1 /*
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
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23 */
24
25 // Classes in support of keeping track of promotions into a non-Contiguous
26 // space, in this case a CompactibleFreeListSpace.
27
28 // Forward declarations
29 class CompactibleFreeListSpace;
30 class BlkClosure;
31 class BlkClosureCareful;
32 class UpwardsObjectClosure;
33 class ObjectClosureCareful;
34 class Klass;
35
36 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
37 public:
38 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
39 _allocation_size_limit(0) {}
40 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
41 size_t allocation_size_limit) {
42 _ptr = ptr;
43 _word_size = word_size;
44 _refillSize = refill_size;
45 _allocation_size_limit = allocation_size_limit;
46 }
47 HeapWord* _ptr;
48 size_t _word_size;
49 size_t _refillSize;
50 size_t _allocation_size_limit; // largest size that will be allocated
51
52 void print_on(outputStream* st) const;
53 };
54
55 // Concrete subclass of CompactibleSpace that implements
56 // a free list space, such as used in the concurrent mark sweep
57 // generation.
58
59 class CompactibleFreeListSpace: public CompactibleSpace {
60 friend class VMStructs;
61 friend class ConcurrentMarkSweepGeneration;
62 friend class ASConcurrentMarkSweepGeneration;
63 friend class CMSCollector;
64 friend class CMSPermGenGen;
65 // Local alloc buffer for promotion into this space.
66 friend class CFLS_LAB;
67
68 // "Size" of chunks of work (executed during parallel remark phases
69 // of CMS collection); this probably belongs in CMSCollector, although
70 // it's cached here because it's used in
71 // initialize_sequential_subtasks_for_rescan() which modifies
72 // par_seq_tasks which also lives in Space. XXX
73 const size_t _rescan_task_size;
74 const size_t _marking_task_size;
75
76 // Yet another sequential tasks done structure. This supports
77 // CMS GC, where we have threads dynamically
78 // claiming sub-tasks from a larger parallel task.
79 SequentialSubTasksDone _conc_par_seq_tasks;
80
81 BlockOffsetArrayNonContigSpace _bt;
82
83 CMSCollector* _collector;
84 ConcurrentMarkSweepGeneration* _gen;
85
86 // Data structures for free blocks (used during allocation/sweeping)
87
88 // Allocation is done linearly from two different blocks depending on
89 // whether the request is small or large, in an effort to reduce
90 // fragmentation. We assume that any locking for allocation is done
91 // by the containing generation. Thus, none of the methods in this
92 // space are re-entrant.
93 enum SomeConstants {
94 SmallForLinearAlloc = 16, // size < this then use _sLAB
95 SmallForDictionary = 257, // size < this then use _indexedFreeList
96 IndexSetSize = SmallForDictionary // keep this odd-sized
97 };
98 static int IndexSetStart;
99 static int IndexSetStride;
100
101 private:
102 enum FitStrategyOptions {
103 FreeBlockStrategyNone = 0,
104 FreeBlockBestFitFirst
105 };
106
107 PromotionInfo _promoInfo;
108
109 // helps to impose a global total order on freelistLock ranks;
110 // assumes that CFLSpace's are allocated in global total order
111 static int _lockRank;
112
113 // a lock protecting the free lists and free blocks;
114 // mutable because of ubiquity of locking even for otherwise const methods
115 mutable Mutex _freelistLock;
116 // locking verifier convenience function
117 void assert_locked() const PRODUCT_RETURN;
118 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
119
120 // Linear allocation blocks
121 LinearAllocBlock _smallLinearAllocBlock;
122
123 FreeBlockDictionary::DictionaryChoice _dictionaryChoice;
124 FreeBlockDictionary* _dictionary; // ptr to dictionary for large size blocks
125
126 FreeList _indexedFreeList[IndexSetSize];
127 // indexed array for small size blocks
128 // allocation stategy
129 bool _fitStrategy; // Use best fit strategy.
130 bool _adaptive_freelists; // Use adaptive freelists
131
132 // This is an address close to the largest free chunk in the heap.
133 // It is currently assumed to be at the end of the heap. Free
134 // chunks with addresses greater than nearLargestChunk are coalesced
135 // in an effort to maintain a large chunk at the end of the heap.
136 HeapWord* _nearLargestChunk;
137
138 // Used to keep track of limit of sweep for the space
139 HeapWord* _sweep_limit;
140
141 // Support for compacting cms
142 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
143 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
144
145 // Initialization helpers.
146 void initializeIndexedFreeListArray();
147
148 // Extra stuff to manage promotion parallelism.
149
150 // a lock protecting the dictionary during par promotion allocation.
151 mutable Mutex _parDictionaryAllocLock;
152 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
153
154 // Locks protecting the exact lists during par promotion allocation.
155 Mutex* _indexedFreeListParLocks[IndexSetSize];
156
157 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
158 // required to be smaller than "IndexSetSize".) If successful,
159 // adds them to "fl", which is required to be an empty free list.
160 // If the count of "fl" is negative, it's absolute value indicates a
161 // number of free chunks that had been previously "borrowed" from global
162 // list of size "word_sz", and must now be decremented.
163 void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl);
164
165 // Allocation helper functions
166 // Allocate using a strategy that takes from the indexed free lists
167 // first. This allocation strategy assumes a companion sweeping
168 // strategy that attempts to keep the needed number of chunks in each
169 // indexed free lists.
170 HeapWord* allocate_adaptive_freelists(size_t size);
171 // Allocate from the linear allocation buffers first. This allocation
172 // strategy assumes maximal coalescing can maintain chunks large enough
173 // to be used as linear allocation buffers.
174 HeapWord* allocate_non_adaptive_freelists(size_t size);
175
176 // Gets a chunk from the linear allocation block (LinAB). If there
177 // is not enough space in the LinAB, refills it.
178 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
179 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
180 // Get a chunk from the space remaining in the linear allocation block. Do
181 // not attempt to refill if the space is not available, return NULL. Do the
182 // repairs on the linear allocation block as appropriate.
183 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
184 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
185
186 // Helper function for getChunkFromIndexedFreeList.
187 // Replenish the indexed free list for this "size". Do not take from an
188 // underpopulated size.
189 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
190
191 // Get a chunk from the indexed free list. If the indexed free list
192 // does not have a free chunk, try to replenish the indexed free list
193 // then get the free chunk from the replenished indexed free list.
194 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
195
196 // The returned chunk may be larger than requested (or null).
197 FreeChunk* getChunkFromDictionary(size_t size);
198 // The returned chunk is the exact size requested (or null).
199 FreeChunk* getChunkFromDictionaryExact(size_t size);
200
201 // Find a chunk in the indexed free list that is the best
202 // fit for size "numWords".
203 FreeChunk* bestFitSmall(size_t numWords);
204 // For free list "fl" of chunks of size > numWords,
205 // remove a chunk, split off a chunk of size numWords
206 // and return it. The split off remainder is returned to
207 // the free lists. The old name for getFromListGreater
208 // was lookInListGreater.
209 FreeChunk* getFromListGreater(FreeList* fl, size_t numWords);
210 // Get a chunk in the indexed free list or dictionary,
211 // by considering a larger chunk and splitting it.
212 FreeChunk* getChunkFromGreater(size_t numWords);
213 // Verify that the given chunk is in the indexed free lists.
214 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
215 // Remove the specified chunk from the indexed free lists.
216 void removeChunkFromIndexedFreeList(FreeChunk* fc);
217 // Remove the specified chunk from the dictionary.
218 void removeChunkFromDictionary(FreeChunk* fc);
219 // Split a free chunk into a smaller free chunk of size "new_size".
220 // Return the smaller free chunk and return the remainder to the
221 // free lists.
222 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
223 // Add a chunk to the free lists.
224 void addChunkToFreeLists(HeapWord* chunk, size_t size);
225 // Add a chunk to the free lists, preferring to suffix it
226 // to the last free chunk at end of space if possible, and
227 // updating the block census stats as well as block offset table.
228 // Take any locks as appropriate if we are multithreaded.
229 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
230 // Add a free chunk to the indexed free lists.
231 void returnChunkToFreeList(FreeChunk* chunk);
232 // Add a free chunk to the dictionary.
233 void returnChunkToDictionary(FreeChunk* chunk);
234
235 // Functions for maintaining the linear allocation buffers (LinAB).
236 // Repairing a linear allocation block refers to operations
237 // performed on the remainder of a LinAB after an allocation
238 // has been made from it.
239 void repairLinearAllocationBlocks();
240 void repairLinearAllocBlock(LinearAllocBlock* blk);
241 void refillLinearAllocBlock(LinearAllocBlock* blk);
242 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
243 void refillLinearAllocBlocksIfNeeded();
244
245 void verify_objects_initialized() const;
246
247 // Statistics reporting helper functions
248 void reportFreeListStatistics() const;
249 void reportIndexedFreeListStatistics() const;
250 size_t maxChunkSizeInIndexedFreeLists() const;
251 size_t numFreeBlocksInIndexedFreeLists() const;
252 // Accessor
253 HeapWord* unallocated_block() const {
254 if (BlockOffsetArrayUseUnallocatedBlock) {
255 HeapWord* ub = _bt.unallocated_block();
256 assert(ub >= bottom() &&
257 ub <= end(), "space invariant");
258 return ub;
259 } else {
260 return end();
261 }
262 }
263 void freed(HeapWord* start, size_t size) {
264 _bt.freed(start, size);
265 }
266
267 protected:
268 // reset the indexed free list to its initial empty condition.
269 void resetIndexedFreeListArray();
270 // reset to an initial state with a single free block described
271 // by the MemRegion parameter.
272 void reset(MemRegion mr);
273 // Return the total number of words in the indexed free lists.
274 size_t totalSizeInIndexedFreeLists() const;
275
276 public:
277 // Constructor...
278 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
279 bool use_adaptive_freelists,
280 FreeBlockDictionary::DictionaryChoice);
281 // accessors
282 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
283 FreeBlockDictionary* dictionary() const { return _dictionary; }
284 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
285 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
286
287 // Set CMS global values
288 static void set_cms_values();
289
290 // Return the free chunk at the end of the space. If no such
291 // chunk exists, return NULL.
292 FreeChunk* find_chunk_at_end();
293
294 bool adaptive_freelists() const { return _adaptive_freelists; }
295
296 void set_collector(CMSCollector* collector) { _collector = collector; }
297
298 // Support for parallelization of rescan and marking
299 const size_t rescan_task_size() const { return _rescan_task_size; }
300 const size_t marking_task_size() const { return _marking_task_size; }
301 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
302 void initialize_sequential_subtasks_for_rescan(int n_threads);
303 void initialize_sequential_subtasks_for_marking(int n_threads,
304 HeapWord* low = NULL);
305
306 // Space enquiries
307 size_t used() const;
308 size_t free() const;
309 size_t max_alloc_in_words() const;
310 // XXX: should have a less conservative used_region() than that of
311 // Space; we could consider keeping track of highest allocated
312 // address and correcting that at each sweep, as the sweeper
313 // goes through the entire allocated part of the generation. We
314 // could also use that information to keep the sweeper from
315 // sweeping more than is necessary. The allocator and sweeper will
316 // of course need to synchronize on this, since the sweeper will
317 // try to bump down the address and the allocator will try to bump it up.
318 // For now, however, we'll just use the default used_region()
319 // which overestimates the region by returning the entire
320 // committed region (this is safe, but inefficient).
321
322 // Returns a subregion of the space containing all the objects in
323 // the space.
324 MemRegion used_region() const {
325 return MemRegion(bottom(),
326 BlockOffsetArrayUseUnallocatedBlock ?
327 unallocated_block() : end());
328 }
329
330 // This is needed because the default implementation uses block_start()
331 // which can;t be used at certain times (for example phase 3 of mark-sweep).
332 // A better fix is to change the assertions in phase 3 of mark-sweep to
333 // use is_in_reserved(), but that is deferred since the is_in() assertions
334 // are buried through several layers of callers and are used elsewhere
335 // as well.
336 bool is_in(const void* p) const {
337 return used_region().contains(p);
338 }
339
340 virtual bool is_free_block(const HeapWord* p) const;
341
342 // Resizing support
343 void set_end(HeapWord* value); // override
344
345 // mutual exclusion support
346 Mutex* freelistLock() const { return &_freelistLock; }
347
348 // Iteration support
349 void oop_iterate(MemRegion mr, OopClosure* cl);
350 void oop_iterate(OopClosure* cl);
351
352 void object_iterate(ObjectClosure* blk);
353 // Apply the closure to each object in the space whose references
354 // point to objects in the heap. The usage of CompactibleFreeListSpace
355 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
356 // objects in the space with references to objects that are no longer
357 // valid. For example, an object may reference another object
358 // that has already been sweep up (collected). This method uses
359 // obj_is_alive() to determine whether it is safe to iterate of
360 // an object.
361 void safe_object_iterate(ObjectClosure* blk);
362 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
363
364 // Requires that "mr" be entirely within the space.
365 // Apply "cl->do_object" to all objects that intersect with "mr".
366 // If the iteration encounters an unparseable portion of the region,
367 // terminate the iteration and return the address of the start of the
368 // subregion that isn't done. Return of "NULL" indicates that the
369 // interation completed.
370 virtual HeapWord*
371 object_iterate_careful_m(MemRegion mr,
372 ObjectClosureCareful* cl);
373 virtual HeapWord*
374 object_iterate_careful(ObjectClosureCareful* cl);
375
376 // Override: provides a DCTO_CL specific to this kind of space.
377 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
378 CardTableModRefBS::PrecisionStyle precision,
379 HeapWord* boundary);
380
381 void blk_iterate(BlkClosure* cl);
382 void blk_iterate_careful(BlkClosureCareful* cl);
383 HeapWord* block_start_const(const void* p) const;
384 HeapWord* block_start_careful(const void* p) const;
385 size_t block_size(const HeapWord* p) const;
386 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
387 bool block_is_obj(const HeapWord* p) const;
388 bool obj_is_alive(const HeapWord* p) const;
389 size_t block_size_nopar(const HeapWord* p) const;
390 bool block_is_obj_nopar(const HeapWord* p) const;
391
392 // iteration support for promotion
393 void save_marks();
394 bool no_allocs_since_save_marks();
395 void object_iterate_since_last_GC(ObjectClosure* cl);
396
397 // iteration support for sweeping
398 void save_sweep_limit() {
399 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
400 unallocated_block() : end();
401 }
402 NOT_PRODUCT(
403 void clear_sweep_limit() { _sweep_limit = NULL; }
404 )
405 HeapWord* sweep_limit() { return _sweep_limit; }
406
407 // Apply "blk->do_oop" to the addresses of all reference fields in objects
408 // promoted into this generation since the most recent save_marks() call.
409 // Fields in objects allocated by applications of the closure
410 // *are* included in the iteration. Thus, when the iteration completes
411 // there should be no further such objects remaining.
412 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
413 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
414 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
415 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
416
417 // Allocation support
418 HeapWord* allocate(size_t size);
419 HeapWord* par_allocate(size_t size);
420
421 oop promote(oop obj, size_t obj_size);
422 void gc_prologue();
423 void gc_epilogue();
424
425 // This call is used by a containing CMS generation / collector
426 // to inform the CFLS space that a sweep has been completed
427 // and that the space can do any related house-keeping functions.
428 void sweep_completed();
429
430 // For an object in this space, the mark-word's two
431 // LSB's having the value [11] indicates that it has been
432 // promoted since the most recent call to save_marks() on
433 // this generation and has not subsequently been iterated
434 // over (using oop_since_save_marks_iterate() above).
435 // This property holds only for single-threaded collections,
436 // and is typically used for Cheney scans; for MT scavenges,
437 // the property holds for all objects promoted during that
438 // scavenge for the duration of the scavenge and is used
439 // by card-scanning to avoid scanning objects (being) promoted
440 // during that scavenge.
441 bool obj_allocated_since_save_marks(const oop obj) const {
442 assert(is_in_reserved(obj), "Wrong space?");
443 return ((PromotedObject*)obj)->hasPromotedMark();
444 }
445
446 // A worst-case estimate of the space required (in HeapWords) to expand the
447 // heap when promoting an obj of size obj_size.
448 size_t expansionSpaceRequired(size_t obj_size) const;
449
450 FreeChunk* allocateScratch(size_t size);
451
452 // returns true if either the small or large linear allocation buffer is empty.
453 bool linearAllocationWouldFail() const;
454
455 // Adjust the chunk for the minimum size. This version is called in
456 // most cases in CompactibleFreeListSpace methods.
457 inline static size_t adjustObjectSize(size_t size) {
458 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
459 }
460 // This is a virtual version of adjustObjectSize() that is called
461 // only occasionally when the compaction space changes and the type
462 // of the new compaction space is is only known to be CompactibleSpace.
463 size_t adjust_object_size_v(size_t size) const {
464 return adjustObjectSize(size);
465 }
466 // Minimum size of a free block.
467 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
468 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
469 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
470 bool coalesced);
471
472 // Support for decisions regarding concurrent collection policy
473 bool should_concurrent_collect() const;
474
475 // Support for compaction
476 void prepare_for_compaction(CompactPoint* cp);
477 void adjust_pointers();
478 void compact();
479 // reset the space to reflect the fact that a compaction of the
480 // space has been done.
481 virtual void reset_after_compaction();
482
483 // Debugging support
484 void print() const;
485 void print_on(outputStream* st) const;
486 void prepare_for_verify();
487 void verify(bool allow_dirty) const;
488 void verifyFreeLists() const PRODUCT_RETURN;
489 void verifyIndexedFreeLists() const;
490 void verifyIndexedFreeList(size_t size) const;
491 // verify that the given chunk is in the free lists.
492 bool verifyChunkInFreeLists(FreeChunk* fc) const;
493 // Do some basic checks on the the free lists.
494 void checkFreeListConsistency() const PRODUCT_RETURN;
495
496 // Printing support
497 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
498 void print_indexed_free_lists(outputStream* st) const;
499 void print_dictionary_free_lists(outputStream* st) const;
500 void print_promo_info_blocks(outputStream* st) const;
501
502 NOT_PRODUCT (
503 void initializeIndexedFreeListArrayReturnedBytes();
504 size_t sumIndexedFreeListArrayReturnedBytes();
505 // Return the total number of chunks in the indexed free lists.
506 size_t totalCountInIndexedFreeLists() const;
507 // Return the total numberof chunks in the space.
508 size_t totalCount();
509 )
510
511 // The census consists of counts of the quantities such as
512 // the current count of the free chunks, number of chunks
513 // created as a result of the split of a larger chunk or
514 // coalescing of smaller chucks, etc. The counts in the
515 // census is used to make decisions on splitting and
516 // coalescing of chunks during the sweep of garbage.
517
518 // Print the statistics for the free lists.
519 void printFLCensus(size_t sweep_count) const;
520
521 // Statistics functions
522 // Initialize census for lists before the sweep.
523 void beginSweepFLCensus(float inter_sweep_current,
524 float inter_sweep_estimate,
525 float intra_sweep_estimate);
526 // Set the surplus for each of the free lists.
527 void setFLSurplus();
528 // Set the hint for each of the free lists.
529 void setFLHints();
530 // Clear the census for each of the free lists.
531 void clearFLCensus();
532 // Perform functions for the census after the end of the sweep.
533 void endSweepFLCensus(size_t sweep_count);
534 // Return true if the count of free chunks is greater
535 // than the desired number of free chunks.
536 bool coalOverPopulated(size_t size);
537
538 // Record (for each size):
539 //
540 // split-births = #chunks added due to splits in (prev-sweep-end,
541 // this-sweep-start)
542 // split-deaths = #chunks removed for splits in (prev-sweep-end,
543 // this-sweep-start)
544 // num-curr = #chunks at start of this sweep
545 // num-prev = #chunks at end of previous sweep
546 //
547 // The above are quantities that are measured. Now define:
548 //
549 // num-desired := num-prev + split-births - split-deaths - num-curr
550 //
551 // Roughly, num-prev + split-births is the supply,
552 // split-deaths is demand due to other sizes
553 // and num-curr is what we have left.
554 //
555 // Thus, num-desired is roughly speaking the "legitimate demand"
556 // for blocks of this size and what we are striving to reach at the
557 // end of the current sweep.
558 //
559 // For a given list, let num-len be its current population.
560 // Define, for a free list of a given size:
561 //
562 // coal-overpopulated := num-len >= num-desired * coal-surplus
563 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
564 // coalescing -- we do not coalesce unless we think that the current
565 // supply has exceeded the estimated demand by more than 5%).
566 //
567 // For the set of sizes in the binary tree, which is neither dense nor
568 // closed, it may be the case that for a particular size we have never
569 // had, or do not now have, or did not have at the previous sweep,
570 // chunks of that size. We need to extend the definition of
571 // coal-overpopulated to such sizes as well:
572 //
573 // For a chunk in/not in the binary tree, extend coal-overpopulated
574 // defined above to include all sizes as follows:
575 //
576 // . a size that is non-existent is coal-overpopulated
577 // . a size that has a num-desired <= 0 as defined above is
578 // coal-overpopulated.
579 //
580 // Also define, for a chunk heap-offset C and mountain heap-offset M:
581 //
582 // close-to-mountain := C >= 0.99 * M
583 //
584 // Now, the coalescing strategy is:
585 //
586 // Coalesce left-hand chunk with right-hand chunk if and
587 // only if:
588 //
589 // EITHER
590 // . left-hand chunk is of a size that is coal-overpopulated
591 // OR
592 // . right-hand chunk is close-to-mountain
593 void smallCoalBirth(size_t size);
594 void smallCoalDeath(size_t size);
595 void coalBirth(size_t size);
596 void coalDeath(size_t size);
597 void smallSplitBirth(size_t size);
598 void smallSplitDeath(size_t size);
599 void splitBirth(size_t size);
600 void splitDeath(size_t size);
601 void split(size_t from, size_t to1);
602
603 double flsFrag() const;
604 };
605
606 // A parallel-GC-thread-local allocation buffer for allocation into a
607 // CompactibleFreeListSpace.
608 class CFLS_LAB : public CHeapObj {
609 // The space that this buffer allocates into.
610 CompactibleFreeListSpace* _cfls;
611
612 // Our local free lists.
613 FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
614
615 // Initialized from a command-line arg.
616
617 // Allocation statistics in support of dynamic adjustment of
618 // #blocks to claim per get_from_global_pool() call below.
619 static AdaptiveWeightedAverage
620 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
621 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
622 static int _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
623 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
624
625 // Internal work method
626 void get_from_global_pool(size_t word_sz, FreeList* fl);
627
628 public:
629 CFLS_LAB(CompactibleFreeListSpace* cfls);
630
631 // Allocate and return a block of the given size, or else return NULL.
632 HeapWord* alloc(size_t word_sz);
633
634 // Return any unused portions of the buffer to the global pool.
635 void retire(int tid);
636
637 // Dynamic OldPLABSize sizing
638 static void compute_desired_plab_size();
639 // When the settings are modified from default static initialization
640 static void modify_initialization(size_t n, unsigned wt);
641 };
642
643 size_t PromotionInfo::refillSize() const {
644 const size_t CMSSpoolBlockSize = 256;
645 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
646 * CMSSpoolBlockSize);
647 return CompactibleFreeListSpace::adjustObjectSize(sz);
648 }