1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc/cms/cmsLockVerifier.hpp"
27 #include "gc/cms/compactibleFreeListSpace.hpp"
28 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
29 #include "gc/cms/concurrentMarkSweepThread.hpp"
30 #include "gc/shared/blockOffsetTable.inline.hpp"
31 #include "gc/shared/collectedHeap.inline.hpp"
32 #include "gc/shared/genCollectedHeap.hpp"
33 #include "gc/shared/space.inline.hpp"
34 #include "gc/shared/spaceDecorator.hpp"
35 #include "logging/logStream.inline.hpp"
36 #include "memory/allocation.inline.hpp"
37 #include "memory/resourceArea.hpp"
38 #include "memory/universe.inline.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/globals.hpp"
41 #include "runtime/handles.inline.hpp"
42 #include "runtime/init.hpp"
43 #include "runtime/java.hpp"
44 #include "runtime/orderAccess.inline.hpp"
45 #include "runtime/vmThread.hpp"
46 #include "utilities/copy.hpp"
47
48 /////////////////////////////////////////////////////////////////////////
49 //// CompactibleFreeListSpace
50 /////////////////////////////////////////////////////////////////////////
51
52 // highest ranked free list lock rank
53 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
54
55 // Defaults are 0 so things will break badly if incorrectly initialized.
56 size_t CompactibleFreeListSpace::IndexSetStart = 0;
57 size_t CompactibleFreeListSpace::IndexSetStride = 0;
58
59 size_t MinChunkSize = 0;
60
61 void CompactibleFreeListSpace::set_cms_values() {
62 // Set CMS global values
63 assert(MinChunkSize == 0, "already set");
64
65 // MinChunkSize should be a multiple of MinObjAlignment and be large enough
66 // for chunks to contain a FreeChunk.
67 size_t min_chunk_size_in_bytes = align_size_up(sizeof(FreeChunk), MinObjAlignmentInBytes);
68 MinChunkSize = min_chunk_size_in_bytes / BytesPerWord;
69
70 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
71 IndexSetStart = MinChunkSize;
72 IndexSetStride = MinObjAlignment;
73 }
74
75 // Constructor
76 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr) :
77 _bt(bs, mr),
78 // free list locks are in the range of values taken by _lockRank
79 // This range currently is [_leaf+2, _leaf+3]
80 // Note: this requires that CFLspace c'tors
81 // are called serially in the order in which the locks are
82 // are acquired in the program text. This is true today.
83 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true,
84 Monitor::_safepoint_check_sometimes),
85 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
86 "CompactibleFreeListSpace._dict_par_lock", true,
87 Monitor::_safepoint_check_never),
88 _rescan_task_size(CardTable::card_size_in_words * BitsPerWord *
89 CMSRescanMultiple),
90 _marking_task_size(CardTable::card_size_in_words * BitsPerWord *
91 CMSConcMarkMultiple),
92 _collector(NULL),
93 _preconsumptionDirtyCardClosure(NULL)
94 {
95 assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize,
96 "FreeChunk is larger than expected");
97 _bt.set_space(this);
98 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
99
100 _dictionary = new AFLBinaryTreeDictionary(mr);
101
102 assert(_dictionary != NULL, "CMS dictionary initialization");
103 // The indexed free lists are initially all empty and are lazily
104 // filled in on demand. Initialize the array elements to NULL.
105 initializeIndexedFreeListArray();
106
107 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
108 SmallForLinearAlloc);
109
110 // CMSIndexedFreeListReplenish should be at least 1
111 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
112 _promoInfo.setSpace(this);
113 if (UseCMSBestFit) {
114 _fitStrategy = FreeBlockBestFitFirst;
115 } else {
116 _fitStrategy = FreeBlockStrategyNone;
117 }
118 check_free_list_consistency();
119
120 // Initialize locks for parallel case.
121 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
122 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
123 "a freelist par lock", true, Mutex::_safepoint_check_sometimes);
124 DEBUG_ONLY(
125 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
126 )
127 }
128 _dictionary->set_par_lock(&_parDictionaryAllocLock);
129 }
130
131 // Like CompactibleSpace forward() but always calls cross_threshold() to
132 // update the block offset table. Removed initialize_threshold call because
133 // CFLS does not use a block offset array for contiguous spaces.
134 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
135 CompactPoint* cp, HeapWord* compact_top) {
136 // q is alive
137 // First check if we should switch compaction space
138 assert(this == cp->space, "'this' should be current compaction space.");
139 size_t compaction_max_size = pointer_delta(end(), compact_top);
140 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
141 "virtual adjustObjectSize_v() method is not correct");
142 size_t adjusted_size = adjustObjectSize(size);
143 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
144 "no small fragments allowed");
145 assert(minimum_free_block_size() == MinChunkSize,
146 "for de-virtualized reference below");
147 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
148 if (adjusted_size + MinChunkSize > compaction_max_size &&
149 adjusted_size != compaction_max_size) {
150 do {
151 // switch to next compaction space
152 cp->space->set_compaction_top(compact_top);
153 cp->space = cp->space->next_compaction_space();
154 if (cp->space == NULL) {
155 cp->gen = GenCollectedHeap::heap()->young_gen();
156 assert(cp->gen != NULL, "compaction must succeed");
157 cp->space = cp->gen->first_compaction_space();
158 assert(cp->space != NULL, "generation must have a first compaction space");
159 }
160 compact_top = cp->space->bottom();
161 cp->space->set_compaction_top(compact_top);
162 // The correct adjusted_size may not be the same as that for this method
163 // (i.e., cp->space may no longer be "this" so adjust the size again.
164 // Use the virtual method which is not used above to save the virtual
165 // dispatch.
166 adjusted_size = cp->space->adjust_object_size_v(size);
167 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
168 assert(cp->space->minimum_free_block_size() == 0, "just checking");
169 } while (adjusted_size > compaction_max_size);
170 }
171
172 // store the forwarding pointer into the mark word
173 if ((HeapWord*)q != compact_top) {
174 q->forward_to(oop(compact_top));
175 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
176 } else {
177 // if the object isn't moving we can just set the mark to the default
178 // mark and handle it specially later on.
179 q->init_mark();
180 assert(q->forwardee() == NULL, "should be forwarded to NULL");
181 }
182
183 compact_top += adjusted_size;
184
185 // we need to update the offset table so that the beginnings of objects can be
186 // found during scavenge. Note that we are updating the offset table based on
187 // where the object will be once the compaction phase finishes.
188
189 // Always call cross_threshold(). A contiguous space can only call it when
190 // the compaction_top exceeds the current threshold but not for an
191 // non-contiguous space.
192 cp->threshold =
193 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
194 return compact_top;
195 }
196
197 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
198 // and use of single_block instead of alloc_block. The name here is not really
199 // appropriate - maybe a more general name could be invented for both the
200 // contiguous and noncontiguous spaces.
201
202 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
203 _bt.single_block(start, the_end);
204 return end();
205 }
206
207 // Initialize them to NULL.
208 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
209 for (size_t i = 0; i < IndexSetSize; i++) {
210 // Note that on platforms where objects are double word aligned,
211 // the odd array elements are not used. It is convenient, however,
212 // to map directly from the object size to the array element.
213 _indexedFreeList[i].reset(IndexSetSize);
214 _indexedFreeList[i].set_size(i);
215 assert(_indexedFreeList[i].count() == 0, "reset check failed");
216 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
217 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
218 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
219 }
220 }
221
222 size_t CompactibleFreeListSpace::obj_size(const HeapWord* addr) const {
223 return adjustObjectSize(oop(addr)->size());
224 }
225
226 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
227 for (size_t i = 1; i < IndexSetSize; i++) {
228 assert(_indexedFreeList[i].size() == (size_t) i,
229 "Indexed free list sizes are incorrect");
230 _indexedFreeList[i].reset(IndexSetSize);
231 assert(_indexedFreeList[i].count() == 0, "reset check failed");
232 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
233 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
234 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
235 }
236 }
237
238 void CompactibleFreeListSpace::reset(MemRegion mr) {
239 resetIndexedFreeListArray();
240 dictionary()->reset();
241 if (BlockOffsetArrayUseUnallocatedBlock) {
242 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
243 // Everything's allocated until proven otherwise.
244 _bt.set_unallocated_block(end());
245 }
246 if (!mr.is_empty()) {
247 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
248 _bt.single_block(mr.start(), mr.word_size());
249 FreeChunk* fc = (FreeChunk*) mr.start();
250 fc->set_size(mr.word_size());
251 if (mr.word_size() >= IndexSetSize ) {
252 returnChunkToDictionary(fc);
253 } else {
254 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
255 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc);
256 }
257 coalBirth(mr.word_size());
258 }
259 _promoInfo.reset();
260 _smallLinearAllocBlock._ptr = NULL;
261 _smallLinearAllocBlock._word_size = 0;
262 }
263
264 void CompactibleFreeListSpace::reset_after_compaction() {
265 // Reset the space to the new reality - one free chunk.
266 MemRegion mr(compaction_top(), end());
267 reset(mr);
268 // Now refill the linear allocation block(s) if possible.
269 refillLinearAllocBlocksIfNeeded();
270 }
271
272 // Walks the entire dictionary, returning a coterminal
273 // chunk, if it exists. Use with caution since it involves
274 // a potentially complete walk of a potentially large tree.
275 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
276
277 assert_lock_strong(&_freelistLock);
278
279 return dictionary()->find_chunk_ends_at(end());
280 }
281
282
283 #ifndef PRODUCT
284 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
285 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
286 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
287 }
288 }
289
290 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
291 size_t sum = 0;
292 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
293 sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
294 }
295 return sum;
296 }
297
298 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
299 size_t count = 0;
300 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
301 debug_only(
302 ssize_t total_list_count = 0;
303 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
304 fc = fc->next()) {
305 total_list_count++;
306 }
307 assert(total_list_count == _indexedFreeList[i].count(),
308 "Count in list is incorrect");
309 )
310 count += _indexedFreeList[i].count();
311 }
312 return count;
313 }
314
315 size_t CompactibleFreeListSpace::totalCount() {
316 size_t num = totalCountInIndexedFreeLists();
317 num += dictionary()->total_count();
318 if (_smallLinearAllocBlock._word_size != 0) {
319 num++;
320 }
321 return num;
322 }
323 #endif
324
325 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
326 FreeChunk* fc = (FreeChunk*) p;
327 return fc->is_free();
328 }
329
330 size_t CompactibleFreeListSpace::used() const {
331 return capacity() - free();
332 }
333
334 size_t CompactibleFreeListSpace::free() const {
335 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
336 // if you do this while the structures are in flux you
337 // may get an approximate answer only; for instance
338 // because there is concurrent allocation either
339 // directly by mutators or for promotion during a GC.
340 // It's "MT-safe", however, in the sense that you are guaranteed
341 // not to crash and burn, for instance, because of walking
342 // pointers that could disappear as you were walking them.
343 // The approximation is because the various components
344 // that are read below are not read atomically (and
345 // further the computation of totalSizeInIndexedFreeLists()
346 // is itself a non-atomic computation. The normal use of
347 // this is during a resize operation at the end of GC
348 // and at that time you are guaranteed to get the
349 // correct actual value. However, for instance, this is
350 // also read completely asynchronously by the "perf-sampler"
351 // that supports jvmstat, and you are apt to see the values
352 // flicker in such cases.
353 assert(_dictionary != NULL, "No _dictionary?");
354 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
355 totalSizeInIndexedFreeLists() +
356 _smallLinearAllocBlock._word_size) * HeapWordSize;
357 }
358
359 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
360 assert(_dictionary != NULL, "No _dictionary?");
361 assert_locked();
362 size_t res = _dictionary->max_chunk_size();
363 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
364 (size_t) SmallForLinearAlloc - 1));
365 // XXX the following could potentially be pretty slow;
366 // should one, pessimistically for the rare cases when res
367 // calculated above is less than IndexSetSize,
368 // just return res calculated above? My reasoning was that
369 // those cases will be so rare that the extra time spent doesn't
370 // really matter....
371 // Note: do not change the loop test i >= res + IndexSetStride
372 // to i > res below, because i is unsigned and res may be zero.
373 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
374 i -= IndexSetStride) {
375 if (_indexedFreeList[i].head() != NULL) {
376 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
377 return i;
378 }
379 }
380 return res;
381 }
382
383 void LinearAllocBlock::print_on(outputStream* st) const {
384 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
385 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
386 p2i(_ptr), _word_size, _refillSize, _allocation_size_limit);
387 }
388
389 void CompactibleFreeListSpace::print_on(outputStream* st) const {
390 st->print_cr("COMPACTIBLE FREELIST SPACE");
391 st->print_cr(" Space:");
392 Space::print_on(st);
393
394 st->print_cr("promoInfo:");
395 _promoInfo.print_on(st);
396
397 st->print_cr("_smallLinearAllocBlock");
398 _smallLinearAllocBlock.print_on(st);
399
400 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
401
402 st->print_cr(" _fitStrategy = %s", BOOL_TO_STR(_fitStrategy));
403 }
404
405 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
406 const {
407 reportIndexedFreeListStatistics(st);
408 st->print_cr("Layout of Indexed Freelists");
409 st->print_cr("---------------------------");
410 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
411 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
412 _indexedFreeList[i].print_on(st);
413 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) {
414 st->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
415 p2i(fc), p2i((HeapWord*)fc + i),
416 fc->cantCoalesce() ? "\t CC" : "");
417 }
418 }
419 }
420
421 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
422 const {
423 _promoInfo.print_on(st);
424 }
425
426 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
427 const {
428 _dictionary->report_statistics(st);
429 st->print_cr("Layout of Freelists in Tree");
430 st->print_cr("---------------------------");
431 _dictionary->print_free_lists(st);
432 }
433
434 class BlkPrintingClosure: public BlkClosure {
435 const CMSCollector* _collector;
436 const CompactibleFreeListSpace* _sp;
437 const CMSBitMap* _live_bit_map;
438 const bool _post_remark;
439 outputStream* _st;
440 public:
441 BlkPrintingClosure(const CMSCollector* collector,
442 const CompactibleFreeListSpace* sp,
443 const CMSBitMap* live_bit_map,
444 outputStream* st):
445 _collector(collector),
446 _sp(sp),
447 _live_bit_map(live_bit_map),
448 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
449 _st(st) { }
450 size_t do_blk(HeapWord* addr);
451 };
452
453 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
454 size_t sz = _sp->block_size_no_stall(addr, _collector);
455 assert(sz != 0, "Should always be able to compute a size");
456 if (_sp->block_is_obj(addr)) {
457 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
458 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
459 p2i(addr),
460 dead ? "dead" : "live",
461 sz,
462 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
463 if (CMSPrintObjectsInDump && !dead) {
464 oop(addr)->print_on(_st);
465 _st->print_cr("--------------------------------------");
466 }
467 } else { // free block
468 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
469 p2i(addr), sz, CMSPrintChunksInDump ? ":" : ".");
470 if (CMSPrintChunksInDump) {
471 ((FreeChunk*)addr)->print_on(_st);
472 _st->print_cr("--------------------------------------");
473 }
474 }
475 return sz;
476 }
477
478 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st) {
479 st->print_cr("=========================");
480 st->print_cr("Block layout in CMS Heap:");
481 st->print_cr("=========================");
482 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
483 blk_iterate(&bpcl);
484
485 st->print_cr("=======================================");
486 st->print_cr("Order & Layout of Promotion Info Blocks");
487 st->print_cr("=======================================");
488 print_promo_info_blocks(st);
489
490 st->print_cr("===========================");
491 st->print_cr("Order of Indexed Free Lists");
492 st->print_cr("=========================");
493 print_indexed_free_lists(st);
494
495 st->print_cr("=================================");
496 st->print_cr("Order of Free Lists in Dictionary");
497 st->print_cr("=================================");
498 print_dictionary_free_lists(st);
499 }
500
501
502 void CompactibleFreeListSpace::reportFreeListStatistics(const char* title) const {
503 assert_lock_strong(&_freelistLock);
504 Log(gc, freelist, stats) log;
505 if (!log.is_debug()) {
506 return;
507 }
508 log.debug("%s", title);
509
510 LogStream out(log.debug());
511 _dictionary->report_statistics(&out);
512
513 if (log.is_trace()) {
514 LogStream trace_out(log.trace());
515 reportIndexedFreeListStatistics(&trace_out);
516 size_t total_size = totalSizeInIndexedFreeLists() +
517 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
518 log.trace(" free=" SIZE_FORMAT " frag=%1.4f", total_size, flsFrag());
519 }
520 }
521
522 void CompactibleFreeListSpace::reportIndexedFreeListStatistics(outputStream* st) const {
523 assert_lock_strong(&_freelistLock);
524 st->print_cr("Statistics for IndexedFreeLists:");
525 st->print_cr("--------------------------------");
526 size_t total_size = totalSizeInIndexedFreeLists();
527 size_t free_blocks = numFreeBlocksInIndexedFreeLists();
528 st->print_cr("Total Free Space: " SIZE_FORMAT, total_size);
529 st->print_cr("Max Chunk Size: " SIZE_FORMAT, maxChunkSizeInIndexedFreeLists());
530 st->print_cr("Number of Blocks: " SIZE_FORMAT, free_blocks);
531 if (free_blocks != 0) {
532 st->print_cr("Av. Block Size: " SIZE_FORMAT, total_size/free_blocks);
533 }
534 }
535
536 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
537 size_t res = 0;
538 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
539 debug_only(
540 ssize_t recount = 0;
541 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
542 fc = fc->next()) {
543 recount += 1;
544 }
545 assert(recount == _indexedFreeList[i].count(),
546 "Incorrect count in list");
547 )
548 res += _indexedFreeList[i].count();
549 }
550 return res;
551 }
552
553 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
554 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
555 if (_indexedFreeList[i].head() != NULL) {
556 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
557 return (size_t)i;
558 }
559 }
560 return 0;
561 }
562
563 void CompactibleFreeListSpace::set_end(HeapWord* value) {
564 HeapWord* prevEnd = end();
565 assert(prevEnd != value, "unnecessary set_end call");
566 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
567 "New end is below unallocated block");
568 _end = value;
569 if (prevEnd != NULL) {
570 // Resize the underlying block offset table.
571 _bt.resize(pointer_delta(value, bottom()));
572 if (value <= prevEnd) {
573 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
574 "New end is below unallocated block");
575 } else {
576 // Now, take this new chunk and add it to the free blocks.
577 // Note that the BOT has not yet been updated for this block.
578 size_t newFcSize = pointer_delta(value, prevEnd);
579 // Add the block to the free lists, if possible coalescing it
580 // with the last free block, and update the BOT and census data.
581 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
582 }
583 }
584 }
585
586 class FreeListSpaceDCTOC : public FilteringDCTOC {
587 CompactibleFreeListSpace* _cfls;
588 CMSCollector* _collector;
589 bool _parallel;
590 protected:
591 // Override.
592 #define walk_mem_region_with_cl_DECL(ClosureType) \
593 virtual void walk_mem_region_with_cl(MemRegion mr, \
594 HeapWord* bottom, HeapWord* top, \
595 ClosureType* cl); \
596 void walk_mem_region_with_cl_par(MemRegion mr, \
597 HeapWord* bottom, HeapWord* top, \
598 ClosureType* cl); \
599 void walk_mem_region_with_cl_nopar(MemRegion mr, \
600 HeapWord* bottom, HeapWord* top, \
601 ClosureType* cl)
602 walk_mem_region_with_cl_DECL(ExtendedOopClosure);
603 walk_mem_region_with_cl_DECL(FilteringClosure);
604
605 public:
606 FreeListSpaceDCTOC(CompactibleFreeListSpace* sp,
607 CMSCollector* collector,
608 ExtendedOopClosure* cl,
609 CardTable::PrecisionStyle precision,
610 HeapWord* boundary,
611 bool parallel) :
612 FilteringDCTOC(sp, cl, precision, boundary),
613 _cfls(sp), _collector(collector), _parallel(parallel) {}
614 };
615
616 // We de-virtualize the block-related calls below, since we know that our
617 // space is a CompactibleFreeListSpace.
618
619 #define FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
620 void FreeListSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr, \
621 HeapWord* bottom, \
622 HeapWord* top, \
623 ClosureType* cl) { \
624 if (_parallel) { \
625 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
626 } else { \
627 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
628 } \
629 } \
630 void FreeListSpaceDCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
631 HeapWord* bottom, \
632 HeapWord* top, \
633 ClosureType* cl) { \
634 /* Skip parts that are before "mr", in case "block_start" sent us \
635 back too far. */ \
636 HeapWord* mr_start = mr.start(); \
637 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
638 HeapWord* next = bottom + bot_size; \
639 while (next < mr_start) { \
640 bottom = next; \
641 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
642 next = bottom + bot_size; \
643 } \
644 \
645 while (bottom < top) { \
646 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
647 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
648 oop(bottom)) && \
649 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
650 size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
651 bottom += _cfls->adjustObjectSize(word_sz); \
652 } else { \
653 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
654 } \
655 } \
656 } \
657 void FreeListSpaceDCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
658 HeapWord* bottom, \
659 HeapWord* top, \
660 ClosureType* cl) { \
661 /* Skip parts that are before "mr", in case "block_start" sent us \
662 back too far. */ \
663 HeapWord* mr_start = mr.start(); \
664 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
665 HeapWord* next = bottom + bot_size; \
666 while (next < mr_start) { \
667 bottom = next; \
668 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
669 next = bottom + bot_size; \
670 } \
671 \
672 while (bottom < top) { \
673 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
674 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
675 oop(bottom)) && \
676 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
677 size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
678 bottom += _cfls->adjustObjectSize(word_sz); \
679 } else { \
680 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
681 } \
682 } \
683 }
684
685 // (There are only two of these, rather than N, because the split is due
686 // only to the introduction of the FilteringClosure, a local part of the
687 // impl of this abstraction.)
688 FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
689 FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
690
691 DirtyCardToOopClosure*
692 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl,
693 CardTable::PrecisionStyle precision,
694 HeapWord* boundary,
695 bool parallel) {
696 return new FreeListSpaceDCTOC(this, _collector, cl, precision, boundary, parallel);
697 }
698
699
700 // Note on locking for the space iteration functions:
701 // since the collector's iteration activities are concurrent with
702 // allocation activities by mutators, absent a suitable mutual exclusion
703 // mechanism the iterators may go awry. For instance a block being iterated
704 // may suddenly be allocated or divided up and part of it allocated and
705 // so on.
706
707 // Apply the given closure to each block in the space.
708 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
709 assert_lock_strong(freelistLock());
710 HeapWord *cur, *limit;
711 for (cur = bottom(), limit = end(); cur < limit;
712 cur += cl->do_blk_careful(cur));
713 }
714
715 // Apply the given closure to each block in the space.
716 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
717 assert_lock_strong(freelistLock());
718 HeapWord *cur, *limit;
719 for (cur = bottom(), limit = end(); cur < limit;
720 cur += cl->do_blk(cur));
721 }
722
723 // Apply the given closure to each oop in the space.
724 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) {
725 assert_lock_strong(freelistLock());
726 HeapWord *cur, *limit;
727 size_t curSize;
728 for (cur = bottom(), limit = end(); cur < limit;
729 cur += curSize) {
730 curSize = block_size(cur);
731 if (block_is_obj(cur)) {
732 oop(cur)->oop_iterate(cl);
733 }
734 }
735 }
736
737 // NOTE: In the following methods, in order to safely be able to
738 // apply the closure to an object, we need to be sure that the
739 // object has been initialized. We are guaranteed that an object
740 // is initialized if we are holding the Heap_lock with the
741 // world stopped.
742 void CompactibleFreeListSpace::verify_objects_initialized() const {
743 if (is_init_completed()) {
744 assert_locked_or_safepoint(Heap_lock);
745 if (Universe::is_fully_initialized()) {
746 guarantee(SafepointSynchronize::is_at_safepoint(),
747 "Required for objects to be initialized");
748 }
749 } // else make a concession at vm start-up
750 }
751
752 // Apply the given closure to each object in the space
753 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
754 assert_lock_strong(freelistLock());
755 NOT_PRODUCT(verify_objects_initialized());
756 HeapWord *cur, *limit;
757 size_t curSize;
758 for (cur = bottom(), limit = end(); cur < limit;
759 cur += curSize) {
760 curSize = block_size(cur);
761 if (block_is_obj(cur)) {
762 blk->do_object(oop(cur));
763 }
764 }
765 }
766
767 // Apply the given closure to each live object in the space
768 // The usage of CompactibleFreeListSpace
769 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
770 // objects in the space with references to objects that are no longer
771 // valid. For example, an object may reference another object
772 // that has already been sweep up (collected). This method uses
773 // obj_is_alive() to determine whether it is safe to apply the closure to
774 // an object. See obj_is_alive() for details on how liveness of an
775 // object is decided.
776
777 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
778 assert_lock_strong(freelistLock());
779 NOT_PRODUCT(verify_objects_initialized());
780 HeapWord *cur, *limit;
781 size_t curSize;
782 for (cur = bottom(), limit = end(); cur < limit;
783 cur += curSize) {
784 curSize = block_size(cur);
785 if (block_is_obj(cur) && obj_is_alive(cur)) {
786 blk->do_object(oop(cur));
787 }
788 }
789 }
790
791 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
792 UpwardsObjectClosure* cl) {
793 assert_locked(freelistLock());
794 NOT_PRODUCT(verify_objects_initialized());
795 assert(!mr.is_empty(), "Should be non-empty");
796 // We use MemRegion(bottom(), end()) rather than used_region() below
797 // because the two are not necessarily equal for some kinds of
798 // spaces, in particular, certain kinds of free list spaces.
799 // We could use the more complicated but more precise:
800 // MemRegion(used_region().start(), round_to(used_region().end(), CardSize))
801 // but the slight imprecision seems acceptable in the assertion check.
802 assert(MemRegion(bottom(), end()).contains(mr),
803 "Should be within used space");
804 HeapWord* prev = cl->previous(); // max address from last time
805 if (prev >= mr.end()) { // nothing to do
806 return;
807 }
808 // This assert will not work when we go from cms space to perm
809 // space, and use same closure. Easy fix deferred for later. XXX YSR
810 // assert(prev == NULL || contains(prev), "Should be within space");
811
812 bool last_was_obj_array = false;
813 HeapWord *blk_start_addr, *region_start_addr;
814 if (prev > mr.start()) {
815 region_start_addr = prev;
816 blk_start_addr = prev;
817 // The previous invocation may have pushed "prev" beyond the
818 // last allocated block yet there may be still be blocks
819 // in this region due to a particular coalescing policy.
820 // Relax the assertion so that the case where the unallocated
821 // block is maintained and "prev" is beyond the unallocated
822 // block does not cause the assertion to fire.
823 assert((BlockOffsetArrayUseUnallocatedBlock &&
824 (!is_in(prev))) ||
825 (blk_start_addr == block_start(region_start_addr)), "invariant");
826 } else {
827 region_start_addr = mr.start();
828 blk_start_addr = block_start(region_start_addr);
829 }
830 HeapWord* region_end_addr = mr.end();
831 MemRegion derived_mr(region_start_addr, region_end_addr);
832 while (blk_start_addr < region_end_addr) {
833 const size_t size = block_size(blk_start_addr);
834 if (block_is_obj(blk_start_addr)) {
835 last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);
836 } else {
837 last_was_obj_array = false;
838 }
839 blk_start_addr += size;
840 }
841 if (!last_was_obj_array) {
842 assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),
843 "Should be within (closed) used space");
844 assert(blk_start_addr > prev, "Invariant");
845 cl->set_previous(blk_start_addr); // min address for next time
846 }
847 }
848
849 // Callers of this iterator beware: The closure application should
850 // be robust in the face of uninitialized objects and should (always)
851 // return a correct size so that the next addr + size below gives us a
852 // valid block boundary. [See for instance,
853 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
854 // in ConcurrentMarkSweepGeneration.cpp.]
855 HeapWord*
856 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
857 ObjectClosureCareful* cl) {
858 assert_lock_strong(freelistLock());
859 // Can't use used_region() below because it may not necessarily
860 // be the same as [bottom(),end()); although we could
861 // use [used_region().start(),round_to(used_region().end(),CardSize)),
862 // that appears too cumbersome, so we just do the simpler check
863 // in the assertion below.
864 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
865 "mr should be non-empty and within used space");
866 HeapWord *addr, *end;
867 size_t size;
868 for (addr = block_start_careful(mr.start()), end = mr.end();
869 addr < end; addr += size) {
870 FreeChunk* fc = (FreeChunk*)addr;
871 if (fc->is_free()) {
872 // Since we hold the free list lock, which protects direct
873 // allocation in this generation by mutators, a free object
874 // will remain free throughout this iteration code.
875 size = fc->size();
876 } else {
877 // Note that the object need not necessarily be initialized,
878 // because (for instance) the free list lock does NOT protect
879 // object initialization. The closure application below must
880 // therefore be correct in the face of uninitialized objects.
881 size = cl->do_object_careful_m(oop(addr), mr);
882 if (size == 0) {
883 // An unparsable object found. Signal early termination.
884 return addr;
885 }
886 }
887 }
888 return NULL;
889 }
890
891
892 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
893 NOT_PRODUCT(verify_objects_initialized());
894 return _bt.block_start(p);
895 }
896
897 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
898 return _bt.block_start_careful(p);
899 }
900
901 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
902 NOT_PRODUCT(verify_objects_initialized());
903 // This must be volatile, or else there is a danger that the compiler
904 // will compile the code below into a sometimes-infinite loop, by keeping
905 // the value read the first time in a register.
906 while (true) {
907 // We must do this until we get a consistent view of the object.
908 if (FreeChunk::indicatesFreeChunk(p)) {
909 volatile FreeChunk* fc = (volatile FreeChunk*)p;
910 size_t res = fc->size();
911
912 // Bugfix for systems with weak memory model (PPC64/IA64). The
913 // block's free bit was set and we have read the size of the
914 // block. Acquire and check the free bit again. If the block is
915 // still free, the read size is correct.
916 OrderAccess::acquire();
917
918 // If the object is still a free chunk, return the size, else it
919 // has been allocated so try again.
920 if (FreeChunk::indicatesFreeChunk(p)) {
921 assert(res != 0, "Block size should not be 0");
922 return res;
923 }
924 } else {
925 // Ensure klass read before size.
926 Klass* k = oop(p)->klass_or_null_acquire();
927 if (k != NULL) {
928 assert(k->is_klass(), "Should really be klass oop.");
929 oop o = (oop)p;
930 assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
931
932 size_t res = o->size_given_klass(k);
933 res = adjustObjectSize(res);
934 assert(res != 0, "Block size should not be 0");
935 return res;
936 }
937 }
938 }
939 }
940
941 // TODO: Now that is_parsable is gone, we should combine these two functions.
942 // A variant of the above that uses the Printezis bits for
943 // unparsable but allocated objects. This avoids any possible
944 // stalls waiting for mutators to initialize objects, and is
945 // thus potentially faster than the variant above. However,
946 // this variant may return a zero size for a block that is
947 // under mutation and for which a consistent size cannot be
948 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
949 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
950 const CMSCollector* c)
951 const {
952 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
953 // This must be volatile, or else there is a danger that the compiler
954 // will compile the code below into a sometimes-infinite loop, by keeping
955 // the value read the first time in a register.
956 DEBUG_ONLY(uint loops = 0;)
957 while (true) {
958 // We must do this until we get a consistent view of the object.
959 if (FreeChunk::indicatesFreeChunk(p)) {
960 volatile FreeChunk* fc = (volatile FreeChunk*)p;
961 size_t res = fc->size();
962
963 // Bugfix for systems with weak memory model (PPC64/IA64). The
964 // free bit of the block was set and we have read the size of
965 // the block. Acquire and check the free bit again. If the
966 // block is still free, the read size is correct.
967 OrderAccess::acquire();
968
969 if (FreeChunk::indicatesFreeChunk(p)) {
970 assert(res != 0, "Block size should not be 0");
971 assert(loops == 0, "Should be 0");
972 return res;
973 }
974 } else {
975 // Ensure klass read before size.
976 Klass* k = oop(p)->klass_or_null_acquire();
977 if (k != NULL) {
978 assert(k->is_klass(), "Should really be klass oop.");
979 oop o = (oop)p;
980 assert(o->is_oop(), "Should be an oop");
981
982 size_t res = o->size_given_klass(k);
983 res = adjustObjectSize(res);
984 assert(res != 0, "Block size should not be 0");
985 return res;
986 } else {
987 // May return 0 if P-bits not present.
988 return c->block_size_if_printezis_bits(p);
989 }
990 }
991 assert(loops == 0, "Can loop at most once");
992 DEBUG_ONLY(loops++;)
993 }
994 }
995
996 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
997 NOT_PRODUCT(verify_objects_initialized());
998 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
999 FreeChunk* fc = (FreeChunk*)p;
1000 if (fc->is_free()) {
1001 return fc->size();
1002 } else {
1003 // Ignore mark word because this may be a recently promoted
1004 // object whose mark word is used to chain together grey
1005 // objects (the last one would have a null value).
1006 assert(oop(p)->is_oop(true), "Should be an oop");
1007 return adjustObjectSize(oop(p)->size());
1008 }
1009 }
1010
1011 // This implementation assumes that the property of "being an object" is
1012 // stable. But being a free chunk may not be (because of parallel
1013 // promotion.)
1014 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1015 FreeChunk* fc = (FreeChunk*)p;
1016 assert(is_in_reserved(p), "Should be in space");
1017 if (FreeChunk::indicatesFreeChunk(p)) return false;
1018 Klass* k = oop(p)->klass_or_null_acquire();
1019 if (k != NULL) {
1020 // Ignore mark word because it may have been used to
1021 // chain together promoted objects (the last one
1022 // would have a null value).
1023 assert(oop(p)->is_oop(true), "Should be an oop");
1024 return true;
1025 } else {
1026 return false; // Was not an object at the start of collection.
1027 }
1028 }
1029
1030 // Check if the object is alive. This fact is checked either by consulting
1031 // the main marking bitmap in the sweeping phase or, if it's a permanent
1032 // generation and we're not in the sweeping phase, by checking the
1033 // perm_gen_verify_bit_map where we store the "deadness" information if
1034 // we did not sweep the perm gen in the most recent previous GC cycle.
1035 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1036 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1037 "Else races are possible");
1038 assert(block_is_obj(p), "The address should point to an object");
1039
1040 // If we're sweeping, we use object liveness information from the main bit map
1041 // for both perm gen and old gen.
1042 // We don't need to lock the bitmap (live_map or dead_map below), because
1043 // EITHER we are in the middle of the sweeping phase, and the
1044 // main marking bit map (live_map below) is locked,
1045 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1046 // is stable, because it's mutated only in the sweeping phase.
1047 // NOTE: This method is also used by jmap where, if class unloading is
1048 // off, the results can return "false" for legitimate perm objects,
1049 // when we are not in the midst of a sweeping phase, which can result
1050 // in jmap not reporting certain perm gen objects. This will be moot
1051 // if/when the perm gen goes away in the future.
1052 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1053 CMSBitMap* live_map = _collector->markBitMap();
1054 return live_map->par_isMarked((HeapWord*) p);
1055 }
1056 return true;
1057 }
1058
1059 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1060 FreeChunk* fc = (FreeChunk*)p;
1061 assert(is_in_reserved(p), "Should be in space");
1062 assert(_bt.block_start(p) == p, "Should be a block boundary");
1063 if (!fc->is_free()) {
1064 // Ignore mark word because it may have been used to
1065 // chain together promoted objects (the last one
1066 // would have a null value).
1067 assert(oop(p)->is_oop(true), "Should be an oop");
1068 return true;
1069 }
1070 return false;
1071 }
1072
1073 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1074 // approximate answer if you don't hold the freelistlock when you call this.
1075 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1076 size_t size = 0;
1077 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1078 debug_only(
1079 // We may be calling here without the lock in which case we
1080 // won't do this modest sanity check.
1081 if (freelistLock()->owned_by_self()) {
1082 size_t total_list_size = 0;
1083 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1084 fc = fc->next()) {
1085 total_list_size += i;
1086 }
1087 assert(total_list_size == i * _indexedFreeList[i].count(),
1088 "Count in list is incorrect");
1089 }
1090 )
1091 size += i * _indexedFreeList[i].count();
1092 }
1093 return size;
1094 }
1095
1096 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1097 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1098 return allocate(size);
1099 }
1100
1101 HeapWord*
1102 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1103 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1104 }
1105
1106 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1107 assert_lock_strong(freelistLock());
1108 HeapWord* res = NULL;
1109 assert(size == adjustObjectSize(size),
1110 "use adjustObjectSize() before calling into allocate()");
1111
1112 res = allocate_adaptive_freelists(size);
1113
1114 if (res != NULL) {
1115 // check that res does lie in this space!
1116 assert(is_in_reserved(res), "Not in this space!");
1117 assert(is_aligned((void*)res), "alignment check");
1118
1119 FreeChunk* fc = (FreeChunk*)res;
1120 fc->markNotFree();
1121 assert(!fc->is_free(), "shouldn't be marked free");
1122 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1123 // Verify that the block offset table shows this to
1124 // be a single block, but not one which is unallocated.
1125 _bt.verify_single_block(res, size);
1126 _bt.verify_not_unallocated(res, size);
1127 // mangle a just allocated object with a distinct pattern.
1128 debug_only(fc->mangleAllocated(size));
1129 }
1130
1131 return res;
1132 }
1133
1134 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1135 assert_lock_strong(freelistLock());
1136 HeapWord* res = NULL;
1137 assert(size == adjustObjectSize(size),
1138 "use adjustObjectSize() before calling into allocate()");
1139
1140 // Strategy
1141 // if small
1142 // exact size from small object indexed list if small
1143 // small or large linear allocation block (linAB) as appropriate
1144 // take from lists of greater sized chunks
1145 // else
1146 // dictionary
1147 // small or large linear allocation block if it has the space
1148 // Try allocating exact size from indexTable first
1149 if (size < IndexSetSize) {
1150 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1151 if(res != NULL) {
1152 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1153 "Not removed from free list");
1154 // no block offset table adjustment is necessary on blocks in
1155 // the indexed lists.
1156
1157 // Try allocating from the small LinAB
1158 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1159 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1160 // if successful, the above also adjusts block offset table
1161 // Note that this call will refill the LinAB to
1162 // satisfy the request. This is different that
1163 // evm.
1164 // Don't record chunk off a LinAB? smallSplitBirth(size);
1165 } else {
1166 // Raid the exact free lists larger than size, even if they are not
1167 // overpopulated.
1168 res = (HeapWord*) getChunkFromGreater(size);
1169 }
1170 } else {
1171 // Big objects get allocated directly from the dictionary.
1172 res = (HeapWord*) getChunkFromDictionaryExact(size);
1173 if (res == NULL) {
1174 // Try hard not to fail since an allocation failure will likely
1175 // trigger a synchronous GC. Try to get the space from the
1176 // allocation blocks.
1177 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1178 }
1179 }
1180
1181 return res;
1182 }
1183
1184 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1185 // when promoting obj.
1186 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1187 // Depending on the object size, expansion may require refilling either a
1188 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1189 // is added because the dictionary may over-allocate to avoid fragmentation.
1190 size_t space = obj_size;
1191 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1192 return space;
1193 }
1194
1195 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1196 FreeChunk* ret;
1197
1198 assert(numWords >= MinChunkSize, "Size is less than minimum");
1199 assert(linearAllocationWouldFail() || bestFitFirst(),
1200 "Should not be here");
1201
1202 size_t i;
1203 size_t currSize = numWords + MinChunkSize;
1204 assert(currSize % MinObjAlignment == 0, "currSize should be aligned");
1205 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1206 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
1207 if (fl->head()) {
1208 ret = getFromListGreater(fl, numWords);
1209 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1210 return ret;
1211 }
1212 }
1213
1214 currSize = MAX2((size_t)SmallForDictionary,
1215 (size_t)(numWords + MinChunkSize));
1216
1217 /* Try to get a chunk that satisfies request, while avoiding
1218 fragmentation that can't be handled. */
1219 {
1220 ret = dictionary()->get_chunk(currSize);
1221 if (ret != NULL) {
1222 assert(ret->size() - numWords >= MinChunkSize,
1223 "Chunk is too small");
1224 _bt.allocated((HeapWord*)ret, ret->size());
1225 /* Carve returned chunk. */
1226 (void) splitChunkAndReturnRemainder(ret, numWords);
1227 /* Label this as no longer a free chunk. */
1228 assert(ret->is_free(), "This chunk should be free");
1229 ret->link_prev(NULL);
1230 }
1231 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1232 return ret;
1233 }
1234 ShouldNotReachHere();
1235 }
1236
1237 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1238 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1239 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
1240 }
1241
1242 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1243 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1244 (_smallLinearAllocBlock._word_size == fc->size()),
1245 "Linear allocation block shows incorrect size");
1246 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1247 (_smallLinearAllocBlock._word_size == fc->size()));
1248 }
1249
1250 // Check if the purported free chunk is present either as a linear
1251 // allocation block, the size-indexed table of (smaller) free blocks,
1252 // or the larger free blocks kept in the binary tree dictionary.
1253 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
1254 if (verify_chunk_is_linear_alloc_block(fc)) {
1255 return true;
1256 } else if (fc->size() < IndexSetSize) {
1257 return verifyChunkInIndexedFreeLists(fc);
1258 } else {
1259 return dictionary()->verify_chunk_in_free_list(fc);
1260 }
1261 }
1262
1263 #ifndef PRODUCT
1264 void CompactibleFreeListSpace::assert_locked() const {
1265 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1266 }
1267
1268 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1269 CMSLockVerifier::assert_locked(lock);
1270 }
1271 #endif
1272
1273 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1274 // In the parallel case, the main thread holds the free list lock
1275 // on behalf the parallel threads.
1276 FreeChunk* fc;
1277 {
1278 // If GC is parallel, this might be called by several threads.
1279 // This should be rare enough that the locking overhead won't affect
1280 // the sequential code.
1281 MutexLockerEx x(parDictionaryAllocLock(),
1282 Mutex::_no_safepoint_check_flag);
1283 fc = getChunkFromDictionary(size);
1284 }
1285 if (fc != NULL) {
1286 fc->dontCoalesce();
1287 assert(fc->is_free(), "Should be free, but not coalescable");
1288 // Verify that the block offset table shows this to
1289 // be a single block, but not one which is unallocated.
1290 _bt.verify_single_block((HeapWord*)fc, fc->size());
1291 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1292 }
1293 return fc;
1294 }
1295
1296 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1297 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1298 assert_locked();
1299
1300 // if we are tracking promotions, then first ensure space for
1301 // promotion (including spooling space for saving header if necessary).
1302 // then allocate and copy, then track promoted info if needed.
1303 // When tracking (see PromotionInfo::track()), the mark word may
1304 // be displaced and in this case restoration of the mark word
1305 // occurs in the (oop_since_save_marks_)iterate phase.
1306 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1307 return NULL;
1308 }
1309 // Call the allocate(size_t, bool) form directly to avoid the
1310 // additional call through the allocate(size_t) form. Having
1311 // the compile inline the call is problematic because allocate(size_t)
1312 // is a virtual method.
1313 HeapWord* res = allocate(adjustObjectSize(obj_size));
1314 if (res != NULL) {
1315 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1316 // if we should be tracking promotions, do so.
1317 if (_promoInfo.tracking()) {
1318 _promoInfo.track((PromotedObject*)res);
1319 }
1320 }
1321 return oop(res);
1322 }
1323
1324 HeapWord*
1325 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1326 assert_locked();
1327 assert(size >= MinChunkSize, "minimum chunk size");
1328 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1329 "maximum from smallLinearAllocBlock");
1330 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1331 }
1332
1333 HeapWord*
1334 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1335 size_t size) {
1336 assert_locked();
1337 assert(size >= MinChunkSize, "too small");
1338 HeapWord* res = NULL;
1339 // Try to do linear allocation from blk, making sure that
1340 if (blk->_word_size == 0) {
1341 // We have probably been unable to fill this either in the prologue or
1342 // when it was exhausted at the last linear allocation. Bail out until
1343 // next time.
1344 assert(blk->_ptr == NULL, "consistency check");
1345 return NULL;
1346 }
1347 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1348 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1349 if (res != NULL) return res;
1350
1351 // about to exhaust this linear allocation block
1352 if (blk->_word_size == size) { // exactly satisfied
1353 res = blk->_ptr;
1354 _bt.allocated(res, blk->_word_size);
1355 } else if (size + MinChunkSize <= blk->_refillSize) {
1356 size_t sz = blk->_word_size;
1357 // Update _unallocated_block if the size is such that chunk would be
1358 // returned to the indexed free list. All other chunks in the indexed
1359 // free lists are allocated from the dictionary so that _unallocated_block
1360 // has already been adjusted for them. Do it here so that the cost
1361 // for all chunks added back to the indexed free lists.
1362 if (sz < SmallForDictionary) {
1363 _bt.allocated(blk->_ptr, sz);
1364 }
1365 // Return the chunk that isn't big enough, and then refill below.
1366 addChunkToFreeLists(blk->_ptr, sz);
1367 split_birth(sz);
1368 // Don't keep statistics on adding back chunk from a LinAB.
1369 } else {
1370 // A refilled block would not satisfy the request.
1371 return NULL;
1372 }
1373
1374 blk->_ptr = NULL; blk->_word_size = 0;
1375 refillLinearAllocBlock(blk);
1376 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1377 "block was replenished");
1378 if (res != NULL) {
1379 split_birth(size);
1380 repairLinearAllocBlock(blk);
1381 } else if (blk->_ptr != NULL) {
1382 res = blk->_ptr;
1383 size_t blk_size = blk->_word_size;
1384 blk->_word_size -= size;
1385 blk->_ptr += size;
1386 split_birth(size);
1387 repairLinearAllocBlock(blk);
1388 // Update BOT last so that other (parallel) GC threads see a consistent
1389 // view of the BOT and free blocks.
1390 // Above must occur before BOT is updated below.
1391 OrderAccess::storestore();
1392 _bt.split_block(res, blk_size, size); // adjust block offset table
1393 }
1394 return res;
1395 }
1396
1397 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1398 LinearAllocBlock* blk,
1399 size_t size) {
1400 assert_locked();
1401 assert(size >= MinChunkSize, "too small");
1402
1403 HeapWord* res = NULL;
1404 // This is the common case. Keep it simple.
1405 if (blk->_word_size >= size + MinChunkSize) {
1406 assert(blk->_ptr != NULL, "consistency check");
1407 res = blk->_ptr;
1408 // Note that the BOT is up-to-date for the linAB before allocation. It
1409 // indicates the start of the linAB. The split_block() updates the
1410 // BOT for the linAB after the allocation (indicates the start of the
1411 // next chunk to be allocated).
1412 size_t blk_size = blk->_word_size;
1413 blk->_word_size -= size;
1414 blk->_ptr += size;
1415 split_birth(size);
1416 repairLinearAllocBlock(blk);
1417 // Update BOT last so that other (parallel) GC threads see a consistent
1418 // view of the BOT and free blocks.
1419 // Above must occur before BOT is updated below.
1420 OrderAccess::storestore();
1421 _bt.split_block(res, blk_size, size); // adjust block offset table
1422 _bt.allocated(res, size);
1423 }
1424 return res;
1425 }
1426
1427 FreeChunk*
1428 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1429 assert_locked();
1430 assert(size < SmallForDictionary, "just checking");
1431 FreeChunk* res;
1432 res = _indexedFreeList[size].get_chunk_at_head();
1433 if (res == NULL) {
1434 res = getChunkFromIndexedFreeListHelper(size);
1435 }
1436 _bt.verify_not_unallocated((HeapWord*) res, size);
1437 assert(res == NULL || res->size() == size, "Incorrect block size");
1438 return res;
1439 }
1440
1441 FreeChunk*
1442 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1443 bool replenish) {
1444 assert_locked();
1445 FreeChunk* fc = NULL;
1446 if (size < SmallForDictionary) {
1447 assert(_indexedFreeList[size].head() == NULL ||
1448 _indexedFreeList[size].surplus() <= 0,
1449 "List for this size should be empty or under populated");
1450 // Try best fit in exact lists before replenishing the list
1451 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1452 // Replenish list.
1453 //
1454 // Things tried that failed.
1455 // Tried allocating out of the two LinAB's first before
1456 // replenishing lists.
1457 // Tried small linAB of size 256 (size in indexed list)
1458 // and replenishing indexed lists from the small linAB.
1459 //
1460 FreeChunk* newFc = NULL;
1461 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1462 if (replenish_size < SmallForDictionary) {
1463 // Do not replenish from an underpopulated size.
1464 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1465 _indexedFreeList[replenish_size].head() != NULL) {
1466 newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
1467 } else if (bestFitFirst()) {
1468 newFc = bestFitSmall(replenish_size);
1469 }
1470 }
1471 if (newFc == NULL && replenish_size > size) {
1472 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1473 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1474 }
1475 // Note: The stats update re split-death of block obtained above
1476 // will be recorded below precisely when we know we are going to
1477 // be actually splitting it into more than one pieces below.
1478 if (newFc != NULL) {
1479 if (replenish || CMSReplenishIntermediate) {
1480 // Replenish this list and return one block to caller.
1481 size_t i;
1482 FreeChunk *curFc, *nextFc;
1483 size_t num_blk = newFc->size() / size;
1484 assert(num_blk >= 1, "Smaller than requested?");
1485 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1486 if (num_blk > 1) {
1487 // we are sure we will be splitting the block just obtained
1488 // into multiple pieces; record the split-death of the original
1489 splitDeath(replenish_size);
1490 }
1491 // carve up and link blocks 0, ..., num_blk - 2
1492 // The last chunk is not added to the lists but is returned as the
1493 // free chunk.
1494 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1495 i = 0;
1496 i < (num_blk - 1);
1497 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1498 i++) {
1499 curFc->set_size(size);
1500 // Don't record this as a return in order to try and
1501 // determine the "returns" from a GC.
1502 _bt.verify_not_unallocated((HeapWord*) fc, size);
1503 _indexedFreeList[size].return_chunk_at_tail(curFc, false);
1504 _bt.mark_block((HeapWord*)curFc, size);
1505 split_birth(size);
1506 // Don't record the initial population of the indexed list
1507 // as a split birth.
1508 }
1509
1510 // check that the arithmetic was OK above
1511 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1512 "inconsistency in carving newFc");
1513 curFc->set_size(size);
1514 _bt.mark_block((HeapWord*)curFc, size);
1515 split_birth(size);
1516 fc = curFc;
1517 } else {
1518 // Return entire block to caller
1519 fc = newFc;
1520 }
1521 }
1522 }
1523 } else {
1524 // Get a free chunk from the free chunk dictionary to be returned to
1525 // replenish the indexed free list.
1526 fc = getChunkFromDictionaryExact(size);
1527 }
1528 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
1529 return fc;
1530 }
1531
1532 FreeChunk*
1533 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1534 assert_locked();
1535 FreeChunk* fc = _dictionary->get_chunk(size,
1536 FreeBlockDictionary<FreeChunk>::atLeast);
1537 if (fc == NULL) {
1538 return NULL;
1539 }
1540 _bt.allocated((HeapWord*)fc, fc->size());
1541 if (fc->size() >= size + MinChunkSize) {
1542 fc = splitChunkAndReturnRemainder(fc, size);
1543 }
1544 assert(fc->size() >= size, "chunk too small");
1545 assert(fc->size() < size + MinChunkSize, "chunk too big");
1546 _bt.verify_single_block((HeapWord*)fc, fc->size());
1547 return fc;
1548 }
1549
1550 FreeChunk*
1551 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1552 assert_locked();
1553 FreeChunk* fc = _dictionary->get_chunk(size,
1554 FreeBlockDictionary<FreeChunk>::atLeast);
1555 if (fc == NULL) {
1556 return fc;
1557 }
1558 _bt.allocated((HeapWord*)fc, fc->size());
1559 if (fc->size() == size) {
1560 _bt.verify_single_block((HeapWord*)fc, size);
1561 return fc;
1562 }
1563 assert(fc->size() > size, "get_chunk() guarantee");
1564 if (fc->size() < size + MinChunkSize) {
1565 // Return the chunk to the dictionary and go get a bigger one.
1566 returnChunkToDictionary(fc);
1567 fc = _dictionary->get_chunk(size + MinChunkSize,
1568 FreeBlockDictionary<FreeChunk>::atLeast);
1569 if (fc == NULL) {
1570 return NULL;
1571 }
1572 _bt.allocated((HeapWord*)fc, fc->size());
1573 }
1574 assert(fc->size() >= size + MinChunkSize, "tautology");
1575 fc = splitChunkAndReturnRemainder(fc, size);
1576 assert(fc->size() == size, "chunk is wrong size");
1577 _bt.verify_single_block((HeapWord*)fc, size);
1578 return fc;
1579 }
1580
1581 void
1582 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
1583 assert_locked();
1584
1585 size_t size = chunk->size();
1586 _bt.verify_single_block((HeapWord*)chunk, size);
1587 // adjust _unallocated_block downward, as necessary
1588 _bt.freed((HeapWord*)chunk, size);
1589 _dictionary->return_chunk(chunk);
1590 #ifndef PRODUCT
1591 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1592 TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >* tc = TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::as_TreeChunk(chunk);
1593 TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* tl = tc->list();
1594 tl->verify_stats();
1595 }
1596 #endif // PRODUCT
1597 }
1598
1599 void
1600 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
1601 assert_locked();
1602 size_t size = fc->size();
1603 _bt.verify_single_block((HeapWord*) fc, size);
1604 _bt.verify_not_unallocated((HeapWord*) fc, size);
1605 _indexedFreeList[size].return_chunk_at_tail(fc);
1606 #ifndef PRODUCT
1607 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
1608 _indexedFreeList[size].verify_stats();
1609 }
1610 #endif // PRODUCT
1611 }
1612
1613 // Add chunk to end of last block -- if it's the largest
1614 // block -- and update BOT and census data. We would
1615 // of course have preferred to coalesce it with the
1616 // last block, but it's currently less expensive to find the
1617 // largest block than it is to find the last.
1618 void
1619 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
1620 HeapWord* chunk, size_t size) {
1621 // check that the chunk does lie in this space!
1622 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1623 // One of the parallel gc task threads may be here
1624 // whilst others are allocating.
1625 Mutex* lock = &_parDictionaryAllocLock;
1626 FreeChunk* ec;
1627 {
1628 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1629 ec = dictionary()->find_largest_dict(); // get largest block
1630 if (ec != NULL && ec->end() == (uintptr_t*) chunk) {
1631 // It's a coterminal block - we can coalesce.
1632 size_t old_size = ec->size();
1633 coalDeath(old_size);
1634 removeChunkFromDictionary(ec);
1635 size += old_size;
1636 } else {
1637 ec = (FreeChunk*)chunk;
1638 }
1639 }
1640 ec->set_size(size);
1641 debug_only(ec->mangleFreed(size));
1642 if (size < SmallForDictionary) {
1643 lock = _indexedFreeListParLocks[size];
1644 }
1645 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
1646 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
1647 // record the birth under the lock since the recording involves
1648 // manipulation of the list on which the chunk lives and
1649 // if the chunk is allocated and is the last on the list,
1650 // the list can go away.
1651 coalBirth(size);
1652 }
1653
1654 void
1655 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
1656 size_t size) {
1657 // check that the chunk does lie in this space!
1658 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
1659 assert_locked();
1660 _bt.verify_single_block(chunk, size);
1661
1662 FreeChunk* fc = (FreeChunk*) chunk;
1663 fc->set_size(size);
1664 debug_only(fc->mangleFreed(size));
1665 if (size < SmallForDictionary) {
1666 returnChunkToFreeList(fc);
1667 } else {
1668 returnChunkToDictionary(fc);
1669 }
1670 }
1671
1672 void
1673 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
1674 size_t size, bool coalesced) {
1675 assert_locked();
1676 assert(chunk != NULL, "null chunk");
1677 if (coalesced) {
1678 // repair BOT
1679 _bt.single_block(chunk, size);
1680 }
1681 addChunkToFreeLists(chunk, size);
1682 }
1683
1684 // We _must_ find the purported chunk on our free lists;
1685 // we assert if we don't.
1686 void
1687 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
1688 size_t size = fc->size();
1689 assert_locked();
1690 debug_only(verifyFreeLists());
1691 if (size < SmallForDictionary) {
1692 removeChunkFromIndexedFreeList(fc);
1693 } else {
1694 removeChunkFromDictionary(fc);
1695 }
1696 _bt.verify_single_block((HeapWord*)fc, size);
1697 debug_only(verifyFreeLists());
1698 }
1699
1700 void
1701 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
1702 size_t size = fc->size();
1703 assert_locked();
1704 assert(fc != NULL, "null chunk");
1705 _bt.verify_single_block((HeapWord*)fc, size);
1706 _dictionary->remove_chunk(fc);
1707 // adjust _unallocated_block upward, as necessary
1708 _bt.allocated((HeapWord*)fc, size);
1709 }
1710
1711 void
1712 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
1713 assert_locked();
1714 size_t size = fc->size();
1715 _bt.verify_single_block((HeapWord*)fc, size);
1716 NOT_PRODUCT(
1717 if (FLSVerifyIndexTable) {
1718 verifyIndexedFreeList(size);
1719 }
1720 )
1721 _indexedFreeList[size].remove_chunk(fc);
1722 NOT_PRODUCT(
1723 if (FLSVerifyIndexTable) {
1724 verifyIndexedFreeList(size);
1725 }
1726 )
1727 }
1728
1729 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
1730 /* A hint is the next larger size that has a surplus.
1731 Start search at a size large enough to guarantee that
1732 the excess is >= MIN_CHUNK. */
1733 size_t start = align_object_size(numWords + MinChunkSize);
1734 if (start < IndexSetSize) {
1735 AdaptiveFreeList<FreeChunk>* it = _indexedFreeList;
1736 size_t hint = _indexedFreeList[start].hint();
1737 while (hint < IndexSetSize) {
1738 assert(hint % MinObjAlignment == 0, "hint should be aligned");
1739 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint];
1740 if (fl->surplus() > 0 && fl->head() != NULL) {
1741 // Found a list with surplus, reset original hint
1742 // and split out a free chunk which is returned.
1743 _indexedFreeList[start].set_hint(hint);
1744 FreeChunk* res = getFromListGreater(fl, numWords);
1745 assert(res == NULL || res->is_free(),
1746 "Should be returning a free chunk");
1747 return res;
1748 }
1749 hint = fl->hint(); /* keep looking */
1750 }
1751 /* None found. */
1752 it[start].set_hint(IndexSetSize);
1753 }
1754 return NULL;
1755 }
1756
1757 /* Requires fl->size >= numWords + MinChunkSize */
1758 FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl,
1759 size_t numWords) {
1760 FreeChunk *curr = fl->head();
1761 size_t oldNumWords = curr->size();
1762 assert(numWords >= MinChunkSize, "Word size is too small");
1763 assert(curr != NULL, "List is empty");
1764 assert(oldNumWords >= numWords + MinChunkSize,
1765 "Size of chunks in the list is too small");
1766
1767 fl->remove_chunk(curr);
1768 // recorded indirectly by splitChunkAndReturnRemainder -
1769 // smallSplit(oldNumWords, numWords);
1770 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
1771 // Does anything have to be done for the remainder in terms of
1772 // fixing the card table?
1773 assert(new_chunk == NULL || new_chunk->is_free(),
1774 "Should be returning a free chunk");
1775 return new_chunk;
1776 }
1777
1778 FreeChunk*
1779 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
1780 size_t new_size) {
1781 assert_locked();
1782 size_t size = chunk->size();
1783 assert(size > new_size, "Split from a smaller block?");
1784 assert(is_aligned(chunk), "alignment problem");
1785 assert(size == adjustObjectSize(size), "alignment problem");
1786 size_t rem_sz = size - new_size;
1787 assert(rem_sz == adjustObjectSize(rem_sz), "alignment problem");
1788 assert(rem_sz >= MinChunkSize, "Free chunk smaller than minimum");
1789 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
1790 assert(is_aligned(ffc), "alignment problem");
1791 ffc->set_size(rem_sz);
1792 ffc->link_next(NULL);
1793 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
1794 // Above must occur before BOT is updated below.
1795 // adjust block offset table
1796 OrderAccess::storestore();
1797 assert(chunk->is_free() && ffc->is_free(), "Error");
1798 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
1799 if (rem_sz < SmallForDictionary) {
1800 // The freeList lock is held, but multiple GC task threads might be executing in parallel.
1801 bool is_par = Thread::current()->is_GC_task_thread();
1802 if (is_par) _indexedFreeListParLocks[rem_sz]->lock();
1803 returnChunkToFreeList(ffc);
1804 split(size, rem_sz);
1805 if (is_par) _indexedFreeListParLocks[rem_sz]->unlock();
1806 } else {
1807 returnChunkToDictionary(ffc);
1808 split(size, rem_sz);
1809 }
1810 chunk->set_size(new_size);
1811 return chunk;
1812 }
1813
1814 void
1815 CompactibleFreeListSpace::sweep_completed() {
1816 // Now that space is probably plentiful, refill linear
1817 // allocation blocks as needed.
1818 refillLinearAllocBlocksIfNeeded();
1819 }
1820
1821 void
1822 CompactibleFreeListSpace::gc_prologue() {
1823 assert_locked();
1824 reportFreeListStatistics("Before GC:");
1825 refillLinearAllocBlocksIfNeeded();
1826 }
1827
1828 void
1829 CompactibleFreeListSpace::gc_epilogue() {
1830 assert_locked();
1831 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1832 _promoInfo.stopTrackingPromotions();
1833 repairLinearAllocationBlocks();
1834 reportFreeListStatistics("After GC:");
1835 }
1836
1837 // Iteration support, mostly delegated from a CMS generation
1838
1839 void CompactibleFreeListSpace::save_marks() {
1840 assert(Thread::current()->is_VM_thread(),
1841 "Global variable should only be set when single-threaded");
1842 // Mark the "end" of the used space at the time of this call;
1843 // note, however, that promoted objects from this point
1844 // on are tracked in the _promoInfo below.
1845 set_saved_mark_word(unallocated_block());
1846 #ifdef ASSERT
1847 // Check the sanity of save_marks() etc.
1848 MemRegion ur = used_region();
1849 MemRegion urasm = used_region_at_save_marks();
1850 assert(ur.contains(urasm),
1851 " Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
1852 " should contain [" PTR_FORMAT "," PTR_FORMAT ")",
1853 p2i(ur.start()), p2i(ur.end()), p2i(urasm.start()), p2i(urasm.end()));
1854 #endif
1855 // inform allocator that promotions should be tracked.
1856 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
1857 _promoInfo.startTrackingPromotions();
1858 }
1859
1860 bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
1861 assert(_promoInfo.tracking(), "No preceding save_marks?");
1862 return _promoInfo.noPromotions();
1863 }
1864
1865 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
1866 \
1867 void CompactibleFreeListSpace:: \
1868 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \
1869 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \
1870 /* \
1871 * This also restores any displaced headers and removes the elements from \
1872 * the iteration set as they are processed, so that we have a clean slate \
1873 * at the end of the iteration. Note, thus, that if new objects are \
1874 * promoted as a result of the iteration they are iterated over as well. \
1875 */ \
1876 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \
1877 }
1878
1879 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN)
1880
1881 bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
1882 return _smallLinearAllocBlock._word_size == 0;
1883 }
1884
1885 void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
1886 // Fix up linear allocation blocks to look like free blocks
1887 repairLinearAllocBlock(&_smallLinearAllocBlock);
1888 }
1889
1890 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
1891 assert_locked();
1892 if (blk->_ptr != NULL) {
1893 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
1894 "Minimum block size requirement");
1895 FreeChunk* fc = (FreeChunk*)(blk->_ptr);
1896 fc->set_size(blk->_word_size);
1897 fc->link_prev(NULL); // mark as free
1898 fc->dontCoalesce();
1899 assert(fc->is_free(), "just marked it free");
1900 assert(fc->cantCoalesce(), "just marked it uncoalescable");
1901 }
1902 }
1903
1904 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
1905 assert_locked();
1906 if (_smallLinearAllocBlock._ptr == NULL) {
1907 assert(_smallLinearAllocBlock._word_size == 0,
1908 "Size of linAB should be zero if the ptr is NULL");
1909 // Reset the linAB refill and allocation size limit.
1910 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
1911 }
1912 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
1913 }
1914
1915 void
1916 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
1917 assert_locked();
1918 assert((blk->_ptr == NULL && blk->_word_size == 0) ||
1919 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
1920 "blk invariant");
1921 if (blk->_ptr == NULL) {
1922 refillLinearAllocBlock(blk);
1923 }
1924 }
1925
1926 void
1927 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
1928 assert_locked();
1929 assert(blk->_word_size == 0 && blk->_ptr == NULL,
1930 "linear allocation block should be empty");
1931 FreeChunk* fc;
1932 if (blk->_refillSize < SmallForDictionary &&
1933 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
1934 // A linAB's strategy might be to use small sizes to reduce
1935 // fragmentation but still get the benefits of allocation from a
1936 // linAB.
1937 } else {
1938 fc = getChunkFromDictionary(blk->_refillSize);
1939 }
1940 if (fc != NULL) {
1941 blk->_ptr = (HeapWord*)fc;
1942 blk->_word_size = fc->size();
1943 fc->dontCoalesce(); // to prevent sweeper from sweeping us up
1944 }
1945 }
1946
1947 // Support for compaction
1948 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
1949 scan_and_forward(this, cp);
1950 // Prepare_for_compaction() uses the space between live objects
1951 // so that later phase can skip dead space quickly. So verification
1952 // of the free lists doesn't work after.
1953 }
1954
1955 void CompactibleFreeListSpace::adjust_pointers() {
1956 // In other versions of adjust_pointers(), a bail out
1957 // based on the amount of live data in the generation
1958 // (i.e., if 0, bail out) may be used.
1959 // Cannot test used() == 0 here because the free lists have already
1960 // been mangled by the compaction.
1961
1962 scan_and_adjust_pointers(this);
1963 // See note about verification in prepare_for_compaction().
1964 }
1965
1966 void CompactibleFreeListSpace::compact() {
1967 scan_and_compact(this);
1968 }
1969
1970 // Fragmentation metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
1971 // where fbs is free block sizes
1972 double CompactibleFreeListSpace::flsFrag() const {
1973 size_t itabFree = totalSizeInIndexedFreeLists();
1974 double frag = 0.0;
1975 size_t i;
1976
1977 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1978 double sz = i;
1979 frag += _indexedFreeList[i].count() * (sz * sz);
1980 }
1981
1982 double totFree = itabFree +
1983 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
1984 if (totFree > 0) {
1985 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
1986 (totFree * totFree));
1987 frag = (double)1.0 - frag;
1988 } else {
1989 assert(frag == 0.0, "Follows from totFree == 0");
1990 }
1991 return frag;
1992 }
1993
1994 void CompactibleFreeListSpace::beginSweepFLCensus(
1995 float inter_sweep_current,
1996 float inter_sweep_estimate,
1997 float intra_sweep_estimate) {
1998 assert_locked();
1999 size_t i;
2000 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2001 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
2002 log_trace(gc, freelist)("size[" SIZE_FORMAT "] : ", i);
2003 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
2004 fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
2005 fl->set_before_sweep(fl->count());
2006 fl->set_bfr_surp(fl->surplus());
2007 }
2008 _dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent,
2009 inter_sweep_current,
2010 inter_sweep_estimate,
2011 intra_sweep_estimate);
2012 }
2013
2014 void CompactibleFreeListSpace::setFLSurplus() {
2015 assert_locked();
2016 size_t i;
2017 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2018 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2019 fl->set_surplus(fl->count() -
2020 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
2021 }
2022 }
2023
2024 void CompactibleFreeListSpace::setFLHints() {
2025 assert_locked();
2026 size_t i;
2027 size_t h = IndexSetSize;
2028 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
2029 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2030 fl->set_hint(h);
2031 if (fl->surplus() > 0) {
2032 h = i;
2033 }
2034 }
2035 }
2036
2037 void CompactibleFreeListSpace::clearFLCensus() {
2038 assert_locked();
2039 size_t i;
2040 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2041 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2042 fl->set_prev_sweep(fl->count());
2043 fl->set_coal_births(0);
2044 fl->set_coal_deaths(0);
2045 fl->set_split_births(0);
2046 fl->set_split_deaths(0);
2047 }
2048 }
2049
2050 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
2051 log_debug(gc, freelist)("CMS: Large block " PTR_FORMAT, p2i(dictionary()->find_largest_dict()));
2052 setFLSurplus();
2053 setFLHints();
2054 printFLCensus(sweep_count);
2055 clearFLCensus();
2056 assert_locked();
2057 _dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent);
2058 }
2059
2060 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
2061 if (size < SmallForDictionary) {
2062 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2063 return (fl->coal_desired() < 0) ||
2064 ((int)fl->count() > fl->coal_desired());
2065 } else {
2066 return dictionary()->coal_dict_over_populated(size);
2067 }
2068 }
2069
2070 void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
2071 assert(size < SmallForDictionary, "Size too large for indexed list");
2072 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2073 fl->increment_coal_births();
2074 fl->increment_surplus();
2075 }
2076
2077 void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
2078 assert(size < SmallForDictionary, "Size too large for indexed list");
2079 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2080 fl->increment_coal_deaths();
2081 fl->decrement_surplus();
2082 }
2083
2084 void CompactibleFreeListSpace::coalBirth(size_t size) {
2085 if (size < SmallForDictionary) {
2086 smallCoalBirth(size);
2087 } else {
2088 dictionary()->dict_census_update(size,
2089 false /* split */,
2090 true /* birth */);
2091 }
2092 }
2093
2094 void CompactibleFreeListSpace::coalDeath(size_t size) {
2095 if(size < SmallForDictionary) {
2096 smallCoalDeath(size);
2097 } else {
2098 dictionary()->dict_census_update(size,
2099 false /* split */,
2100 false /* birth */);
2101 }
2102 }
2103
2104 void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
2105 assert(size < SmallForDictionary, "Size too large for indexed list");
2106 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2107 fl->increment_split_births();
2108 fl->increment_surplus();
2109 }
2110
2111 void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
2112 assert(size < SmallForDictionary, "Size too large for indexed list");
2113 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
2114 fl->increment_split_deaths();
2115 fl->decrement_surplus();
2116 }
2117
2118 void CompactibleFreeListSpace::split_birth(size_t size) {
2119 if (size < SmallForDictionary) {
2120 smallSplitBirth(size);
2121 } else {
2122 dictionary()->dict_census_update(size,
2123 true /* split */,
2124 true /* birth */);
2125 }
2126 }
2127
2128 void CompactibleFreeListSpace::splitDeath(size_t size) {
2129 if (size < SmallForDictionary) {
2130 smallSplitDeath(size);
2131 } else {
2132 dictionary()->dict_census_update(size,
2133 true /* split */,
2134 false /* birth */);
2135 }
2136 }
2137
2138 void CompactibleFreeListSpace::split(size_t from, size_t to1) {
2139 size_t to2 = from - to1;
2140 splitDeath(from);
2141 split_birth(to1);
2142 split_birth(to2);
2143 }
2144
2145 void CompactibleFreeListSpace::print() const {
2146 print_on(tty);
2147 }
2148
2149 void CompactibleFreeListSpace::prepare_for_verify() {
2150 assert_locked();
2151 repairLinearAllocationBlocks();
2152 // Verify that the SpoolBlocks look like free blocks of
2153 // appropriate sizes... To be done ...
2154 }
2155
2156 class VerifyAllBlksClosure: public BlkClosure {
2157 private:
2158 const CompactibleFreeListSpace* _sp;
2159 const MemRegion _span;
2160 HeapWord* _last_addr;
2161 size_t _last_size;
2162 bool _last_was_obj;
2163 bool _last_was_live;
2164
2165 public:
2166 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
2167 MemRegion span) : _sp(sp), _span(span),
2168 _last_addr(NULL), _last_size(0),
2169 _last_was_obj(false), _last_was_live(false) { }
2170
2171 virtual size_t do_blk(HeapWord* addr) {
2172 size_t res;
2173 bool was_obj = false;
2174 bool was_live = false;
2175 if (_sp->block_is_obj(addr)) {
2176 was_obj = true;
2177 oop p = oop(addr);
2178 guarantee(p->is_oop(), "Should be an oop");
2179 res = _sp->adjustObjectSize(p->size());
2180 if (_sp->obj_is_alive(addr)) {
2181 was_live = true;
2182 p->verify();
2183 }
2184 } else {
2185 FreeChunk* fc = (FreeChunk*)addr;
2186 res = fc->size();
2187 if (FLSVerifyLists && !fc->cantCoalesce()) {
2188 guarantee(_sp->verify_chunk_in_free_list(fc),
2189 "Chunk should be on a free list");
2190 }
2191 }
2192 if (res == 0) {
2193 Log(gc, verify) log;
2194 log.error("Livelock: no rank reduction!");
2195 log.error(" Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
2196 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
2197 p2i(addr), res, was_obj ?"true":"false", was_live ?"true":"false",
2198 p2i(_last_addr), _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
2199 ResourceMark rm;
2200 _sp->print_on(log.error_stream());
2201 guarantee(false, "Verification failed.");
2202 }
2203 _last_addr = addr;
2204 _last_size = res;
2205 _last_was_obj = was_obj;
2206 _last_was_live = was_live;
2207 return res;
2208 }
2209 };
2210
2211 class VerifyAllOopsClosure: public OopClosure {
2212 private:
2213 const CMSCollector* _collector;
2214 const CompactibleFreeListSpace* _sp;
2215 const MemRegion _span;
2216 const bool _past_remark;
2217 const CMSBitMap* _bit_map;
2218
2219 protected:
2220 void do_oop(void* p, oop obj) {
2221 if (_span.contains(obj)) { // the interior oop points into CMS heap
2222 if (!_span.contains(p)) { // reference from outside CMS heap
2223 // Should be a valid object; the first disjunct below allows
2224 // us to sidestep an assertion in block_is_obj() that insists
2225 // that p be in _sp. Note that several generations (and spaces)
2226 // are spanned by _span (CMS heap) above.
2227 guarantee(!_sp->is_in_reserved(obj) ||
2228 _sp->block_is_obj((HeapWord*)obj),
2229 "Should be an object");
2230 guarantee(obj->is_oop(), "Should be an oop");
2231 obj->verify();
2232 if (_past_remark) {
2233 // Remark has been completed, the object should be marked
2234 _bit_map->isMarked((HeapWord*)obj);
2235 }
2236 } else { // reference within CMS heap
2237 if (_past_remark) {
2238 // Remark has been completed -- so the referent should have
2239 // been marked, if referring object is.
2240 if (_bit_map->isMarked(_collector->block_start(p))) {
2241 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
2242 }
2243 }
2244 }
2245 } else if (_sp->is_in_reserved(p)) {
2246 // the reference is from FLS, and points out of FLS
2247 guarantee(obj->is_oop(), "Should be an oop");
2248 obj->verify();
2249 }
2250 }
2251
2252 template <class T> void do_oop_work(T* p) {
2253 T heap_oop = oopDesc::load_heap_oop(p);
2254 if (!oopDesc::is_null(heap_oop)) {
2255 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2256 do_oop(p, obj);
2257 }
2258 }
2259
2260 public:
2261 VerifyAllOopsClosure(const CMSCollector* collector,
2262 const CompactibleFreeListSpace* sp, MemRegion span,
2263 bool past_remark, CMSBitMap* bit_map) :
2264 _collector(collector), _sp(sp), _span(span),
2265 _past_remark(past_remark), _bit_map(bit_map) { }
2266
2267 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2268 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
2269 };
2270
2271 void CompactibleFreeListSpace::verify() const {
2272 assert_lock_strong(&_freelistLock);
2273 verify_objects_initialized();
2274 MemRegion span = _collector->_span;
2275 bool past_remark = (_collector->abstract_state() ==
2276 CMSCollector::Sweeping);
2277
2278 ResourceMark rm;
2279 HandleMark hm;
2280
2281 // Check integrity of CFL data structures
2282 _promoInfo.verify();
2283 _dictionary->verify();
2284 if (FLSVerifyIndexTable) {
2285 verifyIndexedFreeLists();
2286 }
2287 // Check integrity of all objects and free blocks in space
2288 {
2289 VerifyAllBlksClosure cl(this, span);
2290 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
2291 }
2292 // Check that all references in the heap to FLS
2293 // are to valid objects in FLS or that references in
2294 // FLS are to valid objects elsewhere in the heap
2295 if (FLSVerifyAllHeapReferences)
2296 {
2297 VerifyAllOopsClosure cl(_collector, this, span, past_remark,
2298 _collector->markBitMap());
2299
2300 // Iterate over all oops in the heap. Uses the _no_header version
2301 // since we are not interested in following the klass pointers.
2302 GenCollectedHeap::heap()->oop_iterate_no_header(&cl);
2303 }
2304
2305 if (VerifyObjectStartArray) {
2306 // Verify the block offset table
2307 _bt.verify();
2308 }
2309 }
2310
2311 #ifndef PRODUCT
2312 void CompactibleFreeListSpace::verifyFreeLists() const {
2313 if (FLSVerifyLists) {
2314 _dictionary->verify();
2315 verifyIndexedFreeLists();
2316 } else {
2317 if (FLSVerifyDictionary) {
2318 _dictionary->verify();
2319 }
2320 if (FLSVerifyIndexTable) {
2321 verifyIndexedFreeLists();
2322 }
2323 }
2324 }
2325 #endif
2326
2327 void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
2328 size_t i = 0;
2329 for (; i < IndexSetStart; i++) {
2330 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
2331 }
2332 for (; i < IndexSetSize; i++) {
2333 verifyIndexedFreeList(i);
2334 }
2335 }
2336
2337 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
2338 FreeChunk* fc = _indexedFreeList[size].head();
2339 FreeChunk* tail = _indexedFreeList[size].tail();
2340 size_t num = _indexedFreeList[size].count();
2341 size_t n = 0;
2342 guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL,
2343 "Slot should have been empty");
2344 for (; fc != NULL; fc = fc->next(), n++) {
2345 guarantee(fc->size() == size, "Size inconsistency");
2346 guarantee(fc->is_free(), "!free?");
2347 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
2348 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
2349 }
2350 guarantee(n == num, "Incorrect count");
2351 }
2352
2353 #ifndef PRODUCT
2354 void CompactibleFreeListSpace::check_free_list_consistency() const {
2355 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size() <= IndexSetSize),
2356 "Some sizes can't be allocated without recourse to"
2357 " linear allocation buffers");
2358 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >)),
2359 "else MIN_TREE_CHUNK_SIZE is wrong");
2360 assert(IndexSetStart != 0, "IndexSetStart not initialized");
2361 assert(IndexSetStride != 0, "IndexSetStride not initialized");
2362 }
2363 #endif
2364
2365 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
2366 assert_lock_strong(&_freelistLock);
2367 LogTarget(Debug, gc, freelist, census) log;
2368 if (!log.is_enabled()) {
2369 return;
2370 }
2371 AdaptiveFreeList<FreeChunk> total;
2372 log.print("end sweep# " SIZE_FORMAT, sweep_count);
2373 ResourceMark rm;
2374 outputStream* out = log.stream();
2375 AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
2376 size_t total_free = 0;
2377 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2378 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2379 total_free += fl->count() * fl->size();
2380 if (i % (40*IndexSetStride) == 0) {
2381 AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
2382 }
2383 fl->print_on(out);
2384 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
2385 total.set_surplus( total.surplus() + fl->surplus() );
2386 total.set_desired( total.desired() + fl->desired() );
2387 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
2388 total.set_before_sweep(total.before_sweep() + fl->before_sweep());
2389 total.set_count( total.count() + fl->count() );
2390 total.set_coal_births( total.coal_births() + fl->coal_births() );
2391 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
2392 total.set_split_births(total.split_births() + fl->split_births());
2393 total.set_split_deaths(total.split_deaths() + fl->split_deaths());
2394 }
2395 total.print_on(out, "TOTAL");
2396 log.print("Total free in indexed lists " SIZE_FORMAT " words", total_free);
2397 log.print("growth: %8.5f deficit: %8.5f",
2398 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
2399 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
2400 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2401 _dictionary->print_dict_census(out);
2402 }
2403
2404 ///////////////////////////////////////////////////////////////////////////
2405 // CompactibleFreeListSpaceLAB
2406 ///////////////////////////////////////////////////////////////////////////
2407
2408 #define VECTOR_257(x) \
2409 /* 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 */ \
2410 { x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2411 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2412 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2413 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2414 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2415 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2416 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2417 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2418 x }
2419
2420 // Initialize with default setting for CMS, _not_
2421 // generic OldPLABSize, whose static default is different; if overridden at the
2422 // command-line, this will get reinitialized via a call to
2423 // modify_initialization() below.
2424 AdaptiveWeightedAverage CompactibleFreeListSpaceLAB::_blocks_to_claim[] =
2425 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CompactibleFreeListSpaceLAB::_default_dynamic_old_plab_size));
2426 size_t CompactibleFreeListSpaceLAB::_global_num_blocks[] = VECTOR_257(0);
2427 uint CompactibleFreeListSpaceLAB::_global_num_workers[] = VECTOR_257(0);
2428
2429 CompactibleFreeListSpaceLAB::CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls) :
2430 _cfls(cfls)
2431 {
2432 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2433 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2434 i < CompactibleFreeListSpace::IndexSetSize;
2435 i += CompactibleFreeListSpace::IndexSetStride) {
2436 _indexedFreeList[i].set_size(i);
2437 _num_blocks[i] = 0;
2438 }
2439 }
2440
2441 static bool _CFLS_LAB_modified = false;
2442
2443 void CompactibleFreeListSpaceLAB::modify_initialization(size_t n, unsigned wt) {
2444 assert(!_CFLS_LAB_modified, "Call only once");
2445 _CFLS_LAB_modified = true;
2446 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2447 i < CompactibleFreeListSpace::IndexSetSize;
2448 i += CompactibleFreeListSpace::IndexSetStride) {
2449 _blocks_to_claim[i].modify(n, wt, true /* force */);
2450 }
2451 }
2452
2453 HeapWord* CompactibleFreeListSpaceLAB::alloc(size_t word_sz) {
2454 FreeChunk* res;
2455 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2456 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2457 // This locking manages sync with other large object allocations.
2458 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2459 Mutex::_no_safepoint_check_flag);
2460 res = _cfls->getChunkFromDictionaryExact(word_sz);
2461 if (res == NULL) return NULL;
2462 } else {
2463 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
2464 if (fl->count() == 0) {
2465 // Attempt to refill this local free list.
2466 get_from_global_pool(word_sz, fl);
2467 // If it didn't work, give up.
2468 if (fl->count() == 0) return NULL;
2469 }
2470 res = fl->get_chunk_at_head();
2471 assert(res != NULL, "Why was count non-zero?");
2472 }
2473 res->markNotFree();
2474 assert(!res->is_free(), "shouldn't be marked free");
2475 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2476 // mangle a just allocated object with a distinct pattern.
2477 debug_only(res->mangleAllocated(word_sz));
2478 return (HeapWord*)res;
2479 }
2480
2481 // Get a chunk of blocks of the right size and update related
2482 // book-keeping stats
2483 void CompactibleFreeListSpaceLAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
2484 // Get the #blocks we want to claim
2485 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2486 assert(n_blks > 0, "Error");
2487 assert(ResizeOldPLAB || n_blks == OldPLABSize, "Error");
2488 // In some cases, when the application has a phase change,
2489 // there may be a sudden and sharp shift in the object survival
2490 // profile, and updating the counts at the end of a scavenge
2491 // may not be quick enough, giving rise to large scavenge pauses
2492 // during these phase changes. It is beneficial to detect such
2493 // changes on-the-fly during a scavenge and avoid such a phase-change
2494 // pothole. The following code is a heuristic attempt to do that.
2495 // It is protected by a product flag until we have gained
2496 // enough experience with this heuristic and fine-tuned its behavior.
2497 // WARNING: This might increase fragmentation if we overreact to
2498 // small spikes, so some kind of historical smoothing based on
2499 // previous experience with the greater reactivity might be useful.
2500 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2501 // default.
2502 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2503 //
2504 // On a 32-bit VM, the denominator can become zero because of integer overflow,
2505 // which is why there is a cast to double.
2506 //
2507 size_t multiple = (size_t) (_num_blocks[word_sz]/(((double)CMSOldPLABToleranceFactor)*CMSOldPLABNumRefills*n_blks));
2508 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2509 n_blks = MIN2(n_blks, CMSOldPLABMax);
2510 }
2511 assert(n_blks > 0, "Error");
2512 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2513 // Update stats table entry for this block size
2514 _num_blocks[word_sz] += fl->count();
2515 }
2516
2517 void CompactibleFreeListSpaceLAB::compute_desired_plab_size() {
2518 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2519 i < CompactibleFreeListSpace::IndexSetSize;
2520 i += CompactibleFreeListSpace::IndexSetStride) {
2521 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2522 "Counter inconsistency");
2523 if (_global_num_workers[i] > 0) {
2524 // Need to smooth wrt historical average
2525 if (ResizeOldPLAB) {
2526 _blocks_to_claim[i].sample(
2527 MAX2(CMSOldPLABMin,
2528 MIN2(CMSOldPLABMax,
2529 _global_num_blocks[i]/_global_num_workers[i]/CMSOldPLABNumRefills)));
2530 }
2531 // Reset counters for next round
2532 _global_num_workers[i] = 0;
2533 _global_num_blocks[i] = 0;
2534 log_trace(gc, plab)("[" SIZE_FORMAT "]: " SIZE_FORMAT, i, (size_t)_blocks_to_claim[i].average());
2535 }
2536 }
2537 }
2538
2539 // If this is changed in the future to allow parallel
2540 // access, one would need to take the FL locks and,
2541 // depending on how it is used, stagger access from
2542 // parallel threads to reduce contention.
2543 void CompactibleFreeListSpaceLAB::retire(int tid) {
2544 // We run this single threaded with the world stopped;
2545 // so no need for locks and such.
2546 NOT_PRODUCT(Thread* t = Thread::current();)
2547 assert(Thread::current()->is_VM_thread(), "Error");
2548 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2549 i < CompactibleFreeListSpace::IndexSetSize;
2550 i += CompactibleFreeListSpace::IndexSetStride) {
2551 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2552 "Can't retire more than what we obtained");
2553 if (_num_blocks[i] > 0) {
2554 size_t num_retire = _indexedFreeList[i].count();
2555 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2556 {
2557 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2558 // Mutex::_no_safepoint_check_flag);
2559
2560 // Update globals stats for num_blocks used
2561 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2562 _global_num_workers[i]++;
2563 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2564 if (num_retire > 0) {
2565 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2566 // Reset this list.
2567 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
2568 _indexedFreeList[i].set_size(i);
2569 }
2570 }
2571 log_trace(gc, plab)("%d[" SIZE_FORMAT "]: " SIZE_FORMAT "/" SIZE_FORMAT "/" SIZE_FORMAT,
2572 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2573 // Reset stats for next round
2574 _num_blocks[i] = 0;
2575 }
2576 }
2577 }
2578
2579 // Used by par_get_chunk_of_blocks() for the chunks from the
2580 // indexed_free_lists. Looks for a chunk with size that is a multiple
2581 // of "word_sz" and if found, splits it into "word_sz" chunks and add
2582 // to the free list "fl". "n" is the maximum number of chunks to
2583 // be added to "fl".
2584 bool CompactibleFreeListSpace:: par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2585
2586 // We'll try all multiples of word_sz in the indexed set, starting with
2587 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2588 // then try getting a big chunk and splitting it.
2589 {
2590 bool found;
2591 int k;
2592 size_t cur_sz;
2593 for (k = 1, cur_sz = k * word_sz, found = false;
2594 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2595 (CMSSplitIndexedFreeListBlocks || k <= 1);
2596 k++, cur_sz = k * word_sz) {
2597 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
2598 fl_for_cur_sz.set_size(cur_sz);
2599 {
2600 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2601 Mutex::_no_safepoint_check_flag);
2602 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
2603 if (gfl->count() != 0) {
2604 // nn is the number of chunks of size cur_sz that
2605 // we'd need to split k-ways each, in order to create
2606 // "n" chunks of size word_sz each.
2607 const size_t nn = MAX2(n/k, (size_t)1);
2608 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2609 found = true;
2610 if (k > 1) {
2611 // Update split death stats for the cur_sz-size blocks list:
2612 // we increment the split death count by the number of blocks
2613 // we just took from the cur_sz-size blocks list and which
2614 // we will be splitting below.
2615 ssize_t deaths = gfl->split_deaths() +
2616 fl_for_cur_sz.count();
2617 gfl->set_split_deaths(deaths);
2618 }
2619 }
2620 }
2621 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2622 if (found) {
2623 if (k == 1) {
2624 fl->prepend(&fl_for_cur_sz);
2625 } else {
2626 // Divide each block on fl_for_cur_sz up k ways.
2627 FreeChunk* fc;
2628 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
2629 // Must do this in reverse order, so that anybody attempting to
2630 // access the main chunk sees it as a single free block until we
2631 // change it.
2632 size_t fc_size = fc->size();
2633 assert(fc->is_free(), "Error");
2634 for (int i = k-1; i >= 0; i--) {
2635 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2636 assert((i != 0) ||
2637 ((fc == ffc) && ffc->is_free() &&
2638 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2639 "Counting error");
2640 ffc->set_size(word_sz);
2641 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2642 ffc->link_next(NULL);
2643 // Above must occur before BOT is updated below.
2644 OrderAccess::storestore();
2645 // splitting from the right, fc_size == i * word_sz
2646 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2647 fc_size -= word_sz;
2648 assert(fc_size == i*word_sz, "Error");
2649 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2650 _bt.verify_single_block((HeapWord*)fc, fc_size);
2651 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2652 // Push this on "fl".
2653 fl->return_chunk_at_head(ffc);
2654 }
2655 // TRAP
2656 assert(fl->tail()->next() == NULL, "List invariant.");
2657 }
2658 }
2659 // Update birth stats for this block size.
2660 size_t num = fl->count();
2661 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2662 Mutex::_no_safepoint_check_flag);
2663 ssize_t births = _indexedFreeList[word_sz].split_births() + num;
2664 _indexedFreeList[word_sz].set_split_births(births);
2665 return true;
2666 }
2667 }
2668 return found;
2669 }
2670 }
2671
2672 FreeChunk* CompactibleFreeListSpace::get_n_way_chunk_to_split(size_t word_sz, size_t n) {
2673
2674 FreeChunk* fc = NULL;
2675 FreeChunk* rem_fc = NULL;
2676 size_t rem;
2677 {
2678 MutexLockerEx x(parDictionaryAllocLock(),
2679 Mutex::_no_safepoint_check_flag);
2680 while (n > 0) {
2681 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()),
2682 FreeBlockDictionary<FreeChunk>::atLeast);
2683 if (fc != NULL) {
2684 break;
2685 } else {
2686 n--;
2687 }
2688 }
2689 if (fc == NULL) return NULL;
2690 // Otherwise, split up that block.
2691 assert((ssize_t)n >= 1, "Control point invariant");
2692 assert(fc->is_free(), "Error: should be a free block");
2693 _bt.verify_single_block((HeapWord*)fc, fc->size());
2694 const size_t nn = fc->size() / word_sz;
2695 n = MIN2(nn, n);
2696 assert((ssize_t)n >= 1, "Control point invariant");
2697 rem = fc->size() - n * word_sz;
2698 // If there is a remainder, and it's too small, allocate one fewer.
2699 if (rem > 0 && rem < MinChunkSize) {
2700 n--; rem += word_sz;
2701 }
2702 // Note that at this point we may have n == 0.
2703 assert((ssize_t)n >= 0, "Control point invariant");
2704
2705 // If n is 0, the chunk fc that was found is not large
2706 // enough to leave a viable remainder. We are unable to
2707 // allocate even one block. Return fc to the
2708 // dictionary and return, leaving "fl" empty.
2709 if (n == 0) {
2710 returnChunkToDictionary(fc);
2711 return NULL;
2712 }
2713
2714 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
2715 dictionary()->dict_census_update(fc->size(),
2716 true /*split*/,
2717 false /*birth*/);
2718
2719 // First return the remainder, if any.
2720 // Note that we hold the lock until we decide if we're going to give
2721 // back the remainder to the dictionary, since a concurrent allocation
2722 // may otherwise see the heap as empty. (We're willing to take that
2723 // hit if the block is a small block.)
2724 if (rem > 0) {
2725 size_t prefix_size = n * word_sz;
2726 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
2727 rem_fc->set_size(rem);
2728 rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2729 rem_fc->link_next(NULL);
2730 // Above must occur before BOT is updated below.
2731 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
2732 OrderAccess::storestore();
2733 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
2734 assert(fc->is_free(), "Error");
2735 fc->set_size(prefix_size);
2736 if (rem >= IndexSetSize) {
2737 returnChunkToDictionary(rem_fc);
2738 dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/);
2739 rem_fc = NULL;
2740 }
2741 // Otherwise, return it to the small list below.
2742 }
2743 }
2744 if (rem_fc != NULL) {
2745 MutexLockerEx x(_indexedFreeListParLocks[rem],
2746 Mutex::_no_safepoint_check_flag);
2747 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
2748 _indexedFreeList[rem].return_chunk_at_head(rem_fc);
2749 smallSplitBirth(rem);
2750 }
2751 assert(n * word_sz == fc->size(),
2752 "Chunk size " SIZE_FORMAT " is not exactly splittable by "
2753 SIZE_FORMAT " sized chunks of size " SIZE_FORMAT,
2754 fc->size(), n, word_sz);
2755 return fc;
2756 }
2757
2758 void CompactibleFreeListSpace:: par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t targetted_number_of_chunks, AdaptiveFreeList<FreeChunk>* fl) {
2759
2760 FreeChunk* fc = get_n_way_chunk_to_split(word_sz, targetted_number_of_chunks);
2761
2762 if (fc == NULL) {
2763 return;
2764 }
2765
2766 size_t n = fc->size() / word_sz;
2767
2768 assert((ssize_t)n > 0, "Consistency");
2769 // Now do the splitting up.
2770 // Must do this in reverse order, so that anybody attempting to
2771 // access the main chunk sees it as a single free block until we
2772 // change it.
2773 size_t fc_size = n * word_sz;
2774 // All but first chunk in this loop
2775 for (ssize_t i = n-1; i > 0; i--) {
2776 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2777 ffc->set_size(word_sz);
2778 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2779 ffc->link_next(NULL);
2780 // Above must occur before BOT is updated below.
2781 OrderAccess::storestore();
2782 // splitting from the right, fc_size == (n - i + 1) * wordsize
2783 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2784 fc_size -= word_sz;
2785 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
2786 _bt.verify_single_block((HeapWord*)ffc, ffc->size());
2787 _bt.verify_single_block((HeapWord*)fc, fc_size);
2788 // Push this on "fl".
2789 fl->return_chunk_at_head(ffc);
2790 }
2791 // First chunk
2792 assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block");
2793 // The blocks above should show their new sizes before the first block below
2794 fc->set_size(word_sz);
2795 fc->link_prev(NULL); // idempotent wrt free-ness, see assert above
2796 fc->link_next(NULL);
2797 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
2798 _bt.verify_single_block((HeapWord*)fc, fc->size());
2799 fl->return_chunk_at_head(fc);
2800
2801 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
2802 {
2803 // Update the stats for this block size.
2804 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2805 Mutex::_no_safepoint_check_flag);
2806 const ssize_t births = _indexedFreeList[word_sz].split_births() + n;
2807 _indexedFreeList[word_sz].set_split_births(births);
2808 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
2809 // _indexedFreeList[word_sz].set_surplus(new_surplus);
2810 }
2811
2812 // TRAP
2813 assert(fl->tail()->next() == NULL, "List invariant.");
2814 }
2815
2816 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2817 assert(fl->count() == 0, "Precondition.");
2818 assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
2819 "Precondition");
2820
2821 if (par_get_chunk_of_blocks_IFL(word_sz, n, fl)) {
2822 // Got it
2823 return;
2824 }
2825
2826 // Otherwise, we'll split a block from the dictionary.
2827 par_get_chunk_of_blocks_dictionary(word_sz, n, fl);
2828 }
2829
2830 const size_t CompactibleFreeListSpace::max_flag_size_for_task_size() const {
2831 const size_t ergo_max = _old_gen->reserved().word_size() / (CardTable::card_size_in_words * BitsPerWord);
2832 return ergo_max;
2833 }
2834
2835 // Set up the space's par_seq_tasks structure for work claiming
2836 // for parallel rescan. See CMSParRemarkTask where this is currently used.
2837 // XXX Need to suitably abstract and generalize this and the next
2838 // method into one.
2839 void
2840 CompactibleFreeListSpace::
2841 initialize_sequential_subtasks_for_rescan(int n_threads) {
2842 // The "size" of each task is fixed according to rescan_task_size.
2843 assert(n_threads > 0, "Unexpected n_threads argument");
2844 const size_t task_size = rescan_task_size();
2845 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
2846 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
2847 assert(n_tasks == 0 ||
2848 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
2849 (used_region().start() + n_tasks*task_size >= used_region().end())),
2850 "n_tasks calculation incorrect");
2851 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2852 assert(!pst->valid(), "Clobbering existing data?");
2853 // Sets the condition for completion of the subtask (how many threads
2854 // need to finish in order to be done).
2855 pst->set_n_threads(n_threads);
2856 pst->set_n_tasks((int)n_tasks);
2857 }
2858
2859 // Set up the space's par_seq_tasks structure for work claiming
2860 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
2861 void
2862 CompactibleFreeListSpace::
2863 initialize_sequential_subtasks_for_marking(int n_threads,
2864 HeapWord* low) {
2865 // The "size" of each task is fixed according to rescan_task_size.
2866 assert(n_threads > 0, "Unexpected n_threads argument");
2867 const size_t task_size = marking_task_size();
2868 assert(task_size > CardTable::card_size_in_words &&
2869 (task_size % CardTable::card_size_in_words == 0),
2870 "Otherwise arithmetic below would be incorrect");
2871 MemRegion span = _old_gen->reserved();
2872 if (low != NULL) {
2873 if (span.contains(low)) {
2874 // Align low down to a card boundary so that
2875 // we can use block_offset_careful() on span boundaries.
2876 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low,
2877 CardTable::card_size);
2878 // Clip span prefix at aligned_low
2879 span = span.intersection(MemRegion(aligned_low, span.end()));
2880 } else if (low > span.end()) {
2881 span = MemRegion(low, low); // Null region
2882 } // else use entire span
2883 }
2884 assert(span.is_empty() ||
2885 ((uintptr_t)span.start() % CardTable::card_size == 0),
2886 "span should start at a card boundary");
2887 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
2888 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
2889 assert(n_tasks == 0 ||
2890 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
2891 (span.start() + n_tasks*task_size >= span.end())),
2892 "n_tasks calculation incorrect");
2893 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2894 assert(!pst->valid(), "Clobbering existing data?");
2895 // Sets the condition for completion of the subtask (how many threads
2896 // need to finish in order to be done).
2897 pst->set_n_threads(n_threads);
2898 pst->set_n_tasks((int)n_tasks);
2899 }