1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc/cms/cmsHeap.hpp"
27 #include "gc/cms/cmsLockVerifier.hpp"
28 #include "gc/cms/compactibleFreeListSpace.hpp"
29 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
30 #include "gc/cms/concurrentMarkSweepThread.hpp"
31 #include "gc/shared/blockOffsetTable.inline.hpp"
32 #include "gc/shared/collectedHeap.inline.hpp"
33 #include "gc/shared/space.inline.hpp"
34 #include "gc/shared/spaceDecorator.hpp"
35 #include "logging/log.hpp"
36 #include "logging/logStream.hpp"
37 #include "memory/allocation.inline.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "runtime/globals.hpp"
42 #include "runtime/handles.inline.hpp"
43 #include "runtime/init.hpp"
44 #include "runtime/java.hpp"
45 #include "runtime/orderAccess.inline.hpp"
46 #include "runtime/vmThread.hpp"
47 #include "utilities/align.hpp"
48 #include "utilities/copy.hpp"
49
50 /////////////////////////////////////////////////////////////////////////
51 //// CompactibleFreeListSpace
52 /////////////////////////////////////////////////////////////////////////
53
54 // highest ranked free list lock rank
55 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
56
57 // Defaults are 0 so things will break badly if incorrectly initialized.
58 size_t CompactibleFreeListSpace::IndexSetStart = 0;
59 size_t CompactibleFreeListSpace::IndexSetStride = 0;
60 size_t CompactibleFreeListSpace::_min_chunk_size_in_bytes = 0;
61
62 size_t MinChunkSize = 0;
63
64 void CompactibleFreeListSpace::set_cms_values() {
65 // Set CMS global values
66 assert(MinChunkSize == 0, "already set");
67
68 // MinChunkSize should be a multiple of MinObjAlignment and be large enough
69 // for chunks to contain a FreeChunk.
70 _min_chunk_size_in_bytes = align_up(sizeof(FreeChunk), MinObjAlignmentInBytes);
71 MinChunkSize = _min_chunk_size_in_bytes / BytesPerWord;
72
73 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
74 IndexSetStart = MinChunkSize;
75 IndexSetStride = MinObjAlignment;
76 }
77
78 // Constructor
79 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr) :
80 _bt(bs, mr),
81 // free list locks are in the range of values taken by _lockRank
82 // This range currently is [_leaf+2, _leaf+3]
83 // Note: this requires that CFLspace c'tors
84 // are called serially in the order in which the locks are
85 // are acquired in the program text. This is true today.
86 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true,
87 Monitor::_safepoint_check_sometimes),
88 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
89 "CompactibleFreeListSpace._dict_par_lock", true,
90 Monitor::_safepoint_check_never),
91 _rescan_task_size(CardTable::card_size_in_words * BitsPerWord *
92 CMSRescanMultiple),
93 _marking_task_size(CardTable::card_size_in_words * BitsPerWord *
94 CMSConcMarkMultiple),
95 _collector(NULL),
96 _preconsumptionDirtyCardClosure(NULL)
97 {
98 assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize,
99 "FreeChunk is larger than expected");
100 _bt.set_space(this);
101 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
102
103 _dictionary = new AFLBinaryTreeDictionary(mr);
104
105 assert(_dictionary != NULL, "CMS dictionary initialization");
106 // The indexed free lists are initially all empty and are lazily
107 // filled in on demand. Initialize the array elements to NULL.
108 initializeIndexedFreeListArray();
109
110 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
111 SmallForLinearAlloc);
112
113 // CMSIndexedFreeListReplenish should be at least 1
114 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
115 _promoInfo.setSpace(this);
116 if (UseCMSBestFit) {
117 _fitStrategy = FreeBlockBestFitFirst;
118 } else {
119 _fitStrategy = FreeBlockStrategyNone;
120 }
121 check_free_list_consistency();
122
123 // Initialize locks for parallel case.
124 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
125 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
126 "a freelist par lock", true, Mutex::_safepoint_check_sometimes);
127 DEBUG_ONLY(
128 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
129 )
130 }
131 _dictionary->set_par_lock(&_parDictionaryAllocLock);
132 }
133
134 // Like CompactibleSpace forward() but always calls cross_threshold() to
135 // update the block offset table. Removed initialize_threshold call because
136 // CFLS does not use a block offset array for contiguous spaces.
137 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
138 CompactPoint* cp, HeapWord* compact_top) {
139 // q is alive
140 // First check if we should switch compaction space
141 assert(this == cp->space, "'this' should be current compaction space.");
142 size_t compaction_max_size = pointer_delta(end(), compact_top);
143 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
144 "virtual adjustObjectSize_v() method is not correct");
145 size_t adjusted_size = adjustObjectSize(size);
146 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
147 "no small fragments allowed");
148 assert(minimum_free_block_size() == MinChunkSize,
149 "for de-virtualized reference below");
150 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize
151 if (adjusted_size + MinChunkSize > compaction_max_size &&
152 adjusted_size != compaction_max_size) {
153 do {
154 // switch to next compaction space
155 cp->space->set_compaction_top(compact_top);
156 cp->space = cp->space->next_compaction_space();
157 if (cp->space == NULL) {
158 cp->gen = CMSHeap::heap()->young_gen();
159 assert(cp->gen != NULL, "compaction must succeed");
160 cp->space = cp->gen->first_compaction_space();
161 assert(cp->space != NULL, "generation must have a first compaction space");
162 }
163 compact_top = cp->space->bottom();
164 cp->space->set_compaction_top(compact_top);
165 // The correct adjusted_size may not be the same as that for this method
166 // (i.e., cp->space may no longer be "this" so adjust the size again.
167 // Use the virtual method which is not used above to save the virtual
168 // dispatch.
169 adjusted_size = cp->space->adjust_object_size_v(size);
170 compaction_max_size = pointer_delta(cp->space->end(), compact_top);
171 assert(cp->space->minimum_free_block_size() == 0, "just checking");
172 } while (adjusted_size > compaction_max_size);
173 }
174
175 // store the forwarding pointer into the mark word
176 if ((HeapWord*)q != compact_top) {
177 q->forward_to(oop(compact_top));
178 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
179 } else {
180 // if the object isn't moving we can just set the mark to the default
181 // mark and handle it specially later on.
182 q->init_mark();
183 assert(q->forwardee() == NULL, "should be forwarded to NULL");
184 }
185
186 compact_top += adjusted_size;
187
188 // we need to update the offset table so that the beginnings of objects can be
189 // found during scavenge. Note that we are updating the offset table based on
190 // where the object will be once the compaction phase finishes.
191
192 // Always call cross_threshold(). A contiguous space can only call it when
193 // the compaction_top exceeds the current threshold but not for an
194 // non-contiguous space.
195 cp->threshold =
196 cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
197 return compact_top;
198 }
199
200 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
201 // and use of single_block instead of alloc_block. The name here is not really
202 // appropriate - maybe a more general name could be invented for both the
203 // contiguous and noncontiguous spaces.
204
205 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
206 _bt.single_block(start, the_end);
207 return end();
208 }
209
210 // Initialize them to NULL.
211 void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
212 for (size_t i = 0; i < IndexSetSize; i++) {
213 // Note that on platforms where objects are double word aligned,
214 // the odd array elements are not used. It is convenient, however,
215 // to map directly from the object size to the array element.
216 _indexedFreeList[i].reset(IndexSetSize);
217 _indexedFreeList[i].set_size(i);
218 assert(_indexedFreeList[i].count() == 0, "reset check failed");
219 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
220 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
221 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
222 }
223 }
224
225 size_t CompactibleFreeListSpace::obj_size(const HeapWord* addr) const {
226 return adjustObjectSize(oop(addr)->size());
227 }
228
229 void CompactibleFreeListSpace::resetIndexedFreeListArray() {
230 for (size_t i = 1; i < IndexSetSize; i++) {
231 assert(_indexedFreeList[i].size() == (size_t) i,
232 "Indexed free list sizes are incorrect");
233 _indexedFreeList[i].reset(IndexSetSize);
234 assert(_indexedFreeList[i].count() == 0, "reset check failed");
235 assert(_indexedFreeList[i].head() == NULL, "reset check failed");
236 assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
237 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
238 }
239 }
240
241 void CompactibleFreeListSpace::reset(MemRegion mr) {
242 resetIndexedFreeListArray();
243 dictionary()->reset();
244 if (BlockOffsetArrayUseUnallocatedBlock) {
245 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
246 // Everything's allocated until proven otherwise.
247 _bt.set_unallocated_block(end());
248 }
249 if (!mr.is_empty()) {
250 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
251 _bt.single_block(mr.start(), mr.word_size());
252 FreeChunk* fc = (FreeChunk*) mr.start();
253 fc->set_size(mr.word_size());
254 if (mr.word_size() >= IndexSetSize ) {
255 returnChunkToDictionary(fc);
256 } else {
257 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
258 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc);
259 }
260 coalBirth(mr.word_size());
261 }
262 _promoInfo.reset();
263 _smallLinearAllocBlock._ptr = NULL;
264 _smallLinearAllocBlock._word_size = 0;
265 }
266
267 void CompactibleFreeListSpace::reset_after_compaction() {
268 // Reset the space to the new reality - one free chunk.
269 MemRegion mr(compaction_top(), end());
270 reset(mr);
271 // Now refill the linear allocation block(s) if possible.
272 refillLinearAllocBlocksIfNeeded();
273 }
274
275 // Walks the entire dictionary, returning a coterminal
276 // chunk, if it exists. Use with caution since it involves
277 // a potentially complete walk of a potentially large tree.
278 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
279
280 assert_lock_strong(&_freelistLock);
281
282 return dictionary()->find_chunk_ends_at(end());
283 }
284
285
286 #ifndef PRODUCT
287 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
288 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
289 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
290 }
291 }
292
293 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
294 size_t sum = 0;
295 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
296 sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
297 }
298 return sum;
299 }
300
301 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
302 size_t count = 0;
303 for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
304 debug_only(
305 ssize_t total_list_count = 0;
306 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
307 fc = fc->next()) {
308 total_list_count++;
309 }
310 assert(total_list_count == _indexedFreeList[i].count(),
311 "Count in list is incorrect");
312 )
313 count += _indexedFreeList[i].count();
314 }
315 return count;
316 }
317
318 size_t CompactibleFreeListSpace::totalCount() {
319 size_t num = totalCountInIndexedFreeLists();
320 num += dictionary()->total_count();
321 if (_smallLinearAllocBlock._word_size != 0) {
322 num++;
323 }
324 return num;
325 }
326 #endif
327
328 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
329 FreeChunk* fc = (FreeChunk*) p;
330 return fc->is_free();
331 }
332
333 size_t CompactibleFreeListSpace::used() const {
334 return capacity() - free();
335 }
336
337 size_t CompactibleFreeListSpace::free() const {
338 // "MT-safe, but not MT-precise"(TM), if you will: i.e.
339 // if you do this while the structures are in flux you
340 // may get an approximate answer only; for instance
341 // because there is concurrent allocation either
342 // directly by mutators or for promotion during a GC.
343 // It's "MT-safe", however, in the sense that you are guaranteed
344 // not to crash and burn, for instance, because of walking
345 // pointers that could disappear as you were walking them.
346 // The approximation is because the various components
347 // that are read below are not read atomically (and
348 // further the computation of totalSizeInIndexedFreeLists()
349 // is itself a non-atomic computation. The normal use of
350 // this is during a resize operation at the end of GC
351 // and at that time you are guaranteed to get the
352 // correct actual value. However, for instance, this is
353 // also read completely asynchronously by the "perf-sampler"
354 // that supports jvmstat, and you are apt to see the values
355 // flicker in such cases.
356 assert(_dictionary != NULL, "No _dictionary?");
357 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
358 totalSizeInIndexedFreeLists() +
359 _smallLinearAllocBlock._word_size) * HeapWordSize;
360 }
361
362 size_t CompactibleFreeListSpace::max_alloc_in_words() const {
363 assert(_dictionary != NULL, "No _dictionary?");
364 assert_locked();
365 size_t res = _dictionary->max_chunk_size();
366 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
367 (size_t) SmallForLinearAlloc - 1));
368 // XXX the following could potentially be pretty slow;
369 // should one, pessimistically for the rare cases when res
370 // calculated above is less than IndexSetSize,
371 // just return res calculated above? My reasoning was that
372 // those cases will be so rare that the extra time spent doesn't
373 // really matter....
374 // Note: do not change the loop test i >= res + IndexSetStride
375 // to i > res below, because i is unsigned and res may be zero.
376 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
377 i -= IndexSetStride) {
378 if (_indexedFreeList[i].head() != NULL) {
379 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
380 return i;
381 }
382 }
383 return res;
384 }
385
386 void LinearAllocBlock::print_on(outputStream* st) const {
387 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
388 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
389 p2i(_ptr), _word_size, _refillSize, _allocation_size_limit);
390 }
391
392 void CompactibleFreeListSpace::print_on(outputStream* st) const {
393 st->print_cr("COMPACTIBLE FREELIST SPACE");
394 st->print_cr(" Space:");
395 Space::print_on(st);
396
397 st->print_cr("promoInfo:");
398 _promoInfo.print_on(st);
399
400 st->print_cr("_smallLinearAllocBlock");
401 _smallLinearAllocBlock.print_on(st);
402
403 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
404
405 st->print_cr(" _fitStrategy = %s", BOOL_TO_STR(_fitStrategy));
406 }
407
408 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
409 const {
410 reportIndexedFreeListStatistics(st);
411 st->print_cr("Layout of Indexed Freelists");
412 st->print_cr("---------------------------");
413 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
414 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
415 _indexedFreeList[i].print_on(st);
416 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) {
417 st->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
418 p2i(fc), p2i((HeapWord*)fc + i),
419 fc->cantCoalesce() ? "\t CC" : "");
420 }
421 }
422 }
423
424 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
425 const {
426 _promoInfo.print_on(st);
427 }
428
429 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
430 const {
431 _dictionary->report_statistics(st);
432 st->print_cr("Layout of Freelists in Tree");
433 st->print_cr("---------------------------");
434 _dictionary->print_free_lists(st);
435 }
436
437 class BlkPrintingClosure: public BlkClosure {
438 const CMSCollector* _collector;
439 const CompactibleFreeListSpace* _sp;
440 const CMSBitMap* _live_bit_map;
441 const bool _post_remark;
442 outputStream* _st;
443 public:
444 BlkPrintingClosure(const CMSCollector* collector,
445 const CompactibleFreeListSpace* sp,
446 const CMSBitMap* live_bit_map,
447 outputStream* st):
448 _collector(collector),
449 _sp(sp),
450 _live_bit_map(live_bit_map),
451 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
452 _st(st) { }
453 size_t do_blk(HeapWord* addr);
454 };
455
456 size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
457 size_t sz = _sp->block_size_no_stall(addr, _collector);
458 assert(sz != 0, "Should always be able to compute a size");
459 if (_sp->block_is_obj(addr)) {
460 const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
461 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
462 p2i(addr),
463 dead ? "dead" : "live",
464 sz,
465 (!dead && CMSPrintObjectsInDump) ? ":" : ".");
466 if (CMSPrintObjectsInDump && !dead) {
467 oop(addr)->print_on(_st);
468 _st->print_cr("--------------------------------------");
469 }
470 } else { // free block
471 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
472 p2i(addr), sz, CMSPrintChunksInDump ? ":" : ".");
473 if (CMSPrintChunksInDump) {
474 ((FreeChunk*)addr)->print_on(_st);
475 _st->print_cr("--------------------------------------");
476 }
477 }
478 return sz;
479 }
480
481 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st) {
482 st->print_cr("=========================");
483 st->print_cr("Block layout in CMS Heap:");
484 st->print_cr("=========================");
485 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
486 blk_iterate(&bpcl);
487
488 st->print_cr("=======================================");
489 st->print_cr("Order & Layout of Promotion Info Blocks");
490 st->print_cr("=======================================");
491 print_promo_info_blocks(st);
492
493 st->print_cr("===========================");
494 st->print_cr("Order of Indexed Free Lists");
495 st->print_cr("=========================");
496 print_indexed_free_lists(st);
497
498 st->print_cr("=================================");
499 st->print_cr("Order of Free Lists in Dictionary");
500 st->print_cr("=================================");
501 print_dictionary_free_lists(st);
502 }
503
504
505 void CompactibleFreeListSpace::reportFreeListStatistics(const char* title) const {
506 assert_lock_strong(&_freelistLock);
507 Log(gc, freelist, stats) log;
508 if (!log.is_debug()) {
509 return;
510 }
511 log.debug("%s", title);
512
513 LogStream out(log.debug());
514 _dictionary->report_statistics(&out);
515
516 if (log.is_trace()) {
517 LogStream trace_out(log.trace());
518 reportIndexedFreeListStatistics(&trace_out);
519 size_t total_size = totalSizeInIndexedFreeLists() +
520 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
521 log.trace(" free=" SIZE_FORMAT " frag=%1.4f", total_size, flsFrag());
522 }
523 }
524
525 void CompactibleFreeListSpace::reportIndexedFreeListStatistics(outputStream* st) const {
526 assert_lock_strong(&_freelistLock);
527 st->print_cr("Statistics for IndexedFreeLists:");
528 st->print_cr("--------------------------------");
529 size_t total_size = totalSizeInIndexedFreeLists();
530 size_t free_blocks = numFreeBlocksInIndexedFreeLists();
531 st->print_cr("Total Free Space: " SIZE_FORMAT, total_size);
532 st->print_cr("Max Chunk Size: " SIZE_FORMAT, maxChunkSizeInIndexedFreeLists());
533 st->print_cr("Number of Blocks: " SIZE_FORMAT, free_blocks);
534 if (free_blocks != 0) {
535 st->print_cr("Av. Block Size: " SIZE_FORMAT, total_size/free_blocks);
536 }
537 }
538
539 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
540 size_t res = 0;
541 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
542 debug_only(
543 ssize_t recount = 0;
544 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
545 fc = fc->next()) {
546 recount += 1;
547 }
548 assert(recount == _indexedFreeList[i].count(),
549 "Incorrect count in list");
550 )
551 res += _indexedFreeList[i].count();
552 }
553 return res;
554 }
555
556 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
557 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
558 if (_indexedFreeList[i].head() != NULL) {
559 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
560 return (size_t)i;
561 }
562 }
563 return 0;
564 }
565
566 void CompactibleFreeListSpace::set_end(HeapWord* value) {
567 HeapWord* prevEnd = end();
568 assert(prevEnd != value, "unnecessary set_end call");
569 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
570 "New end is below unallocated block");
571 _end = value;
572 if (prevEnd != NULL) {
573 // Resize the underlying block offset table.
574 _bt.resize(pointer_delta(value, bottom()));
575 if (value <= prevEnd) {
576 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
577 "New end is below unallocated block");
578 } else {
579 // Now, take this new chunk and add it to the free blocks.
580 // Note that the BOT has not yet been updated for this block.
581 size_t newFcSize = pointer_delta(value, prevEnd);
582 // Add the block to the free lists, if possible coalescing it
583 // with the last free block, and update the BOT and census data.
584 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
585 }
586 }
587 }
588
589 class FreeListSpaceDCTOC : public FilteringDCTOC {
590 CompactibleFreeListSpace* _cfls;
591 CMSCollector* _collector;
592 bool _parallel;
593 protected:
594 // Override.
595 #define walk_mem_region_with_cl_DECL(ClosureType) \
596 virtual void walk_mem_region_with_cl(MemRegion mr, \
597 HeapWord* bottom, HeapWord* top, \
598 ClosureType* cl); \
599 void walk_mem_region_with_cl_par(MemRegion mr, \
600 HeapWord* bottom, HeapWord* top, \
601 ClosureType* cl); \
602 void walk_mem_region_with_cl_nopar(MemRegion mr, \
603 HeapWord* bottom, HeapWord* top, \
604 ClosureType* cl)
605 walk_mem_region_with_cl_DECL(ExtendedOopClosure);
606 walk_mem_region_with_cl_DECL(FilteringClosure);
607
608 public:
609 FreeListSpaceDCTOC(CompactibleFreeListSpace* sp,
610 CMSCollector* collector,
611 ExtendedOopClosure* cl,
612 CardTable::PrecisionStyle precision,
613 HeapWord* boundary,
614 bool parallel) :
615 FilteringDCTOC(sp, cl, precision, boundary),
616 _cfls(sp), _collector(collector), _parallel(parallel) {}
617 };
618
619 // We de-virtualize the block-related calls below, since we know that our
620 // space is a CompactibleFreeListSpace.
621
622 #define FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
623 void FreeListSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr, \
624 HeapWord* bottom, \
625 HeapWord* top, \
626 ClosureType* cl) { \
627 if (_parallel) { \
628 walk_mem_region_with_cl_par(mr, bottom, top, cl); \
629 } else { \
630 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
631 } \
632 } \
633 void FreeListSpaceDCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
634 HeapWord* bottom, \
635 HeapWord* top, \
636 ClosureType* cl) { \
637 /* Skip parts that are before "mr", in case "block_start" sent us \
638 back too far. */ \
639 HeapWord* mr_start = mr.start(); \
640 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
641 HeapWord* next = bottom + bot_size; \
642 while (next < mr_start) { \
643 bottom = next; \
644 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
645 next = bottom + bot_size; \
646 } \
647 \
648 while (bottom < top) { \
649 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
650 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
651 oop(bottom)) && \
652 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
653 size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
654 bottom += _cfls->adjustObjectSize(word_sz); \
655 } else { \
656 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
657 } \
658 } \
659 } \
660 void FreeListSpaceDCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
661 HeapWord* bottom, \
662 HeapWord* top, \
663 ClosureType* cl) { \
664 /* Skip parts that are before "mr", in case "block_start" sent us \
665 back too far. */ \
666 HeapWord* mr_start = mr.start(); \
667 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
668 HeapWord* next = bottom + bot_size; \
669 while (next < mr_start) { \
670 bottom = next; \
671 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
672 next = bottom + bot_size; \
673 } \
674 \
675 while (bottom < top) { \
676 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
677 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
678 oop(bottom)) && \
679 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
680 size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
681 bottom += _cfls->adjustObjectSize(word_sz); \
682 } else { \
683 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
684 } \
685 } \
686 }
687
688 // (There are only two of these, rather than N, because the split is due
689 // only to the introduction of the FilteringClosure, a local part of the
690 // impl of this abstraction.)
691 FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
692 FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
693
694 DirtyCardToOopClosure*
695 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl,
696 CardTable::PrecisionStyle precision,
697 HeapWord* boundary,
698 bool parallel) {
699 return new FreeListSpaceDCTOC(this, _collector, cl, precision, boundary, parallel);
700 }
701
702
703 // Note on locking for the space iteration functions:
704 // since the collector's iteration activities are concurrent with
705 // allocation activities by mutators, absent a suitable mutual exclusion
706 // mechanism the iterators may go awry. For instance a block being iterated
707 // may suddenly be allocated or divided up and part of it allocated and
708 // so on.
709
710 // Apply the given closure to each block in the space.
711 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
712 assert_lock_strong(freelistLock());
713 HeapWord *cur, *limit;
714 for (cur = bottom(), limit = end(); cur < limit;
715 cur += cl->do_blk_careful(cur));
716 }
717
718 // Apply the given closure to each block in the space.
719 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
720 assert_lock_strong(freelistLock());
721 HeapWord *cur, *limit;
722 for (cur = bottom(), limit = end(); cur < limit;
723 cur += cl->do_blk(cur));
724 }
725
726 // Apply the given closure to each oop in the space.
727 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) {
728 assert_lock_strong(freelistLock());
729 HeapWord *cur, *limit;
730 size_t curSize;
731 for (cur = bottom(), limit = end(); cur < limit;
732 cur += curSize) {
733 curSize = block_size(cur);
734 if (block_is_obj(cur)) {
735 oop(cur)->oop_iterate(cl);
736 }
737 }
738 }
739
740 // NOTE: In the following methods, in order to safely be able to
741 // apply the closure to an object, we need to be sure that the
742 // object has been initialized. We are guaranteed that an object
743 // is initialized if we are holding the Heap_lock with the
744 // world stopped.
745 void CompactibleFreeListSpace::verify_objects_initialized() const {
746 if (is_init_completed()) {
747 assert_locked_or_safepoint(Heap_lock);
748 if (Universe::is_fully_initialized()) {
749 guarantee(SafepointSynchronize::is_at_safepoint(),
750 "Required for objects to be initialized");
751 }
752 } // else make a concession at vm start-up
753 }
754
755 // Apply the given closure to each object in the space
756 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
757 assert_lock_strong(freelistLock());
758 NOT_PRODUCT(verify_objects_initialized());
759 HeapWord *cur, *limit;
760 size_t curSize;
761 for (cur = bottom(), limit = end(); cur < limit;
762 cur += curSize) {
763 curSize = block_size(cur);
764 if (block_is_obj(cur)) {
765 blk->do_object(oop(cur));
766 }
767 }
768 }
769
770 // Apply the given closure to each live object in the space
771 // The usage of CompactibleFreeListSpace
772 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
773 // objects in the space with references to objects that are no longer
774 // valid. For example, an object may reference another object
775 // that has already been sweep up (collected). This method uses
776 // obj_is_alive() to determine whether it is safe to apply the closure to
777 // an object. See obj_is_alive() for details on how liveness of an
778 // object is decided.
779
780 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
781 assert_lock_strong(freelistLock());
782 NOT_PRODUCT(verify_objects_initialized());
783 HeapWord *cur, *limit;
784 size_t curSize;
785 for (cur = bottom(), limit = end(); cur < limit;
786 cur += curSize) {
787 curSize = block_size(cur);
788 if (block_is_obj(cur) && obj_is_alive(cur)) {
789 blk->do_object(oop(cur));
790 }
791 }
792 }
793
794 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
795 UpwardsObjectClosure* cl) {
796 assert_locked(freelistLock());
797 NOT_PRODUCT(verify_objects_initialized());
798 assert(!mr.is_empty(), "Should be non-empty");
799 // We use MemRegion(bottom(), end()) rather than used_region() below
800 // because the two are not necessarily equal for some kinds of
801 // spaces, in particular, certain kinds of free list spaces.
802 // We could use the more complicated but more precise:
803 // MemRegion(used_region().start(), align_up(used_region().end(), CardSize))
804 // but the slight imprecision seems acceptable in the assertion check.
805 assert(MemRegion(bottom(), end()).contains(mr),
806 "Should be within used space");
807 HeapWord* prev = cl->previous(); // max address from last time
808 if (prev >= mr.end()) { // nothing to do
809 return;
810 }
811 // This assert will not work when we go from cms space to perm
812 // space, and use same closure. Easy fix deferred for later. XXX YSR
813 // assert(prev == NULL || contains(prev), "Should be within space");
814
815 bool last_was_obj_array = false;
816 HeapWord *blk_start_addr, *region_start_addr;
817 if (prev > mr.start()) {
818 region_start_addr = prev;
819 blk_start_addr = prev;
820 // The previous invocation may have pushed "prev" beyond the
821 // last allocated block yet there may be still be blocks
822 // in this region due to a particular coalescing policy.
823 // Relax the assertion so that the case where the unallocated
824 // block is maintained and "prev" is beyond the unallocated
825 // block does not cause the assertion to fire.
826 assert((BlockOffsetArrayUseUnallocatedBlock &&
827 (!is_in(prev))) ||
828 (blk_start_addr == block_start(region_start_addr)), "invariant");
829 } else {
830 region_start_addr = mr.start();
831 blk_start_addr = block_start(region_start_addr);
832 }
833 HeapWord* region_end_addr = mr.end();
834 MemRegion derived_mr(region_start_addr, region_end_addr);
835 while (blk_start_addr < region_end_addr) {
836 const size_t size = block_size(blk_start_addr);
837 if (block_is_obj(blk_start_addr)) {
838 last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);
839 } else {
840 last_was_obj_array = false;
841 }
842 blk_start_addr += size;
843 }
844 if (!last_was_obj_array) {
845 assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),
846 "Should be within (closed) used space");
847 assert(blk_start_addr > prev, "Invariant");
848 cl->set_previous(blk_start_addr); // min address for next time
849 }
850 }
851
852 // Callers of this iterator beware: The closure application should
853 // be robust in the face of uninitialized objects and should (always)
854 // return a correct size so that the next addr + size below gives us a
855 // valid block boundary. [See for instance,
856 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
857 // in ConcurrentMarkSweepGeneration.cpp.]
858 HeapWord*
859 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
860 ObjectClosureCareful* cl) {
861 assert_lock_strong(freelistLock());
862 // Can't use used_region() below because it may not necessarily
863 // be the same as [bottom(),end()); although we could
864 // use [used_region().start(),align_up(used_region().end(),CardSize)),
865 // that appears too cumbersome, so we just do the simpler check
866 // in the assertion below.
867 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
868 "mr should be non-empty and within used space");
869 HeapWord *addr, *end;
870 size_t size;
871 for (addr = block_start_careful(mr.start()), end = mr.end();
872 addr < end; addr += size) {
873 FreeChunk* fc = (FreeChunk*)addr;
874 if (fc->is_free()) {
875 // Since we hold the free list lock, which protects direct
876 // allocation in this generation by mutators, a free object
877 // will remain free throughout this iteration code.
878 size = fc->size();
879 } else {
880 // Note that the object need not necessarily be initialized,
881 // because (for instance) the free list lock does NOT protect
882 // object initialization. The closure application below must
883 // therefore be correct in the face of uninitialized objects.
884 size = cl->do_object_careful_m(oop(addr), mr);
885 if (size == 0) {
886 // An unparsable object found. Signal early termination.
887 return addr;
888 }
889 }
890 }
891 return NULL;
892 }
893
894
895 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
896 NOT_PRODUCT(verify_objects_initialized());
897 return _bt.block_start(p);
898 }
899
900 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
901 return _bt.block_start_careful(p);
902 }
903
904 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
905 NOT_PRODUCT(verify_objects_initialized());
906 // This must be volatile, or else there is a danger that the compiler
907 // will compile the code below into a sometimes-infinite loop, by keeping
908 // the value read the first time in a register.
909 while (true) {
910 // We must do this until we get a consistent view of the object.
911 if (FreeChunk::indicatesFreeChunk(p)) {
912 volatile FreeChunk* fc = (volatile FreeChunk*)p;
913 size_t res = fc->size();
914
915 // Bugfix for systems with weak memory model (PPC64/IA64). The
916 // block's free bit was set and we have read the size of the
917 // block. Acquire and check the free bit again. If the block is
918 // still free, the read size is correct.
919 OrderAccess::acquire();
920
921 // If the object is still a free chunk, return the size, else it
922 // has been allocated so try again.
923 if (FreeChunk::indicatesFreeChunk(p)) {
924 assert(res != 0, "Block size should not be 0");
925 return res;
926 }
927 } else {
928 // Ensure klass read before size.
929 Klass* k = oop(p)->klass_or_null_acquire();
930 if (k != NULL) {
931 assert(k->is_klass(), "Should really be klass oop.");
932 oop o = (oop)p;
933 assert(oopDesc::is_oop(o, true /* ignore mark word */), "Should be an oop.");
934
935 size_t res = o->size_given_klass(k);
936 res = adjustObjectSize(res);
937 assert(res != 0, "Block size should not be 0");
938 return res;
939 }
940 }
941 }
942 }
943
944 // TODO: Now that is_parsable is gone, we should combine these two functions.
945 // A variant of the above that uses the Printezis bits for
946 // unparsable but allocated objects. This avoids any possible
947 // stalls waiting for mutators to initialize objects, and is
948 // thus potentially faster than the variant above. However,
949 // this variant may return a zero size for a block that is
950 // under mutation and for which a consistent size cannot be
951 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
952 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
953 const CMSCollector* c)
954 const {
955 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
956 // This must be volatile, or else there is a danger that the compiler
957 // will compile the code below into a sometimes-infinite loop, by keeping
958 // the value read the first time in a register.
959 DEBUG_ONLY(uint loops = 0;)
960 while (true) {
961 // We must do this until we get a consistent view of the object.
962 if (FreeChunk::indicatesFreeChunk(p)) {
963 volatile FreeChunk* fc = (volatile FreeChunk*)p;
964 size_t res = fc->size();
965
966 // Bugfix for systems with weak memory model (PPC64/IA64). The
967 // free bit of the block was set and we have read the size of
968 // the block. Acquire and check the free bit again. If the
969 // block is still free, the read size is correct.
970 OrderAccess::acquire();
971
972 if (FreeChunk::indicatesFreeChunk(p)) {
973 assert(res != 0, "Block size should not be 0");
974 assert(loops == 0, "Should be 0");
975 return res;
976 }
977 } else {
978 // Ensure klass read before size.
979 Klass* k = oop(p)->klass_or_null_acquire();
980 if (k != NULL) {
981 assert(k->is_klass(), "Should really be klass oop.");
982 oop o = (oop)p;
983 assert(oopDesc::is_oop(o), "Should be an oop");
984
985 size_t res = o->size_given_klass(k);
986 res = adjustObjectSize(res);
987 assert(res != 0, "Block size should not be 0");
988 return res;
989 } else {
990 // May return 0 if P-bits not present.
991 return c->block_size_if_printezis_bits(p);
992 }
993 }
994 assert(loops == 0, "Can loop at most once");
995 DEBUG_ONLY(loops++;)
996 }
997 }
998
999 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
1000 NOT_PRODUCT(verify_objects_initialized());
1001 assert(MemRegion(bottom(), end()).contains(p), "p not in space");
1002 FreeChunk* fc = (FreeChunk*)p;
1003 if (fc->is_free()) {
1004 return fc->size();
1005 } else {
1006 // Ignore mark word because this may be a recently promoted
1007 // object whose mark word is used to chain together grey
1008 // objects (the last one would have a null value).
1009 assert(oopDesc::is_oop(oop(p), true), "Should be an oop");
1010 return adjustObjectSize(oop(p)->size());
1011 }
1012 }
1013
1014 // This implementation assumes that the property of "being an object" is
1015 // stable. But being a free chunk may not be (because of parallel
1016 // promotion.)
1017 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
1018 FreeChunk* fc = (FreeChunk*)p;
1019 assert(is_in_reserved(p), "Should be in space");
1020 if (FreeChunk::indicatesFreeChunk(p)) return false;
1021 Klass* k = oop(p)->klass_or_null_acquire();
1022 if (k != NULL) {
1023 // Ignore mark word because it may have been used to
1024 // chain together promoted objects (the last one
1025 // would have a null value).
1026 assert(oopDesc::is_oop(oop(p), true), "Should be an oop");
1027 return true;
1028 } else {
1029 return false; // Was not an object at the start of collection.
1030 }
1031 }
1032
1033 // Check if the object is alive. This fact is checked either by consulting
1034 // the main marking bitmap in the sweeping phase or, if it's a permanent
1035 // generation and we're not in the sweeping phase, by checking the
1036 // perm_gen_verify_bit_map where we store the "deadness" information if
1037 // we did not sweep the perm gen in the most recent previous GC cycle.
1038 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
1039 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
1040 "Else races are possible");
1041 assert(block_is_obj(p), "The address should point to an object");
1042
1043 // If we're sweeping, we use object liveness information from the main bit map
1044 // for both perm gen and old gen.
1045 // We don't need to lock the bitmap (live_map or dead_map below), because
1046 // EITHER we are in the middle of the sweeping phase, and the
1047 // main marking bit map (live_map below) is locked,
1048 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
1049 // is stable, because it's mutated only in the sweeping phase.
1050 // NOTE: This method is also used by jmap where, if class unloading is
1051 // off, the results can return "false" for legitimate perm objects,
1052 // when we are not in the midst of a sweeping phase, which can result
1053 // in jmap not reporting certain perm gen objects. This will be moot
1054 // if/when the perm gen goes away in the future.
1055 if (_collector->abstract_state() == CMSCollector::Sweeping) {
1056 CMSBitMap* live_map = _collector->markBitMap();
1057 return live_map->par_isMarked((HeapWord*) p);
1058 }
1059 return true;
1060 }
1061
1062 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
1063 FreeChunk* fc = (FreeChunk*)p;
1064 assert(is_in_reserved(p), "Should be in space");
1065 assert(_bt.block_start(p) == p, "Should be a block boundary");
1066 if (!fc->is_free()) {
1067 // Ignore mark word because it may have been used to
1068 // chain together promoted objects (the last one
1069 // would have a null value).
1070 assert(oopDesc::is_oop(oop(p), true), "Should be an oop");
1071 return true;
1072 }
1073 return false;
1074 }
1075
1076 // "MT-safe but not guaranteed MT-precise" (TM); you may get an
1077 // approximate answer if you don't hold the freelistlock when you call this.
1078 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
1079 size_t size = 0;
1080 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
1081 debug_only(
1082 // We may be calling here without the lock in which case we
1083 // won't do this modest sanity check.
1084 if (freelistLock()->owned_by_self()) {
1085 size_t total_list_size = 0;
1086 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
1087 fc = fc->next()) {
1088 total_list_size += i;
1089 }
1090 assert(total_list_size == i * _indexedFreeList[i].count(),
1091 "Count in list is incorrect");
1092 }
1093 )
1094 size += i * _indexedFreeList[i].count();
1095 }
1096 return size;
1097 }
1098
1099 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
1100 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
1101 return allocate(size);
1102 }
1103
1104 HeapWord*
1105 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
1106 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
1107 }
1108
1109 HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
1110 assert_lock_strong(freelistLock());
1111 HeapWord* res = NULL;
1112 assert(size == adjustObjectSize(size),
1113 "use adjustObjectSize() before calling into allocate()");
1114
1115 res = allocate_adaptive_freelists(size);
1116
1117 if (res != NULL) {
1118 // check that res does lie in this space!
1119 assert(is_in_reserved(res), "Not in this space!");
1120 assert(is_aligned((void*)res), "alignment check");
1121
1122 FreeChunk* fc = (FreeChunk*)res;
1123 fc->markNotFree();
1124 assert(!fc->is_free(), "shouldn't be marked free");
1125 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
1126 // Verify that the block offset table shows this to
1127 // be a single block, but not one which is unallocated.
1128 _bt.verify_single_block(res, size);
1129 _bt.verify_not_unallocated(res, size);
1130 // mangle a just allocated object with a distinct pattern.
1131 debug_only(fc->mangleAllocated(size));
1132 }
1133
1134 return res;
1135 }
1136
1137 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
1138 assert_lock_strong(freelistLock());
1139 HeapWord* res = NULL;
1140 assert(size == adjustObjectSize(size),
1141 "use adjustObjectSize() before calling into allocate()");
1142
1143 // Strategy
1144 // if small
1145 // exact size from small object indexed list if small
1146 // small or large linear allocation block (linAB) as appropriate
1147 // take from lists of greater sized chunks
1148 // else
1149 // dictionary
1150 // small or large linear allocation block if it has the space
1151 // Try allocating exact size from indexTable first
1152 if (size < IndexSetSize) {
1153 res = (HeapWord*) getChunkFromIndexedFreeList(size);
1154 if(res != NULL) {
1155 assert(res != (HeapWord*)_indexedFreeList[size].head(),
1156 "Not removed from free list");
1157 // no block offset table adjustment is necessary on blocks in
1158 // the indexed lists.
1159
1160 // Try allocating from the small LinAB
1161 } else if (size < _smallLinearAllocBlock._allocation_size_limit &&
1162 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
1163 // if successful, the above also adjusts block offset table
1164 // Note that this call will refill the LinAB to
1165 // satisfy the request. This is different that
1166 // evm.
1167 // Don't record chunk off a LinAB? smallSplitBirth(size);
1168 } else {
1169 // Raid the exact free lists larger than size, even if they are not
1170 // overpopulated.
1171 res = (HeapWord*) getChunkFromGreater(size);
1172 }
1173 } else {
1174 // Big objects get allocated directly from the dictionary.
1175 res = (HeapWord*) getChunkFromDictionaryExact(size);
1176 if (res == NULL) {
1177 // Try hard not to fail since an allocation failure will likely
1178 // trigger a synchronous GC. Try to get the space from the
1179 // allocation blocks.
1180 res = getChunkFromSmallLinearAllocBlockRemainder(size);
1181 }
1182 }
1183
1184 return res;
1185 }
1186
1187 // A worst-case estimate of the space required (in HeapWords) to expand the heap
1188 // when promoting obj.
1189 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
1190 // Depending on the object size, expansion may require refilling either a
1191 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
1192 // is added because the dictionary may over-allocate to avoid fragmentation.
1193 size_t space = obj_size;
1194 space += _promoInfo.refillSize() + 2 * MinChunkSize;
1195 return space;
1196 }
1197
1198 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
1199 FreeChunk* ret;
1200
1201 assert(numWords >= MinChunkSize, "Size is less than minimum");
1202 assert(linearAllocationWouldFail() || bestFitFirst(),
1203 "Should not be here");
1204
1205 size_t i;
1206 size_t currSize = numWords + MinChunkSize;
1207 assert(is_object_aligned(currSize), "currSize should be aligned");
1208 for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
1209 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
1210 if (fl->head()) {
1211 ret = getFromListGreater(fl, numWords);
1212 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1213 return ret;
1214 }
1215 }
1216
1217 currSize = MAX2((size_t)SmallForDictionary,
1218 (size_t)(numWords + MinChunkSize));
1219
1220 /* Try to get a chunk that satisfies request, while avoiding
1221 fragmentation that can't be handled. */
1222 {
1223 ret = dictionary()->get_chunk(currSize);
1224 if (ret != NULL) {
1225 assert(ret->size() - numWords >= MinChunkSize,
1226 "Chunk is too small");
1227 _bt.allocated((HeapWord*)ret, ret->size());
1228 /* Carve returned chunk. */
1229 (void) splitChunkAndReturnRemainder(ret, numWords);
1230 /* Label this as no longer a free chunk. */
1231 assert(ret->is_free(), "This chunk should be free");
1232 ret->link_prev(NULL);
1233 }
1234 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
1235 return ret;
1236 }
1237 ShouldNotReachHere();
1238 }
1239
1240 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
1241 assert(fc->size() < IndexSetSize, "Size of chunk is too large");
1242 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
1243 }
1244
1245 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
1246 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
1247 (_smallLinearAllocBlock._word_size == fc->size()),
1248 "Linear allocation block shows incorrect size");
1249 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
1250 (_smallLinearAllocBlock._word_size == fc->size()));
1251 }
1252
1253 // Check if the purported free chunk is present either as a linear
1254 // allocation block, the size-indexed table of (smaller) free blocks,
1255 // or the larger free blocks kept in the binary tree dictionary.
1256 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
1257 if (verify_chunk_is_linear_alloc_block(fc)) {
1258 return true;
1259 } else if (fc->size() < IndexSetSize) {
1260 return verifyChunkInIndexedFreeLists(fc);
1261 } else {
1262 return dictionary()->verify_chunk_in_free_list(fc);
1263 }
1264 }
1265
1266 #ifndef PRODUCT
1267 void CompactibleFreeListSpace::assert_locked() const {
1268 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
1269 }
1270
1271 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
1272 CMSLockVerifier::assert_locked(lock);
1273 }
1274 #endif
1275
1276 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
1277 // In the parallel case, the main thread holds the free list lock
1278 // on behalf the parallel threads.
1279 FreeChunk* fc;
1280 {
1281 // If GC is parallel, this might be called by several threads.
1282 // This should be rare enough that the locking overhead won't affect
1283 // the sequential code.
1284 MutexLockerEx x(parDictionaryAllocLock(),
1285 Mutex::_no_safepoint_check_flag);
1286 fc = getChunkFromDictionary(size);
1287 }
1288 if (fc != NULL) {
1289 fc->dontCoalesce();
1290 assert(fc->is_free(), "Should be free, but not coalescable");
1291 // Verify that the block offset table shows this to
1292 // be a single block, but not one which is unallocated.
1293 _bt.verify_single_block((HeapWord*)fc, fc->size());
1294 _bt.verify_not_unallocated((HeapWord*)fc, fc->size());
1295 }
1296 return fc;
1297 }
1298
1299 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
1300 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1301 assert_locked();
1302
1303 // if we are tracking promotions, then first ensure space for
1304 // promotion (including spooling space for saving header if necessary).
1305 // then allocate and copy, then track promoted info if needed.
1306 // When tracking (see PromotionInfo::track()), the mark word may
1307 // be displaced and in this case restoration of the mark word
1308 // occurs in the (oop_since_save_marks_)iterate phase.
1309 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
1310 return NULL;
1311 }
1312 // Call the allocate(size_t, bool) form directly to avoid the
1313 // additional call through the allocate(size_t) form. Having
1314 // the compile inline the call is problematic because allocate(size_t)
1315 // is a virtual method.
1316 HeapWord* res = allocate(adjustObjectSize(obj_size));
1317 if (res != NULL) {
1318 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
1319 // if we should be tracking promotions, do so.
1320 if (_promoInfo.tracking()) {
1321 _promoInfo.track((PromotedObject*)res);
1322 }
1323 }
1324 return oop(res);
1325 }
1326
1327 HeapWord*
1328 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
1329 assert_locked();
1330 assert(size >= MinChunkSize, "minimum chunk size");
1331 assert(size < _smallLinearAllocBlock._allocation_size_limit,
1332 "maximum from smallLinearAllocBlock");
1333 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
1334 }
1335
1336 HeapWord*
1337 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
1338 size_t size) {
1339 assert_locked();
1340 assert(size >= MinChunkSize, "too small");
1341 HeapWord* res = NULL;
1342 // Try to do linear allocation from blk, making sure that
1343 if (blk->_word_size == 0) {
1344 // We have probably been unable to fill this either in the prologue or
1345 // when it was exhausted at the last linear allocation. Bail out until
1346 // next time.
1347 assert(blk->_ptr == NULL, "consistency check");
1348 return NULL;
1349 }
1350 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
1351 res = getChunkFromLinearAllocBlockRemainder(blk, size);
1352 if (res != NULL) return res;
1353
1354 // about to exhaust this linear allocation block
1355 if (blk->_word_size == size) { // exactly satisfied
1356 res = blk->_ptr;
1357 _bt.allocated(res, blk->_word_size);
1358 } else if (size + MinChunkSize <= blk->_refillSize) {
1359 size_t sz = blk->_word_size;
1360 // Update _unallocated_block if the size is such that chunk would be
1361 // returned to the indexed free list. All other chunks in the indexed
1362 // free lists are allocated from the dictionary so that _unallocated_block
1363 // has already been adjusted for them. Do it here so that the cost
1364 // for all chunks added back to the indexed free lists.
1365 if (sz < SmallForDictionary) {
1366 _bt.allocated(blk->_ptr, sz);
1367 }
1368 // Return the chunk that isn't big enough, and then refill below.
1369 addChunkToFreeLists(blk->_ptr, sz);
1370 split_birth(sz);
1371 // Don't keep statistics on adding back chunk from a LinAB.
1372 } else {
1373 // A refilled block would not satisfy the request.
1374 return NULL;
1375 }
1376
1377 blk->_ptr = NULL; blk->_word_size = 0;
1378 refillLinearAllocBlock(blk);
1379 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
1380 "block was replenished");
1381 if (res != NULL) {
1382 split_birth(size);
1383 repairLinearAllocBlock(blk);
1384 } else if (blk->_ptr != NULL) {
1385 res = blk->_ptr;
1386 size_t blk_size = blk->_word_size;
1387 blk->_word_size -= size;
1388 blk->_ptr += size;
1389 split_birth(size);
1390 repairLinearAllocBlock(blk);
1391 // Update BOT last so that other (parallel) GC threads see a consistent
1392 // view of the BOT and free blocks.
1393 // Above must occur before BOT is updated below.
1394 OrderAccess::storestore();
1395 _bt.split_block(res, blk_size, size); // adjust block offset table
1396 }
1397 return res;
1398 }
1399
1400 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
1401 LinearAllocBlock* blk,
1402 size_t size) {
1403 assert_locked();
1404 assert(size >= MinChunkSize, "too small");
1405
1406 HeapWord* res = NULL;
1407 // This is the common case. Keep it simple.
1408 if (blk->_word_size >= size + MinChunkSize) {
1409 assert(blk->_ptr != NULL, "consistency check");
1410 res = blk->_ptr;
1411 // Note that the BOT is up-to-date for the linAB before allocation. It
1412 // indicates the start of the linAB. The split_block() updates the
1413 // BOT for the linAB after the allocation (indicates the start of the
1414 // next chunk to be allocated).
1415 size_t blk_size = blk->_word_size;
1416 blk->_word_size -= size;
1417 blk->_ptr += size;
1418 split_birth(size);
1419 repairLinearAllocBlock(blk);
1420 // Update BOT last so that other (parallel) GC threads see a consistent
1421 // view of the BOT and free blocks.
1422 // Above must occur before BOT is updated below.
1423 OrderAccess::storestore();
1424 _bt.split_block(res, blk_size, size); // adjust block offset table
1425 _bt.allocated(res, size);
1426 }
1427 return res;
1428 }
1429
1430 FreeChunk*
1431 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
1432 assert_locked();
1433 assert(size < SmallForDictionary, "just checking");
1434 FreeChunk* res;
1435 res = _indexedFreeList[size].get_chunk_at_head();
1436 if (res == NULL) {
1437 res = getChunkFromIndexedFreeListHelper(size);
1438 }
1439 _bt.verify_not_unallocated((HeapWord*) res, size);
1440 assert(res == NULL || res->size() == size, "Incorrect block size");
1441 return res;
1442 }
1443
1444 FreeChunk*
1445 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
1446 bool replenish) {
1447 assert_locked();
1448 FreeChunk* fc = NULL;
1449 if (size < SmallForDictionary) {
1450 assert(_indexedFreeList[size].head() == NULL ||
1451 _indexedFreeList[size].surplus() <= 0,
1452 "List for this size should be empty or under populated");
1453 // Try best fit in exact lists before replenishing the list
1454 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
1455 // Replenish list.
1456 //
1457 // Things tried that failed.
1458 // Tried allocating out of the two LinAB's first before
1459 // replenishing lists.
1460 // Tried small linAB of size 256 (size in indexed list)
1461 // and replenishing indexed lists from the small linAB.
1462 //
1463 FreeChunk* newFc = NULL;
1464 const size_t replenish_size = CMSIndexedFreeListReplenish * size;
1465 if (replenish_size < SmallForDictionary) {
1466 // Do not replenish from an underpopulated size.
1467 if (_indexedFreeList[replenish_size].surplus() > 0 &&
1468 _indexedFreeList[replenish_size].head() != NULL) {
1469 newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
1470 } else if (bestFitFirst()) {
1471 newFc = bestFitSmall(replenish_size);
1472 }
1473 }
1474 if (newFc == NULL && replenish_size > size) {
1475 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
1476 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
1477 }
1478 // Note: The stats update re split-death of block obtained above
1479 // will be recorded below precisely when we know we are going to
1480 // be actually splitting it into more than one pieces below.
1481 if (newFc != NULL) {
1482 if (replenish || CMSReplenishIntermediate) {
1483 // Replenish this list and return one block to caller.
1484 size_t i;
1485 FreeChunk *curFc, *nextFc;
1486 size_t num_blk = newFc->size() / size;
1487 assert(num_blk >= 1, "Smaller than requested?");
1488 assert(newFc->size() % size == 0, "Should be integral multiple of request");
1489 if (num_blk > 1) {
1490 // we are sure we will be splitting the block just obtained
1491 // into multiple pieces; record the split-death of the original
1492 splitDeath(replenish_size);
1493 }
1494 // carve up and link blocks 0, ..., num_blk - 2
1495 // The last chunk is not added to the lists but is returned as the
1496 // free chunk.
1497 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
1498 i = 0;
1499 i < (num_blk - 1);
1500 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
1501 i++) {
1502 curFc->set_size(size);
1503 // Don't record this as a return in order to try and
1504 // determine the "returns" from a GC.
1505 _bt.verify_not_unallocated((HeapWord*) fc, size);
1506 _indexedFreeList[size].return_chunk_at_tail(curFc, false);
1507 _bt.mark_block((HeapWord*)curFc, size);
1508 split_birth(size);
1509 // Don't record the initial population of the indexed list
1510 // as a split birth.
1511 }
1512
1513 // check that the arithmetic was OK above
1514 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
1515 "inconsistency in carving newFc");
1516 curFc->set_size(size);
1517 _bt.mark_block((HeapWord*)curFc, size);
1518 split_birth(size);
1519 fc = curFc;
1520 } else {
1521 // Return entire block to caller
1522 fc = newFc;
1523 }
1524 }
1525 }
1526 } else {
1527 // Get a free chunk from the free chunk dictionary to be returned to
1528 // replenish the indexed free list.
1529 fc = getChunkFromDictionaryExact(size);
1530 }
1531 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
1532 return fc;
1533 }
1534
1535 FreeChunk*
1536 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
1537 assert_locked();
1538 FreeChunk* fc = _dictionary->get_chunk(size);
1539 if (fc == NULL) {
1540 return NULL;
1541 }
1542 _bt.allocated((HeapWord*)fc, fc->size());
1543 if (fc->size() >= size + MinChunkSize) {
1544 fc = splitChunkAndReturnRemainder(fc, size);
1545 }
1546 assert(fc->size() >= size, "chunk too small");
1547 assert(fc->size() < size + MinChunkSize, "chunk too big");
1548 _bt.verify_single_block((HeapWord*)fc, fc->size());
1549 return fc;
1550 }
1551
1552 FreeChunk*
1553 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
1554 assert_locked();
1555 FreeChunk* fc = _dictionary->get_chunk(size);
1556 if (fc == NULL) {
1557 return fc;
1558 }
1559 _bt.allocated((HeapWord*)fc, fc->size());
1560 if (fc->size() == size) {
1561 _bt.verify_single_block((HeapWord*)fc, size);
1562 return fc;
1563 }
1564 assert(fc->size() > size, "get_chunk() guarantee");
1565 if (fc->size() < size + MinChunkSize) {
1566 // Return the chunk to the dictionary and go get a bigger one.
1567 returnChunkToDictionary(fc);
1568 fc = _dictionary->get_chunk(size + MinChunkSize);
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(is_object_aligned(hint), "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(oopDesc::is_oop(p), "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 LogStream ls(log.error());
2200 _sp->print_on(&ls);
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(oopDesc::is_oop(obj), "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(oopDesc::is_oop(obj), "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 CMSHeap::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 LogStream ls(log);
2375 outputStream* out = &ls;
2376 AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
2377 size_t total_free = 0;
2378 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
2379 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
2380 total_free += fl->count() * fl->size();
2381 if (i % (40*IndexSetStride) == 0) {
2382 AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
2383 }
2384 fl->print_on(out);
2385 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
2386 total.set_surplus( total.surplus() + fl->surplus() );
2387 total.set_desired( total.desired() + fl->desired() );
2388 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
2389 total.set_before_sweep(total.before_sweep() + fl->before_sweep());
2390 total.set_count( total.count() + fl->count() );
2391 total.set_coal_births( total.coal_births() + fl->coal_births() );
2392 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
2393 total.set_split_births(total.split_births() + fl->split_births());
2394 total.set_split_deaths(total.split_deaths() + fl->split_deaths());
2395 }
2396 total.print_on(out, "TOTAL");
2397 log.print("Total free in indexed lists " SIZE_FORMAT " words", total_free);
2398 log.print("growth: %8.5f deficit: %8.5f",
2399 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
2400 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
2401 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
2402 _dictionary->print_dict_census(out);
2403 }
2404
2405 ///////////////////////////////////////////////////////////////////////////
2406 // CompactibleFreeListSpaceLAB
2407 ///////////////////////////////////////////////////////////////////////////
2408
2409 #define VECTOR_257(x) \
2410 /* 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 */ \
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, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
2419 x }
2420
2421 // Initialize with default setting for CMS, _not_
2422 // generic OldPLABSize, whose static default is different; if overridden at the
2423 // command-line, this will get reinitialized via a call to
2424 // modify_initialization() below.
2425 AdaptiveWeightedAverage CompactibleFreeListSpaceLAB::_blocks_to_claim[] =
2426 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CompactibleFreeListSpaceLAB::_default_dynamic_old_plab_size));
2427 size_t CompactibleFreeListSpaceLAB::_global_num_blocks[] = VECTOR_257(0);
2428 uint CompactibleFreeListSpaceLAB::_global_num_workers[] = VECTOR_257(0);
2429
2430 CompactibleFreeListSpaceLAB::CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls) :
2431 _cfls(cfls)
2432 {
2433 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
2434 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2435 i < CompactibleFreeListSpace::IndexSetSize;
2436 i += CompactibleFreeListSpace::IndexSetStride) {
2437 _indexedFreeList[i].set_size(i);
2438 _num_blocks[i] = 0;
2439 }
2440 }
2441
2442 static bool _CFLS_LAB_modified = false;
2443
2444 void CompactibleFreeListSpaceLAB::modify_initialization(size_t n, unsigned wt) {
2445 assert(!_CFLS_LAB_modified, "Call only once");
2446 _CFLS_LAB_modified = true;
2447 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2448 i < CompactibleFreeListSpace::IndexSetSize;
2449 i += CompactibleFreeListSpace::IndexSetStride) {
2450 _blocks_to_claim[i].modify(n, wt, true /* force */);
2451 }
2452 }
2453
2454 HeapWord* CompactibleFreeListSpaceLAB::alloc(size_t word_sz) {
2455 FreeChunk* res;
2456 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
2457 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
2458 // This locking manages sync with other large object allocations.
2459 MutexLockerEx x(_cfls->parDictionaryAllocLock(),
2460 Mutex::_no_safepoint_check_flag);
2461 res = _cfls->getChunkFromDictionaryExact(word_sz);
2462 if (res == NULL) return NULL;
2463 } else {
2464 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
2465 if (fl->count() == 0) {
2466 // Attempt to refill this local free list.
2467 get_from_global_pool(word_sz, fl);
2468 // If it didn't work, give up.
2469 if (fl->count() == 0) return NULL;
2470 }
2471 res = fl->get_chunk_at_head();
2472 assert(res != NULL, "Why was count non-zero?");
2473 }
2474 res->markNotFree();
2475 assert(!res->is_free(), "shouldn't be marked free");
2476 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
2477 // mangle a just allocated object with a distinct pattern.
2478 debug_only(res->mangleAllocated(word_sz));
2479 return (HeapWord*)res;
2480 }
2481
2482 // Get a chunk of blocks of the right size and update related
2483 // book-keeping stats
2484 void CompactibleFreeListSpaceLAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
2485 // Get the #blocks we want to claim
2486 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
2487 assert(n_blks > 0, "Error");
2488 assert(ResizeOldPLAB || n_blks == OldPLABSize, "Error");
2489 // In some cases, when the application has a phase change,
2490 // there may be a sudden and sharp shift in the object survival
2491 // profile, and updating the counts at the end of a scavenge
2492 // may not be quick enough, giving rise to large scavenge pauses
2493 // during these phase changes. It is beneficial to detect such
2494 // changes on-the-fly during a scavenge and avoid such a phase-change
2495 // pothole. The following code is a heuristic attempt to do that.
2496 // It is protected by a product flag until we have gained
2497 // enough experience with this heuristic and fine-tuned its behavior.
2498 // WARNING: This might increase fragmentation if we overreact to
2499 // small spikes, so some kind of historical smoothing based on
2500 // previous experience with the greater reactivity might be useful.
2501 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
2502 // default.
2503 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
2504 //
2505 // On a 32-bit VM, the denominator can become zero because of integer overflow,
2506 // which is why there is a cast to double.
2507 //
2508 size_t multiple = (size_t) (_num_blocks[word_sz]/(((double)CMSOldPLABToleranceFactor)*CMSOldPLABNumRefills*n_blks));
2509 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
2510 n_blks = MIN2(n_blks, CMSOldPLABMax);
2511 }
2512 assert(n_blks > 0, "Error");
2513 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
2514 // Update stats table entry for this block size
2515 _num_blocks[word_sz] += fl->count();
2516 }
2517
2518 void CompactibleFreeListSpaceLAB::compute_desired_plab_size() {
2519 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2520 i < CompactibleFreeListSpace::IndexSetSize;
2521 i += CompactibleFreeListSpace::IndexSetStride) {
2522 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
2523 "Counter inconsistency");
2524 if (_global_num_workers[i] > 0) {
2525 // Need to smooth wrt historical average
2526 if (ResizeOldPLAB) {
2527 _blocks_to_claim[i].sample(
2528 MAX2(CMSOldPLABMin,
2529 MIN2(CMSOldPLABMax,
2530 _global_num_blocks[i]/_global_num_workers[i]/CMSOldPLABNumRefills)));
2531 }
2532 // Reset counters for next round
2533 _global_num_workers[i] = 0;
2534 _global_num_blocks[i] = 0;
2535 log_trace(gc, plab)("[" SIZE_FORMAT "]: " SIZE_FORMAT, i, (size_t)_blocks_to_claim[i].average());
2536 }
2537 }
2538 }
2539
2540 // If this is changed in the future to allow parallel
2541 // access, one would need to take the FL locks and,
2542 // depending on how it is used, stagger access from
2543 // parallel threads to reduce contention.
2544 void CompactibleFreeListSpaceLAB::retire(int tid) {
2545 // We run this single threaded with the world stopped;
2546 // so no need for locks and such.
2547 NOT_PRODUCT(Thread* t = Thread::current();)
2548 assert(Thread::current()->is_VM_thread(), "Error");
2549 for (size_t i = CompactibleFreeListSpace::IndexSetStart;
2550 i < CompactibleFreeListSpace::IndexSetSize;
2551 i += CompactibleFreeListSpace::IndexSetStride) {
2552 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
2553 "Can't retire more than what we obtained");
2554 if (_num_blocks[i] > 0) {
2555 size_t num_retire = _indexedFreeList[i].count();
2556 assert(_num_blocks[i] > num_retire, "Should have used at least one");
2557 {
2558 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i],
2559 // Mutex::_no_safepoint_check_flag);
2560
2561 // Update globals stats for num_blocks used
2562 _global_num_blocks[i] += (_num_blocks[i] - num_retire);
2563 _global_num_workers[i]++;
2564 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
2565 if (num_retire > 0) {
2566 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
2567 // Reset this list.
2568 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
2569 _indexedFreeList[i].set_size(i);
2570 }
2571 }
2572 log_trace(gc, plab)("%d[" SIZE_FORMAT "]: " SIZE_FORMAT "/" SIZE_FORMAT "/" SIZE_FORMAT,
2573 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
2574 // Reset stats for next round
2575 _num_blocks[i] = 0;
2576 }
2577 }
2578 }
2579
2580 // Used by par_get_chunk_of_blocks() for the chunks from the
2581 // indexed_free_lists. Looks for a chunk with size that is a multiple
2582 // of "word_sz" and if found, splits it into "word_sz" chunks and add
2583 // to the free list "fl". "n" is the maximum number of chunks to
2584 // be added to "fl".
2585 bool CompactibleFreeListSpace:: par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
2586
2587 // We'll try all multiples of word_sz in the indexed set, starting with
2588 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
2589 // then try getting a big chunk and splitting it.
2590 {
2591 bool found;
2592 int k;
2593 size_t cur_sz;
2594 for (k = 1, cur_sz = k * word_sz, found = false;
2595 (cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
2596 (CMSSplitIndexedFreeListBlocks || k <= 1);
2597 k++, cur_sz = k * word_sz) {
2598 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
2599 fl_for_cur_sz.set_size(cur_sz);
2600 {
2601 MutexLockerEx x(_indexedFreeListParLocks[cur_sz],
2602 Mutex::_no_safepoint_check_flag);
2603 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
2604 if (gfl->count() != 0) {
2605 // nn is the number of chunks of size cur_sz that
2606 // we'd need to split k-ways each, in order to create
2607 // "n" chunks of size word_sz each.
2608 const size_t nn = MAX2(n/k, (size_t)1);
2609 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
2610 found = true;
2611 if (k > 1) {
2612 // Update split death stats for the cur_sz-size blocks list:
2613 // we increment the split death count by the number of blocks
2614 // we just took from the cur_sz-size blocks list and which
2615 // we will be splitting below.
2616 ssize_t deaths = gfl->split_deaths() +
2617 fl_for_cur_sz.count();
2618 gfl->set_split_deaths(deaths);
2619 }
2620 }
2621 }
2622 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
2623 if (found) {
2624 if (k == 1) {
2625 fl->prepend(&fl_for_cur_sz);
2626 } else {
2627 // Divide each block on fl_for_cur_sz up k ways.
2628 FreeChunk* fc;
2629 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
2630 // Must do this in reverse order, so that anybody attempting to
2631 // access the main chunk sees it as a single free block until we
2632 // change it.
2633 size_t fc_size = fc->size();
2634 assert(fc->is_free(), "Error");
2635 for (int i = k-1; i >= 0; i--) {
2636 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
2637 assert((i != 0) ||
2638 ((fc == ffc) && ffc->is_free() &&
2639 (ffc->size() == k*word_sz) && (fc_size == word_sz)),
2640 "Counting error");
2641 ffc->set_size(word_sz);
2642 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
2643 ffc->link_next(NULL);
2644 // Above must occur before BOT is updated below.
2645 OrderAccess::storestore();
2646 // splitting from the right, fc_size == i * word_sz
2647 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
2648 fc_size -= word_sz;
2649 assert(fc_size == i*word_sz, "Error");
2650 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
2651 _bt.verify_single_block((HeapWord*)fc, fc_size);
2652 _bt.verify_single_block((HeapWord*)ffc, word_sz);
2653 // Push this on "fl".
2654 fl->return_chunk_at_head(ffc);
2655 }
2656 // TRAP
2657 assert(fl->tail()->next() == NULL, "List invariant.");
2658 }
2659 }
2660 // Update birth stats for this block size.
2661 size_t num = fl->count();
2662 MutexLockerEx x(_indexedFreeListParLocks[word_sz],
2663 Mutex::_no_safepoint_check_flag);
2664 ssize_t births = _indexedFreeList[word_sz].split_births() + num;
2665 _indexedFreeList[word_sz].set_split_births(births);
2666 return true;
2667 }
2668 }
2669 return found;
2670 }
2671 }
2672
2673 FreeChunk* CompactibleFreeListSpace::get_n_way_chunk_to_split(size_t word_sz, size_t n) {
2674
2675 FreeChunk* fc = NULL;
2676 FreeChunk* rem_fc = NULL;
2677 size_t rem;
2678 {
2679 MutexLockerEx x(parDictionaryAllocLock(),
2680 Mutex::_no_safepoint_check_flag);
2681 while (n > 0) {
2682 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()));
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 = align_down(low, CardTable::card_size);
2877 // Clip span prefix at aligned_low
2878 span = span.intersection(MemRegion(aligned_low, span.end()));
2879 } else if (low > span.end()) {
2880 span = MemRegion(low, low); // Null region
2881 } // else use entire span
2882 }
2883 assert(span.is_empty() ||
2884 ((uintptr_t)span.start() % CardTable::card_size == 0),
2885 "span should start at a card boundary");
2886 size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
2887 assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
2888 assert(n_tasks == 0 ||
2889 ((span.start() + (n_tasks - 1)*task_size < span.end()) &&
2890 (span.start() + n_tasks*task_size >= span.end())),
2891 "n_tasks calculation incorrect");
2892 SequentialSubTasksDone* pst = conc_par_seq_tasks();
2893 assert(!pst->valid(), "Clobbering existing data?");
2894 // Sets the condition for completion of the subtask (how many threads
2895 // need to finish in order to be done).
2896 pst->set_n_threads(n_threads);
2897 pst->set_n_tasks((int)n_tasks);
2898 }