_ptr), _word_size, _refillSize, _allocation_size_limit);
434 }
435
436 void CompactibleFreeListSpace::print_on(outputStream* st) const {
437 st->print_cr("COMPACTIBLE FREELIST SPACE");
438 st->print_cr(" Space:");
439 Space::print_on(st);
440
441 st->print_cr("promoInfo:");
442 _promoInfo.print_on(st);
443
444 st->print_cr("_smallLinearAllocBlock");
445 _smallLinearAllocBlock.print_on(st);
446
447 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
448
449 st->print_cr(" _fitStrategy = %s, _adaptive_freelists = %s",
450 _fitStrategy?"true":"false", _adaptive_freelists?"true":"false");
451 }
452
453 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
454 const {
455 reportIndexedFreeListStatistics();
456 gclog_or_tty->print_cr("Layout of Indexed Freelists");
457 gclog_or_tty->print_cr("---------------------------");
458 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
459 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
460 _indexedFreeList[i].print_on(gclog_or_tty);
461 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
462 fc = fc->next()) {
463 gclog_or_tty->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
464 p2i(fc), p2i((HeapWord*)fc + i),
465 fc->cantCoalesce() ? "\t CC" : "");
466 }
467 }
468 }
469
470 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
471 const {
472 _promoInfo.print_on(st);
473 }
474
475 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
476 const {
477 _dictionary->report_statistics();
478 st->print_cr("Layout of Freelists in Tree");
479 st->print_cr("---------------------------");
480 _dictionary->print_free_lists(st);
481 }
482
483 class BlkPrintingClosure: public BlkClosure {
484 const CMSCollector* _collector;
485 const CompactibleFreeListSpace* _sp;
486 const CMSBitMap* _live_bit_map;
487 const bool _post_remark;
488 outputStream* _st;
489 public:
490 BlkPrintingClosure(const CMSCollector* collector,
491 const CompactibleFreeListSpace* sp,
492 const CMSBitMap* live_bit_map,
493 outputStream* st):
494 _collector(collector),
495 _sp(sp),
496 _live_bit_map(live_bit_map),
497 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
498 _st(st) { }
499 size_t do_blk(HeapWord* addr);
500 };
501
502 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
503 size_t sz = _sp->block_size_no_stall(addr, _collector);
504 assert(sz != 0, "Should always be able to compute a size");
505 if (_sp->block_is_obj(addr)) {
506 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
507 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
508 p2i(addr),
509 dead ? "dead" : "live",
510 sz,
511 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
512 if (CMSPrintObjectsInDump && !dead) {
513 oop(addr)->print_on(_st);
514 _st->print_cr("--------------------------------------");
515 }
516 } else { // free block
517 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
518 p2i(addr), sz, CMSPrintChunksInDump ? ":" : ".");
519 if (CMSPrintChunksInDump) {
520 ((FreeChunk*)addr)->print_on(_st);
521 _st->print_cr("--------------------------------------");
522 }
523 }
524 return sz;
525 }
526
527 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c,
528 outputStream* st) {
529 st->print_cr("\n=========================");
530 st->print_cr("Block layout in CMS Heap:");
531 st->print_cr("=========================");
532 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
533 blk_iterate(&bpcl);
534
535 st->print_cr("\n=======================================");
536 st->print_cr("Order & Layout of Promotion Info Blocks");
537 st->print_cr("=======================================");
538 print_promo_info_blocks(st);
539
540 st->print_cr("\n===========================");
541 st->print_cr("Order of Indexed Free Lists");
542 st->print_cr("=========================");
543 print_indexed_free_lists(st);
544
545 st->print_cr("\n=================================");
546 st->print_cr("Order of Free Lists in Dictionary");
547 st->print_cr("=================================");
548 print_dictionary_free_lists(st);
549 }
550
551
552 void CompactibleFreeListSpace::reportFreeListStatistics() const {
553 assert_lock_strong(&_freelistLock);
554 assert(PrintFLSStatistics != 0, "Reporting error");
555 _dictionary->report_statistics();
556 if (PrintFLSStatistics > 1) {
557 reportIndexedFreeListStatistics();
558 size_t total_size = totalSizeInIndexedFreeLists() +
559 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
560 gclog_or_tty->print(" free=" SIZE_FORMAT " frag=%1.4f\n", total_size, flsFrag());
561 }
562 }
563
564 void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const {
565 assert_lock_strong(&_freelistLock);
566 gclog_or_tty->print("Statistics for IndexedFreeLists:\n"
567 "--------------------------------\n");
568 size_t total_size = totalSizeInIndexedFreeLists();
569 size_t free_blocks = numFreeBlocksInIndexedFreeLists();
570 gclog_or_tty->print("Total Free Space: " SIZE_FORMAT "\n", total_size);
571 gclog_or_tty->print("Max Chunk Size: " SIZE_FORMAT "\n", maxChunkSizeInIndexedFreeLists());
572 gclog_or_tty->print("Number of Blocks: " SIZE_FORMAT "\n", free_blocks);
573 if (free_blocks != 0) {
574 gclog_or_tty->print("Av. Block Size: " SIZE_FORMAT "\n", total_size/free_blocks);
575 }
576 }
577
578 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
579 size_t res = 0;
580 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
581 debug_only(
582 ssize_t recount = 0;
583 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
584 fc = fc->next()) {
585 recount += 1;
586 }
587 assert(recount == _indexedFreeList[i].count(),
588 "Incorrect count in list");
589 )
590 res += _indexedFreeList[i].count();
591 }
592 return res;
593 }
594
595 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
596 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
597 if (_indexedFreeList[i].head() != NULL) {
598 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
599 return (size_t)i;
600 }
601 }
602 return 0;
603 }
604
605 void CompactibleFreeListSpace::set_end(HeapWord* value) {
606 HeapWord* prevEnd = end();
607 assert(prevEnd != value, "unnecessary set_end call");
608 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
609 "New end is below unallocated block");
610 _end = value;
611 if (prevEnd != NULL) {
612 // Resize the underlying block offset table.
613 _bt.resize(pointer_delta(value, bottom()));
614 if (value <= prevEnd) {
615 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
616 "New end is below unallocated block");
617 } else {
618 // Now, take this new chunk and add it to the free blocks.
619 // Note that the BOT has not yet been updated for this block.
620 size_t newFcSize = pointer_delta(value, prevEnd);
621 // XXX This is REALLY UGLY and should be fixed up. XXX
622 if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) {
623 // Mark the boundary of the new block in BOT
624 _bt.mark_block(prevEnd, value);
625 // put it all in the linAB
626 MutexLockerEx x(parDictionaryAllocLock(),
627 Mutex::_no_safepoint_check_flag);
628 _smallLinearAllocBlock._ptr = prevEnd;
629 _smallLinearAllocBlock._word_size = newFcSize;
630 repairLinearAllocBlock(&_smallLinearAllocBlock);
631 // Births of chunks put into a LinAB are not recorded. Births
632 // of chunks as they are allocated out of a LinAB are.
633 } else {
634 // Add the block to the free lists, if possible coalescing it
635 // with the last free block, and update the BOT and census data.
636 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
637 }
638 }
639 }
640 }
641
642 class FreeListSpace_DCTOC : public Filtering_DCTOC {
643 CompactibleFreeListSpace* _cfls;
644 CMSCollector* _collector;
645 bool _parallel;
646 protected:
647 // Override.
648 #define walk_mem_region_with_cl_DECL(ClosureType) \
649 virtual void walk_mem_region_with_cl(MemRegion mr, \
650 HeapWord* bottom, HeapWord* top, \
651 ClosureType* cl); \
652 void walk_mem_region_with_cl_par(MemRegion mr, \
653 HeapWord* bottom, HeapWord* top, \
654 ClosureType* cl); \
655 void walk_mem_region_with_cl_nopar(MemRegion mr, \
656 HeapWord* bottom, HeapWord* top, \
657 ClosureType* cl)
658 walk_mem_region_with_cl_DECL(ExtendedOopClosure);
659 walk_mem_region_with_cl_DECL(FilteringClosure);
660
661 public:
662 FreeListSpace_DCTOC(CompactibleFreeListSpace* sp,
663 CMSCollector* collector,
664 ExtendedOopClosure* cl,
665 CardTableModRefBS::PrecisionStyle precision,
666 HeapWord* boundary,
667 bool parallel) :
668 Filtering_DCTOC(sp, cl, precision, boundary),
669 _cfls(sp), _collector(collector), _parallel(parallel) {}
670 };
671
672 // We de-virtualize the block-related calls below, since we know that our
673 // space is a CompactibleFreeListSpace.
674
675 #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
676 void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \
677 HeapWord* bottom, \
678 HeapWord* top, \
679 ClosureType* cl) { \
680 if (_parallel) { \
681 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
682 } else { \
683 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
684 } \
685 } \
686 void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
687 HeapWord* bottom, \
688 HeapWord* top, \
689 ClosureType* cl) { \
690 /* Skip parts that are before "mr", in case "block_start" sent us \
691 back too far. */ \
692 HeapWord* mr_start = mr.start(); \
693 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
694 HeapWord* next = bottom + bot_size; \
695 while (next < mr_start) { \
696 bottom = next; \
697 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
698 next = bottom + bot_size; \
699 } \
700 \
701 while (bottom < top) { \
702 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
703 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
704 oop(bottom)) && \
705 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
706 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
707 bottom += _cfls->adjustObjectSize(word_sz); \
708 } else { \
709 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
710 } \
711 } \
712 } \
713 void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
714 HeapWord* bottom, \
715 HeapWord* top, \
716 ClosureType* cl) { \
717 /* Skip parts that are before "mr", in case "block_start" sent us \
718 back too far. */ \
719 HeapWord* mr_start = mr.start(); \
720 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
721 HeapWord* next = bottom + bot_size; \
722 while (next < mr_start) { \
723 bottom = next; \
724 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
725 next = bottom + bot_size; \
726 } \
727 \
728 while (bottom < top) { \
729 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
730 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
731 oop(bottom)) && \
732 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
733 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
734 bottom += _cfls->adjustObjectSize(word_sz); \
735 } else { \
736 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
737 } \
738 } \
739 }
740
741 // (There are only two of these, rather than N, because the split is due
742 // only to the introduction of the FilteringClosure, a local part of the
743 // impl of this abstraction.)
744 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
745 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
746
747 DirtyCardToOopClosure*
748 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl,
749 CardTableModRefBS::PrecisionStyle precision,
750 HeapWord* boundary,
751 bool parallel) {
752 return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary, parallel);
753 }
754
755
756 // Note on locking for the space iteration functions:
757 // since the collector's iteration activities are concurrent with
758 // allocation activities by mutators, absent a suitable mutual exclusion
759 // mechanism the iterators may go awry. For instance a block being iterated
760 // may suddenly be allocated or divided up and part of it allocated and
761 // so on.
762
763 // Apply the given closure to each block in the space.
764 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
765 assert_lock_strong(freelistLock());
766 HeapWord *cur, *limit;
767 for (cur = bottom(), limit = end(); cur < limit;
768 cur += cl->do_blk_careful(cur));
769 }
770
771 // Apply the given closure to each block in the space.
772 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
773 assert_lock_strong(freelistLock());
774 HeapWord *cur, *limit;
775 for (cur = bottom(), limit = end(); cur < limit;
776 cur += cl->do_blk(cur));
777 }
778
779 // Apply the given closure to each oop in the space.
780 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) {
781 assert_lock_strong(freelistLock());
782 HeapWord *cur, *limit;
783 size_t curSize;
784 for (cur = bottom(), limit = end(); cur < limit;
785 cur += curSize) {
786 curSize = block_size(cur);
787 if (block_is_obj(cur)) {
788 oop(cur)->oop_iterate(cl);
789 }
790 }
791 }
792
793 // NOTE: In the following methods, in order to safely be able to
794 // apply the closure to an object, we need to be sure that the
795 // object has been initialized. We are guaranteed that an object
796 // is initialized if we are holding the Heap_lock with the
797 // world stopped.
798 void CompactibleFreeListSpace::verify_objects_initialized() const {
799 if (is_init_completed()) {
800 assert_locked_or_safepoint(Heap_lock);
801 if (Universe::is_fully_initialized()) {
802 guarantee(SafepointSynchronize::is_at_safepoint(),
803 "Required for objects to be initialized");
804 }
805 } // else make a concession at vm start-up
806 }
807
808 // Apply the given closure to each object in the space
809 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
810 assert_lock_strong(freelistLock());
811 NOT_PRODUCT(verify_objects_initialized());
812 HeapWord *cur, *limit;
813 size_t curSize;
814 for (cur = bottom(), limit = end(); cur < limit;
815 cur += curSize) {
816 curSize = block_size(cur);
817 if (block_is_obj(cur)) {
818 blk->do_object(oop(cur));
819 }
820 }
821 }
822
823 // Apply the given closure to each live object in the space
824 // The usage of CompactibleFreeListSpace
825 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
826 // objects in the space with references to objects that are no longer
827 // valid. For example, an object may reference another object
828 // that has already been sweep up (collected). This method uses
829 // obj_is_alive() to determine whether it is safe to apply the closure to
830 // an object. See obj_is_alive() for details on how liveness of an
831 // object is decided.
832
833 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
834 assert_lock_strong(freelistLock());
835 NOT_PRODUCT(verify_objects_initialized());
836 HeapWord *cur, *limit;
837 size_t curSize;
838 for (cur = bottom(), limit = end(); cur < limit;
839 cur += curSize) {
840 curSize = block_size(cur);
841 if (block_is_obj(cur) && obj_is_alive(cur)) {
842 blk->do_object(oop(cur));
843 }
844 }
845 }
846
847 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
848 UpwardsObjectClosure* cl) {
849 assert_locked(freelistLock());
850 NOT_PRODUCT(verify_objects_initialized());
851 assert(!mr.is_empty(), "Should be non-empty");
852 // We use MemRegion(bottom(), end()) rather than used_region() below
853 // because the two are not necessarily equal for some kinds of
854 // spaces, in particular, certain kinds of free list spaces.
855 // We could use the more complicated but more precise:
856 // MemRegion(used_region().start(), round_to(used_region().end(), CardSize))
857 // but the slight imprecision seems acceptable in the assertion check.
858 assert(MemRegion(bottom(), end()).contains(mr),
859 "Should be within used space");
860 HeapWord* prev = cl->previous(); // max address from last time
861 if (prev >= mr.end()) { // nothing to do
862 return;
863 }
864 // This assert will not work when we go from cms space to perm
865 // space, and use same closure. Easy fix deferred for later. XXX YSR
866 // assert(prev == NULL || contains(prev), "Should be within space");
867
868 bool last_was_obj_array = false;
869 HeapWord *blk_start_addr, *region_start_addr;
870 if (prev > mr.start()) {
871 region_start_addr = prev;
872 blk_start_addr = prev;
873 // The previous invocation may have pushed "prev" beyond the
874 // last allocated block yet there may be still be blocks
875 // in this region due to a particular coalescing policy.
876 // Relax the assertion so that the case where the unallocated
877 // block is maintained and "prev" is beyond the unallocated
878 // block does not cause the assertion to fire.
879 assert((BlockOffsetArrayUseUnallocatedBlock &&
880 (!is_in(prev))) ||
881 (blk_start_addr == block_start(region_start_addr)), "invariant");
882 } else {
883 region_start_addr = mr.start();
884 blk_start_addr = block_start(region_start_addr);
885 }
886 HeapWord* region_end_addr = mr.end();
887 MemRegion derived_mr(region_start_addr, region_end_addr);
888 while (blk_start_addr < region_end_addr) {
889 const size_t size = block_size(blk_start_addr);
890 if (block_is_obj(blk_start_addr)) {
891 last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);
892 } else {
893 last_was_obj_array = false;
894 }
895 blk_start_addr += size;
896 }
897 if (!last_was_obj_array) {
898 assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),
899 "Should be within (closed) used space");
900 assert(blk_start_addr > prev, "Invariant");
901 cl->set_previous(blk_start_addr); // min address for next time
902 }
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_m(MemRegion mr,
913 ObjectClosureCareful* cl) {
914 assert_lock_strong(freelistLock());
915 // Can't use used_region() below because it may not necessarily
916 // be the same as [bottom(),end()); although we could
917 // use [used_region().start(),round_to(used_region().end(),CardSize)),
918 // that appears too cumbersome, so we just do the simpler check
919 // in the assertion below.
920 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
921 "mr should be non-empty and within used space");
922 HeapWord *addr, *end;
923 size_t size;
924 for (addr = block_start_careful(mr.start()), end = mr.end();
925 addr < end; addr += size) {
926 FreeChunk* fc = (FreeChunk*)addr;
927 if (fc->is_free()) {
928 // Since we hold the free list lock, which protects direct
929 // allocation in this generation by mutators, a free object
930 // will remain free throughout this iteration code.
931 size = fc->size();
932 } else {
933 // Note that the object need not necessarily be initialized,
934 // because (for instance) the free list lock does NOT protect
935 // object initialization. The closure application below must
936 // therefore be correct in the face of uninitialized objects.
937 size = cl->do_object_careful_m(oop(addr), mr);
938 if (size == 0) {
939 // An unparsable object found. Signal early termination.
940 return addr;
941 }
942 }
943 }
944 return NULL;
945 }
946
947
948 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
949 NOT_PRODUCT(verify_objects_initialized());
950 return _bt.block_start(p);
951 }
952
953 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
954 return _bt.block_start_careful(p);
955 }
956
957 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
958 NOT_PRODUCT(verify_objects_initialized());
959 // This must be volatile, or else there is a danger that the compiler
960 // will compile the code below into a sometimes-infinite loop, by keeping
961 // the value read the first time in a register.
962 while (true) {
963 // We must do this until we get a consistent view of the object.
964 if (FreeChunk::indicatesFreeChunk(p)) {
965 volatile FreeChunk* fc = (volatile FreeChunk*)p;
966 size_t res = fc->size();
967
968 // Bugfix for systems with weak memory model (PPC64/IA64). The
969 // block's free bit was set and we have read the size of the
970 // block. Acquire and check the free bit again. If the block is
971 // still free, the read size is correct.
972 OrderAccess::acquire();
973
974 // If the object is still a free chunk, return the size, else it
975 // has been allocated so try again.
976 if (FreeChunk::indicatesFreeChunk(p)) {
977 assert(res != 0, "Block size should not be 0");
978 return res;
979 }
980 } else {
981 // must read from what 'p' points to in each loop.
982 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
983 if (k != NULL) {
984 assert(k->is_klass(), "Should really be klass oop.");
985 oop o = (oop)p;
986 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
987
988 // Bugfix for systems with weak memory model (PPC64/IA64).
989 // The object o may be an array. Acquire to make sure that the array
990 // size (third word) is consistent.
991 OrderAccess::acquire();
992
993 size_t res = o->size_given_klass(k);
994 res = adjustObjectSize(res);
995 assert(res != 0, "Block size should not be 0");
996 return res;
997 }
998 }
999 }
1000 }
1001
1002 // TODO: Now that is_parsable is gone, we should combine these two functions.
1003 // A variant of the above that uses the Printezis bits for
1004 // unparsable but allocated objects. This avoids any possible
1005 // stalls waiting for mutators to initialize objects, and is
1006 // thus potentially faster than the variant above. However,
1007 // this variant may return a zero size for a block that is
1008 // under mutation and for which a consistent size cannot be
1009 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
1010 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
1011 const CMSCollector* c)
1012 const {
1013 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1014 // This must be volatile, or else there is a danger that the compiler
1015 // will compile the code below into a sometimes-infinite loop, by keeping
1016 // the value read the first time in a register.
1017 DEBUG_ONLY(uint loops = 0;)
1018 while (true) {
1019 // We must do this until we get a consistent view of the object.
1020 if (FreeChunk::indicatesFreeChunk(p)) {
1021 volatile FreeChunk* fc = (volatile FreeChunk*)p;
1022 size_t res = fc->size();
1023
1024 // Bugfix for systems with weak memory model (PPC64/IA64). The
1025 // free bit of the block was set and we have read the size of
1026 // the block. Acquire and check the free bit again. If the
1027 // block is still free, the read size is correct.
1028 OrderAccess::acquire();
1029
1030 if (FreeChunk::indicatesFreeChunk(p)) {
1031 assert(res != 0, "Block size should not be 0");
1032 assert(loops == 0, "Should be 0");
1033 return res;
1034 }
1035 } else {
1036 // must read from what 'p' points to in each loop.
1037 Klass* k = ((volatile oopDesc*)p)->klass_or_null();
1038 // We trust the size of any object that has a non-NULL
1039 // klass and (for those in the perm gen) is parsable
1040 // -- irrespective of its conc_safe-ty.
1041 if (k != NULL) {
1042 assert(k->is_klass(), "Should really be klass oop.");
1043 oop o = (oop)p;
1044 assert(o->is_oop(), "Should be an oop");
1045
1046 // Bugfix for systems with weak memory model (PPC64/IA64).
1047 // The object o may be an array. Acquire to make sure that the array
1048 // size (third word) is consistent.
1049 OrderAccess::acquire();
1050
1051 size_t res = o->size_given_klass(k);
1052 res = adjustObjectSize(res);
1053 assert(res != 0, "Block size should not be 0");
1054 return res;
1055 } else {
1056 // May return 0 if P-bits not present.
1057 return c->block_size_if_printezis_bits(p);
1058 }
1059 }
1060 assert(loops == 0, "Can loop at most once");
1061 DEBUG_ONLY(loops++;)
1062 }
1063 }
1064
1065 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1066 NOT_PRODUCT(verify_objects_initialized());
1067 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1068 FreeChunk* fc = (FreeChunk*)p;
1069 if (fc->is_free()) {
1070 return fc->size();
1071 } else {
1072 // Ignore mark word because this may be a recently promoted
1073 // object whose mark word is used to chain together grey
1074 // objects (the last one would have a null value).
1075 assert(oop(p)->is_oop(true), "Should be an oop");
1076 return adjustObjectSize(oop(p)->size());
1077 }
1078 }
1079
1080 // This implementation assumes that the property of "being an object" is
1081 // stable. But being a free chunk may not be (because of parallel
1082 // promotion.)
1083 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1084 FreeChunk* fc = (FreeChunk*)p;
1085 assert(is_in_reserved(p), "Should be in space");
1086 if (FreeChunk::indicatesFreeChunk(p)) return false;
1087 Klass* k = oop(p)->klass_or_null();
1088 if (k != NULL) {
1089 // Ignore mark word because it may have been used to
1090 // chain together promoted objects (the last one
1091 // would have a null value).
1092 assert(oop(p)->is_oop(true), "Should be an oop");
1093 return true;
1094 } else {
1095 return false; // Was not an object at the start of collection.
1096 }
1097 }
1098
1099 // Check if the object is alive. This fact is checked either by consulting
1100 // the main marking bitmap in the sweeping phase or, if it's a permanent
1101 // generation and we're not in the sweeping phase, by checking the
1102 // perm_gen_verify_bit_map where we store the "deadness" information if
1103 // we did not sweep the perm gen in the most recent previous GC cycle.
1104 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1105 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1106 "Else races are possible");
1107 assert(block_is_obj(p), "The address should point to an object");
1108
1109 // If we're sweeping, we use object liveness information from the main bit map
1110 // for both perm gen and old gen.
1111 // We don't need to lock the bitmap (live_map or dead_map below), because
1112 // EITHER we are in the middle of the sweeping phase, and the
1113 // main marking bit map (live_map below) is locked,
1114 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1115 // is stable, because it's mutated only in the sweeping phase.
1116 // NOTE: This method is also used by jmap where, if class unloading is
1117 // off, the results can return "false" for legitimate perm objects,
1118 // when we are not in the midst of a sweeping phase, which can result
1119 // in jmap not reporting certain perm gen objects. This will be moot
1120 // if/when the perm gen goes away in the future.
1121 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1122 CMSBitMap* live_map = _collector->markBitMap();
1123 return live_map->par_isMarked((HeapWord*) p);
1124 }
1125 return true;
1126 }
1127
1128 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1129 FreeChunk* fc = (FreeChunk*)p;
1130 assert(is_in_reserved(p), "Should be in space");
1131 assert(_bt.block_start(p) == p, "Should be a block boundary");
1132 if (!fc->is_free()) {
1133 // Ignore mark word because it may have been used to
1134 // chain together promoted objects (the last one
1135 // would have a null value).
1136 assert(oop(p)->is_oop(true), "Should be an oop");
1137 return true;
1138 }
1139 return false;
1140 }
1141
1142 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1143 // approximate answer if you don't hold the freelistlock when you call this.
1144 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1145 size_t size = 0;
1146 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1147 debug_only(
1148 // We may be calling here without the lock in which case we
1149 // won't do this modest sanity check.
1150 if (freelistLock()->owned_by_self()) {
1151 size_t total_list_size = 0;
1152 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1153 fc = fc->next()) {
1154 total_list_size += i;
1155 }
1156 assert(total_list_size == i * _indexedFreeList[i].count(),
1157 "Count in list is incorrect");
1158 }
1159 )
1160 size += i * _indexedFreeList[i].count();
1161 }
1162 return size;
1163 }
1164
1165 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1166 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1167 return allocate(size);
1168 }
1169
1170 HeapWord*
1171 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1172 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1173 }
1174
1175 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1176 assert_lock_strong(freelistLock());
1177 HeapWord* res = NULL;
1178 assert(size == adjustObjectSize(size),
1179 "use adjustObjectSize() before calling into allocate()");
1180
1181 if (_adaptive_freelists) {
1182 res = allocate_adaptive_freelists(size);
1183 } else { // non-adaptive free lists
1184 res = allocate_non_adaptive_freelists(size);
1185 }
1186
1187 if (res != NULL) {
1188 // check that res does lie in this space!
1189 assert(is_in_reserved(res), "Not in this space!");
1190 assert(is_aligned((void*)res), "alignment check");
1191
1192 FreeChunk* fc = (FreeChunk*)res;
1193 fc->markNotFree();
1194 assert(!fc->is_free(), "shouldn't be marked free");
1195 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1196 // Verify that the block offset table shows this to
1197 // be a single block, but not one which is unallocated.
1198 _bt.verify_single_block(res, size);
1199 _bt.verify_not_unallocated(res, size);
1200 // mangle a just allocated object with a distinct pattern.
1201 debug_only(fc->mangleAllocated(size));
1202 }
1203
1204 return res;
1205 }
1206
1207 HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) {
1208 HeapWord* res = NULL;
1209 // try and use linear allocation for smaller blocks
1210 if (size < _smallLinearAllocBlock._allocation_size_limit) {
1211 // if successful, the following also adjusts block offset table
1212 res = getChunkFromSmallLinearAllocBlock(size);
1213 }
1214 // Else triage to indexed lists for smaller sizes
1215 if (res == NULL) {
1216 if (size < SmallForDictionary) {
1217 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1218 } else {
1219 // else get it from the big dictionary; if even this doesn't
1220 // work we are out of luck.
1221 res = (HeapWord*)getChunkFromDictionaryExact(size);
1222 }
1223 }
1224
1225 return res;
1226 }
1227
1228 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1229 assert_lock_strong(freelistLock());
1230 HeapWord* res = NULL;
1231 assert(size == adjustObjectSize(size),
1232 "use adjustObjectSize() before calling into allocate()");
1233
1234 // Strategy
1235 // if small
1236 // exact size from small object indexed list if small
1237 // small or large linear allocation block (linAB) as appropriate
1238 // take from lists of greater sized chunks
1239 // else
1240 // dictionary
1241 // small or large linear allocation block if it has the space
1242 // Try allocating exact size from indexTable first
1243 if (size < IndexSetSize) {
1244 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1245 if(res != NULL) {
1246 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1247 "Not removed from free list");
1248 // no block offset table adjustment is necessary on blocks in
1249 // the indexed lists.
1250
1251 // Try allocating from the small LinAB
1252 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1253 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1254 // if successful, the above also adjusts block offset table
1255 // Note that this call will refill the LinAB to
1256 // satisfy the request. This is different that
1257 // evm.
1258 // Don't record chunk off a LinAB? smallSplitBirth(size);
1259 } else {
1260 // Raid the exact free lists larger than size, even if they are not
1261 // overpopulated.
1262 res = (HeapWord*) getChunkFromGreater(size);
1263 }
1264 } else {
1265 // Big objects get allocated directly from the dictionary.
1266 res = (HeapWord*) getChunkFromDictionaryExact(size);
1267 if (res == NULL) {
1268 // Try hard not to fail since an allocation failure will likely
1269 // trigger a synchronous GC. Try to get the space from the
1270 // allocation blocks.
1271 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1272 }
1273 }
1274
1275 return res;
1276 }
1277
1278 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1279 // when promoting obj.
1280 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1281 // Depending on the object size, expansion may require refilling either a
1282 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1283 // is added because the dictionary may over-allocate to avoid fragmentation.
1284 size_t space = obj_size;
1285 if (!_adaptive_freelists) {
1286 space = MAX2(space, _smallLinearAllocBlock._refillSize);
1287 }
1288 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1289 return space;
1290 }
1291
1292 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1293 FreeChunk* ret;
1294
1295 assert(numWords >= MinChunkSize, "Size is less than minimum");
1296 assert(linearAllocationWouldFail() || bestFitFirst(),
1297 "Should not be here");
1298
1299 size_t i;
1300 size_t currSize = numWords + MinChunkSize;
1301 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1302 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1303 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
1304 if (fl->head()) {
1305 ret = getFromListGreater(fl, numWords);
1306 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1307 return ret;
1308 }
1309 }
1310
1311 currSize = MAX2((size_t)SmallForDictionary,
1312 (size_t)(numWords + MinChunkSize));
1313
1314 /* Try to get a chunk that satisfies request, while avoiding
1315 fragmentation that can't be handled. */
1316 {
1317 ret = dictionary()->get_chunk(currSize);
1318 if (ret != NULL) {
1319 assert(ret->size() - numWords >= MinChunkSize,
1320 "Chunk is too small");
1321 _bt.allocated((HeapWord*)ret, ret->size());
1322 /* Carve returned chunk. */
1323 (void) splitChunkAndReturnRemainder(ret, numWords);
1324 /* Label this as no longer a free chunk. */
1325 assert(ret->is_free(), "This chunk should be free");
1326 ret->link_prev(NULL);
1327 }
1328 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1329 return ret;
1330 }
1331 ShouldNotReachHere();
1332 }
1333
1334 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1335 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1336 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
1337 }
1338
1339 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1340 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1341 (_smallLinearAllocBlock._word_size == fc->size()),
1342 "Linear allocation block shows incorrect size");
1343 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1344 (_smallLinearAllocBlock._word_size == fc->size()));
1345 }
1346
1347 // Check if the purported free chunk is present either as a linear
1348 // allocation block, the size-indexed table of (smaller) free blocks,
1349 // or the larger free blocks kept in the binary tree dictionary.
1350 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
1351 if (verify_chunk_is_linear_alloc_block(fc)) {
1352 return true;
1353 } else if (fc->size() < IndexSetSize) {
1354 return verifyChunkInIndexedFreeLists(fc);
1355 } else {
1356 return dictionary()->verify_chunk_in_free_list(fc);
1357 }
1358 }
1359
1360 #ifndef PRODUCT
1361 void CompactibleFreeListSpace::assert_locked() const {
1362 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1363 }
1364
1365 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1366 CMSLockVerifier::assert_locked(lock);
1367 }
1368 #endif
1369
1370 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1371 // In the parallel case, the main thread holds the free list lock
1372 // on behalf the parallel threads.
1373 FreeChunk* fc;
1374 {
1375 // If GC is parallel, this might be called by several threads.
1376 // This should be rare enough that the locking overhead won't affect
1377 // the sequential code.
1378 MutexLockerEx x(parDictionaryAllocLock(),
1379 Mutex::_no_safepoint_check_flag);
1380 fc = getChunkFromDictionary(size);
1381 }
1382 if (fc != NULL) {
1383 fc->dontCoalesce();
1384 assert(fc->is_free(), "Should be free, but not coalescable");
1385 // Verify that the block offset table shows this to
1386 // be a single block, but not one which is unallocated.
1387 _bt.verify_single_block((HeapWord*)fc, fc->size());
1388 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1389 }
1390 return fc;
1391 }
1392
1393 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1394 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1395 assert_locked();
1396
1397 // if we are tracking promotions, then first ensure space for
1398 // promotion (including spooling space for saving header if necessary).
1399 // then allocate and copy, then track promoted info if needed.
1400 // When tracking (see PromotionInfo::track()), the mark word may
1401 // be displaced and in this case restoration of the mark word
1402 // occurs in the (oop_since_save_marks_)iterate phase.
1403 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1404 return NULL;
1405 }
1406 // Call the allocate(size_t, bool) form directly to avoid the
1407 // additional call through the allocate(size_t) form. Having
1408 // the compile inline the call is problematic because allocate(size_t)
1409 // is a virtual method.
1410 HeapWord* res = allocate(adjustObjectSize(obj_size));
1411 if (res != NULL) {
1412 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1413 // if we should be tracking promotions, do so.
1414 if (_promoInfo.tracking()) {
1415 _promoInfo.track((PromotedObject*)res);
1416 }
1417 }
1418 return oop(res);
1419 }
1420
1421 HeapWord*
1422 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1423 assert_locked();
1424 assert(size >= MinChunkSize, "minimum chunk size");
1425 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1426 "maximum from smallLinearAllocBlock");
1427 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1428 }
1429
1430 HeapWord*
1431 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1432 size_t size) {
1433 assert_locked();
1434 assert(size >= MinChunkSize, "too small");
1435 HeapWord* res = NULL;
1436 // Try to do linear allocation from blk, making sure that
1437 if (blk->_word_size == 0) {
1438 // We have probably been unable to fill this either in the prologue or
1439 // when it was exhausted at the last linear allocation. Bail out until
1440 // next time.
1441 assert(blk->_ptr == NULL, "consistency check");
1442 return NULL;
1443 }
1444 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1445 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1446 if (res != NULL) return res;
1447
1448 // about to exhaust this linear allocation block
1449 if (blk->_word_size == size) { // exactly satisfied
1450 res = blk->_ptr;
1451 _bt.allocated(res, blk->_word_size);
1452 } else if (size + MinChunkSize <= blk->_refillSize) {
1453 size_t sz = blk->_word_size;
1454 // Update _unallocated_block if the size is such that chunk would be
1455 // returned to the indexed free list. All other chunks in the indexed
1456 // free lists are allocated from the dictionary so that _unallocated_block
1457 // has already been adjusted for them. Do it here so that the cost
1458 // for all chunks added back to the indexed free lists.
1459 if (sz < SmallForDictionary) {
1460 _bt.allocated(blk->_ptr, sz);
1461 }
1462 // Return the chunk that isn't big enough, and then refill below.
1463 addChunkToFreeLists(blk->_ptr, sz);
1464 split_birth(sz);
1465 // Don't keep statistics on adding back chunk from a LinAB.
1466 } else {
1467 // A refilled block would not satisfy the request.
1468 return NULL;
1469 }
1470
1471 blk->_ptr = NULL; blk->_word_size = 0;
1472 refillLinearAllocBlock(blk);
1473 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1474 "block was replenished");
1475 if (res != NULL) {
1476 split_birth(size);
1477 repairLinearAllocBlock(blk);
1478 } else if (blk->_ptr != NULL) {
1479 res = blk->_ptr;
1480 size_t blk_size = blk->_word_size;
1481 blk->_word_size -= size;
1482 blk->_ptr += size;
1483 split_birth(size);
1484 repairLinearAllocBlock(blk);
1485 // Update BOT last so that other (parallel) GC threads see a consistent
1486 // view of the BOT and free blocks.
1487 // Above must occur before BOT is updated below.
1488 OrderAccess::storestore();
1489 _bt.split_block(res, blk_size, size); // adjust block offset table
1490 }
1491 return res;
1492 }
1493
1494 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1495 LinearAllocBlock* blk,
1496 size_t size) {
1497 assert_locked();
1498 assert(size >= MinChunkSize, "too small");
1499
1500 HeapWord* res = NULL;
1501 // This is the common case. Keep it simple.
1502 if (blk->_word_size >= size + MinChunkSize) {
1503 assert(blk->_ptr != NULL, "consistency check");
1504 res = blk->_ptr;
1505 // Note that the BOT is up-to-date for the linAB before allocation. It
1506 // indicates the start of the linAB. The split_block() updates the
1507 // BOT for the linAB after the allocation (indicates the start of the
1508 // next chunk to be allocated).
1509 size_t blk_size = blk->_word_size;
1510 blk->_word_size -= size;
1511 blk->_ptr += size;
1512 split_birth(size);
1513 repairLinearAllocBlock(blk);
1514 // Update BOT last so that other (parallel) GC threads see a consistent
1515 // view of the BOT and free blocks.
1516 // Above must occur before BOT is updated below.
1517 OrderAccess::storestore();
1518 _bt.split_block(res, blk_size, size); // adjust block offset table
1519 _bt.allocated(res, size);
1520 }
1521 return res;
1522 }
1523
1524 FreeChunk*
1525 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1526 assert_locked();
1527 assert(size < SmallForDictionary, "just checking");
1528 FreeChunk* res;
1529 res = _indexedFreeList[size].get_chunk_at_head();
1530 if (res == NULL) {
1531 res = getChunkFromIndexedFreeListHelper(size);
1532 }
1533 _bt.verify_not_unallocated((HeapWord*) res, size);
1534 assert(res == NULL || res->size() == size, "Incorrect block size");
1535 return res;
1536 }
1537
1538 FreeChunk*
1539 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1540 bool replenish) {
1541 assert_locked();
1542 FreeChunk* fc = NULL;
1543 if (size < SmallForDictionary) {
1544 assert(_indexedFreeList[size].head() == NULL ||
1545 _indexedFreeList[size].surplus() <= 0,
1546 "List for this size should be empty or under populated");
1547 // Try best fit in exact lists before replenishing the list
1548 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1549 // Replenish list.
1550 //
1551 // Things tried that failed.
1552 // Tried allocating out of the two LinAB's first before
1553 // replenishing lists.
1554 // Tried small linAB of size 256 (size in indexed list)
1555 // and replenishing indexed lists from the small linAB.
1556 //
1557 FreeChunk* newFc = NULL;
1558 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1559 if (replenish_size < SmallForDictionary) {
1560 // Do not replenish from an underpopulated size.
1561 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1562 _indexedFreeList[replenish_size].head() != NULL) {
1563 newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
1564 } else if (bestFitFirst()) {
1565 newFc = bestFitSmall(replenish_size);
1566 }
1567 }
1568 if (newFc == NULL && replenish_size > size) {
1569 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1570 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1571 }
1572 // Note: The stats update re split-death of block obtained above
1573 // will be recorded below precisely when we know we are going to
1574 // be actually splitting it into more than one pieces below.
1575 if (newFc != NULL) {
1576 if (replenish || CMSReplenishIntermediate) {
1577 // Replenish this list and return one block to caller.
1578 size_t i;
1579 FreeChunk *curFc, *nextFc;
1580 size_t num_blk = newFc->size() / size;
1581 assert(num_blk >= 1, "Smaller than requested?");
1582 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1583 if (num_blk > 1) {
1584 // we are sure we will be splitting the block just obtained
1585 // into multiple pieces; record the split-death of the original
1586 splitDeath(replenish_size);
1587 }
1588 // carve up and link blocks 0, ..., num_blk - 2
1589 // The last chunk is not added to the lists but is returned as the
1590 // free chunk.
1591 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1592 i = 0;
1593 i < (num_blk - 1);
1594 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1595 i++) {
1596 curFc->set_size(size);
1597 // Don't record this as a return in order to try and
1598 // determine the "returns" from a GC.
1599 _bt.verify_not_unallocated((HeapWord*) fc, size);
1600 _indexedFreeList[size].return_chunk_at_tail(curFc, false);
1601 _bt.mark_block((HeapWord*)curFc, size);
1602 split_birth(size);
1603 // Don't record the initial population of the indexed list
1604 // as a split birth.
1605 }
1606
1607 // check that the arithmetic was OK above
1608 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1609 "inconsistency in carving newFc");
1610 curFc->set_size(size);
1611 _bt.mark_block((HeapWord*)curFc, size);
1612 split_birth(size);
1613 fc = curFc;
1614 } else {
1615 // Return entire block to caller
1616 fc = newFc;
1617 }
1618 }
1619 }
1620 } else {
1621 // Get a free chunk from the free chunk dictionary to be returned to
1622 // replenish the indexed free list.
1623 fc = getChunkFromDictionaryExact(size);
1624 }
1625 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
1626 return fc;
1627 }
1628
1629 FreeChunk*
1630 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1631 assert_locked();
1632 FreeChunk* fc = _dictionary->get_chunk(size,
1633 FreeBlockDictionary<FreeChunk>::atLeast);
1634 if (fc == NULL) {
1635 return NULL;
1636 }
1637 _bt.allocated((HeapWord*)fc, fc->size());
1638 if (fc->size() >= size + MinChunkSize) {
1639 fc = splitChunkAndReturnRemainder(fc, size);
1640 }
1641 assert(fc->size() >= size, "chunk too small");
1642 assert(fc->size() < size + MinChunkSize, "chunk too big");
1643 _bt.verify_single_block((HeapWord*)fc, fc->size());
1644 return fc;
1645 }
1646
1647 FreeChunk*
1648 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1649 assert_locked();
1650 FreeChunk* fc = _dictionary->get_chunk(size,
1651 FreeBlockDictionary<FreeChunk>::atLeast);
1652 if (fc == NULL) {
1653 return fc;
1654 }
1655 _bt.allocated((HeapWord*)fc, fc->size());
1656 if (fc->size() == size) {
1657 _bt.verify_single_block((HeapWord*)fc, size);
1658 return fc;
1659 }
1660 assert(fc->size() > size, "get_chunk() guarantee");
1661 if (fc->size() < size + MinChunkSize) {
1662 // Return the chunk to the dictionary and go get a bigger one.
1663 returnChunkToDictionary(fc);
1664 fc = _dictionary->get_chunk(size + MinChunkSize,
1665 FreeBlockDictionary<FreeChunk>::atLeast);
1666 if (fc == NULL) {
1667 return NULL;
1668 }
1669 _bt.allocated((HeapWord*)fc, fc->size());
1670 }
1671 assert(fc->size() >= size + MinChunkSize, "tautology");
1672 fc = splitChunkAndReturnRemainder(fc, size);
1673 assert(fc->size() == size, "chunk is wrong size");
1674 _bt.verify_single_block((HeapWord*)fc, size);
1675 return fc;
1676 }
1677
1678 void
1679 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
1680 assert_locked();
1681
1682 size_t size = chunk->size();
1683 _bt.verify_single_block((HeapWord*)chunk, size);
1684 // adjust _unallocated_block downward, as necessary
1685 _bt.freed((HeapWord*)chunk, size);
1686 _dictionary->return_chunk(chunk);
1687 #ifndef PRODUCT
1688 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1689 TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >* tc = TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::as_TreeChunk(chunk);
1690 TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* tl = tc->list();
1691 tl->verify_stats();
1692 }
1693 #endif // PRODUCT
1694 }
1695
1696 void
1697 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
1698 assert_locked();
1699 size_t size = fc->size();
1700 _bt.verify_single_block((HeapWord*) fc, size);
1701 _bt.verify_not_unallocated((HeapWord*) fc, size);
1702 if (_adaptive_freelists) {
1703 _indexedFreeList[size].return_chunk_at_tail(fc);
1704 } else {
1705 _indexedFreeList[size].return_chunk_at_head(fc);
1706 }
1707 #ifndef PRODUCT
1708 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1709 _indexedFreeList[size].verify_stats();
1710 }
1711 #endif // PRODUCT
1712 }
1713
1714 // Add chunk to end of last block -- if it's the largest
1715 // block -- and update BOT and census data. We would
1716 // of course have preferred to coalesce it with the
1717 // last block, but it's currently less expensive to find the
1718 // largest block than it is to find the last.
1719 void
1720 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1721 HeapWord* chunk, size_t size) {
1722 // check that the chunk does lie in this space!
1723 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1724 // One of the parallel gc task threads may be here
1725 // whilst others are allocating.
1726 Mutex* lock = &_parDictionaryAllocLock;
1727 FreeChunk* ec;
1728 {
1729 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1730 ec = dictionary()->find_largest_dict(); // get largest block
1731 if (ec != NULL && ec->end() == (uintptr_t*) chunk) {
1732 // It's a coterminal block - we can coalesce.
1733 size_t old_size = ec->size();
1734 coalDeath(old_size);
1735 removeChunkFromDictionary(ec);
1736 size += old_size;
1737 } else {
1738 ec = (FreeChunk*)chunk;
1739 }
1740 }
1741 ec->set_size(size);
1742 debug_only(ec->mangleFreed(size));
1743 if (size < SmallForDictionary) {
1744 lock = _indexedFreeListParLocks[size];
1745 }
1746 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1747 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
1748 // record the birth under the lock since the recording involves
1749 // manipulation of the list on which the chunk lives and
1750 // if the chunk is allocated and is the last on the list,
1751 // the list can go away.
1752 coalBirth(size);
1753 }
1754
1755 void
1756 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1757 size_t size) {
1758 // check that the chunk does lie in this space!
1759 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1760 assert_locked();
1761 _bt.verify_single_block(chunk, size);
1762
1763 FreeChunk* fc = (FreeChunk*) chunk;
1764 fc->set_size(size);
1765 debug_only(fc->mangleFreed(size));
1766 if (size < SmallForDictionary) {
1767 returnChunkToFreeList(fc);
1768 } else {
1769 returnChunkToDictionary(fc);
1770 }
1771 }
1772
1773 void
1774 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1775 size_t size, bool coalesced) {
1776 assert_locked();
1777 assert(chunk != NULL, "null chunk");
1778 if (coalesced) {
1779 // repair BOT
1780 _bt.single_block(chunk, size);
1781 }
1782 addChunkToFreeLists(chunk, size);
1783 }
1784
1785 // We _must_ find the purported chunk on our free lists;
1786 // we assert if we don't.
1787 void
1788 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1789 size_t size = fc->size();
1790 assert_locked();
1791 debug_only(verifyFreeLists());
1792 if (size < SmallForDictionary) {
1793 removeChunkFromIndexedFreeList(fc);
1794 } else {
1795 removeChunkFromDictionary(fc);
1796 }
1797 _bt.verify_single_block((HeapWord*)fc, size);
1798 debug_only(verifyFreeLists());
1799 }
1800
1801 void
1802 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1803 size_t size = fc->size();
1804 assert_locked();
1805 assert(fc != NULL, "null chunk");
1806 _bt.verify_single_block((HeapWord*)fc, size);
1807 _dictionary->remove_chunk(fc);
1808 // adjust _unallocated_block upward, as necessary
1809 _bt.allocated((HeapWord*)fc, size);
1810 }
1811
1812 void
1813 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1814 assert_locked();
1815 size_t size = fc->size();
1816 _bt.verify_single_block((HeapWord*)fc, size);
1817 NOT_PRODUCT(
1818 if (FLSVerifyIndexTable) {
1819 verifyIndexedFreeList(size);
1820 }
1821 )
1822 _indexedFreeList[size].remove_chunk(fc);
1823 NOT_PRODUCT(
1824 if (FLSVerifyIndexTable) {
1825 verifyIndexedFreeList(size);
1826 }
1827 )
1828 }
1829
1830 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1831 /* A hint is the next larger size that has a surplus.
1832 Start search at a size large enough to guarantee that
1833 the excess is >= MIN_CHUNK. */
1834 size_t start = align_object_size(numWords + MinChunkSize);
1835 if (start < IndexSetSize) {
1836 AdaptiveFreeList<FreeChunk>* it = _indexedFreeList;
1837 size_t hint = _indexedFreeList[start].hint();
1838 while (hint < IndexSetSize) {
1839 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1840 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint];
1841 if (fl->surplus() > 0 && fl->head() != NULL) {
1842 // Found a list with surplus, reset original hint
1843 // and split out a free chunk which is returned.
1844 _indexedFreeList[start].set_hint(hint);
1845 FreeChunk* res = getFromListGreater(fl, numWords);
1846 assert(res == NULL || res->is_free(),
1847 "Should be returning a free chunk");
1848 return res;
1849 }
1850 hint = fl->hint(); /* keep looking */
1851 }
1852 /* None found. */
1853 it[start].set_hint(IndexSetSize);
1854 }
1855 return NULL;
1856 }
1857
1858 /* Requires fl->size >= numWords + MinChunkSize */
1859 FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl,
1860 size_t numWords) {
1861 FreeChunk *curr = fl->head();
1862 size_t oldNumWords = curr->size();
1863 assert(numWords >= MinChunkSize, "Word size is too small");
1864 assert(curr != NULL, "List is empty");
1865 assert(oldNumWords >= numWords + MinChunkSize,
1866 "Size of chunks in the list is too small");
1867
1868 fl->remove_chunk(curr);
1869 // recorded indirectly by splitChunkAndReturnRemainder -
1870 // smallSplit(oldNumWords, numWords);
1871 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1872 // Does anything have to be done for the remainder in terms of
1873 // fixing the card table?
1874 assert(new_chunk == NULL || new_chunk->is_free(),
1875 "Should be returning a free chunk");
1876 return new_chunk;
1877 }
1878
1879 FreeChunk*
1880 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1881 size_t new_size) {
1882 assert_locked();
1883 size_t size = chunk->size();
1884 assert(size > new_size, "Split from a smaller block?");
1885 assert(is_aligned(chunk), "alignment problem");
1886 assert(size == adjustObjectSize(size), "alignment problem");
1887 size_t rem_sz = size - new_size;
1888 assert(rem_sz == adjustObjectSize(rem_sz), "alignment problem");
1889 assert(rem_sz >= MinChunkSize, "Free chunk smaller than minimum");
1890 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1891 assert(is_aligned(ffc), "alignment problem");
1892 ffc->set_size(rem_sz);
1893 ffc->link_next(NULL);
1894 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
1895 // Above must occur before BOT is updated below.
1896 // adjust block offset table
1897 OrderAccess::storestore();
1898 assert(chunk->is_free() && ffc->is_free(), "Error");
1899 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1900 if (rem_sz < SmallForDictionary) {
1901 // The freeList lock is held, but multiple GC task threads might be executing in parallel.
1902 bool is_par = Thread::current()->is_GC_task_thread();
1903 if (is_par) _indexedFreeListParLocks[rem_sz]->lock();
1904 returnChunkToFreeList(ffc);
1905 split(size, rem_sz);
1906 if (is_par) _indexedFreeListParLocks[rem_sz]->unlock();
1907 } else {
1908 returnChunkToDictionary(ffc);
1909 split(size, rem_sz);
1910 }
1911 chunk->set_size(new_size);
1912 return chunk;
1913 }
1914
1915 void
1916 CompactibleFreeListSpace::sweep_completed() {
1917 // Now that space is probably plentiful, refill linear
1918 // allocation blocks as needed.
1919 refillLinearAllocBlocksIfNeeded();
1920 }
1921
1922 void
1923 CompactibleFreeListSpace::gc_prologue() {
1924 assert_locked();
1925 if (PrintFLSStatistics != 0) {
1926 gclog_or_tty->print("Before GC:\n");
1927 reportFreeListStatistics();
1928 }
1929 refillLinearAllocBlocksIfNeeded();
1930 }
1931
1932 void
1933 CompactibleFreeListSpace::gc_epilogue() {
1934 assert_locked();
1935 if (PrintGCDetails && Verbose && !_adaptive_freelists) {
1936 if (_smallLinearAllocBlock._word_size == 0)
1937 warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure");
1938 }
1939 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1940 _promoInfo.stopTrackingPromotions();
1941 repairLinearAllocationBlocks();
1942 // Print Space's stats
1943 if (PrintFLSStatistics != 0) {
1944 gclog_or_tty->print("After GC:\n");
1945 reportFreeListStatistics();
1946 }
1947 }
1948
1949 // Iteration support, mostly delegated from a CMS generation
1950
1951 void CompactibleFreeListSpace::save_marks() {
1952 assert(Thread::current()->is_VM_thread(),
1953 "Global variable should only be set when single-threaded");
1954 // Mark the "end" of the used space at the time of this call;
1955 // note, however, that promoted objects from this point
1956 // on are tracked in the _promoInfo below.
1957 set_saved_mark_word(unallocated_block());
1958 #ifdef ASSERT
1959 // Check the sanity of save_marks() etc.
1960 MemRegion ur = used_region();
1961 MemRegion urasm = used_region_at_save_marks();
1962 assert(ur.contains(urasm),
1963 err_msg(" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
1964 " should contain [" PTR_FORMAT "," PTR_FORMAT ")",
1965 p2i(ur.start()), p2i(ur.end()), p2i(urasm.start()), p2i(urasm.end())));
1966 #endif
1967 // inform allocator that promotions should be tracked.
1968 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1969 _promoInfo.startTrackingPromotions();
1970 }
1971
1972 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
1973 assert(_promoInfo.tracking(), "No preceding save_marks?");
1974 return _promoInfo.noPromotions();
1975 }
1976
1977 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
1978 \
1979 void CompactibleFreeListSpace:: \
1980 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
1981 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
1982 /* \
1983 * This also restores any displaced headers and removes the elements from \
1984 * the iteration set as they are processed, so that we have a clean slate \
1985 * at the end of the iteration. Note, thus, that if new objects are \
1986 * promoted as a result of the iteration they are iterated over as well. \
1987 */ \
1988 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
1989 }
1990
1991 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
1992
1993 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
1994 return _smallLinearAllocBlock._word_size == 0;
1995 }
1996
1997 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
1998 // Fix up linear allocation blocks to look like free blocks
1999 repairLinearAllocBlock(&_smallLinearAllocBlock);
2000 }
2001
2002 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
2003 assert_locked();
2004 if (blk->_ptr != NULL) {
2005 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
2006 "Minimum block size requirement");
2007 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
2008 fc->set_size(blk->_word_size);
2009 fc->link_prev(NULL); // mark as free
2010 fc->dontCoalesce();
2011 assert(fc->is_free(), "just marked it free");
2012 assert(fc->cantCoalesce(), "just marked it uncoalescable");
2013 }
2014 }
2015
2016 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
2017 assert_locked();
2018 if (_smallLinearAllocBlock._ptr == NULL) {
2019 assert(_smallLinearAllocBlock._word_size == 0,
2020 "Size of linAB should be zero if the ptr is NULL");
2021 // Reset the linAB refill and allocation size limit.
2022 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
2023 }
2024 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
2025 }
2026
2027 void
2028 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
2029 assert_locked();
2030 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
2031 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
2032 "blk invariant");
2033 if (blk->_ptr == NULL) {
2034 refillLinearAllocBlock(blk);
2035 }
2036 if (PrintMiscellaneous && Verbose) {
2037 if (blk->_word_size == 0) {
2038 warning("CompactibleFreeListSpace(prologue):: Linear allocation failure");
2039 }
2040 }
2041 }
2042
2043 void
2044 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
2045 assert_locked();
2046 assert(blk->_word_size == 0 && blk->_ptr == NULL,
2047 "linear allocation block should be empty");
2048 FreeChunk* fc;
2049 if (blk->_refillSize < SmallForDictionary &&
2050 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
2051 // A linAB's strategy might be to use small sizes to reduce
2052 // fragmentation but still get the benefits of allocation from a
2053 // linAB.
2054 } else {
2055 fc = getChunkFromDictionary(blk->_refillSize);
2056 }
2057 if (fc != NULL) {
2058 blk->_ptr = (HeapWord*)fc;
2059 blk->_word_size = fc->size();
2060 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
2061 }
2062 }
2063
2064 // Support for concurrent collection policy decisions.
2065 bool CompactibleFreeListSpace::should_concurrent_collect() const {
2066 // In the future we might want to add in fragmentation stats --
2067 // including erosion of the "mountain" into this decision as well.
2068 return !adaptive_freelists() && linearAllocationWouldFail();
2069 }
2070
2071 #define cfls_obj_size(q) CompactibleFreeListSpace::adjustObjectSize(oop(q)->size())
2072 DECLARE_PMS_SPECIALIZED_CODE(CompactibleFreeListSpace, cfls_obj_size);
2073
2074 // Support for compaction
2075 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
2076 if (CMSParallelFullGC) {
2077 pms_prepare_for_compaction_work(cp);
2078 } else {
2079 scan_and_forward(this, cp);
2080 }
2081 // Prepare_for_compaction() uses the space between live objects
2082 // so that later phase can skip dead space quickly. So verification
2083 // of the free lists doesn't work after.
2084 }
2085
2086 void CompactibleFreeListSpace::adjust_pointers() {
2087 if (CMSParallelFullGC) {
2088 pms_adjust_pointers_work();
2089 } else {
2090 // In other versions of adjust_pointers(), a bail out
2091 // based on the amount of live data in the generation
2092 // (i.e., if 0, bail out) may be used.
2093 // Cannot test used() == 0 here because the free lists have already
2094 // been mangled by the compaction.
2095 scan_and_adjust_pointers(this);
2096 }
2097 // See note about verification in prepare_for_compaction().
2098 }
2099
2100 void CompactibleFreeListSpace::compact() {
2101 if (CMSParallelFullGC) {
2102 pms_compact_work();
2103 } else {
2104 scan_and_compact(this);
2105 }
2106 }
2107
2108 // Fragmentation metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
2109 // where fbs is free block sizes
2110 double CompactibleFreeListSpace::flsFrag() const {
2111 size_t itabFree = totalSizeInIndexedFreeLists();
2112 double frag = 0.0;
2113 size_t i;
2114
2115 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2116 double sz = i;
2117 frag += _indexedFreeList[i].count() * (sz * sz);
2118 }
2119
2120 double totFree = itabFree +
2121 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
2122 if (totFree > 0) {
2123 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
2124 (totFree * totFree));
2125 frag = (double)1.0 - frag;
2126 } else {
2127 assert(frag == 0.0, "Follows from totFree == 0");
2128 }
2129 return frag;
2130 }
2131
2132 void CompactibleFreeListSpace::beginSweepFLCensus(
2133 float inter_sweep_current,
2134 float inter_sweep_estimate,
2135 float intra_sweep_estimate) {
2136 assert_locked();
2137 size_t i;
2138 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2139 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
2140 if (PrintFLSStatistics > 1) {
2141 gclog_or_tty->print("size[" SIZE_FORMAT "] : ", i);
2142 }
2143 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2144 fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2145 fl->set_before_sweep(fl->count());
2146 fl->set_bfr_surp(fl->surplus());
2147 }
2148 _dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent,
2149 inter_sweep_current,
2150 inter_sweep_estimate,
2151 intra_sweep_estimate);
2152 }
2153
2154 void CompactibleFreeListSpace::setFLSurplus() {
2155 assert_locked();
2156 size_t i;
2157 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2158 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2159 fl->set_surplus(fl->count() -
2160 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2161 }
2162 }
2163
2164 void CompactibleFreeListSpace::setFLHints() {
2165 assert_locked();
2166 size_t i;
2167 size_t h = IndexSetSize;
2168 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2169 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2170 fl->set_hint(h);
2171 if (fl->surplus() > 0) {
2172 h = i;
2173 }
2174 }
2175 }
2176
2177 void CompactibleFreeListSpace::clearFLCensus() {
2178 assert_locked();
2179 size_t i;
2180 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2181 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2182 fl->set_prev_sweep(fl->count());
2183 fl->set_coal_births(0);
2184 fl->set_coal_deaths(0);
2185 fl->set_split_births(0);
2186 fl->set_split_deaths(0);
2187 }
2188 }
2189
2190 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2191 if (PrintFLSStatistics > 0) {
2192 HeapWord* largestAddr = (HeapWord*) dictionary()->find_largest_dict();
2193 gclog_or_tty->print_cr("CMS: Large block " PTR_FORMAT,
2194 p2i(largestAddr));
2195 }
2196 setFLSurplus();
2197 setFLHints();
2198 if (PrintGC && PrintFLSCensus > 0) {
2199 printFLCensus(sweep_count);
2200 }
2201 clearFLCensus();
2202 assert_locked();
2203 _dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent);
2204 }
2205
2206 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2207 if (size < SmallForDictionary) {
2208 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2209 return (fl->coal_desired() < 0) ||
2210 ((int)fl->count() > fl->coal_desired());
2211 } else {
2212 return dictionary()->coal_dict_over_populated(size);
2213 }
2214 }
2215
2216 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2217 assert(size < SmallForDictionary, "Size too large for indexed list");
2218 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2219 fl->increment_coal_births();
2220 fl->increment_surplus();
2221 }
2222
2223 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2224 assert(size < SmallForDictionary, "Size too large for indexed list");
2225 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2226 fl->increment_coal_deaths();
2227 fl->decrement_surplus();
2228 }
2229
2230 void CompactibleFreeListSpace::coalBirth(size_t size) {
2231 if (size < SmallForDictionary) {
2232 smallCoalBirth(size);
2233 } else {
2234 dictionary()->dict_census_update(size,
2235 false /* split */,
2236 true /* birth */);
2237 }
2238 }
2239
2240 void CompactibleFreeListSpace::coalDeath(size_t size) {
2241 if(size < SmallForDictionary) {
2242 smallCoalDeath(size);
2243 } else {
2244 dictionary()->dict_census_update(size,
2245 false /* split */,
2246 false /* birth */);
2247 }
2248 }
2249
2250 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2251 assert(size < SmallForDictionary, "Size too large for indexed list");
2252 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2253 fl->increment_split_births();
2254 fl->increment_surplus();
2255 }
2256
2257 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2258 assert(size < SmallForDictionary, "Size too large for indexed list");
2259 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2260 fl->increment_split_deaths();
2261 fl->decrement_surplus();
2262 }
2263
2264 void CompactibleFreeListSpace::split_birth(size_t size) {
2265 if (size < SmallForDictionary) {
2266 smallSplitBirth(size);
2267 } else {
2268 dictionary()->dict_census_update(size,
2269 true /* split */,
2270 true /* birth */);
2271 }
2272 }
2273
2274 void CompactibleFreeListSpace::splitDeath(size_t size) {
2275 if (size < SmallForDictionary) {
2276 smallSplitDeath(size);
2277 } else {
2278 dictionary()->dict_census_update(size,
2279 true /* split */,
2280 false /* birth */);
2281 }
2282 }
2283
2284 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2285 size_t to2 = from - to1;
2286 splitDeath(from);
2287 split_birth(to1);
2288 split_birth(to2);
2289 }
2290
2291 void CompactibleFreeListSpace::print() const {
2292 print_on(tty);
2293 }
2294
2295 void CompactibleFreeListSpace::prepare_for_verify() {
2296 assert_locked();
2297 repairLinearAllocationBlocks();
2298 // Verify that the SpoolBlocks look like free blocks of
2299 // appropriate sizes... To be done ...
2300 }
2301
2302 class VerifyAllBlksClosure: public BlkClosure {
2303 private:
2304 const CompactibleFreeListSpace* _sp;
2305 const MemRegion _span;
2306 HeapWord* _last_addr;
2307 size_t _last_size;
2308 bool _last_was_obj;
2309 bool _last_was_live;
2310
2311 public:
2312 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2313 MemRegion span) : _sp(sp), _span(span),
2314 _last_addr(NULL), _last_size(0),
2315 _last_was_obj(false), _last_was_live(false) { }
2316
2317 virtual size_t do_blk(HeapWord* addr) {
2318 size_t res;
2319 bool was_obj = false;
2320 bool was_live = false;
2321 if (_sp->block_is_obj(addr)) {
2322 was_obj = true;
2323 oop p = oop(addr);
2324 guarantee(p->is_oop(), "Should be an oop");
2325 res = _sp->adjustObjectSize(p->size());
2326 if (_sp->obj_is_alive(addr)) {
2327 was_live = true;
2328 p->verify();
2329 }
2330 } else {
2331 FreeChunk* fc = (FreeChunk*)addr;
2332 res = fc->size();
2333 if (FLSVerifyLists && !fc->cantCoalesce()) {
2334 guarantee(_sp->verify_chunk_in_free_list(fc),
2335 "Chunk should be on a free list");
2336 }
2337 }
2338 if (res == 0) {
2339 gclog_or_tty->print_cr("Livelock: no rank reduction!");
2340 gclog_or_tty->print_cr(
2341 " Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2342 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2343 p2i(addr), res, was_obj ?"true":"false", was_live ?"true":"false",
2344 p2i(_last_addr), _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2345 _sp->print_on(gclog_or_tty);
2346 guarantee(false, "Seppuku!");
2347 }
2348 _last_addr = addr;
2349 _last_size = res;
2350 _last_was_obj = was_obj;
2351 _last_was_live = was_live;
2352 return res;
2353 }
2354 };
2355
2356 class VerifyAllOopsClosure: public OopClosure {
2357 private:
2358 const CMSCollector* _collector;
2359 const CompactibleFreeListSpace* _sp;
2360 const MemRegion _span;
2361 const bool _past_remark;
2362 const CMSBitMap* _bit_map;
2363
2364 protected:
2365 void do_oop(void* p, oop obj) {
2366 if (_span.contains(obj)) { // the interior oop points into CMS heap
2367 if (!_span.contains(p)) { // reference from outside CMS heap
2368 // Should be a valid object; the first disjunct below allows
2369 // us to sidestep an assertion in block_is_obj() that insists
2370 // that p be in _sp. Note that several generations (and spaces)
2371 // are spanned by _span (CMS heap) above.
2372 guarantee(!_sp->is_in_reserved(obj) ||
2373 _sp->block_is_obj((HeapWord*)obj),
2374 "Should be an object");
2375 guarantee(obj->is_oop(), "Should be an oop");
2376 obj->verify();
2377 if (_past_remark) {
2378 // Remark has been completed, the object should be marked
2379 _bit_map->isMarked((HeapWord*)obj);
2380 }
2381 } else { // reference within CMS heap
2382 if (_past_remark) {
2383 // Remark has been completed -- so the referent should have
2384 // been marked, if referring object is.
2385 if (_bit_map->isMarked(_collector->block_start(p))) {
2386 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2387 }
2388 }
2389 }
2390 } else if (_sp->is_in_reserved(p)) {
2391 // the reference is from FLS, and points out of FLS
2392 guarantee(obj->is_oop(), "Should be an oop");
2393 obj->verify();
2394 }
2395 }
2396
2397 template <class T> void do_oop_work(T* p) {
2398 T heap_oop = oopDesc::load_heap_oop(p);
2399 if (!oopDesc::is_null(heap_oop)) {
2400 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2401 do_oop(p, obj);
2402 }
2403 }
2404
2405 public:
2406 VerifyAllOopsClosure(const CMSCollector* collector,
2407 const CompactibleFreeListSpace* sp, MemRegion span,
2408 bool past_remark, CMSBitMap* bit_map) :
2409 _collector(collector), _sp(sp), _span(span),
2410 _past_remark(past_remark), _bit_map(bit_map) { }
2411
2412 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2413 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2414 };
2415
2416 void CompactibleFreeListSpace::verify() const {
2417 assert_lock_strong(&_freelistLock);
2418 verify_objects_initialized();
2419 MemRegion span = _collector->_span;
2420 bool past_remark = (_collector->abstract_state() ==
2421 CMSCollector::Sweeping);
2422
2423 ResourceMark rm;
2424 HandleMark hm;
2425
2426 // Check integrity of CFL data structures
2427 _promoInfo.verify();
2428 _dictionary->verify();
2429 if (FLSVerifyIndexTable) {
2430 verifyIndexedFreeLists();
2431 }
2432 // Check integrity of all objects and free blocks in space
2433 {
2434 VerifyAllBlksClosure cl(this, span);
2435 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2436 }
2437 // Check that all references in the heap to FLS
2438 // are to valid objects in FLS or that references in
2439 // FLS are to valid objects elsewhere in the heap
2440 if (FLSVerifyAllHeapReferences)
2441 {
2442 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2443 _collector->markBitMap());
2444
2445 // Iterate over all oops in the heap. Uses the _no_header version
2446 // since we are not interested in following the klass pointers.
2447 GenCollectedHeap::heap()->oop_iterate_no_header(&cl);
2448 }
2449
2450 if (VerifyObjectStartArray) {
2451 // Verify the block offset table
2452 _bt.verify();
2453 }
2454 }
2455
2456 #ifndef PRODUCT
2457 void CompactibleFreeListSpace::verifyFreeLists() const {
2458 if (FLSVerifyLists) {
2459 _dictionary->verify();
2460 verifyIndexedFreeLists();
2461 } else {
2462 if (FLSVerifyDictionary) {
2463 _dictionary->verify();
2464 }
2465 if (FLSVerifyIndexTable) {
2466 verifyIndexedFreeLists();
2467 }
2468 }
2469 }
2470 #endif
2471
2472 void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
2473 size_t i = 0;
2474 for (; i < IndexSetStart; i++) {
2475 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
2476 }
2477 for (; i < IndexSetSize; i++) {
2478 verifyIndexedFreeList(i);
2479 }
2480 }
2481
2482 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
2483 FreeChunk* fc = _indexedFreeList[size].head();
2484 FreeChunk* tail = _indexedFreeList[size].tail();
2485 size_t num = _indexedFreeList[size].count();
2486 size_t n = 0;
2487 guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL,
2488 "Slot should have been empty");
2489 for (; fc != NULL; fc = fc->next(), n++) {
2490 guarantee(fc->size() == size, "Size inconsistency");
2491 guarantee(fc->is_free(), "!free?");
2492 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
2493 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
2494 }
2495 guarantee(n == num, "Incorrect count");
2496 }
2497
2498 #ifndef PRODUCT
2499 void CompactibleFreeListSpace::check_free_list_consistency() const {
2500 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size() <= IndexSetSize),
2501 "Some sizes can't be allocated without recourse to"
2502 " linear allocation buffers");
2503 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >)),
2504 "else MIN_TREE_CHUNK_SIZE is wrong");
2505 assert(IndexSetStart != 0, "IndexSetStart not initialized");
2506 assert(IndexSetStride != 0, "IndexSetStride not initialized");
2507 }
2508 #endif
2509
2510 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2511 assert_lock_strong(&_freelistLock);
2512 AdaptiveFreeList<FreeChunk> total;
2513 gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count);
2514 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size");
2515 size_t total_free = 0;
2516 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2517 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2518 total_free += fl->count() * fl->size();
2519 if (i % (40*IndexSetStride) == 0) {
2520 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size");
2521 }
2522 fl->print_on(gclog_or_tty);
2523 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
2524 total.set_surplus( total.surplus() + fl->surplus() );
2525 total.set_desired( total.desired() + fl->desired() );
2526 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
2527 total.set_before_sweep(total.before_sweep() + fl->before_sweep());
2528 total.set_count( total.count() + fl->count() );
2529 total.set_coal_births( total.coal_births() + fl->coal_births() );
2530 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
2531 total.set_split_births(total.split_births() + fl->split_births());
2532 total.set_split_deaths(total.split_deaths() + fl->split_deaths());
2533 }
2534 total.print_on(gclog_or_tty, "TOTAL");
2535 gclog_or_tty->print_cr("Total free in indexed lists "
2536 SIZE_FORMAT " words", total_free);
2537 gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n",
2538 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
2539 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
2540 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2541 _dictionary->print_dict_census();
2542 }
2543
2544 ///////////////////////////////////////////////////////////////////////////
2545 // CFLS_LAB
2546 ///////////////////////////////////////////////////////////////////////////
2547
2548 #define VECTOR_257(x) \
2549 /* 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 */ \
2550 { 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, \
2551 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, \
2552 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, \
2553 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, \
2554 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, \
2555 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, \
2556 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, \
2557 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, \
2558 x }
2559
2560 // Initialize with default setting for CMS, _not_
2561 // generic OldPLABSize, whose static default is different; if overridden at the
2562 // command-line, this will get reinitialized via a call to
2563 // modify_initialization() below.
2564 AdaptiveWeightedAverage CFLS_LAB::_blocks_to_claim[] =
2565 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CFLS_LAB::_default_dynamic_old_plab_size));
2566 size_t CFLS_LAB::_global_num_blocks[] = VECTOR_257(0);
2567 uint CFLS_LAB::_global_num_workers[] = VECTOR_257(0);
2568
2569 CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) :
2570 _cfls(cfls)
2571 {
2572 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2573 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2574 i < CompactibleFreeListSpace::IndexSetSize;
2575 i += CompactibleFreeListSpace::IndexSetStride) {
2576 _indexedFreeList[i].set_size(i);
2577 _num_blocks[i] = 0;
2578 }
2579 }
2580
2581 static bool _CFLS_LAB_modified = false;
2582
2583 void CFLS_LAB::modify_initialization(size_t n, unsigned wt) {
2584 assert(!_CFLS_LAB_modified, "Call only once");
2585 _CFLS_LAB_modified = true;
2586 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2587 i < CompactibleFreeListSpace::IndexSetSize;
2588 i += CompactibleFreeListSpace::IndexSetStride) {
2589 _blocks_to_claim[i].modify(n, wt, true /* force */);
2590 }
2591 }
2592
2593 HeapWord* CFLS_LAB::alloc(size_t word_sz) {
2594 FreeChunk* res;
2595 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2596 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2597 // This locking manages sync with other large object allocations.
2598 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2599 Mutex::_no_safepoint_check_flag);
2600 res = _cfls->getChunkFromDictionaryExact(word_sz);
2601 if (res == NULL) return NULL;
2602 } else {
2603 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
2604 if (fl->count() == 0) {
2605 // Attempt to refill this local free list.
2606 get_from_global_pool(word_sz, fl);
2607 // If it didn't work, give up.
2608 if (fl->count() == 0) return NULL;
2609 }
2610 res = fl->get_chunk_at_head();
2611 assert(res != NULL, "Why was count non-zero?");
2612 }
2613 res->markNotFree();
2614 assert(!res->is_free(), "shouldn't be marked free");
2615 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2616 // mangle a just allocated object with a distinct pattern.
2617 debug_only(res->mangleAllocated(word_sz));
2618 return (HeapWord*)res;
2619 }
2620
2621 // Get a chunk of blocks of the right size and update related
2622 // book-keeping stats
2623 void CFLS_LAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
2624 // Get the #blocks we want to claim
2625 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2626 assert(n_blks > 0, "Error");
2627 assert(ResizeOldPLAB || n_blks == OldPLABSize, "Error");
2628 // In some cases, when the application has a phase change,
2629 // there may be a sudden and sharp shift in the object survival
2630 // profile, and updating the counts at the end of a scavenge
2631 // may not be quick enough, giving rise to large scavenge pauses
2632 // during these phase changes. It is beneficial to detect such
2633 // changes on-the-fly during a scavenge and avoid such a phase-change
2634 // pothole. The following code is a heuristic attempt to do that.
2635 // It is protected by a product flag until we have gained
2636 // enough experience with this heuristic and fine-tuned its behavior.
2637 // WARNING: This might increase fragmentation if we overreact to
2638 // small spikes, so some kind of historical smoothing based on
2639 // previous experience with the greater reactivity might be useful.
2640 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2641 // default.
2642 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2643 size_t multiple = _num_blocks[word_sz]/(CMSOldPLABToleranceFactor*CMSOldPLABNumRefills*n_blks);
2644 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2645 n_blks = MIN2(n_blks, CMSOldPLABMax);
2646 }
2647 assert(n_blks > 0, "Error");
2648 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2649 // Update stats table entry for this block size
2650 _num_blocks[word_sz] += fl->count();
2651 }
2652
2653 void CFLS_LAB::compute_desired_plab_size() {
2654 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2655 i < CompactibleFreeListSpace::IndexSetSize;
2656 i += CompactibleFreeListSpace::IndexSetStride) {
2657 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2658 "Counter inconsistency");
2659 if (_global_num_workers[i] > 0) {
2660 // Need to smooth wrt historical average
2661 if (ResizeOldPLAB) {
2662 _blocks_to_claim[i].sample(
2663 MAX2(CMSOldPLABMin,
2664 MIN2(CMSOldPLABMax,
2665 _global_num_blocks[i]/(_global_num_workers[i]*CMSOldPLABNumRefills))));
2666 }
2667 // Reset counters for next round
2668 _global_num_workers[i] = 0;
2669 _global_num_blocks[i] = 0;
2670 if (PrintOldPLAB) {
2671 gclog_or_tty->print_cr("[" SIZE_FORMAT "]: " SIZE_FORMAT,
2672 i, (size_t)_blocks_to_claim[i].average());
2673 }
2674 }
2675 }
2676 }
2677
2678 // If this is changed in the future to allow parallel
2679 // access, one would need to take the FL locks and,
2680 // depending on how it is used, stagger access from
2681 // parallel threads to reduce contention.
2682 void CFLS_LAB::retire(int tid) {
2683 // We run this single threaded with the world stopped;
2684 // so no need for locks and such.
2685 NOT_PRODUCT(Thread* t = Thread::current();)
2686 assert(Thread::current()->is_VM_thread(), "Error");
2687 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2688 i < CompactibleFreeListSpace::IndexSetSize;
2689 i += CompactibleFreeListSpace::IndexSetStride) {
2690 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2691 "Can't retire more than what we obtained");
2692 if (_num_blocks[i] > 0) {
2693 size_t num_retire = _indexedFreeList[i].count();
2694 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2695 {
2696 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2697 // Mutex::_no_safepoint_check_flag);
2698
2699 // Update globals stats for num_blocks used
2700 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2701 _global_num_workers[i]++;
2702 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2703 if (num_retire > 0) {
2704 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2705 // Reset this list.
2706 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
2707 _indexedFreeList[i].set_size(i);
2708 }
2709 }
2710 if (PrintOldPLAB) {
2711 gclog_or_tty->print_cr("%d[" SIZE_FORMAT "]: " SIZE_FORMAT "/" SIZE_FORMAT "/" SIZE_FORMAT,
2712 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2713 }
2714 // Reset stats for next round
2715 _num_blocks[i] = 0;
2716 }
2717 }
2718 }
2719
2720 // Used by par_get_chunk_of_blocks() for the chunks from the
2721 // indexed_free_lists. Looks for a chunk with size that is a multiple
2722 // of "word_sz" and if found, splits it into "word_sz" chunks and add
2723 // to the free list "fl". "n" is the maximum number of chunks to
2724 // be added to "fl".
2725 bool CompactibleFreeListSpace:: par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2726
2727 // We'll try all multiples of word_sz in the indexed set, starting with
2728 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2729 // then try getting a big chunk and splitting it.
2730 {
2731 bool found;
2732 int k;
2733 size_t cur_sz;
2734 for (k = 1, cur_sz = k * word_sz, found = false;
2735 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2736 (CMSSplitIndexedFreeListBlocks || k <= 1);
2737 k++, cur_sz = k * word_sz) {
2738 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
2739 fl_for_cur_sz.set_size(cur_sz);
2740 {
2741 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2742 Mutex::_no_safepoint_check_flag);
2743 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
2744 if (gfl->count() != 0) {
2745 // nn is the number of chunks of size cur_sz that
2746 // we'd need to split k-ways each, in order to create
2747 // "n" chunks of size word_sz each.
2748 const size_t nn = MAX2(n/k, (size_t)1);
2749 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2750 found = true;
2751 if (k > 1) {
2752 // Update split death stats for the cur_sz-size blocks list:
2753 // we increment the split death count by the number of blocks
2754 // we just took from the cur_sz-size blocks list and which
2755 // we will be splitting below.
2756 ssize_t deaths = gfl->split_deaths() +
2757 fl_for_cur_sz.count();
2758 gfl->set_split_deaths(deaths);
2759 }
2760 }
2761 }
2762 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2763 if (found) {
2764 if (k == 1) {
2765 fl->prepend(&fl_for_cur_sz);
2766 } else {
2767 // Divide each block on fl_for_cur_sz up k ways.
2768 FreeChunk* fc;
2769 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
2770 // Must do this in reverse order, so that anybody attempting to
2771 // access the main chunk sees it as a single free block until we
2772 // change it.
2773 size_t fc_size = fc->size();
2774 assert(fc->is_free(), "Error");
2775 for (int i = k-1; i >= 0; i--) {
2776 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2777 assert((i != 0) ||
2778 ((fc == ffc) && ffc->is_free() &&
2779 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2780 "Counting error");
2781 ffc->set_size(word_sz);
2782 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2783 ffc->link_next(NULL);
2784 // Above must occur before BOT is updated below.
2785 OrderAccess::storestore();
2786 // splitting from the right, fc_size == i * word_sz
2787 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2788 fc_size -= word_sz;
2789 assert(fc_size == i*word_sz, "Error");
2790 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2791 _bt.verify_single_block((HeapWord*)fc, fc_size);
2792 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2793 // Push this on "fl".
2794 fl->return_chunk_at_head(ffc);
2795 }
2796 // TRAP
2797 assert(fl->tail()->next() == NULL, "List invariant.");
2798 }
2799 }
2800 // Update birth stats for this block size.
2801 size_t num = fl->count();
2802 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2803 Mutex::_no_safepoint_check_flag);
2804 ssize_t births = _indexedFreeList[word_sz].split_births() + num;
2805 _indexedFreeList[word_sz].set_split_births(births);
2806 return true;
2807 }
2808 }
2809 return found;
2810 }
2811 }
2812
2813 FreeChunk* CompactibleFreeListSpace::get_n_way_chunk_to_split(size_t word_sz, size_t n) {
2814
2815 FreeChunk* fc = NULL;
2816 FreeChunk* rem_fc = NULL;
2817 size_t rem;
2818 {
2819 MutexLockerEx x(parDictionaryAllocLock(),
2820 Mutex::_no_safepoint_check_flag);
2821 while (n > 0) {
2822 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()),
2823 FreeBlockDictionary<FreeChunk>::atLeast);
2824 if (fc != NULL) {
2825 break;
2826 } else {
2827 n--;
2828 }
2829 }
2830 if (fc == NULL) return NULL;
2831 // Otherwise, split up that block.
2832 assert((ssize_t)n >= 1, "Control point invariant");
2833 assert(fc->is_free(), "Error: should be a free block");
2834 _bt.verify_single_block((HeapWord*)fc, fc->size());
2835 const size_t nn = fc->size() / word_sz;
2836 n = MIN2(nn, n);
2837 assert((ssize_t)n >= 1, "Control point invariant");
2838 rem = fc->size() - n * word_sz;
2839 // If there is a remainder, and it's too small, allocate one fewer.
2840 if (rem > 0 && rem < MinChunkSize) {
2841 n--; rem += word_sz;
2842 }
2843 // Note that at this point we may have n == 0.
2844 assert((ssize_t)n >= 0, "Control point invariant");
2845
2846 // If n is 0, the chunk fc that was found is not large
2847 // enough to leave a viable remainder. We are unable to
2848 // allocate even one block. Return fc to the
2849 // dictionary and return, leaving "fl" empty.
2850 if (n == 0) {
2851 returnChunkToDictionary(fc);
2852 return NULL;
2853 }
2854
2855 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2856 dictionary()->dict_census_update(fc->size(),
2857 true /*split*/,
2858 false /*birth*/);
2859
2860 // First return the remainder, if any.
2861 // Note that we hold the lock until we decide if we're going to give
2862 // back the remainder to the dictionary, since a concurrent allocation
2863 // may otherwise see the heap as empty. (We're willing to take that
2864 // hit if the block is a small block.)
2865 if (rem > 0) {
2866 size_t prefix_size = n * word_sz;
2867 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2868 rem_fc->set_size(rem);
2869 rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2870 rem_fc->link_next(NULL);
2871 // Above must occur before BOT is updated below.
2872 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2873 OrderAccess::storestore();
2874 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2875 assert(fc->is_free(), "Error");
2876 fc->set_size(prefix_size);
2877 if (rem >= IndexSetSize) {
2878 returnChunkToDictionary(rem_fc);
2879 dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/);
2880 rem_fc = NULL;
2881 }
2882 // Otherwise, return it to the small list below.
2883 }
2884 }
2885 if (rem_fc != NULL) {
2886 MutexLockerEx x(_indexedFreeListParLocks[rem],
2887 Mutex::_no_safepoint_check_flag);
2888 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2889 _indexedFreeList[rem].return_chunk_at_head(rem_fc);
2890 smallSplitBirth(rem);
2891 }
2892 assert(n * word_sz == fc->size(),
2893 err_msg("Chunk size " SIZE_FORMAT " is not exactly splittable by "
2894 SIZE_FORMAT " sized chunks of size " SIZE_FORMAT,
2895 fc->size(), n, word_sz));
2896 return fc;
2897 }
2898
2899 void CompactibleFreeListSpace:: par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t targetted_number_of_chunks, AdaptiveFreeList<FreeChunk>* fl) {
2900
2901 FreeChunk* fc = get_n_way_chunk_to_split(word_sz, targetted_number_of_chunks);
2902
2903 if (fc == NULL) {
2904 return;
2905 }
2906
2907 size_t n = fc->size() / word_sz;
2908
2909 assert((ssize_t)n > 0, "Consistency");
2910 // Now do the splitting up.
2911 // Must do this in reverse order, so that anybody attempting to
2912 // access the main chunk sees it as a single free block until we
2913 // change it.
2914 size_t fc_size = n * word_sz;
2915 // All but first chunk in this loop
2916 for (ssize_t i = n-1; i > 0; i--) {
2917 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2918 ffc->set_size(word_sz);
2919 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2920 ffc->link_next(NULL);
2921 // Above must occur before BOT is updated below.
2922 OrderAccess::storestore();
2923 // splitting from the right, fc_size == (n - i + 1) * wordsize
2924 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2925 fc_size -= word_sz;
2926 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2927 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2928 _bt.verify_single_block((HeapWord*)fc, fc_size);
2929 // Push this on "fl".
2930 fl->return_chunk_at_head(ffc);
2931 }
2932 // First chunk
2933 assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block");
2934 // The blocks above should show their new sizes before the first block below
2935 fc->set_size(word_sz);
2936 fc->link_prev(NULL); // idempotent wrt free-ness, see assert above
2937 fc->link_next(NULL);
2938 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2939 _bt.verify_single_block((HeapWord*)fc, fc->size());
2940 fl->return_chunk_at_head(fc);
2941
2942 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2943 {
2944 // Update the stats for this block size.
2945 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2946 Mutex::_no_safepoint_check_flag);
2947 const ssize_t births = _indexedFreeList[word_sz].split_births() + n;
2948 _indexedFreeList[word_sz].set_split_births(births);
2949 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2950 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2951 }
2952
2953 // TRAP
2954 assert(fl->tail()->next() == NULL, "List invariant.");
2955 }
2956
2957 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2958 assert(fl->count() == 0, "Precondition.");
2959 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2960 "Precondition");
2961
2962 if (par_get_chunk_of_blocks_IFL(word_sz, n, fl)) {
2963 // Got it
2964 return;
2965 }
2966
2967 // Otherwise, we'll split a block from the dictionary.
2968 par_get_chunk_of_blocks_dictionary(word_sz, n, fl);
2969 }
2970
2971 // Set up the space's par_seq_tasks structure for work claiming
2972 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2973 // XXX Need to suitably abstract and generalize this and the next
2974 // method into one.
2975 void
2976 CompactibleFreeListSpace::
2977 initialize_sequential_subtasks_for_rescan(int n_threads) {
2978 // The "size" of each task is fixed according to rescan_task_size.
2979 assert(n_threads > 0, "Unexpected n_threads argument");
2980 const size_t task_size = rescan_task_size();
2981 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2982 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2983 assert(n_tasks == 0 ||
2984 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2985 (used_region().start() + n_tasks*task_size >= used_region().end())),
2986 "n_tasks calculation incorrect");
2987 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2988 assert(!pst->valid(), "Clobbering existing data?");
2989 // Sets the condition for completion of the subtask (how many threads
2990 // need to finish in order to be done).
2991 pst->set_n_threads(n_threads);
2992 pst->set_n_tasks((int)n_tasks);
2993 }
2994
2995 // Set up the space's par_seq_tasks structure for work claiming
2996 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2997 void
2998 CompactibleFreeListSpace::
2999 initialize_sequential_subtasks_for_marking(int n_threads,
3000 HeapWord* low) {
3001 // The "size" of each task is fixed according to rescan_task_size.
3002 assert(n_threads > 0, "Unexpected n_threads argument");
3003 const size_t task_size = marking_task_size();
3004 assert(task_size > CardTableModRefBS::card_size_in_words &&
3005 (task_size % CardTableModRefBS::card_size_in_words == 0),
3006 "Otherwise arithmetic below would be incorrect");
3007 MemRegion span = _gen->reserved();
3008 if (low != NULL) {
3009 if (span.contains(low)) {
3010 // Align low down to a card boundary so that
3011 // we can use block_offset_careful() on span boundaries.
3012 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
3013 CardTableModRefBS::card_size);
3014 // Clip span prefix at aligned_low
3015 span = span.intersection(MemRegion(aligned_low, span.end()));
3016 } else if (low > span.end()) {
3017 span = MemRegion(low, low); // Null region
3018 } // else use entire span
3019 }
3020 assert(span.is_empty() ||
3021 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
3022 "span should start at a card boundary");
3023 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
3024 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
3025 assert(n_tasks == 0 ||
3026 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
3027 (span.start() + n_tasks*task_size >= span.end())),
3028 "n_tasks calculation incorrect");
3029 SequentialSubTasksDone* pst = conc_par_seq_tasks();
3030 assert(!pst->valid(), "Clobbering existing data?");
3031 // Sets the condition for completion of the subtask (how many threads
3032 // need to finish in order to be done).
3033 pst->set_n_threads(n_threads);
3034 pst->set_n_tasks((int)n_tasks);
3035 }