Mon, 07 Feb 2011 22:19:57 -0800
6912621: iCMS: Error: assert(_markBitMap.isMarked(addr + 1),"Missing Printezis bit?")
Summary: Fix block_size_if_printezis_bits() so it does not expect the bits, only uses them when available. Fix block_size_no_stall() so it does not stall when the bits are missing such cases, letting the caller deal with zero size returns. Constant pool cache oops do not need to be unparsable or conc_unsafe after their klass pointer is installed. Some cosmetic clean-ups and some assertion checking for conc-usafety which, in the presence of class file redefinition, has no a-priori time boundedness, so all GCs must be able to safely deal with putatively conc-unsafe objects in a stop-world pause.
Reviewed-by: jmasa, johnc
1 /*
2 * Copyright (c) 2001, 2010, 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
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/concurrentMarkSweep/cmsLockVerifier.hpp"
27 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp"
28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
29 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
30 #include "gc_implementation/shared/liveRange.hpp"
31 #include "gc_implementation/shared/spaceDecorator.hpp"
32 #include "gc_interface/collectedHeap.hpp"
33 #include "memory/allocation.inline.hpp"
34 #include "memory/blockOffsetTable.inline.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/globals.hpp"
39 #include "runtime/handles.inline.hpp"
40 #include "runtime/init.hpp"
41 #include "runtime/java.hpp"
42 #include "runtime/vmThread.hpp"
43 #include "utilities/copy.hpp"
45 /////////////////////////////////////////////////////////////////////////
46 //// CompactibleFreeListSpace
47 /////////////////////////////////////////////////////////////////////////
49 // highest ranked free list lock rank
50 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
52 // Defaults are 0 so things will break badly if incorrectly initialized.
53 int CompactibleFreeListSpace::IndexSetStart = 0;
54 int CompactibleFreeListSpace::IndexSetStride = 0;
56 size_t MinChunkSize = 0;
58 void CompactibleFreeListSpace::set_cms_values() {
59 // Set CMS global values
60 assert(MinChunkSize == 0, "already set");
61 #define numQuanta(x,y) ((x+y-1)/y)
62 MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment;
64 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
65 IndexSetStart = MinObjAlignment;
66 IndexSetStride = MinObjAlignment;
67 }
69 // Constructor
70 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs,
71 MemRegion mr, bool use_adaptive_freelists,
72 FreeBlockDictionary::DictionaryChoice dictionaryChoice) :
73 _dictionaryChoice(dictionaryChoice),
74 _adaptive_freelists(use_adaptive_freelists),
75 _bt(bs, mr),
76 // free list locks are in the range of values taken by _lockRank
77 // This range currently is [_leaf+2, _leaf+3]
78 // Note: this requires that CFLspace c'tors
79 // are called serially in the order in which the locks are
80 // are acquired in the program text. This is true today.
81 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true),
82 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
83 "CompactibleFreeListSpace._dict_par_lock", true),
84 _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
85 CMSRescanMultiple),
86 _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord *
87 CMSConcMarkMultiple),
88 _collector(NULL)
89 {
90 _bt.set_space(this);
91 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
92 // We have all of "mr", all of which we place in the dictionary
93 // as one big chunk. We'll need to decide here which of several
94 // possible alternative dictionary implementations to use. For
95 // now the choice is easy, since we have only one working
96 // implementation, namely, the simple binary tree (splaying
97 // temporarily disabled).
98 switch (dictionaryChoice) {
99 case FreeBlockDictionary::dictionarySplayTree:
100 case FreeBlockDictionary::dictionarySkipList:
101 default:
102 warning("dictionaryChoice: selected option not understood; using"
103 " default BinaryTreeDictionary implementation instead.");
104 case FreeBlockDictionary::dictionaryBinaryTree:
105 _dictionary = new BinaryTreeDictionary(mr);
106 break;
107 }
108 assert(_dictionary != NULL, "CMS dictionary initialization");
109 // The indexed free lists are initially all empty and are lazily
110 // filled in on demand. Initialize the array elements to NULL.
111 initializeIndexedFreeListArray();
113 // Not using adaptive free lists assumes that allocation is first
114 // from the linAB's. Also a cms perm gen which can be compacted
115 // has to have the klass's klassKlass allocated at a lower
116 // address in the heap than the klass so that the klassKlass is
117 // moved to its new location before the klass is moved.
118 // Set the _refillSize for the linear allocation blocks
119 if (!use_adaptive_freelists) {
120 FreeChunk* fc = _dictionary->getChunk(mr.word_size());
121 // The small linAB initially has all the space and will allocate
122 // a chunk of any size.
123 HeapWord* addr = (HeapWord*) fc;
124 _smallLinearAllocBlock.set(addr, fc->size() ,
125 1024*SmallForLinearAlloc, fc->size());
126 // Note that _unallocated_block is not updated here.
127 // Allocations from the linear allocation block should
128 // update it.
129 } else {
130 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
131 SmallForLinearAlloc);
132 }
133 // CMSIndexedFreeListReplenish should be at least 1
134 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
135 _promoInfo.setSpace(this);
136 if (UseCMSBestFit) {
137 _fitStrategy = FreeBlockBestFitFirst;
138 } else {
139 _fitStrategy = FreeBlockStrategyNone;
140 }
141 checkFreeListConsistency();
143 // Initialize locks for parallel case.
145 if (CollectedHeap::use_parallel_gc_threads()) {
146 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
147 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
148 "a freelist par lock",
149 true);
150 if (_indexedFreeListParLocks[i] == NULL)
151 vm_exit_during_initialization("Could not allocate a par lock");
152 DEBUG_ONLY(
153 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
154 )
155 }
156 _dictionary->set_par_lock(&_parDictionaryAllocLock);
157 }
158 }
160 // Like CompactibleSpace forward() but always calls cross_threshold() to
161 // update the block offset table. Removed initialize_threshold call because
162 // CFLS does not use a block offset array for contiguous spaces.
163 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
164 CompactPoint* cp, HeapWord* compact_top) {
165 // q is alive
166 // First check if we should switch compaction space
167 assert(this == cp->space, "'this' should be current compaction space.");
168 size_t compaction_max_size = pointer_delta(end(), compact_top);
169 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
170 "virtual adjustObjectSize_v() method is not correct");
171 size_t adjusted_size = adjustObjectSize(size);
172 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
173 "no small fragments allowed");
174 assert(minimum_free_block_size() == MinChunkSize,
175 "for de-virtualized reference below");
176 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
177 if (adjusted_size + MinChunkSize > compaction_max_size &&
178 adjusted_size != compaction_max_size) {
179 do {
180 // switch to next compaction space
181 cp->space->set_compaction_top(compact_top);
182 cp->space = cp->space->next_compaction_space();
183 if (cp->space == NULL) {
184 cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen);
185 assert(cp->gen != NULL, "compaction must succeed");
186 cp->space = cp->gen->first_compaction_space();
187 assert(cp->space != NULL, "generation must have a first compaction space");
188 }
189 compact_top = cp->space->bottom();
190 cp->space->set_compaction_top(compact_top);
191 // The correct adjusted_size may not be the same as that for this method
192 // (i.e., cp->space may no longer be "this" so adjust the size again.
193 // Use the virtual method which is not used above to save the virtual
194 // dispatch.
195 adjusted_size = cp->space->adjust_object_size_v(size);
196 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
197 assert(cp->space->minimum_free_block_size() == 0, "just checking");
198 } while (adjusted_size > compaction_max_size);
199 }
201 // store the forwarding pointer into the mark word
202 if ((HeapWord*)q != compact_top) {
203 q->forward_to(oop(compact_top));
204 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
205 } else {
206 // if the object isn't moving we can just set the mark to the default
207 // mark and handle it specially later on.
208 q->init_mark();
209 assert(q->forwardee() == NULL, "should be forwarded to NULL");
210 }
212 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(q, adjusted_size));
213 compact_top += adjusted_size;
215 // we need to update the offset table so that the beginnings of objects can be
216 // found during scavenge. Note that we are updating the offset table based on
217 // where the object will be once the compaction phase finishes.
219 // Always call cross_threshold(). A contiguous space can only call it when
220 // the compaction_top exceeds the current threshold but not for an
221 // non-contiguous space.
222 cp->threshold =
223 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
224 return compact_top;
225 }
227 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
228 // and use of single_block instead of alloc_block. The name here is not really
229 // appropriate - maybe a more general name could be invented for both the
230 // contiguous and noncontiguous spaces.
232 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
233 _bt.single_block(start, the_end);
234 return end();
235 }
237 // Initialize them to NULL.
238 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
239 for (size_t i = 0; i < IndexSetSize; i++) {
240 // Note that on platforms where objects are double word aligned,
241 // the odd array elements are not used. It is convenient, however,
242 // to map directly from the object size to the array element.
243 _indexedFreeList[i].reset(IndexSetSize);
244 _indexedFreeList[i].set_size(i);
245 assert(_indexedFreeList[i].count() == 0, "reset check failed");
246 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
247 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
248 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
249 }
250 }
252 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
253 for (int i = 1; i < IndexSetSize; i++) {
254 assert(_indexedFreeList[i].size() == (size_t) i,
255 "Indexed free list sizes are incorrect");
256 _indexedFreeList[i].reset(IndexSetSize);
257 assert(_indexedFreeList[i].count() == 0, "reset check failed");
258 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
259 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
260 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
261 }
262 }
264 void CompactibleFreeListSpace::reset(MemRegion mr) {
265 resetIndexedFreeListArray();
266 dictionary()->reset();
267 if (BlockOffsetArrayUseUnallocatedBlock) {
268 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
269 // Everything's allocated until proven otherwise.
270 _bt.set_unallocated_block(end());
271 }
272 if (!mr.is_empty()) {
273 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
274 _bt.single_block(mr.start(), mr.word_size());
275 FreeChunk* fc = (FreeChunk*) mr.start();
276 fc->setSize(mr.word_size());
277 if (mr.word_size() >= IndexSetSize ) {
278 returnChunkToDictionary(fc);
279 } else {
280 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
281 _indexedFreeList[mr.word_size()].returnChunkAtHead(fc);
282 }
283 }
284 _promoInfo.reset();
285 _smallLinearAllocBlock._ptr = NULL;
286 _smallLinearAllocBlock._word_size = 0;
287 }
289 void CompactibleFreeListSpace::reset_after_compaction() {
290 // Reset the space to the new reality - one free chunk.
291 MemRegion mr(compaction_top(), end());
292 reset(mr);
293 // Now refill the linear allocation block(s) if possible.
294 if (_adaptive_freelists) {
295 refillLinearAllocBlocksIfNeeded();
296 } else {
297 // Place as much of mr in the linAB as we can get,
298 // provided it was big enough to go into the dictionary.
299 FreeChunk* fc = dictionary()->findLargestDict();
300 if (fc != NULL) {
301 assert(fc->size() == mr.word_size(),
302 "Why was the chunk broken up?");
303 removeChunkFromDictionary(fc);
304 HeapWord* addr = (HeapWord*) fc;
305 _smallLinearAllocBlock.set(addr, fc->size() ,
306 1024*SmallForLinearAlloc, fc->size());
307 // Note that _unallocated_block is not updated here.
308 }
309 }
310 }
312 // Walks the entire dictionary, returning a coterminal
313 // chunk, if it exists. Use with caution since it involves
314 // a potentially complete walk of a potentially large tree.
315 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
317 assert_lock_strong(&_freelistLock);
319 return dictionary()->find_chunk_ends_at(end());
320 }
323 #ifndef PRODUCT
324 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
325 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
326 _indexedFreeList[i].allocation_stats()->set_returnedBytes(0);
327 }
328 }
330 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
331 size_t sum = 0;
332 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
333 sum += _indexedFreeList[i].allocation_stats()->returnedBytes();
334 }
335 return sum;
336 }
338 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
339 size_t count = 0;
340 for (int i = (int)MinChunkSize; i < IndexSetSize; i++) {
341 debug_only(
342 ssize_t total_list_count = 0;
343 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
344 fc = fc->next()) {
345 total_list_count++;
346 }
347 assert(total_list_count == _indexedFreeList[i].count(),
348 "Count in list is incorrect");
349 )
350 count += _indexedFreeList[i].count();
351 }
352 return count;
353 }
355 size_t CompactibleFreeListSpace::totalCount() {
356 size_t num = totalCountInIndexedFreeLists();
357 num += dictionary()->totalCount();
358 if (_smallLinearAllocBlock._word_size != 0) {
359 num++;
360 }
361 return num;
362 }
363 #endif
365 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
366 FreeChunk* fc = (FreeChunk*) p;
367 return fc->isFree();
368 }
370 size_t CompactibleFreeListSpace::used() const {
371 return capacity() - free();
372 }
374 size_t CompactibleFreeListSpace::free() const {
375 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
376 // if you do this while the structures are in flux you
377 // may get an approximate answer only; for instance
378 // because there is concurrent allocation either
379 // directly by mutators or for promotion during a GC.
380 // It's "MT-safe", however, in the sense that you are guaranteed
381 // not to crash and burn, for instance, because of walking
382 // pointers that could disappear as you were walking them.
383 // The approximation is because the various components
384 // that are read below are not read atomically (and
385 // further the computation of totalSizeInIndexedFreeLists()
386 // is itself a non-atomic computation. The normal use of
387 // this is during a resize operation at the end of GC
388 // and at that time you are guaranteed to get the
389 // correct actual value. However, for instance, this is
390 // also read completely asynchronously by the "perf-sampler"
391 // that supports jvmstat, and you are apt to see the values
392 // flicker in such cases.
393 assert(_dictionary != NULL, "No _dictionary?");
394 return (_dictionary->totalChunkSize(DEBUG_ONLY(freelistLock())) +
395 totalSizeInIndexedFreeLists() +
396 _smallLinearAllocBlock._word_size) * HeapWordSize;
397 }
399 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
400 assert(_dictionary != NULL, "No _dictionary?");
401 assert_locked();
402 size_t res = _dictionary->maxChunkSize();
403 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
404 (size_t) SmallForLinearAlloc - 1));
405 // XXX the following could potentially be pretty slow;
406 // should one, pesimally for the rare cases when res
407 // caclulated above is less than IndexSetSize,
408 // just return res calculated above? My reasoning was that
409 // those cases will be so rare that the extra time spent doesn't
410 // really matter....
411 // Note: do not change the loop test i >= res + IndexSetStride
412 // to i > res below, because i is unsigned and res may be zero.
413 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
414 i -= IndexSetStride) {
415 if (_indexedFreeList[i].head() != NULL) {
416 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
417 return i;
418 }
419 }
420 return res;
421 }
423 void LinearAllocBlock::print_on(outputStream* st) const {
424 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
425 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
426 _ptr, _word_size, _refillSize, _allocation_size_limit);
427 }
429 void CompactibleFreeListSpace::print_on(outputStream* st) const {
430 st->print_cr("COMPACTIBLE FREELIST SPACE");
431 st->print_cr(" Space:");
432 Space::print_on(st);
434 st->print_cr("promoInfo:");
435 _promoInfo.print_on(st);
437 st->print_cr("_smallLinearAllocBlock");
438 _smallLinearAllocBlock.print_on(st);
440 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
442 st->print_cr(" _fitStrategy = %s, _adaptive_freelists = %s",
443 _fitStrategy?"true":"false", _adaptive_freelists?"true":"false");
444 }
446 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
447 const {
448 reportIndexedFreeListStatistics();
449 gclog_or_tty->print_cr("Layout of Indexed Freelists");
450 gclog_or_tty->print_cr("---------------------------");
451 FreeList::print_labels_on(st, "size");
452 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
453 _indexedFreeList[i].print_on(gclog_or_tty);
454 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
455 fc = fc->next()) {
456 gclog_or_tty->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
457 fc, (HeapWord*)fc + i,
458 fc->cantCoalesce() ? "\t CC" : "");
459 }
460 }
461 }
463 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
464 const {
465 _promoInfo.print_on(st);
466 }
468 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
469 const {
470 _dictionary->reportStatistics();
471 st->print_cr("Layout of Freelists in Tree");
472 st->print_cr("---------------------------");
473 _dictionary->print_free_lists(st);
474 }
476 class BlkPrintingClosure: public BlkClosure {
477 const CMSCollector* _collector;
478 const CompactibleFreeListSpace* _sp;
479 const CMSBitMap* _live_bit_map;
480 const bool _post_remark;
481 outputStream* _st;
482 public:
483 BlkPrintingClosure(const CMSCollector* collector,
484 const CompactibleFreeListSpace* sp,
485 const CMSBitMap* live_bit_map,
486 outputStream* st):
487 _collector(collector),
488 _sp(sp),
489 _live_bit_map(live_bit_map),
490 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
491 _st(st) { }
492 size_t do_blk(HeapWord* addr);
493 };
495 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
496 size_t sz = _sp->block_size_no_stall(addr, _collector);
497 assert(sz != 0, "Should always be able to compute a size");
498 if (_sp->block_is_obj(addr)) {
499 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
500 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
501 addr,
502 dead ? "dead" : "live",
503 sz,
504 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
505 if (CMSPrintObjectsInDump && !dead) {
506 oop(addr)->print_on(_st);
507 _st->print_cr("--------------------------------------");
508 }
509 } else { // free block
510 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
511 addr, sz, CMSPrintChunksInDump ? ":" : ".");
512 if (CMSPrintChunksInDump) {
513 ((FreeChunk*)addr)->print_on(_st);
514 _st->print_cr("--------------------------------------");
515 }
516 }
517 return sz;
518 }
520 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c,
521 outputStream* st) {
522 st->print_cr("\n=========================");
523 st->print_cr("Block layout in CMS Heap:");
524 st->print_cr("=========================");
525 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
526 blk_iterate(&bpcl);
528 st->print_cr("\n=======================================");
529 st->print_cr("Order & Layout of Promotion Info Blocks");
530 st->print_cr("=======================================");
531 print_promo_info_blocks(st);
533 st->print_cr("\n===========================");
534 st->print_cr("Order of Indexed Free Lists");
535 st->print_cr("=========================");
536 print_indexed_free_lists(st);
538 st->print_cr("\n=================================");
539 st->print_cr("Order of Free Lists in Dictionary");
540 st->print_cr("=================================");
541 print_dictionary_free_lists(st);
542 }
545 void CompactibleFreeListSpace::reportFreeListStatistics() const {
546 assert_lock_strong(&_freelistLock);
547 assert(PrintFLSStatistics != 0, "Reporting error");
548 _dictionary->reportStatistics();
549 if (PrintFLSStatistics > 1) {
550 reportIndexedFreeListStatistics();
551 size_t totalSize = totalSizeInIndexedFreeLists() +
552 _dictionary->totalChunkSize(DEBUG_ONLY(freelistLock()));
553 gclog_or_tty->print(" free=%ld frag=%1.4f\n", totalSize, flsFrag());
554 }
555 }
557 void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const {
558 assert_lock_strong(&_freelistLock);
559 gclog_or_tty->print("Statistics for IndexedFreeLists:\n"
560 "--------------------------------\n");
561 size_t totalSize = totalSizeInIndexedFreeLists();
562 size_t freeBlocks = numFreeBlocksInIndexedFreeLists();
563 gclog_or_tty->print("Total Free Space: %d\n", totalSize);
564 gclog_or_tty->print("Max Chunk Size: %d\n", maxChunkSizeInIndexedFreeLists());
565 gclog_or_tty->print("Number of Blocks: %d\n", freeBlocks);
566 if (freeBlocks != 0) {
567 gclog_or_tty->print("Av. Block Size: %d\n", totalSize/freeBlocks);
568 }
569 }
571 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
572 size_t res = 0;
573 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
574 debug_only(
575 ssize_t recount = 0;
576 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
577 fc = fc->next()) {
578 recount += 1;
579 }
580 assert(recount == _indexedFreeList[i].count(),
581 "Incorrect count in list");
582 )
583 res += _indexedFreeList[i].count();
584 }
585 return res;
586 }
588 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
589 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
590 if (_indexedFreeList[i].head() != NULL) {
591 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
592 return (size_t)i;
593 }
594 }
595 return 0;
596 }
598 void CompactibleFreeListSpace::set_end(HeapWord* value) {
599 HeapWord* prevEnd = end();
600 assert(prevEnd != value, "unnecessary set_end call");
601 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
602 "New end is below unallocated block");
603 _end = value;
604 if (prevEnd != NULL) {
605 // Resize the underlying block offset table.
606 _bt.resize(pointer_delta(value, bottom()));
607 if (value <= prevEnd) {
608 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
609 "New end is below unallocated block");
610 } else {
611 // Now, take this new chunk and add it to the free blocks.
612 // Note that the BOT has not yet been updated for this block.
613 size_t newFcSize = pointer_delta(value, prevEnd);
614 // XXX This is REALLY UGLY and should be fixed up. XXX
615 if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) {
616 // Mark the boundary of the new block in BOT
617 _bt.mark_block(prevEnd, value);
618 // put it all in the linAB
619 if (ParallelGCThreads == 0) {
620 _smallLinearAllocBlock._ptr = prevEnd;
621 _smallLinearAllocBlock._word_size = newFcSize;
622 repairLinearAllocBlock(&_smallLinearAllocBlock);
623 } else { // ParallelGCThreads > 0
624 MutexLockerEx x(parDictionaryAllocLock(),
625 Mutex::_no_safepoint_check_flag);
626 _smallLinearAllocBlock._ptr = prevEnd;
627 _smallLinearAllocBlock._word_size = newFcSize;
628 repairLinearAllocBlock(&_smallLinearAllocBlock);
629 }
630 // Births of chunks put into a LinAB are not recorded. Births
631 // of chunks as they are allocated out of a LinAB are.
632 } else {
633 // Add the block to the free lists, if possible coalescing it
634 // with the last free block, and update the BOT and census data.
635 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
636 }
637 }
638 }
639 }
641 class FreeListSpace_DCTOC : public Filtering_DCTOC {
642 CompactibleFreeListSpace* _cfls;
643 CMSCollector* _collector;
644 protected:
645 // Override.
646 #define walk_mem_region_with_cl_DECL(ClosureType) \
647 virtual void walk_mem_region_with_cl(MemRegion mr, \
648 HeapWord* bottom, HeapWord* top, \
649 ClosureType* cl); \
650 void walk_mem_region_with_cl_par(MemRegion mr, \
651 HeapWord* bottom, HeapWord* top, \
652 ClosureType* cl); \
653 void walk_mem_region_with_cl_nopar(MemRegion mr, \
654 HeapWord* bottom, HeapWord* top, \
655 ClosureType* cl)
656 walk_mem_region_with_cl_DECL(OopClosure);
657 walk_mem_region_with_cl_DECL(FilteringClosure);
659 public:
660 FreeListSpace_DCTOC(CompactibleFreeListSpace* sp,
661 CMSCollector* collector,
662 OopClosure* cl,
663 CardTableModRefBS::PrecisionStyle precision,
664 HeapWord* boundary) :
665 Filtering_DCTOC(sp, cl, precision, boundary),
666 _cfls(sp), _collector(collector) {}
667 };
669 // We de-virtualize the block-related calls below, since we know that our
670 // space is a CompactibleFreeListSpace.
671 #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
672 void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \
673 HeapWord* bottom, \
674 HeapWord* top, \
675 ClosureType* cl) { \
676 if (SharedHeap::heap()->n_par_threads() > 0) { \
677 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
678 } else { \
679 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
680 } \
681 } \
682 void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
683 HeapWord* bottom, \
684 HeapWord* top, \
685 ClosureType* cl) { \
686 /* Skip parts that are before "mr", in case "block_start" sent us \
687 back too far. */ \
688 HeapWord* mr_start = mr.start(); \
689 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
690 HeapWord* next = bottom + bot_size; \
691 while (next < mr_start) { \
692 bottom = next; \
693 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
694 next = bottom + bot_size; \
695 } \
696 \
697 while (bottom < top) { \
698 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
699 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
700 oop(bottom)) && \
701 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
702 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
703 bottom += _cfls->adjustObjectSize(word_sz); \
704 } else { \
705 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
706 } \
707 } \
708 } \
709 void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
710 HeapWord* bottom, \
711 HeapWord* top, \
712 ClosureType* cl) { \
713 /* Skip parts that are before "mr", in case "block_start" sent us \
714 back too far. */ \
715 HeapWord* mr_start = mr.start(); \
716 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
717 HeapWord* next = bottom + bot_size; \
718 while (next < mr_start) { \
719 bottom = next; \
720 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
721 next = bottom + bot_size; \
722 } \
723 \
724 while (bottom < top) { \
725 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
726 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
727 oop(bottom)) && \
728 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
729 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \
730 bottom += _cfls->adjustObjectSize(word_sz); \
731 } else { \
732 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
733 } \
734 } \
735 }
737 // (There are only two of these, rather than N, because the split is due
738 // only to the introduction of the FilteringClosure, a local part of the
739 // impl of this abstraction.)
740 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(OopClosure)
741 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
743 DirtyCardToOopClosure*
744 CompactibleFreeListSpace::new_dcto_cl(OopClosure* cl,
745 CardTableModRefBS::PrecisionStyle precision,
746 HeapWord* boundary) {
747 return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary);
748 }
751 // Note on locking for the space iteration functions:
752 // since the collector's iteration activities are concurrent with
753 // allocation activities by mutators, absent a suitable mutual exclusion
754 // mechanism the iterators may go awry. For instace a block being iterated
755 // may suddenly be allocated or divided up and part of it allocated and
756 // so on.
758 // Apply the given closure to each block in the space.
759 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
760 assert_lock_strong(freelistLock());
761 HeapWord *cur, *limit;
762 for (cur = bottom(), limit = end(); cur < limit;
763 cur += cl->do_blk_careful(cur));
764 }
766 // Apply the given closure to each block in the space.
767 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
768 assert_lock_strong(freelistLock());
769 HeapWord *cur, *limit;
770 for (cur = bottom(), limit = end(); cur < limit;
771 cur += cl->do_blk(cur));
772 }
774 // Apply the given closure to each oop in the space.
775 void CompactibleFreeListSpace::oop_iterate(OopClosure* cl) {
776 assert_lock_strong(freelistLock());
777 HeapWord *cur, *limit;
778 size_t curSize;
779 for (cur = bottom(), limit = end(); cur < limit;
780 cur += curSize) {
781 curSize = block_size(cur);
782 if (block_is_obj(cur)) {
783 oop(cur)->oop_iterate(cl);
784 }
785 }
786 }
788 // Apply the given closure to each oop in the space \intersect memory region.
789 void CompactibleFreeListSpace::oop_iterate(MemRegion mr, OopClosure* cl) {
790 assert_lock_strong(freelistLock());
791 if (is_empty()) {
792 return;
793 }
794 MemRegion cur = MemRegion(bottom(), end());
795 mr = mr.intersection(cur);
796 if (mr.is_empty()) {
797 return;
798 }
799 if (mr.equals(cur)) {
800 oop_iterate(cl);
801 return;
802 }
803 assert(mr.end() <= end(), "just took an intersection above");
804 HeapWord* obj_addr = block_start(mr.start());
805 HeapWord* t = mr.end();
807 SpaceMemRegionOopsIterClosure smr_blk(cl, mr);
808 if (block_is_obj(obj_addr)) {
809 // Handle first object specially.
810 oop obj = oop(obj_addr);
811 obj_addr += adjustObjectSize(obj->oop_iterate(&smr_blk));
812 } else {
813 FreeChunk* fc = (FreeChunk*)obj_addr;
814 obj_addr += fc->size();
815 }
816 while (obj_addr < t) {
817 HeapWord* obj = obj_addr;
818 obj_addr += block_size(obj_addr);
819 // If "obj_addr" is not greater than top, then the
820 // entire object "obj" is within the region.
821 if (obj_addr <= t) {
822 if (block_is_obj(obj)) {
823 oop(obj)->oop_iterate(cl);
824 }
825 } else {
826 // "obj" extends beyond end of region
827 if (block_is_obj(obj)) {
828 oop(obj)->oop_iterate(&smr_blk);
829 }
830 break;
831 }
832 }
833 }
835 // NOTE: In the following methods, in order to safely be able to
836 // apply the closure to an object, we need to be sure that the
837 // object has been initialized. We are guaranteed that an object
838 // is initialized if we are holding the Heap_lock with the
839 // world stopped.
840 void CompactibleFreeListSpace::verify_objects_initialized() const {
841 if (is_init_completed()) {
842 assert_locked_or_safepoint(Heap_lock);
843 if (Universe::is_fully_initialized()) {
844 guarantee(SafepointSynchronize::is_at_safepoint(),
845 "Required for objects to be initialized");
846 }
847 } // else make a concession at vm start-up
848 }
850 // Apply the given closure to each object in the space
851 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
852 assert_lock_strong(freelistLock());
853 NOT_PRODUCT(verify_objects_initialized());
854 HeapWord *cur, *limit;
855 size_t curSize;
856 for (cur = bottom(), limit = end(); cur < limit;
857 cur += curSize) {
858 curSize = block_size(cur);
859 if (block_is_obj(cur)) {
860 blk->do_object(oop(cur));
861 }
862 }
863 }
865 // Apply the given closure to each live object in the space
866 // The usage of CompactibleFreeListSpace
867 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
868 // objects in the space with references to objects that are no longer
869 // valid. For example, an object may reference another object
870 // that has already been sweep up (collected). This method uses
871 // obj_is_alive() to determine whether it is safe to apply the closure to
872 // an object. See obj_is_alive() for details on how liveness of an
873 // object is decided.
875 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
876 assert_lock_strong(freelistLock());
877 NOT_PRODUCT(verify_objects_initialized());
878 HeapWord *cur, *limit;
879 size_t curSize;
880 for (cur = bottom(), limit = end(); cur < limit;
881 cur += curSize) {
882 curSize = block_size(cur);
883 if (block_is_obj(cur) && obj_is_alive(cur)) {
884 blk->do_object(oop(cur));
885 }
886 }
887 }
889 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
890 UpwardsObjectClosure* cl) {
891 assert_locked(freelistLock());
892 NOT_PRODUCT(verify_objects_initialized());
893 Space::object_iterate_mem(mr, cl);
894 }
896 // Callers of this iterator beware: The closure application should
897 // be robust in the face of uninitialized objects and should (always)
898 // return a correct size so that the next addr + size below gives us a
899 // valid block boundary. [See for instance,
900 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
901 // in ConcurrentMarkSweepGeneration.cpp.]
902 HeapWord*
903 CompactibleFreeListSpace::object_iterate_careful(ObjectClosureCareful* cl) {
904 assert_lock_strong(freelistLock());
905 HeapWord *addr, *last;
906 size_t size;
907 for (addr = bottom(), last = end();
908 addr < last; addr += size) {
909 FreeChunk* fc = (FreeChunk*)addr;
910 if (fc->isFree()) {
911 // Since we hold the free list lock, which protects direct
912 // allocation in this generation by mutators, a free object
913 // will remain free throughout this iteration code.
914 size = fc->size();
915 } else {
916 // Note that the object need not necessarily be initialized,
917 // because (for instance) the free list lock does NOT protect
918 // object initialization. The closure application below must
919 // therefore be correct in the face of uninitialized objects.
920 size = cl->do_object_careful(oop(addr));
921 if (size == 0) {
922 // An unparsable object found. Signal early termination.
923 return addr;
924 }
925 }
926 }
927 return NULL;
928 }
930 // Callers of this iterator beware: The closure application should
931 // be robust in the face of uninitialized objects and should (always)
932 // return a correct size so that the next addr + size below gives us a
933 // valid block boundary. [See for instance,
934 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
935 // in ConcurrentMarkSweepGeneration.cpp.]
936 HeapWord*
937 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
938 ObjectClosureCareful* cl) {
939 assert_lock_strong(freelistLock());
940 // Can't use used_region() below because it may not necessarily
941 // be the same as [bottom(),end()); although we could
942 // use [used_region().start(),round_to(used_region().end(),CardSize)),
943 // that appears too cumbersome, so we just do the simpler check
944 // in the assertion below.
945 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
946 "mr should be non-empty and within used space");
947 HeapWord *addr, *end;
948 size_t size;
949 for (addr = block_start_careful(mr.start()), end = mr.end();
950 addr < end; addr += size) {
951 FreeChunk* fc = (FreeChunk*)addr;
952 if (fc->isFree()) {
953 // Since we hold the free list lock, which protects direct
954 // allocation in this generation by mutators, a free object
955 // will remain free throughout this iteration code.
956 size = fc->size();
957 } else {
958 // Note that the object need not necessarily be initialized,
959 // because (for instance) the free list lock does NOT protect
960 // object initialization. The closure application below must
961 // therefore be correct in the face of uninitialized objects.
962 size = cl->do_object_careful_m(oop(addr), mr);
963 if (size == 0) {
964 // An unparsable object found. Signal early termination.
965 return addr;
966 }
967 }
968 }
969 return NULL;
970 }
973 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
974 NOT_PRODUCT(verify_objects_initialized());
975 return _bt.block_start(p);
976 }
978 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
979 return _bt.block_start_careful(p);
980 }
982 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
983 NOT_PRODUCT(verify_objects_initialized());
984 // This must be volatile, or else there is a danger that the compiler
985 // will compile the code below into a sometimes-infinite loop, by keeping
986 // the value read the first time in a register.
987 while (true) {
988 // We must do this until we get a consistent view of the object.
989 if (FreeChunk::indicatesFreeChunk(p)) {
990 volatile FreeChunk* fc = (volatile FreeChunk*)p;
991 size_t res = fc->size();
992 // If the object is still a free chunk, return the size, else it
993 // has been allocated so try again.
994 if (FreeChunk::indicatesFreeChunk(p)) {
995 assert(res != 0, "Block size should not be 0");
996 return res;
997 }
998 } else {
999 // must read from what 'p' points to in each loop.
1000 klassOop k = ((volatile oopDesc*)p)->klass_or_null();
1001 if (k != NULL) {
1002 assert(k->is_oop(true /* ignore mark word */), "Should be klass oop");
1003 oop o = (oop)p;
1004 assert(o->is_parsable(), "Should be parsable");
1005 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
1006 size_t res = o->size_given_klass(k->klass_part());
1007 res = adjustObjectSize(res);
1008 assert(res != 0, "Block size should not be 0");
1009 return res;
1010 }
1011 }
1012 }
1013 }
1015 // A variant of the above that uses the Printezis bits for
1016 // unparsable but allocated objects. This avoids any possible
1017 // stalls waiting for mutators to initialize objects, and is
1018 // thus potentially faster than the variant above. However,
1019 // this variant may return a zero size for a block that is
1020 // under mutation and for which a consistent size cannot be
1021 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
1022 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
1023 const CMSCollector* c)
1024 const {
1025 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1026 // This must be volatile, or else there is a danger that the compiler
1027 // will compile the code below into a sometimes-infinite loop, by keeping
1028 // the value read the first time in a register.
1029 DEBUG_ONLY(uint loops = 0;)
1030 while (true) {
1031 // We must do this until we get a consistent view of the object.
1032 if (FreeChunk::indicatesFreeChunk(p)) {
1033 volatile FreeChunk* fc = (volatile FreeChunk*)p;
1034 size_t res = fc->size();
1035 if (FreeChunk::indicatesFreeChunk(p)) {
1036 assert(res != 0, "Block size should not be 0");
1037 assert(loops == 0, "Should be 0");
1038 return res;
1039 }
1040 } else {
1041 // must read from what 'p' points to in each loop.
1042 klassOop k = ((volatile oopDesc*)p)->klass_or_null();
1043 // We trust the size of any object that has a non-NULL
1044 // klass and (for those in the perm gen) is parsable
1045 // -- irrespective of its conc_safe-ty.
1046 if (k != NULL && ((oopDesc*)p)->is_parsable()) {
1047 assert(k->is_oop(), "Should really be klass oop.");
1048 oop o = (oop)p;
1049 assert(o->is_oop(), "Should be an oop");
1050 size_t res = o->size_given_klass(k->klass_part());
1051 res = adjustObjectSize(res);
1052 assert(res != 0, "Block size should not be 0");
1053 return res;
1054 } else {
1055 // May return 0 if P-bits not present.
1056 return c->block_size_if_printezis_bits(p);
1057 }
1058 }
1059 assert(loops == 0, "Can loop at most once");
1060 DEBUG_ONLY(loops++;)
1061 }
1062 }
1064 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1065 NOT_PRODUCT(verify_objects_initialized());
1066 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1067 FreeChunk* fc = (FreeChunk*)p;
1068 if (fc->isFree()) {
1069 return fc->size();
1070 } else {
1071 // Ignore mark word because this may be a recently promoted
1072 // object whose mark word is used to chain together grey
1073 // objects (the last one would have a null value).
1074 assert(oop(p)->is_oop(true), "Should be an oop");
1075 return adjustObjectSize(oop(p)->size());
1076 }
1077 }
1079 // This implementation assumes that the property of "being an object" is
1080 // stable. But being a free chunk may not be (because of parallel
1081 // promotion.)
1082 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1083 FreeChunk* fc = (FreeChunk*)p;
1084 assert(is_in_reserved(p), "Should be in space");
1085 // When doing a mark-sweep-compact of the CMS generation, this
1086 // assertion may fail because prepare_for_compaction() uses
1087 // space that is garbage to maintain information on ranges of
1088 // live objects so that these live ranges can be moved as a whole.
1089 // Comment out this assertion until that problem can be solved
1090 // (i.e., that the block start calculation may look at objects
1091 // at address below "p" in finding the object that contains "p"
1092 // and those objects (if garbage) may have been modified to hold
1093 // live range information.
1094 // assert(CollectedHeap::use_parallel_gc_threads() || _bt.block_start(p) == p,
1095 // "Should be a block boundary");
1096 if (FreeChunk::indicatesFreeChunk(p)) return false;
1097 klassOop k = oop(p)->klass_or_null();
1098 if (k != NULL) {
1099 // Ignore mark word because it may have been used to
1100 // chain together promoted objects (the last one
1101 // would have a null value).
1102 assert(oop(p)->is_oop(true), "Should be an oop");
1103 return true;
1104 } else {
1105 return false; // Was not an object at the start of collection.
1106 }
1107 }
1109 // Check if the object is alive. This fact is checked either by consulting
1110 // the main marking bitmap in the sweeping phase or, if it's a permanent
1111 // generation and we're not in the sweeping phase, by checking the
1112 // perm_gen_verify_bit_map where we store the "deadness" information if
1113 // we did not sweep the perm gen in the most recent previous GC cycle.
1114 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1115 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1116 "Else races are possible");
1117 assert(block_is_obj(p), "The address should point to an object");
1119 // If we're sweeping, we use object liveness information from the main bit map
1120 // for both perm gen and old gen.
1121 // We don't need to lock the bitmap (live_map or dead_map below), because
1122 // EITHER we are in the middle of the sweeping phase, and the
1123 // main marking bit map (live_map below) is locked,
1124 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1125 // is stable, because it's mutated only in the sweeping phase.
1126 // NOTE: This method is also used by jmap where, if class unloading is
1127 // off, the results can return "false" for legitimate perm objects,
1128 // when we are not in the midst of a sweeping phase, which can result
1129 // in jmap not reporting certain perm gen objects. This will be moot
1130 // if/when the perm gen goes away in the future.
1131 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1132 CMSBitMap* live_map = _collector->markBitMap();
1133 return live_map->par_isMarked((HeapWord*) p);
1134 } else {
1135 // If we're not currently sweeping and we haven't swept the perm gen in
1136 // the previous concurrent cycle then we may have dead but unswept objects
1137 // in the perm gen. In this case, we use the "deadness" information
1138 // that we had saved in perm_gen_verify_bit_map at the last sweep.
1139 if (!CMSClassUnloadingEnabled && _collector->_permGen->reserved().contains(p)) {
1140 if (_collector->verifying()) {
1141 CMSBitMap* dead_map = _collector->perm_gen_verify_bit_map();
1142 // Object is marked in the dead_map bitmap at the previous sweep
1143 // when we know that it's dead; if the bitmap is not allocated then
1144 // the object is alive.
1145 return (dead_map->sizeInBits() == 0) // bit_map has been allocated
1146 || !dead_map->par_isMarked((HeapWord*) p);
1147 } else {
1148 return false; // We can't say for sure if it's live, so we say that it's dead.
1149 }
1150 }
1151 }
1152 return true;
1153 }
1155 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1156 FreeChunk* fc = (FreeChunk*)p;
1157 assert(is_in_reserved(p), "Should be in space");
1158 assert(_bt.block_start(p) == p, "Should be a block boundary");
1159 if (!fc->isFree()) {
1160 // Ignore mark word because it may have been used to
1161 // chain together promoted objects (the last one
1162 // would have a null value).
1163 assert(oop(p)->is_oop(true), "Should be an oop");
1164 return true;
1165 }
1166 return false;
1167 }
1169 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1170 // approximate answer if you don't hold the freelistlock when you call this.
1171 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1172 size_t size = 0;
1173 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1174 debug_only(
1175 // We may be calling here without the lock in which case we
1176 // won't do this modest sanity check.
1177 if (freelistLock()->owned_by_self()) {
1178 size_t total_list_size = 0;
1179 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1180 fc = fc->next()) {
1181 total_list_size += i;
1182 }
1183 assert(total_list_size == i * _indexedFreeList[i].count(),
1184 "Count in list is incorrect");
1185 }
1186 )
1187 size += i * _indexedFreeList[i].count();
1188 }
1189 return size;
1190 }
1192 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1193 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1194 return allocate(size);
1195 }
1197 HeapWord*
1198 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1199 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1200 }
1202 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1203 assert_lock_strong(freelistLock());
1204 HeapWord* res = NULL;
1205 assert(size == adjustObjectSize(size),
1206 "use adjustObjectSize() before calling into allocate()");
1208 if (_adaptive_freelists) {
1209 res = allocate_adaptive_freelists(size);
1210 } else { // non-adaptive free lists
1211 res = allocate_non_adaptive_freelists(size);
1212 }
1214 if (res != NULL) {
1215 // check that res does lie in this space!
1216 assert(is_in_reserved(res), "Not in this space!");
1217 assert(is_aligned((void*)res), "alignment check");
1219 FreeChunk* fc = (FreeChunk*)res;
1220 fc->markNotFree();
1221 assert(!fc->isFree(), "shouldn't be marked free");
1222 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1223 // Verify that the block offset table shows this to
1224 // be a single block, but not one which is unallocated.
1225 _bt.verify_single_block(res, size);
1226 _bt.verify_not_unallocated(res, size);
1227 // mangle a just allocated object with a distinct pattern.
1228 debug_only(fc->mangleAllocated(size));
1229 }
1231 return res;
1232 }
1234 HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) {
1235 HeapWord* res = NULL;
1236 // try and use linear allocation for smaller blocks
1237 if (size < _smallLinearAllocBlock._allocation_size_limit) {
1238 // if successful, the following also adjusts block offset table
1239 res = getChunkFromSmallLinearAllocBlock(size);
1240 }
1241 // Else triage to indexed lists for smaller sizes
1242 if (res == NULL) {
1243 if (size < SmallForDictionary) {
1244 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1245 } else {
1246 // else get it from the big dictionary; if even this doesn't
1247 // work we are out of luck.
1248 res = (HeapWord*)getChunkFromDictionaryExact(size);
1249 }
1250 }
1252 return res;
1253 }
1255 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1256 assert_lock_strong(freelistLock());
1257 HeapWord* res = NULL;
1258 assert(size == adjustObjectSize(size),
1259 "use adjustObjectSize() before calling into allocate()");
1261 // Strategy
1262 // if small
1263 // exact size from small object indexed list if small
1264 // small or large linear allocation block (linAB) as appropriate
1265 // take from lists of greater sized chunks
1266 // else
1267 // dictionary
1268 // small or large linear allocation block if it has the space
1269 // Try allocating exact size from indexTable first
1270 if (size < IndexSetSize) {
1271 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1272 if(res != NULL) {
1273 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1274 "Not removed from free list");
1275 // no block offset table adjustment is necessary on blocks in
1276 // the indexed lists.
1278 // Try allocating from the small LinAB
1279 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1280 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1281 // if successful, the above also adjusts block offset table
1282 // Note that this call will refill the LinAB to
1283 // satisfy the request. This is different that
1284 // evm.
1285 // Don't record chunk off a LinAB? smallSplitBirth(size);
1286 } else {
1287 // Raid the exact free lists larger than size, even if they are not
1288 // overpopulated.
1289 res = (HeapWord*) getChunkFromGreater(size);
1290 }
1291 } else {
1292 // Big objects get allocated directly from the dictionary.
1293 res = (HeapWord*) getChunkFromDictionaryExact(size);
1294 if (res == NULL) {
1295 // Try hard not to fail since an allocation failure will likely
1296 // trigger a synchronous GC. Try to get the space from the
1297 // allocation blocks.
1298 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1299 }
1300 }
1302 return res;
1303 }
1305 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1306 // when promoting obj.
1307 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1308 // Depending on the object size, expansion may require refilling either a
1309 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1310 // is added because the dictionary may over-allocate to avoid fragmentation.
1311 size_t space = obj_size;
1312 if (!_adaptive_freelists) {
1313 space = MAX2(space, _smallLinearAllocBlock._refillSize);
1314 }
1315 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1316 return space;
1317 }
1319 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1320 FreeChunk* ret;
1322 assert(numWords >= MinChunkSize, "Size is less than minimum");
1323 assert(linearAllocationWouldFail() || bestFitFirst(),
1324 "Should not be here");
1326 size_t i;
1327 size_t currSize = numWords + MinChunkSize;
1328 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1329 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1330 FreeList* fl = &_indexedFreeList[i];
1331 if (fl->head()) {
1332 ret = getFromListGreater(fl, numWords);
1333 assert(ret == NULL || ret->isFree(), "Should be returning a free chunk");
1334 return ret;
1335 }
1336 }
1338 currSize = MAX2((size_t)SmallForDictionary,
1339 (size_t)(numWords + MinChunkSize));
1341 /* Try to get a chunk that satisfies request, while avoiding
1342 fragmentation that can't be handled. */
1343 {
1344 ret = dictionary()->getChunk(currSize);
1345 if (ret != NULL) {
1346 assert(ret->size() - numWords >= MinChunkSize,
1347 "Chunk is too small");
1348 _bt.allocated((HeapWord*)ret, ret->size());
1349 /* Carve returned chunk. */
1350 (void) splitChunkAndReturnRemainder(ret, numWords);
1351 /* Label this as no longer a free chunk. */
1352 assert(ret->isFree(), "This chunk should be free");
1353 ret->linkPrev(NULL);
1354 }
1355 assert(ret == NULL || ret->isFree(), "Should be returning a free chunk");
1356 return ret;
1357 }
1358 ShouldNotReachHere();
1359 }
1361 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc)
1362 const {
1363 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1364 return _indexedFreeList[fc->size()].verifyChunkInFreeLists(fc);
1365 }
1367 bool CompactibleFreeListSpace::verifyChunkInFreeLists(FreeChunk* fc) const {
1368 if (fc->size() >= IndexSetSize) {
1369 return dictionary()->verifyChunkInFreeLists(fc);
1370 } else {
1371 return verifyChunkInIndexedFreeLists(fc);
1372 }
1373 }
1375 #ifndef PRODUCT
1376 void CompactibleFreeListSpace::assert_locked() const {
1377 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1378 }
1380 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1381 CMSLockVerifier::assert_locked(lock);
1382 }
1383 #endif
1385 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1386 // In the parallel case, the main thread holds the free list lock
1387 // on behalf the parallel threads.
1388 FreeChunk* fc;
1389 {
1390 // If GC is parallel, this might be called by several threads.
1391 // This should be rare enough that the locking overhead won't affect
1392 // the sequential code.
1393 MutexLockerEx x(parDictionaryAllocLock(),
1394 Mutex::_no_safepoint_check_flag);
1395 fc = getChunkFromDictionary(size);
1396 }
1397 if (fc != NULL) {
1398 fc->dontCoalesce();
1399 assert(fc->isFree(), "Should be free, but not coalescable");
1400 // Verify that the block offset table shows this to
1401 // be a single block, but not one which is unallocated.
1402 _bt.verify_single_block((HeapWord*)fc, fc->size());
1403 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1404 }
1405 return fc;
1406 }
1408 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1409 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1410 assert_locked();
1412 // if we are tracking promotions, then first ensure space for
1413 // promotion (including spooling space for saving header if necessary).
1414 // then allocate and copy, then track promoted info if needed.
1415 // When tracking (see PromotionInfo::track()), the mark word may
1416 // be displaced and in this case restoration of the mark word
1417 // occurs in the (oop_since_save_marks_)iterate phase.
1418 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1419 return NULL;
1420 }
1421 // Call the allocate(size_t, bool) form directly to avoid the
1422 // additional call through the allocate(size_t) form. Having
1423 // the compile inline the call is problematic because allocate(size_t)
1424 // is a virtual method.
1425 HeapWord* res = allocate(adjustObjectSize(obj_size));
1426 if (res != NULL) {
1427 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1428 // if we should be tracking promotions, do so.
1429 if (_promoInfo.tracking()) {
1430 _promoInfo.track((PromotedObject*)res);
1431 }
1432 }
1433 return oop(res);
1434 }
1436 HeapWord*
1437 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1438 assert_locked();
1439 assert(size >= MinChunkSize, "minimum chunk size");
1440 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1441 "maximum from smallLinearAllocBlock");
1442 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1443 }
1445 HeapWord*
1446 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1447 size_t size) {
1448 assert_locked();
1449 assert(size >= MinChunkSize, "too small");
1450 HeapWord* res = NULL;
1451 // Try to do linear allocation from blk, making sure that
1452 if (blk->_word_size == 0) {
1453 // We have probably been unable to fill this either in the prologue or
1454 // when it was exhausted at the last linear allocation. Bail out until
1455 // next time.
1456 assert(blk->_ptr == NULL, "consistency check");
1457 return NULL;
1458 }
1459 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1460 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1461 if (res != NULL) return res;
1463 // about to exhaust this linear allocation block
1464 if (blk->_word_size == size) { // exactly satisfied
1465 res = blk->_ptr;
1466 _bt.allocated(res, blk->_word_size);
1467 } else if (size + MinChunkSize <= blk->_refillSize) {
1468 size_t sz = blk->_word_size;
1469 // Update _unallocated_block if the size is such that chunk would be
1470 // returned to the indexed free list. All other chunks in the indexed
1471 // free lists are allocated from the dictionary so that _unallocated_block
1472 // has already been adjusted for them. Do it here so that the cost
1473 // for all chunks added back to the indexed free lists.
1474 if (sz < SmallForDictionary) {
1475 _bt.allocated(blk->_ptr, sz);
1476 }
1477 // Return the chunk that isn't big enough, and then refill below.
1478 addChunkToFreeLists(blk->_ptr, sz);
1479 splitBirth(sz);
1480 // Don't keep statistics on adding back chunk from a LinAB.
1481 } else {
1482 // A refilled block would not satisfy the request.
1483 return NULL;
1484 }
1486 blk->_ptr = NULL; blk->_word_size = 0;
1487 refillLinearAllocBlock(blk);
1488 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1489 "block was replenished");
1490 if (res != NULL) {
1491 splitBirth(size);
1492 repairLinearAllocBlock(blk);
1493 } else if (blk->_ptr != NULL) {
1494 res = blk->_ptr;
1495 size_t blk_size = blk->_word_size;
1496 blk->_word_size -= size;
1497 blk->_ptr += size;
1498 splitBirth(size);
1499 repairLinearAllocBlock(blk);
1500 // Update BOT last so that other (parallel) GC threads see a consistent
1501 // view of the BOT and free blocks.
1502 // Above must occur before BOT is updated below.
1503 OrderAccess::storestore();
1504 _bt.split_block(res, blk_size, size); // adjust block offset table
1505 }
1506 return res;
1507 }
1509 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1510 LinearAllocBlock* blk,
1511 size_t size) {
1512 assert_locked();
1513 assert(size >= MinChunkSize, "too small");
1515 HeapWord* res = NULL;
1516 // This is the common case. Keep it simple.
1517 if (blk->_word_size >= size + MinChunkSize) {
1518 assert(blk->_ptr != NULL, "consistency check");
1519 res = blk->_ptr;
1520 // Note that the BOT is up-to-date for the linAB before allocation. It
1521 // indicates the start of the linAB. The split_block() updates the
1522 // BOT for the linAB after the allocation (indicates the start of the
1523 // next chunk to be allocated).
1524 size_t blk_size = blk->_word_size;
1525 blk->_word_size -= size;
1526 blk->_ptr += size;
1527 splitBirth(size);
1528 repairLinearAllocBlock(blk);
1529 // Update BOT last so that other (parallel) GC threads see a consistent
1530 // view of the BOT and free blocks.
1531 // Above must occur before BOT is updated below.
1532 OrderAccess::storestore();
1533 _bt.split_block(res, blk_size, size); // adjust block offset table
1534 _bt.allocated(res, size);
1535 }
1536 return res;
1537 }
1539 FreeChunk*
1540 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1541 assert_locked();
1542 assert(size < SmallForDictionary, "just checking");
1543 FreeChunk* res;
1544 res = _indexedFreeList[size].getChunkAtHead();
1545 if (res == NULL) {
1546 res = getChunkFromIndexedFreeListHelper(size);
1547 }
1548 _bt.verify_not_unallocated((HeapWord*) res, size);
1549 assert(res == NULL || res->size() == size, "Incorrect block size");
1550 return res;
1551 }
1553 FreeChunk*
1554 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1555 bool replenish) {
1556 assert_locked();
1557 FreeChunk* fc = NULL;
1558 if (size < SmallForDictionary) {
1559 assert(_indexedFreeList[size].head() == NULL ||
1560 _indexedFreeList[size].surplus() <= 0,
1561 "List for this size should be empty or under populated");
1562 // Try best fit in exact lists before replenishing the list
1563 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1564 // Replenish list.
1565 //
1566 // Things tried that failed.
1567 // Tried allocating out of the two LinAB's first before
1568 // replenishing lists.
1569 // Tried small linAB of size 256 (size in indexed list)
1570 // and replenishing indexed lists from the small linAB.
1571 //
1572 FreeChunk* newFc = NULL;
1573 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1574 if (replenish_size < SmallForDictionary) {
1575 // Do not replenish from an underpopulated size.
1576 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1577 _indexedFreeList[replenish_size].head() != NULL) {
1578 newFc = _indexedFreeList[replenish_size].getChunkAtHead();
1579 } else if (bestFitFirst()) {
1580 newFc = bestFitSmall(replenish_size);
1581 }
1582 }
1583 if (newFc == NULL && replenish_size > size) {
1584 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1585 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1586 }
1587 // Note: The stats update re split-death of block obtained above
1588 // will be recorded below precisely when we know we are going to
1589 // be actually splitting it into more than one pieces below.
1590 if (newFc != NULL) {
1591 if (replenish || CMSReplenishIntermediate) {
1592 // Replenish this list and return one block to caller.
1593 size_t i;
1594 FreeChunk *curFc, *nextFc;
1595 size_t num_blk = newFc->size() / size;
1596 assert(num_blk >= 1, "Smaller than requested?");
1597 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1598 if (num_blk > 1) {
1599 // we are sure we will be splitting the block just obtained
1600 // into multiple pieces; record the split-death of the original
1601 splitDeath(replenish_size);
1602 }
1603 // carve up and link blocks 0, ..., num_blk - 2
1604 // The last chunk is not added to the lists but is returned as the
1605 // free chunk.
1606 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1607 i = 0;
1608 i < (num_blk - 1);
1609 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1610 i++) {
1611 curFc->setSize(size);
1612 // Don't record this as a return in order to try and
1613 // determine the "returns" from a GC.
1614 _bt.verify_not_unallocated((HeapWord*) fc, size);
1615 _indexedFreeList[size].returnChunkAtTail(curFc, false);
1616 _bt.mark_block((HeapWord*)curFc, size);
1617 splitBirth(size);
1618 // Don't record the initial population of the indexed list
1619 // as a split birth.
1620 }
1622 // check that the arithmetic was OK above
1623 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1624 "inconsistency in carving newFc");
1625 curFc->setSize(size);
1626 _bt.mark_block((HeapWord*)curFc, size);
1627 splitBirth(size);
1628 fc = curFc;
1629 } else {
1630 // Return entire block to caller
1631 fc = newFc;
1632 }
1633 }
1634 }
1635 } else {
1636 // Get a free chunk from the free chunk dictionary to be returned to
1637 // replenish the indexed free list.
1638 fc = getChunkFromDictionaryExact(size);
1639 }
1640 // assert(fc == NULL || fc->isFree(), "Should be returning a free chunk");
1641 return fc;
1642 }
1644 FreeChunk*
1645 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1646 assert_locked();
1647 FreeChunk* fc = _dictionary->getChunk(size);
1648 if (fc == NULL) {
1649 return NULL;
1650 }
1651 _bt.allocated((HeapWord*)fc, fc->size());
1652 if (fc->size() >= size + MinChunkSize) {
1653 fc = splitChunkAndReturnRemainder(fc, size);
1654 }
1655 assert(fc->size() >= size, "chunk too small");
1656 assert(fc->size() < size + MinChunkSize, "chunk too big");
1657 _bt.verify_single_block((HeapWord*)fc, fc->size());
1658 return fc;
1659 }
1661 FreeChunk*
1662 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1663 assert_locked();
1664 FreeChunk* fc = _dictionary->getChunk(size);
1665 if (fc == NULL) {
1666 return fc;
1667 }
1668 _bt.allocated((HeapWord*)fc, fc->size());
1669 if (fc->size() == size) {
1670 _bt.verify_single_block((HeapWord*)fc, size);
1671 return fc;
1672 }
1673 assert(fc->size() > size, "getChunk() guarantee");
1674 if (fc->size() < size + MinChunkSize) {
1675 // Return the chunk to the dictionary and go get a bigger one.
1676 returnChunkToDictionary(fc);
1677 fc = _dictionary->getChunk(size + MinChunkSize);
1678 if (fc == NULL) {
1679 return NULL;
1680 }
1681 _bt.allocated((HeapWord*)fc, fc->size());
1682 }
1683 assert(fc->size() >= size + MinChunkSize, "tautology");
1684 fc = splitChunkAndReturnRemainder(fc, size);
1685 assert(fc->size() == size, "chunk is wrong size");
1686 _bt.verify_single_block((HeapWord*)fc, size);
1687 return fc;
1688 }
1690 void
1691 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
1692 assert_locked();
1694 size_t size = chunk->size();
1695 _bt.verify_single_block((HeapWord*)chunk, size);
1696 // adjust _unallocated_block downward, as necessary
1697 _bt.freed((HeapWord*)chunk, size);
1698 _dictionary->returnChunk(chunk);
1699 #ifndef PRODUCT
1700 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1701 TreeChunk::as_TreeChunk(chunk)->list()->verify_stats();
1702 }
1703 #endif // PRODUCT
1704 }
1706 void
1707 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
1708 assert_locked();
1709 size_t size = fc->size();
1710 _bt.verify_single_block((HeapWord*) fc, size);
1711 _bt.verify_not_unallocated((HeapWord*) fc, size);
1712 if (_adaptive_freelists) {
1713 _indexedFreeList[size].returnChunkAtTail(fc);
1714 } else {
1715 _indexedFreeList[size].returnChunkAtHead(fc);
1716 }
1717 #ifndef PRODUCT
1718 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1719 _indexedFreeList[size].verify_stats();
1720 }
1721 #endif // PRODUCT
1722 }
1724 // Add chunk to end of last block -- if it's the largest
1725 // block -- and update BOT and census data. We would
1726 // of course have preferred to coalesce it with the
1727 // last block, but it's currently less expensive to find the
1728 // largest block than it is to find the last.
1729 void
1730 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1731 HeapWord* chunk, size_t size) {
1732 // check that the chunk does lie in this space!
1733 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1734 // One of the parallel gc task threads may be here
1735 // whilst others are allocating.
1736 Mutex* lock = NULL;
1737 if (ParallelGCThreads != 0) {
1738 lock = &_parDictionaryAllocLock;
1739 }
1740 FreeChunk* ec;
1741 {
1742 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1743 ec = dictionary()->findLargestDict(); // get largest block
1744 if (ec != NULL && ec->end() == chunk) {
1745 // It's a coterminal block - we can coalesce.
1746 size_t old_size = ec->size();
1747 coalDeath(old_size);
1748 removeChunkFromDictionary(ec);
1749 size += old_size;
1750 } else {
1751 ec = (FreeChunk*)chunk;
1752 }
1753 }
1754 ec->setSize(size);
1755 debug_only(ec->mangleFreed(size));
1756 if (size < SmallForDictionary) {
1757 lock = _indexedFreeListParLocks[size];
1758 }
1759 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1760 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
1761 // record the birth under the lock since the recording involves
1762 // manipulation of the list on which the chunk lives and
1763 // if the chunk is allocated and is the last on the list,
1764 // the list can go away.
1765 coalBirth(size);
1766 }
1768 void
1769 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1770 size_t size) {
1771 // check that the chunk does lie in this space!
1772 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1773 assert_locked();
1774 _bt.verify_single_block(chunk, size);
1776 FreeChunk* fc = (FreeChunk*) chunk;
1777 fc->setSize(size);
1778 debug_only(fc->mangleFreed(size));
1779 if (size < SmallForDictionary) {
1780 returnChunkToFreeList(fc);
1781 } else {
1782 returnChunkToDictionary(fc);
1783 }
1784 }
1786 void
1787 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1788 size_t size, bool coalesced) {
1789 assert_locked();
1790 assert(chunk != NULL, "null chunk");
1791 if (coalesced) {
1792 // repair BOT
1793 _bt.single_block(chunk, size);
1794 }
1795 addChunkToFreeLists(chunk, size);
1796 }
1798 // We _must_ find the purported chunk on our free lists;
1799 // we assert if we don't.
1800 void
1801 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1802 size_t size = fc->size();
1803 assert_locked();
1804 debug_only(verifyFreeLists());
1805 if (size < SmallForDictionary) {
1806 removeChunkFromIndexedFreeList(fc);
1807 } else {
1808 removeChunkFromDictionary(fc);
1809 }
1810 _bt.verify_single_block((HeapWord*)fc, size);
1811 debug_only(verifyFreeLists());
1812 }
1814 void
1815 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1816 size_t size = fc->size();
1817 assert_locked();
1818 assert(fc != NULL, "null chunk");
1819 _bt.verify_single_block((HeapWord*)fc, size);
1820 _dictionary->removeChunk(fc);
1821 // adjust _unallocated_block upward, as necessary
1822 _bt.allocated((HeapWord*)fc, size);
1823 }
1825 void
1826 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1827 assert_locked();
1828 size_t size = fc->size();
1829 _bt.verify_single_block((HeapWord*)fc, size);
1830 NOT_PRODUCT(
1831 if (FLSVerifyIndexTable) {
1832 verifyIndexedFreeList(size);
1833 }
1834 )
1835 _indexedFreeList[size].removeChunk(fc);
1836 debug_only(fc->clearNext());
1837 debug_only(fc->clearPrev());
1838 NOT_PRODUCT(
1839 if (FLSVerifyIndexTable) {
1840 verifyIndexedFreeList(size);
1841 }
1842 )
1843 }
1845 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1846 /* A hint is the next larger size that has a surplus.
1847 Start search at a size large enough to guarantee that
1848 the excess is >= MIN_CHUNK. */
1849 size_t start = align_object_size(numWords + MinChunkSize);
1850 if (start < IndexSetSize) {
1851 FreeList* it = _indexedFreeList;
1852 size_t hint = _indexedFreeList[start].hint();
1853 while (hint < IndexSetSize) {
1854 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1855 FreeList *fl = &_indexedFreeList[hint];
1856 if (fl->surplus() > 0 && fl->head() != NULL) {
1857 // Found a list with surplus, reset original hint
1858 // and split out a free chunk which is returned.
1859 _indexedFreeList[start].set_hint(hint);
1860 FreeChunk* res = getFromListGreater(fl, numWords);
1861 assert(res == NULL || res->isFree(),
1862 "Should be returning a free chunk");
1863 return res;
1864 }
1865 hint = fl->hint(); /* keep looking */
1866 }
1867 /* None found. */
1868 it[start].set_hint(IndexSetSize);
1869 }
1870 return NULL;
1871 }
1873 /* Requires fl->size >= numWords + MinChunkSize */
1874 FreeChunk* CompactibleFreeListSpace::getFromListGreater(FreeList* fl,
1875 size_t numWords) {
1876 FreeChunk *curr = fl->head();
1877 size_t oldNumWords = curr->size();
1878 assert(numWords >= MinChunkSize, "Word size is too small");
1879 assert(curr != NULL, "List is empty");
1880 assert(oldNumWords >= numWords + MinChunkSize,
1881 "Size of chunks in the list is too small");
1883 fl->removeChunk(curr);
1884 // recorded indirectly by splitChunkAndReturnRemainder -
1885 // smallSplit(oldNumWords, numWords);
1886 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1887 // Does anything have to be done for the remainder in terms of
1888 // fixing the card table?
1889 assert(new_chunk == NULL || new_chunk->isFree(),
1890 "Should be returning a free chunk");
1891 return new_chunk;
1892 }
1894 FreeChunk*
1895 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1896 size_t new_size) {
1897 assert_locked();
1898 size_t size = chunk->size();
1899 assert(size > new_size, "Split from a smaller block?");
1900 assert(is_aligned(chunk), "alignment problem");
1901 assert(size == adjustObjectSize(size), "alignment problem");
1902 size_t rem_size = size - new_size;
1903 assert(rem_size == adjustObjectSize(rem_size), "alignment problem");
1904 assert(rem_size >= MinChunkSize, "Free chunk smaller than minimum");
1905 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1906 assert(is_aligned(ffc), "alignment problem");
1907 ffc->setSize(rem_size);
1908 ffc->linkNext(NULL);
1909 ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
1910 // Above must occur before BOT is updated below.
1911 // adjust block offset table
1912 OrderAccess::storestore();
1913 assert(chunk->isFree() && ffc->isFree(), "Error");
1914 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1915 if (rem_size < SmallForDictionary) {
1916 bool is_par = (SharedHeap::heap()->n_par_threads() > 0);
1917 if (is_par) _indexedFreeListParLocks[rem_size]->lock();
1918 returnChunkToFreeList(ffc);
1919 split(size, rem_size);
1920 if (is_par) _indexedFreeListParLocks[rem_size]->unlock();
1921 } else {
1922 returnChunkToDictionary(ffc);
1923 split(size ,rem_size);
1924 }
1925 chunk->setSize(new_size);
1926 return chunk;
1927 }
1929 void
1930 CompactibleFreeListSpace::sweep_completed() {
1931 // Now that space is probably plentiful, refill linear
1932 // allocation blocks as needed.
1933 refillLinearAllocBlocksIfNeeded();
1934 }
1936 void
1937 CompactibleFreeListSpace::gc_prologue() {
1938 assert_locked();
1939 if (PrintFLSStatistics != 0) {
1940 gclog_or_tty->print("Before GC:\n");
1941 reportFreeListStatistics();
1942 }
1943 refillLinearAllocBlocksIfNeeded();
1944 }
1946 void
1947 CompactibleFreeListSpace::gc_epilogue() {
1948 assert_locked();
1949 if (PrintGCDetails && Verbose && !_adaptive_freelists) {
1950 if (_smallLinearAllocBlock._word_size == 0)
1951 warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure");
1952 }
1953 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1954 _promoInfo.stopTrackingPromotions();
1955 repairLinearAllocationBlocks();
1956 // Print Space's stats
1957 if (PrintFLSStatistics != 0) {
1958 gclog_or_tty->print("After GC:\n");
1959 reportFreeListStatistics();
1960 }
1961 }
1963 // Iteration support, mostly delegated from a CMS generation
1965 void CompactibleFreeListSpace::save_marks() {
1966 // mark the "end" of the used space at the time of this call;
1967 // note, however, that promoted objects from this point
1968 // on are tracked in the _promoInfo below.
1969 set_saved_mark_word(unallocated_block());
1970 // inform allocator that promotions should be tracked.
1971 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1972 _promoInfo.startTrackingPromotions();
1973 }
1975 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
1976 assert(_promoInfo.tracking(), "No preceding save_marks?");
1977 assert(SharedHeap::heap()->n_par_threads() == 0,
1978 "Shouldn't be called if using parallel gc.");
1979 return _promoInfo.noPromotions();
1980 }
1982 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
1983 \
1984 void CompactibleFreeListSpace:: \
1985 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
1986 assert(SharedHeap::heap()->n_par_threads() == 0, \
1987 "Shouldn't be called (yet) during parallel part of gc."); \
1988 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
1989 /* \
1990 * This also restores any displaced headers and removes the elements from \
1991 * the iteration set as they are processed, so that we have a clean slate \
1992 * at the end of the iteration. Note, thus, that if new objects are \
1993 * promoted as a result of the iteration they are iterated over as well. \
1994 */ \
1995 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
1996 }
1998 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
2001 void CompactibleFreeListSpace::object_iterate_since_last_GC(ObjectClosure* cl) {
2002 // ugghh... how would one do this efficiently for a non-contiguous space?
2003 guarantee(false, "NYI");
2004 }
2006 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
2007 return _smallLinearAllocBlock._word_size == 0;
2008 }
2010 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
2011 // Fix up linear allocation blocks to look like free blocks
2012 repairLinearAllocBlock(&_smallLinearAllocBlock);
2013 }
2015 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
2016 assert_locked();
2017 if (blk->_ptr != NULL) {
2018 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
2019 "Minimum block size requirement");
2020 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
2021 fc->setSize(blk->_word_size);
2022 fc->linkPrev(NULL); // mark as free
2023 fc->dontCoalesce();
2024 assert(fc->isFree(), "just marked it free");
2025 assert(fc->cantCoalesce(), "just marked it uncoalescable");
2026 }
2027 }
2029 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
2030 assert_locked();
2031 if (_smallLinearAllocBlock._ptr == NULL) {
2032 assert(_smallLinearAllocBlock._word_size == 0,
2033 "Size of linAB should be zero if the ptr is NULL");
2034 // Reset the linAB refill and allocation size limit.
2035 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
2036 }
2037 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
2038 }
2040 void
2041 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
2042 assert_locked();
2043 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
2044 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
2045 "blk invariant");
2046 if (blk->_ptr == NULL) {
2047 refillLinearAllocBlock(blk);
2048 }
2049 if (PrintMiscellaneous && Verbose) {
2050 if (blk->_word_size == 0) {
2051 warning("CompactibleFreeListSpace(prologue):: Linear allocation failure");
2052 }
2053 }
2054 }
2056 void
2057 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
2058 assert_locked();
2059 assert(blk->_word_size == 0 && blk->_ptr == NULL,
2060 "linear allocation block should be empty");
2061 FreeChunk* fc;
2062 if (blk->_refillSize < SmallForDictionary &&
2063 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
2064 // A linAB's strategy might be to use small sizes to reduce
2065 // fragmentation but still get the benefits of allocation from a
2066 // linAB.
2067 } else {
2068 fc = getChunkFromDictionary(blk->_refillSize);
2069 }
2070 if (fc != NULL) {
2071 blk->_ptr = (HeapWord*)fc;
2072 blk->_word_size = fc->size();
2073 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
2074 }
2075 }
2077 // Support for concurrent collection policy decisions.
2078 bool CompactibleFreeListSpace::should_concurrent_collect() const {
2079 // In the future we might want to add in frgamentation stats --
2080 // including erosion of the "mountain" into this decision as well.
2081 return !adaptive_freelists() && linearAllocationWouldFail();
2082 }
2084 // Support for compaction
2086 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
2087 SCAN_AND_FORWARD(cp,end,block_is_obj,block_size);
2088 // prepare_for_compaction() uses the space between live objects
2089 // so that later phase can skip dead space quickly. So verification
2090 // of the free lists doesn't work after.
2091 }
2093 #define obj_size(q) adjustObjectSize(oop(q)->size())
2094 #define adjust_obj_size(s) adjustObjectSize(s)
2096 void CompactibleFreeListSpace::adjust_pointers() {
2097 // In other versions of adjust_pointers(), a bail out
2098 // based on the amount of live data in the generation
2099 // (i.e., if 0, bail out) may be used.
2100 // Cannot test used() == 0 here because the free lists have already
2101 // been mangled by the compaction.
2103 SCAN_AND_ADJUST_POINTERS(adjust_obj_size);
2104 // See note about verification in prepare_for_compaction().
2105 }
2107 void CompactibleFreeListSpace::compact() {
2108 SCAN_AND_COMPACT(obj_size);
2109 }
2111 // fragmentation_metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
2112 // where fbs is free block sizes
2113 double CompactibleFreeListSpace::flsFrag() const {
2114 size_t itabFree = totalSizeInIndexedFreeLists();
2115 double frag = 0.0;
2116 size_t i;
2118 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2119 double sz = i;
2120 frag += _indexedFreeList[i].count() * (sz * sz);
2121 }
2123 double totFree = itabFree +
2124 _dictionary->totalChunkSize(DEBUG_ONLY(freelistLock()));
2125 if (totFree > 0) {
2126 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
2127 (totFree * totFree));
2128 frag = (double)1.0 - frag;
2129 } else {
2130 assert(frag == 0.0, "Follows from totFree == 0");
2131 }
2132 return frag;
2133 }
2135 void CompactibleFreeListSpace::beginSweepFLCensus(
2136 float inter_sweep_current,
2137 float inter_sweep_estimate,
2138 float intra_sweep_estimate) {
2139 assert_locked();
2140 size_t i;
2141 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2142 FreeList* fl = &_indexedFreeList[i];
2143 if (PrintFLSStatistics > 1) {
2144 gclog_or_tty->print("size[%d] : ", i);
2145 }
2146 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2147 fl->set_coalDesired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2148 fl->set_beforeSweep(fl->count());
2149 fl->set_bfrSurp(fl->surplus());
2150 }
2151 _dictionary->beginSweepDictCensus(CMSLargeCoalSurplusPercent,
2152 inter_sweep_current,
2153 inter_sweep_estimate,
2154 intra_sweep_estimate);
2155 }
2157 void CompactibleFreeListSpace::setFLSurplus() {
2158 assert_locked();
2159 size_t i;
2160 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2161 FreeList *fl = &_indexedFreeList[i];
2162 fl->set_surplus(fl->count() -
2163 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2164 }
2165 }
2167 void CompactibleFreeListSpace::setFLHints() {
2168 assert_locked();
2169 size_t i;
2170 size_t h = IndexSetSize;
2171 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2172 FreeList *fl = &_indexedFreeList[i];
2173 fl->set_hint(h);
2174 if (fl->surplus() > 0) {
2175 h = i;
2176 }
2177 }
2178 }
2180 void CompactibleFreeListSpace::clearFLCensus() {
2181 assert_locked();
2182 int i;
2183 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2184 FreeList *fl = &_indexedFreeList[i];
2185 fl->set_prevSweep(fl->count());
2186 fl->set_coalBirths(0);
2187 fl->set_coalDeaths(0);
2188 fl->set_splitBirths(0);
2189 fl->set_splitDeaths(0);
2190 }
2191 }
2193 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2194 if (PrintFLSStatistics > 0) {
2195 HeapWord* largestAddr = (HeapWord*) dictionary()->findLargestDict();
2196 gclog_or_tty->print_cr("CMS: Large block " PTR_FORMAT,
2197 largestAddr);
2198 }
2199 setFLSurplus();
2200 setFLHints();
2201 if (PrintGC && PrintFLSCensus > 0) {
2202 printFLCensus(sweep_count);
2203 }
2204 clearFLCensus();
2205 assert_locked();
2206 _dictionary->endSweepDictCensus(CMSLargeSplitSurplusPercent);
2207 }
2209 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2210 if (size < SmallForDictionary) {
2211 FreeList *fl = &_indexedFreeList[size];
2212 return (fl->coalDesired() < 0) ||
2213 ((int)fl->count() > fl->coalDesired());
2214 } else {
2215 return dictionary()->coalDictOverPopulated(size);
2216 }
2217 }
2219 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2220 assert(size < SmallForDictionary, "Size too large for indexed list");
2221 FreeList *fl = &_indexedFreeList[size];
2222 fl->increment_coalBirths();
2223 fl->increment_surplus();
2224 }
2226 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2227 assert(size < SmallForDictionary, "Size too large for indexed list");
2228 FreeList *fl = &_indexedFreeList[size];
2229 fl->increment_coalDeaths();
2230 fl->decrement_surplus();
2231 }
2233 void CompactibleFreeListSpace::coalBirth(size_t size) {
2234 if (size < SmallForDictionary) {
2235 smallCoalBirth(size);
2236 } else {
2237 dictionary()->dictCensusUpdate(size,
2238 false /* split */,
2239 true /* birth */);
2240 }
2241 }
2243 void CompactibleFreeListSpace::coalDeath(size_t size) {
2244 if(size < SmallForDictionary) {
2245 smallCoalDeath(size);
2246 } else {
2247 dictionary()->dictCensusUpdate(size,
2248 false /* split */,
2249 false /* birth */);
2250 }
2251 }
2253 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2254 assert(size < SmallForDictionary, "Size too large for indexed list");
2255 FreeList *fl = &_indexedFreeList[size];
2256 fl->increment_splitBirths();
2257 fl->increment_surplus();
2258 }
2260 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2261 assert(size < SmallForDictionary, "Size too large for indexed list");
2262 FreeList *fl = &_indexedFreeList[size];
2263 fl->increment_splitDeaths();
2264 fl->decrement_surplus();
2265 }
2267 void CompactibleFreeListSpace::splitBirth(size_t size) {
2268 if (size < SmallForDictionary) {
2269 smallSplitBirth(size);
2270 } else {
2271 dictionary()->dictCensusUpdate(size,
2272 true /* split */,
2273 true /* birth */);
2274 }
2275 }
2277 void CompactibleFreeListSpace::splitDeath(size_t size) {
2278 if (size < SmallForDictionary) {
2279 smallSplitDeath(size);
2280 } else {
2281 dictionary()->dictCensusUpdate(size,
2282 true /* split */,
2283 false /* birth */);
2284 }
2285 }
2287 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2288 size_t to2 = from - to1;
2289 splitDeath(from);
2290 splitBirth(to1);
2291 splitBirth(to2);
2292 }
2294 void CompactibleFreeListSpace::print() const {
2295 print_on(tty);
2296 }
2298 void CompactibleFreeListSpace::prepare_for_verify() {
2299 assert_locked();
2300 repairLinearAllocationBlocks();
2301 // Verify that the SpoolBlocks look like free blocks of
2302 // appropriate sizes... To be done ...
2303 }
2305 class VerifyAllBlksClosure: public BlkClosure {
2306 private:
2307 const CompactibleFreeListSpace* _sp;
2308 const MemRegion _span;
2309 HeapWord* _last_addr;
2310 size_t _last_size;
2311 bool _last_was_obj;
2312 bool _last_was_live;
2314 public:
2315 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2316 MemRegion span) : _sp(sp), _span(span),
2317 _last_addr(NULL), _last_size(0),
2318 _last_was_obj(false), _last_was_live(false) { }
2320 virtual size_t do_blk(HeapWord* addr) {
2321 size_t res;
2322 bool was_obj = false;
2323 bool was_live = false;
2324 if (_sp->block_is_obj(addr)) {
2325 was_obj = true;
2326 oop p = oop(addr);
2327 guarantee(p->is_oop(), "Should be an oop");
2328 res = _sp->adjustObjectSize(p->size());
2329 if (_sp->obj_is_alive(addr)) {
2330 was_live = true;
2331 p->verify();
2332 }
2333 } else {
2334 FreeChunk* fc = (FreeChunk*)addr;
2335 res = fc->size();
2336 if (FLSVerifyLists && !fc->cantCoalesce()) {
2337 guarantee(_sp->verifyChunkInFreeLists(fc),
2338 "Chunk should be on a free list");
2339 }
2340 }
2341 if (res == 0) {
2342 gclog_or_tty->print_cr("Livelock: no rank reduction!");
2343 gclog_or_tty->print_cr(
2344 " Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2345 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2346 addr, res, was_obj ?"true":"false", was_live ?"true":"false",
2347 _last_addr, _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2348 _sp->print_on(gclog_or_tty);
2349 guarantee(false, "Seppuku!");
2350 }
2351 _last_addr = addr;
2352 _last_size = res;
2353 _last_was_obj = was_obj;
2354 _last_was_live = was_live;
2355 return res;
2356 }
2357 };
2359 class VerifyAllOopsClosure: public OopClosure {
2360 private:
2361 const CMSCollector* _collector;
2362 const CompactibleFreeListSpace* _sp;
2363 const MemRegion _span;
2364 const bool _past_remark;
2365 const CMSBitMap* _bit_map;
2367 protected:
2368 void do_oop(void* p, oop obj) {
2369 if (_span.contains(obj)) { // the interior oop points into CMS heap
2370 if (!_span.contains(p)) { // reference from outside CMS heap
2371 // Should be a valid object; the first disjunct below allows
2372 // us to sidestep an assertion in block_is_obj() that insists
2373 // that p be in _sp. Note that several generations (and spaces)
2374 // are spanned by _span (CMS heap) above.
2375 guarantee(!_sp->is_in_reserved(obj) ||
2376 _sp->block_is_obj((HeapWord*)obj),
2377 "Should be an object");
2378 guarantee(obj->is_oop(), "Should be an oop");
2379 obj->verify();
2380 if (_past_remark) {
2381 // Remark has been completed, the object should be marked
2382 _bit_map->isMarked((HeapWord*)obj);
2383 }
2384 } else { // reference within CMS heap
2385 if (_past_remark) {
2386 // Remark has been completed -- so the referent should have
2387 // been marked, if referring object is.
2388 if (_bit_map->isMarked(_collector->block_start(p))) {
2389 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2390 }
2391 }
2392 }
2393 } else if (_sp->is_in_reserved(p)) {
2394 // the reference is from FLS, and points out of FLS
2395 guarantee(obj->is_oop(), "Should be an oop");
2396 obj->verify();
2397 }
2398 }
2400 template <class T> void do_oop_work(T* p) {
2401 T heap_oop = oopDesc::load_heap_oop(p);
2402 if (!oopDesc::is_null(heap_oop)) {
2403 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2404 do_oop(p, obj);
2405 }
2406 }
2408 public:
2409 VerifyAllOopsClosure(const CMSCollector* collector,
2410 const CompactibleFreeListSpace* sp, MemRegion span,
2411 bool past_remark, CMSBitMap* bit_map) :
2412 OopClosure(), _collector(collector), _sp(sp), _span(span),
2413 _past_remark(past_remark), _bit_map(bit_map) { }
2415 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2416 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2417 };
2419 void CompactibleFreeListSpace::verify(bool ignored) const {
2420 assert_lock_strong(&_freelistLock);
2421 verify_objects_initialized();
2422 MemRegion span = _collector->_span;
2423 bool past_remark = (_collector->abstract_state() ==
2424 CMSCollector::Sweeping);
2426 ResourceMark rm;
2427 HandleMark hm;
2429 // Check integrity of CFL data structures
2430 _promoInfo.verify();
2431 _dictionary->verify();
2432 if (FLSVerifyIndexTable) {
2433 verifyIndexedFreeLists();
2434 }
2435 // Check integrity of all objects and free blocks in space
2436 {
2437 VerifyAllBlksClosure cl(this, span);
2438 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2439 }
2440 // Check that all references in the heap to FLS
2441 // are to valid objects in FLS or that references in
2442 // FLS are to valid objects elsewhere in the heap
2443 if (FLSVerifyAllHeapReferences)
2444 {
2445 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2446 _collector->markBitMap());
2447 CollectedHeap* ch = Universe::heap();
2448 ch->oop_iterate(&cl); // all oops in generations
2449 ch->permanent_oop_iterate(&cl); // all oops in perm gen
2450 }
2452 if (VerifyObjectStartArray) {
2453 // Verify the block offset table
2454 _bt.verify();
2455 }
2456 }
2458 #ifndef PRODUCT
2459 void CompactibleFreeListSpace::verifyFreeLists() const {
2460 if (FLSVerifyLists) {
2461 _dictionary->verify();
2462 verifyIndexedFreeLists();
2463 } else {
2464 if (FLSVerifyDictionary) {
2465 _dictionary->verify();
2466 }
2467 if (FLSVerifyIndexTable) {
2468 verifyIndexedFreeLists();
2469 }
2470 }
2471 }
2472 #endif
2474 void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
2475 size_t i = 0;
2476 for (; i < MinChunkSize; i++) {
2477 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
2478 }
2479 for (; i < IndexSetSize; i++) {
2480 verifyIndexedFreeList(i);
2481 }
2482 }
2484 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
2485 FreeChunk* fc = _indexedFreeList[size].head();
2486 FreeChunk* tail = _indexedFreeList[size].tail();
2487 size_t num = _indexedFreeList[size].count();
2488 size_t n = 0;
2489 guarantee((size % 2 == 0) || fc == NULL, "Odd slots should be empty");
2490 for (; fc != NULL; fc = fc->next(), n++) {
2491 guarantee(fc->size() == size, "Size inconsistency");
2492 guarantee(fc->isFree(), "!free?");
2493 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
2494 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
2495 }
2496 guarantee(n == num, "Incorrect count");
2497 }
2499 #ifndef PRODUCT
2500 void CompactibleFreeListSpace::checkFreeListConsistency() const {
2501 assert(_dictionary->minSize() <= IndexSetSize,
2502 "Some sizes can't be allocated without recourse to"
2503 " linear allocation buffers");
2504 assert(MIN_TREE_CHUNK_SIZE*HeapWordSize == sizeof(TreeChunk),
2505 "else MIN_TREE_CHUNK_SIZE is wrong");
2506 assert((IndexSetStride == 2 && IndexSetStart == 2) ||
2507 (IndexSetStride == 1 && IndexSetStart == 1), "just checking");
2508 assert((IndexSetStride != 2) || (MinChunkSize % 2 == 0),
2509 "Some for-loops may be incorrectly initialized");
2510 assert((IndexSetStride != 2) || (IndexSetSize % 2 == 1),
2511 "For-loops that iterate over IndexSet with stride 2 may be wrong");
2512 }
2513 #endif
2515 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2516 assert_lock_strong(&_freelistLock);
2517 FreeList total;
2518 gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count);
2519 FreeList::print_labels_on(gclog_or_tty, "size");
2520 size_t totalFree = 0;
2521 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2522 const FreeList *fl = &_indexedFreeList[i];
2523 totalFree += fl->count() * fl->size();
2524 if (i % (40*IndexSetStride) == 0) {
2525 FreeList::print_labels_on(gclog_or_tty, "size");
2526 }
2527 fl->print_on(gclog_or_tty);
2528 total.set_bfrSurp( total.bfrSurp() + fl->bfrSurp() );
2529 total.set_surplus( total.surplus() + fl->surplus() );
2530 total.set_desired( total.desired() + fl->desired() );
2531 total.set_prevSweep( total.prevSweep() + fl->prevSweep() );
2532 total.set_beforeSweep(total.beforeSweep() + fl->beforeSweep());
2533 total.set_count( total.count() + fl->count() );
2534 total.set_coalBirths( total.coalBirths() + fl->coalBirths() );
2535 total.set_coalDeaths( total.coalDeaths() + fl->coalDeaths() );
2536 total.set_splitBirths(total.splitBirths() + fl->splitBirths());
2537 total.set_splitDeaths(total.splitDeaths() + fl->splitDeaths());
2538 }
2539 total.print_on(gclog_or_tty, "TOTAL");
2540 gclog_or_tty->print_cr("Total free in indexed lists "
2541 SIZE_FORMAT " words", totalFree);
2542 gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n",
2543 (double)(total.splitBirths()+total.coalBirths()-total.splitDeaths()-total.coalDeaths())/
2544 (total.prevSweep() != 0 ? (double)total.prevSweep() : 1.0),
2545 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2546 _dictionary->printDictCensus();
2547 }
2549 ///////////////////////////////////////////////////////////////////////////
2550 // CFLS_LAB
2551 ///////////////////////////////////////////////////////////////////////////
2553 #define VECTOR_257(x) \
2554 /* 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 */ \
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, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2559 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2560 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2561 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2562 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2563 x }
2565 // Initialize with default setting of CMSParPromoteBlocksToClaim, _not_
2566 // OldPLABSize, whose static default is different; if overridden at the
2567 // command-line, this will get reinitialized via a call to
2568 // modify_initialization() below.
2569 AdaptiveWeightedAverage CFLS_LAB::_blocks_to_claim[] =
2570 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CMSParPromoteBlocksToClaim));
2571 size_t CFLS_LAB::_global_num_blocks[] = VECTOR_257(0);
2572 int CFLS_LAB::_global_num_workers[] = VECTOR_257(0);
2574 CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) :
2575 _cfls(cfls)
2576 {
2577 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2578 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2579 i < CompactibleFreeListSpace::IndexSetSize;
2580 i += CompactibleFreeListSpace::IndexSetStride) {
2581 _indexedFreeList[i].set_size(i);
2582 _num_blocks[i] = 0;
2583 }
2584 }
2586 static bool _CFLS_LAB_modified = false;
2588 void CFLS_LAB::modify_initialization(size_t n, unsigned wt) {
2589 assert(!_CFLS_LAB_modified, "Call only once");
2590 _CFLS_LAB_modified = true;
2591 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2592 i < CompactibleFreeListSpace::IndexSetSize;
2593 i += CompactibleFreeListSpace::IndexSetStride) {
2594 _blocks_to_claim[i].modify(n, wt, true /* force */);
2595 }
2596 }
2598 HeapWord* CFLS_LAB::alloc(size_t word_sz) {
2599 FreeChunk* res;
2600 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2601 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2602 // This locking manages sync with other large object allocations.
2603 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2604 Mutex::_no_safepoint_check_flag);
2605 res = _cfls->getChunkFromDictionaryExact(word_sz);
2606 if (res == NULL) return NULL;
2607 } else {
2608 FreeList* fl = &_indexedFreeList[word_sz];
2609 if (fl->count() == 0) {
2610 // Attempt to refill this local free list.
2611 get_from_global_pool(word_sz, fl);
2612 // If it didn't work, give up.
2613 if (fl->count() == 0) return NULL;
2614 }
2615 res = fl->getChunkAtHead();
2616 assert(res != NULL, "Why was count non-zero?");
2617 }
2618 res->markNotFree();
2619 assert(!res->isFree(), "shouldn't be marked free");
2620 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2621 // mangle a just allocated object with a distinct pattern.
2622 debug_only(res->mangleAllocated(word_sz));
2623 return (HeapWord*)res;
2624 }
2626 // Get a chunk of blocks of the right size and update related
2627 // book-keeping stats
2628 void CFLS_LAB::get_from_global_pool(size_t word_sz, FreeList* fl) {
2629 // Get the #blocks we want to claim
2630 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2631 assert(n_blks > 0, "Error");
2632 assert(ResizePLAB || n_blks == OldPLABSize, "Error");
2633 // In some cases, when the application has a phase change,
2634 // there may be a sudden and sharp shift in the object survival
2635 // profile, and updating the counts at the end of a scavenge
2636 // may not be quick enough, giving rise to large scavenge pauses
2637 // during these phase changes. It is beneficial to detect such
2638 // changes on-the-fly during a scavenge and avoid such a phase-change
2639 // pothole. The following code is a heuristic attempt to do that.
2640 // It is protected by a product flag until we have gained
2641 // enough experience with this heuristic and fine-tuned its behaviour.
2642 // WARNING: This might increase fragmentation if we overreact to
2643 // small spikes, so some kind of historical smoothing based on
2644 // previous experience with the greater reactivity might be useful.
2645 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2646 // default.
2647 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2648 size_t multiple = _num_blocks[word_sz]/(CMSOldPLABToleranceFactor*CMSOldPLABNumRefills*n_blks);
2649 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2650 n_blks = MIN2(n_blks, CMSOldPLABMax);
2651 }
2652 assert(n_blks > 0, "Error");
2653 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2654 // Update stats table entry for this block size
2655 _num_blocks[word_sz] += fl->count();
2656 }
2658 void CFLS_LAB::compute_desired_plab_size() {
2659 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2660 i < CompactibleFreeListSpace::IndexSetSize;
2661 i += CompactibleFreeListSpace::IndexSetStride) {
2662 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2663 "Counter inconsistency");
2664 if (_global_num_workers[i] > 0) {
2665 // Need to smooth wrt historical average
2666 if (ResizeOldPLAB) {
2667 _blocks_to_claim[i].sample(
2668 MAX2((size_t)CMSOldPLABMin,
2669 MIN2((size_t)CMSOldPLABMax,
2670 _global_num_blocks[i]/(_global_num_workers[i]*CMSOldPLABNumRefills))));
2671 }
2672 // Reset counters for next round
2673 _global_num_workers[i] = 0;
2674 _global_num_blocks[i] = 0;
2675 if (PrintOldPLAB) {
2676 gclog_or_tty->print_cr("[%d]: %d", i, (size_t)_blocks_to_claim[i].average());
2677 }
2678 }
2679 }
2680 }
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 #define CFLS_LAB_PARALLEL_ACCESS 0
2686 NOT_PRODUCT(Thread* t = Thread::current();)
2687 assert(Thread::current()->is_VM_thread(), "Error");
2688 assert(CompactibleFreeListSpace::IndexSetStart == CompactibleFreeListSpace::IndexSetStride,
2689 "Will access to uninitialized slot below");
2690 #if CFLS_LAB_PARALLEL_ACCESS
2691 for (size_t i = CompactibleFreeListSpace::IndexSetSize - 1;
2692 i > 0;
2693 i -= CompactibleFreeListSpace::IndexSetStride) {
2694 #else // CFLS_LAB_PARALLEL_ACCESS
2695 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2696 i < CompactibleFreeListSpace::IndexSetSize;
2697 i += CompactibleFreeListSpace::IndexSetStride) {
2698 #endif // !CFLS_LAB_PARALLEL_ACCESS
2699 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2700 "Can't retire more than what we obtained");
2701 if (_num_blocks[i] > 0) {
2702 size_t num_retire = _indexedFreeList[i].count();
2703 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2704 {
2705 #if CFLS_LAB_PARALLEL_ACCESS
2706 MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2707 Mutex::_no_safepoint_check_flag);
2708 #endif // CFLS_LAB_PARALLEL_ACCESS
2709 // Update globals stats for num_blocks used
2710 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2711 _global_num_workers[i]++;
2712 assert(_global_num_workers[i] <= (ssize_t)ParallelGCThreads, "Too big");
2713 if (num_retire > 0) {
2714 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2715 // Reset this list.
2716 _indexedFreeList[i] = FreeList();
2717 _indexedFreeList[i].set_size(i);
2718 }
2719 }
2720 if (PrintOldPLAB) {
2721 gclog_or_tty->print_cr("%d[%d]: %d/%d/%d",
2722 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2723 }
2724 // Reset stats for next round
2725 _num_blocks[i] = 0;
2726 }
2727 }
2728 }
2730 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl) {
2731 assert(fl->count() == 0, "Precondition.");
2732 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2733 "Precondition");
2735 // We'll try all multiples of word_sz in the indexed set, starting with
2736 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2737 // then try getting a big chunk and splitting it.
2738 {
2739 bool found;
2740 int k;
2741 size_t cur_sz;
2742 for (k = 1, cur_sz = k * word_sz, found = false;
2743 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2744 (CMSSplitIndexedFreeListBlocks || k <= 1);
2745 k++, cur_sz = k * word_sz) {
2746 FreeList fl_for_cur_sz; // Empty.
2747 fl_for_cur_sz.set_size(cur_sz);
2748 {
2749 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2750 Mutex::_no_safepoint_check_flag);
2751 FreeList* gfl = &_indexedFreeList[cur_sz];
2752 if (gfl->count() != 0) {
2753 // nn is the number of chunks of size cur_sz that
2754 // we'd need to split k-ways each, in order to create
2755 // "n" chunks of size word_sz each.
2756 const size_t nn = MAX2(n/k, (size_t)1);
2757 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2758 found = true;
2759 if (k > 1) {
2760 // Update split death stats for the cur_sz-size blocks list:
2761 // we increment the split death count by the number of blocks
2762 // we just took from the cur_sz-size blocks list and which
2763 // we will be splitting below.
2764 ssize_t deaths = gfl->splitDeaths() +
2765 fl_for_cur_sz.count();
2766 gfl->set_splitDeaths(deaths);
2767 }
2768 }
2769 }
2770 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2771 if (found) {
2772 if (k == 1) {
2773 fl->prepend(&fl_for_cur_sz);
2774 } else {
2775 // Divide each block on fl_for_cur_sz up k ways.
2776 FreeChunk* fc;
2777 while ((fc = fl_for_cur_sz.getChunkAtHead()) != NULL) {
2778 // Must do this in reverse order, so that anybody attempting to
2779 // access the main chunk sees it as a single free block until we
2780 // change it.
2781 size_t fc_size = fc->size();
2782 assert(fc->isFree(), "Error");
2783 for (int i = k-1; i >= 0; i--) {
2784 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2785 assert((i != 0) ||
2786 ((fc == ffc) && ffc->isFree() &&
2787 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2788 "Counting error");
2789 ffc->setSize(word_sz);
2790 ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
2791 ffc->linkNext(NULL);
2792 // Above must occur before BOT is updated below.
2793 OrderAccess::storestore();
2794 // splitting from the right, fc_size == i * word_sz
2795 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2796 fc_size -= word_sz;
2797 assert(fc_size == i*word_sz, "Error");
2798 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2799 _bt.verify_single_block((HeapWord*)fc, fc_size);
2800 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2801 // Push this on "fl".
2802 fl->returnChunkAtHead(ffc);
2803 }
2804 // TRAP
2805 assert(fl->tail()->next() == NULL, "List invariant.");
2806 }
2807 }
2808 // Update birth stats for this block size.
2809 size_t num = fl->count();
2810 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2811 Mutex::_no_safepoint_check_flag);
2812 ssize_t births = _indexedFreeList[word_sz].splitBirths() + num;
2813 _indexedFreeList[word_sz].set_splitBirths(births);
2814 return;
2815 }
2816 }
2817 }
2818 // Otherwise, we'll split a block from the dictionary.
2819 FreeChunk* fc = NULL;
2820 FreeChunk* rem_fc = NULL;
2821 size_t rem;
2822 {
2823 MutexLockerEx x(parDictionaryAllocLock(),
2824 Mutex::_no_safepoint_check_flag);
2825 while (n > 0) {
2826 fc = dictionary()->getChunk(MAX2(n * word_sz,
2827 _dictionary->minSize()),
2828 FreeBlockDictionary::atLeast);
2829 if (fc != NULL) {
2830 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2831 dictionary()->dictCensusUpdate(fc->size(),
2832 true /*split*/,
2833 false /*birth*/);
2834 break;
2835 } else {
2836 n--;
2837 }
2838 }
2839 if (fc == NULL) return;
2840 // Otherwise, split up that block.
2841 assert((ssize_t)n >= 1, "Control point invariant");
2842 assert(fc->isFree(), "Error: should be a free block");
2843 _bt.verify_single_block((HeapWord*)fc, fc->size());
2844 const size_t nn = fc->size() / word_sz;
2845 n = MIN2(nn, n);
2846 assert((ssize_t)n >= 1, "Control point invariant");
2847 rem = fc->size() - n * word_sz;
2848 // If there is a remainder, and it's too small, allocate one fewer.
2849 if (rem > 0 && rem < MinChunkSize) {
2850 n--; rem += word_sz;
2851 }
2852 // Note that at this point we may have n == 0.
2853 assert((ssize_t)n >= 0, "Control point invariant");
2855 // If n is 0, the chunk fc that was found is not large
2856 // enough to leave a viable remainder. We are unable to
2857 // allocate even one block. Return fc to the
2858 // dictionary and return, leaving "fl" empty.
2859 if (n == 0) {
2860 returnChunkToDictionary(fc);
2861 assert(fl->count() == 0, "We never allocated any blocks");
2862 return;
2863 }
2865 // First return the remainder, if any.
2866 // Note that we hold the lock until we decide if we're going to give
2867 // back the remainder to the dictionary, since a concurrent allocation
2868 // may otherwise see the heap as empty. (We're willing to take that
2869 // hit if the block is a small block.)
2870 if (rem > 0) {
2871 size_t prefix_size = n * word_sz;
2872 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2873 rem_fc->setSize(rem);
2874 rem_fc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
2875 rem_fc->linkNext(NULL);
2876 // Above must occur before BOT is updated below.
2877 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2878 OrderAccess::storestore();
2879 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2880 assert(fc->isFree(), "Error");
2881 fc->setSize(prefix_size);
2882 if (rem >= IndexSetSize) {
2883 returnChunkToDictionary(rem_fc);
2884 dictionary()->dictCensusUpdate(rem, true /*split*/, true /*birth*/);
2885 rem_fc = NULL;
2886 }
2887 // Otherwise, return it to the small list below.
2888 }
2889 }
2890 if (rem_fc != NULL) {
2891 MutexLockerEx x(_indexedFreeListParLocks[rem],
2892 Mutex::_no_safepoint_check_flag);
2893 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2894 _indexedFreeList[rem].returnChunkAtHead(rem_fc);
2895 smallSplitBirth(rem);
2896 }
2897 assert((ssize_t)n > 0 && fc != NULL, "Consistency");
2898 // Now do the splitting up.
2899 // Must do this in reverse order, so that anybody attempting to
2900 // access the main chunk sees it as a single free block until we
2901 // change it.
2902 size_t fc_size = n * word_sz;
2903 // All but first chunk in this loop
2904 for (ssize_t i = n-1; i > 0; i--) {
2905 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2906 ffc->setSize(word_sz);
2907 ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads.
2908 ffc->linkNext(NULL);
2909 // Above must occur before BOT is updated below.
2910 OrderAccess::storestore();
2911 // splitting from the right, fc_size == (n - i + 1) * wordsize
2912 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2913 fc_size -= word_sz;
2914 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2915 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2916 _bt.verify_single_block((HeapWord*)fc, fc_size);
2917 // Push this on "fl".
2918 fl->returnChunkAtHead(ffc);
2919 }
2920 // First chunk
2921 assert(fc->isFree() && fc->size() == n*word_sz, "Error: should still be a free block");
2922 // The blocks above should show their new sizes before the first block below
2923 fc->setSize(word_sz);
2924 fc->linkPrev(NULL); // idempotent wrt free-ness, see assert above
2925 fc->linkNext(NULL);
2926 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2927 _bt.verify_single_block((HeapWord*)fc, fc->size());
2928 fl->returnChunkAtHead(fc);
2930 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2931 {
2932 // Update the stats for this block size.
2933 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2934 Mutex::_no_safepoint_check_flag);
2935 const ssize_t births = _indexedFreeList[word_sz].splitBirths() + n;
2936 _indexedFreeList[word_sz].set_splitBirths(births);
2937 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2938 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2939 }
2941 // TRAP
2942 assert(fl->tail()->next() == NULL, "List invariant.");
2943 }
2945 // Set up the space's par_seq_tasks structure for work claiming
2946 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2947 // XXX Need to suitably abstract and generalize this and the next
2948 // method into one.
2949 void
2950 CompactibleFreeListSpace::
2951 initialize_sequential_subtasks_for_rescan(int n_threads) {
2952 // The "size" of each task is fixed according to rescan_task_size.
2953 assert(n_threads > 0, "Unexpected n_threads argument");
2954 const size_t task_size = rescan_task_size();
2955 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2956 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2957 assert(n_tasks == 0 ||
2958 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2959 (used_region().start() + n_tasks*task_size >= used_region().end())),
2960 "n_tasks calculation incorrect");
2961 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2962 assert(!pst->valid(), "Clobbering existing data?");
2963 // Sets the condition for completion of the subtask (how many threads
2964 // need to finish in order to be done).
2965 pst->set_n_threads(n_threads);
2966 pst->set_n_tasks((int)n_tasks);
2967 }
2969 // Set up the space's par_seq_tasks structure for work claiming
2970 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2971 void
2972 CompactibleFreeListSpace::
2973 initialize_sequential_subtasks_for_marking(int n_threads,
2974 HeapWord* low) {
2975 // The "size" of each task is fixed according to rescan_task_size.
2976 assert(n_threads > 0, "Unexpected n_threads argument");
2977 const size_t task_size = marking_task_size();
2978 assert(task_size > CardTableModRefBS::card_size_in_words &&
2979 (task_size % CardTableModRefBS::card_size_in_words == 0),
2980 "Otherwise arithmetic below would be incorrect");
2981 MemRegion span = _gen->reserved();
2982 if (low != NULL) {
2983 if (span.contains(low)) {
2984 // Align low down to a card boundary so that
2985 // we can use block_offset_careful() on span boundaries.
2986 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
2987 CardTableModRefBS::card_size);
2988 // Clip span prefix at aligned_low
2989 span = span.intersection(MemRegion(aligned_low, span.end()));
2990 } else if (low > span.end()) {
2991 span = MemRegion(low, low); // Null region
2992 } // else use entire span
2993 }
2994 assert(span.is_empty() ||
2995 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0),
2996 "span should start at a card boundary");
2997 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
2998 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
2999 assert(n_tasks == 0 ||
3000 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
3001 (span.start() + n_tasks*task_size >= span.end())),
3002 "n_tasks calculation incorrect");
3003 SequentialSubTasksDone* pst = conc_par_seq_tasks();
3004 assert(!pst->valid(), "Clobbering existing data?");
3005 // Sets the condition for completion of the subtask (how many threads
3006 // need to finish in order to be done).
3007 pst->set_n_threads(n_threads);
3008 pst->set_n_tasks((int)n_tasks);
3009 }