1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
27
28 #include "gc_implementation/concurrentMarkSweep/binaryTreeDictionary.hpp"
29 #include "gc_implementation/concurrentMarkSweep/freeList.hpp"
30 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp"
31 #include "memory/blockOffsetTable.inline.hpp"
32 #include "memory/space.hpp"
33
34 // Classes in support of keeping track of promotions into a non-Contiguous
35 // space, in this case a CompactibleFreeListSpace.
36
37 // Forward declarations
38 class CompactibleFreeListSpace;
39 class BlkClosure;
40 class BlkClosureCareful;
41 class UpwardsObjectClosure;
42 class ObjectClosureCareful;
43 class Klass;
44
45 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
46 public:
47 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
48 _allocation_size_limit(0) {}
49 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
50 size_t allocation_size_limit) {
51 _ptr = ptr;
52 _word_size = word_size;
53 _refillSize = refill_size;
54 _allocation_size_limit = allocation_size_limit;
55 }
56 HeapWord* _ptr;
57 size_t _word_size;
58 size_t _refillSize;
59 size_t _allocation_size_limit; // largest size that will be allocated
60
61 void print_on(outputStream* st) const;
62 };
63
64 // Concrete subclass of CompactibleSpace that implements
65 // a free list space, such as used in the concurrent mark sweep
66 // generation.
67
68 class CompactibleFreeListSpace: public CompactibleSpace {
69 friend class VMStructs;
70 friend class ConcurrentMarkSweepGeneration;
71 friend class ASConcurrentMarkSweepGeneration;
72 friend class CMSCollector;
73 friend class CMSPermGenGen;
74 // Local alloc buffer for promotion into this space.
75 friend class CFLS_LAB;
76
77 // "Size" of chunks of work (executed during parallel remark phases
78 // of CMS collection); this probably belongs in CMSCollector, although
79 // it's cached here because it's used in
80 // initialize_sequential_subtasks_for_rescan() which modifies
81 // par_seq_tasks which also lives in Space. XXX
82 const size_t _rescan_task_size;
83 const size_t _marking_task_size;
84
85 // Yet another sequential tasks done structure. This supports
86 // CMS GC, where we have threads dynamically
87 // claiming sub-tasks from a larger parallel task.
88 SequentialSubTasksDone _conc_par_seq_tasks;
89
90 BlockOffsetArrayNonContigSpace _bt;
91
92 CMSCollector* _collector;
93 ConcurrentMarkSweepGeneration* _gen;
94
95 // Data structures for free blocks (used during allocation/sweeping)
96
97 // Allocation is done linearly from two different blocks depending on
98 // whether the request is small or large, in an effort to reduce
99 // fragmentation. We assume that any locking for allocation is done
100 // by the containing generation. Thus, none of the methods in this
101 // space are re-entrant.
102 enum SomeConstants {
103 SmallForLinearAlloc = 16, // size < this then use _sLAB
104 SmallForDictionary = 257, // size < this then use _indexedFreeList
105 IndexSetSize = SmallForDictionary // keep this odd-sized
106 };
107 static int IndexSetStart;
108 static int IndexSetStride;
109
110 private:
111 enum FitStrategyOptions {
112 FreeBlockStrategyNone = 0,
113 FreeBlockBestFitFirst
114 };
115
116 PromotionInfo _promoInfo;
117
118 // helps to impose a global total order on freelistLock ranks;
119 // assumes that CFLSpace's are allocated in global total order
120 static int _lockRank;
121
122 // a lock protecting the free lists and free blocks;
123 // mutable because of ubiquity of locking even for otherwise const methods
124 mutable Mutex _freelistLock;
125 // locking verifier convenience function
126 void assert_locked() const PRODUCT_RETURN;
127 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
128
129 // Linear allocation blocks
130 LinearAllocBlock _smallLinearAllocBlock;
131
132 FreeBlockDictionary::DictionaryChoice _dictionaryChoice;
133 FreeBlockDictionary* _dictionary; // ptr to dictionary for large size blocks
134
135 FreeList _indexedFreeList[IndexSetSize];
136 // indexed array for small size blocks
137 // allocation stategy
138 bool _fitStrategy; // Use best fit strategy.
139 bool _adaptive_freelists; // Use adaptive freelists
140
141 // This is an address close to the largest free chunk in the heap.
142 // It is currently assumed to be at the end of the heap. Free
143 // chunks with addresses greater than nearLargestChunk are coalesced
144 // in an effort to maintain a large chunk at the end of the heap.
145 HeapWord* _nearLargestChunk;
146
147 // Used to keep track of limit of sweep for the space
148 HeapWord* _sweep_limit;
149
150 // Support for compacting cms
151 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
152 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
153
154 // Initialization helpers.
155 void initializeIndexedFreeListArray();
156
157 // Extra stuff to manage promotion parallelism.
158
159 // a lock protecting the dictionary during par promotion allocation.
160 mutable Mutex _parDictionaryAllocLock;
161 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
162
163 // Locks protecting the exact lists during par promotion allocation.
164 Mutex* _indexedFreeListParLocks[IndexSetSize];
165
166 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
167 // required to be smaller than "IndexSetSize".) If successful,
168 // adds them to "fl", which is required to be an empty free list.
169 // If the count of "fl" is negative, it's absolute value indicates a
170 // number of free chunks that had been previously "borrowed" from global
171 // list of size "word_sz", and must now be decremented.
172 void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl);
173
174 // Allocation helper functions
175 // Allocate using a strategy that takes from the indexed free lists
176 // first. This allocation strategy assumes a companion sweeping
177 // strategy that attempts to keep the needed number of chunks in each
178 // indexed free lists.
179 HeapWord* allocate_adaptive_freelists(size_t size);
180 // Allocate from the linear allocation buffers first. This allocation
181 // strategy assumes maximal coalescing can maintain chunks large enough
182 // to be used as linear allocation buffers.
183 HeapWord* allocate_non_adaptive_freelists(size_t size);
184
185 // Gets a chunk from the linear allocation block (LinAB). If there
186 // is not enough space in the LinAB, refills it.
187 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
188 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
189 // Get a chunk from the space remaining in the linear allocation block. Do
190 // not attempt to refill if the space is not available, return NULL. Do the
191 // repairs on the linear allocation block as appropriate.
192 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
193 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
194
195 // Helper function for getChunkFromIndexedFreeList.
196 // Replenish the indexed free list for this "size". Do not take from an
197 // underpopulated size.
198 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
199
200 // Get a chunk from the indexed free list. If the indexed free list
201 // does not have a free chunk, try to replenish the indexed free list
202 // then get the free chunk from the replenished indexed free list.
203 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
204
205 // The returned chunk may be larger than requested (or null).
206 FreeChunk* getChunkFromDictionary(size_t size);
207 // The returned chunk is the exact size requested (or null).
208 FreeChunk* getChunkFromDictionaryExact(size_t size);
209
210 // Find a chunk in the indexed free list that is the best
211 // fit for size "numWords".
212 FreeChunk* bestFitSmall(size_t numWords);
213 // For free list "fl" of chunks of size > numWords,
214 // remove a chunk, split off a chunk of size numWords
215 // and return it. The split off remainder is returned to
216 // the free lists. The old name for getFromListGreater
217 // was lookInListGreater.
218 FreeChunk* getFromListGreater(FreeList* fl, size_t numWords);
219 // Get a chunk in the indexed free list or dictionary,
220 // by considering a larger chunk and splitting it.
221 FreeChunk* getChunkFromGreater(size_t numWords);
222 // Verify that the given chunk is in the indexed free lists.
223 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
224 // Remove the specified chunk from the indexed free lists.
225 void removeChunkFromIndexedFreeList(FreeChunk* fc);
226 // Remove the specified chunk from the dictionary.
227 void removeChunkFromDictionary(FreeChunk* fc);
228 // Split a free chunk into a smaller free chunk of size "new_size".
229 // Return the smaller free chunk and return the remainder to the
230 // free lists.
231 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
232 // Add a chunk to the free lists.
233 void addChunkToFreeLists(HeapWord* chunk, size_t size);
234 // Add a chunk to the free lists, preferring to suffix it
235 // to the last free chunk at end of space if possible, and
236 // updating the block census stats as well as block offset table.
237 // Take any locks as appropriate if we are multithreaded.
238 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
239 // Add a free chunk to the indexed free lists.
240 void returnChunkToFreeList(FreeChunk* chunk);
241 // Add a free chunk to the dictionary.
242 void returnChunkToDictionary(FreeChunk* chunk);
243
244 // Functions for maintaining the linear allocation buffers (LinAB).
245 // Repairing a linear allocation block refers to operations
246 // performed on the remainder of a LinAB after an allocation
247 // has been made from it.
248 void repairLinearAllocationBlocks();
249 void repairLinearAllocBlock(LinearAllocBlock* blk);
250 void refillLinearAllocBlock(LinearAllocBlock* blk);
251 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
252 void refillLinearAllocBlocksIfNeeded();
253
254 void verify_objects_initialized() const;
255
256 // Statistics reporting helper functions
257 void reportFreeListStatistics() const;
258 void reportIndexedFreeListStatistics() const;
259 size_t maxChunkSizeInIndexedFreeLists() const;
260 size_t numFreeBlocksInIndexedFreeLists() const;
261 // Accessor
262 HeapWord* unallocated_block() const {
263 if (BlockOffsetArrayUseUnallocatedBlock) {
264 HeapWord* ub = _bt.unallocated_block();
265 assert(ub >= bottom() &&
266 ub <= end(), "space invariant");
267 return ub;
268 } else {
269 return end();
270 }
271 }
272 void freed(HeapWord* start, size_t size) {
273 _bt.freed(start, size);
274 }
275
276 protected:
277 // reset the indexed free list to its initial empty condition.
278 void resetIndexedFreeListArray();
279 // reset to an initial state with a single free block described
280 // by the MemRegion parameter.
281 void reset(MemRegion mr);
282 // Return the total number of words in the indexed free lists.
283 size_t totalSizeInIndexedFreeLists() const;
284
285 public:
286 // Constructor...
287 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
288 bool use_adaptive_freelists,
289 FreeBlockDictionary::DictionaryChoice);
290 // accessors
291 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
292 FreeBlockDictionary* dictionary() const { return _dictionary; }
293 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
294 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
295
296 // Set CMS global values
297 static void set_cms_values();
298
299 // Return the free chunk at the end of the space. If no such
300 // chunk exists, return NULL.
301 FreeChunk* find_chunk_at_end();
302
303 bool adaptive_freelists() const { return _adaptive_freelists; }
304
305 void set_collector(CMSCollector* collector) { _collector = collector; }
306
307 // Support for parallelization of rescan and marking
308 const size_t rescan_task_size() const { return _rescan_task_size; }
309 const size_t marking_task_size() const { return _marking_task_size; }
310 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
311 void initialize_sequential_subtasks_for_rescan(int n_threads);
312 void initialize_sequential_subtasks_for_marking(int n_threads,
313 HeapWord* low = NULL);
314
315 // Space enquiries
316 size_t used() const;
317 size_t free() const;
318 size_t max_alloc_in_words() const;
319 // XXX: should have a less conservative used_region() than that of
320 // Space; we could consider keeping track of highest allocated
321 // address and correcting that at each sweep, as the sweeper
322 // goes through the entire allocated part of the generation. We
323 // could also use that information to keep the sweeper from
324 // sweeping more than is necessary. The allocator and sweeper will
325 // of course need to synchronize on this, since the sweeper will
326 // try to bump down the address and the allocator will try to bump it up.
327 // For now, however, we'll just use the default used_region()
328 // which overestimates the region by returning the entire
329 // committed region (this is safe, but inefficient).
330
331 // Returns a subregion of the space containing all the objects in
332 // the space.
333 MemRegion used_region() const {
334 return MemRegion(bottom(),
335 BlockOffsetArrayUseUnallocatedBlock ?
336 unallocated_block() : end());
337 }
338
339 // This is needed because the default implementation uses block_start()
340 // which can;t be used at certain times (for example phase 3 of mark-sweep).
341 // A better fix is to change the assertions in phase 3 of mark-sweep to
342 // use is_in_reserved(), but that is deferred since the is_in() assertions
343 // are buried through several layers of callers and are used elsewhere
344 // as well.
345 bool is_in(const void* p) const {
346 return used_region().contains(p);
347 }
348
349 virtual bool is_free_block(const HeapWord* p) const;
350
351 // Resizing support
352 void set_end(HeapWord* value); // override
353
354 // mutual exclusion support
355 Mutex* freelistLock() const { return &_freelistLock; }
356
357 // Iteration support
358 void oop_iterate(MemRegion mr, OopClosure* cl);
359 void oop_iterate(OopClosure* cl);
360
361 void object_iterate(ObjectClosure* blk);
362 // Apply the closure to each object in the space whose references
363 // point to objects in the heap. The usage of CompactibleFreeListSpace
364 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
365 // objects in the space with references to objects that are no longer
366 // valid. For example, an object may reference another object
367 // that has already been sweep up (collected). This method uses
368 // obj_is_alive() to determine whether it is safe to iterate of
369 // an object.
370 void safe_object_iterate(ObjectClosure* blk);
371 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
372
373 // Requires that "mr" be entirely within the space.
374 // Apply "cl->do_object" to all objects that intersect with "mr".
375 // If the iteration encounters an unparseable portion of the region,
376 // terminate the iteration and return the address of the start of the
377 // subregion that isn't done. Return of "NULL" indicates that the
378 // interation completed.
379 virtual HeapWord*
380 object_iterate_careful_m(MemRegion mr,
381 ObjectClosureCareful* cl);
382 virtual HeapWord*
383 object_iterate_careful(ObjectClosureCareful* cl);
384
385 // Override: provides a DCTO_CL specific to this kind of space.
386 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
387 CardTableModRefBS::PrecisionStyle precision,
388 HeapWord* boundary);
389
390 void blk_iterate(BlkClosure* cl);
391 void blk_iterate_careful(BlkClosureCareful* cl);
392 HeapWord* block_start_const(const void* p) const;
393 HeapWord* block_start_careful(const void* p) const;
394 size_t block_size(const HeapWord* p) const;
395 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
396 bool block_is_obj(const HeapWord* p) const;
397 bool obj_is_alive(const HeapWord* p) const;
398 size_t block_size_nopar(const HeapWord* p) const;
399 bool block_is_obj_nopar(const HeapWord* p) const;
400
401 // iteration support for promotion
402 void save_marks();
403 bool no_allocs_since_save_marks();
404 void object_iterate_since_last_GC(ObjectClosure* cl);
405
406 // iteration support for sweeping
407 void save_sweep_limit() {
408 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
409 unallocated_block() : end();
410 }
411 NOT_PRODUCT(
412 void clear_sweep_limit() { _sweep_limit = NULL; }
413 )
414 HeapWord* sweep_limit() { return _sweep_limit; }
415
416 // Apply "blk->do_oop" to the addresses of all reference fields in objects
417 // promoted into this generation since the most recent save_marks() call.
418 // Fields in objects allocated by applications of the closure
419 // *are* included in the iteration. Thus, when the iteration completes
420 // there should be no further such objects remaining.
421 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
422 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
423 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
424 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
425
426 // Allocation support
427 HeapWord* allocate(size_t size);
428 HeapWord* par_allocate(size_t size);
429
430 oop promote(oop obj, size_t obj_size);
431 void gc_prologue();
432 void gc_epilogue();
433
434 // This call is used by a containing CMS generation / collector
435 // to inform the CFLS space that a sweep has been completed
436 // and that the space can do any related house-keeping functions.
437 void sweep_completed();
438
439 // For an object in this space, the mark-word's two
440 // LSB's having the value [11] indicates that it has been
441 // promoted since the most recent call to save_marks() on
442 // this generation and has not subsequently been iterated
443 // over (using oop_since_save_marks_iterate() above).
444 // This property holds only for single-threaded collections,
445 // and is typically used for Cheney scans; for MT scavenges,
446 // the property holds for all objects promoted during that
447 // scavenge for the duration of the scavenge and is used
448 // by card-scanning to avoid scanning objects (being) promoted
449 // during that scavenge.
450 bool obj_allocated_since_save_marks(const oop obj) const {
451 assert(is_in_reserved(obj), "Wrong space?");
452 return ((PromotedObject*)obj)->hasPromotedMark();
453 }
454
455 // A worst-case estimate of the space required (in HeapWords) to expand the
456 // heap when promoting an obj of size obj_size.
457 size_t expansionSpaceRequired(size_t obj_size) const;
458
459 FreeChunk* allocateScratch(size_t size);
460
461 // returns true if either the small or large linear allocation buffer is empty.
462 bool linearAllocationWouldFail() const;
463
464 // Adjust the chunk for the minimum size. This version is called in
465 // most cases in CompactibleFreeListSpace methods.
466 inline static size_t adjustObjectSize(size_t size) {
467 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
468 }
469 // This is a virtual version of adjustObjectSize() that is called
470 // only occasionally when the compaction space changes and the type
471 // of the new compaction space is is only known to be CompactibleSpace.
472 size_t adjust_object_size_v(size_t size) const {
473 return adjustObjectSize(size);
474 }
475 // Minimum size of a free block.
476 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
477 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
478 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
479 bool coalesced);
480
481 // Support for decisions regarding concurrent collection policy
482 bool should_concurrent_collect() const;
483
484 // Support for compaction
485 void prepare_for_compaction(CompactPoint* cp);
486 void adjust_pointers();
487 void compact();
488 // reset the space to reflect the fact that a compaction of the
489 // space has been done.
490 virtual void reset_after_compaction();
491
492 // Debugging support
493 void print() const;
494 void print_on(outputStream* st) const;
495 void prepare_for_verify();
496 void verify(bool allow_dirty) const;
497 void verifyFreeLists() const PRODUCT_RETURN;
498 void verifyIndexedFreeLists() const;
499 void verifyIndexedFreeList(size_t size) const;
500 // verify that the given chunk is in the free lists.
501 bool verifyChunkInFreeLists(FreeChunk* fc) const;
502 // Do some basic checks on the the free lists.
503 void checkFreeListConsistency() const PRODUCT_RETURN;
504
505 // Printing support
506 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
507 void print_indexed_free_lists(outputStream* st) const;
508 void print_dictionary_free_lists(outputStream* st) const;
509 void print_promo_info_blocks(outputStream* st) const;
510
511 NOT_PRODUCT (
512 void initializeIndexedFreeListArrayReturnedBytes();
513 size_t sumIndexedFreeListArrayReturnedBytes();
514 // Return the total number of chunks in the indexed free lists.
515 size_t totalCountInIndexedFreeLists() const;
516 // Return the total numberof chunks in the space.
517 size_t totalCount();
518 )
519
520 // The census consists of counts of the quantities such as
521 // the current count of the free chunks, number of chunks
522 // created as a result of the split of a larger chunk or
523 // coalescing of smaller chucks, etc. The counts in the
524 // census is used to make decisions on splitting and
525 // coalescing of chunks during the sweep of garbage.
526
527 // Print the statistics for the free lists.
528 void printFLCensus(size_t sweep_count) const;
529
530 // Statistics functions
531 // Initialize census for lists before the sweep.
532 void beginSweepFLCensus(float inter_sweep_current,
533 float inter_sweep_estimate,
534 float intra_sweep_estimate);
535 // Set the surplus for each of the free lists.
536 void setFLSurplus();
537 // Set the hint for each of the free lists.
538 void setFLHints();
539 // Clear the census for each of the free lists.
540 void clearFLCensus();
541 // Perform functions for the census after the end of the sweep.
542 void endSweepFLCensus(size_t sweep_count);
543 // Return true if the count of free chunks is greater
544 // than the desired number of free chunks.
545 bool coalOverPopulated(size_t size);
546
547 // Record (for each size):
548 //
549 // split-births = #chunks added due to splits in (prev-sweep-end,
550 // this-sweep-start)
551 // split-deaths = #chunks removed for splits in (prev-sweep-end,
552 // this-sweep-start)
553 // num-curr = #chunks at start of this sweep
554 // num-prev = #chunks at end of previous sweep
555 //
556 // The above are quantities that are measured. Now define:
557 //
558 // num-desired := num-prev + split-births - split-deaths - num-curr
559 //
560 // Roughly, num-prev + split-births is the supply,
561 // split-deaths is demand due to other sizes
562 // and num-curr is what we have left.
563 //
564 // Thus, num-desired is roughly speaking the "legitimate demand"
565 // for blocks of this size and what we are striving to reach at the
566 // end of the current sweep.
567 //
568 // For a given list, let num-len be its current population.
569 // Define, for a free list of a given size:
570 //
571 // coal-overpopulated := num-len >= num-desired * coal-surplus
572 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
573 // coalescing -- we do not coalesce unless we think that the current
574 // supply has exceeded the estimated demand by more than 5%).
575 //
576 // For the set of sizes in the binary tree, which is neither dense nor
577 // closed, it may be the case that for a particular size we have never
578 // had, or do not now have, or did not have at the previous sweep,
579 // chunks of that size. We need to extend the definition of
580 // coal-overpopulated to such sizes as well:
581 //
582 // For a chunk in/not in the binary tree, extend coal-overpopulated
583 // defined above to include all sizes as follows:
584 //
585 // . a size that is non-existent is coal-overpopulated
586 // . a size that has a num-desired <= 0 as defined above is
587 // coal-overpopulated.
588 //
589 // Also define, for a chunk heap-offset C and mountain heap-offset M:
590 //
591 // close-to-mountain := C >= 0.99 * M
592 //
593 // Now, the coalescing strategy is:
594 //
595 // Coalesce left-hand chunk with right-hand chunk if and
596 // only if:
597 //
598 // EITHER
599 // . left-hand chunk is of a size that is coal-overpopulated
600 // OR
601 // . right-hand chunk is close-to-mountain
602 void smallCoalBirth(size_t size);
603 void smallCoalDeath(size_t size);
604 void coalBirth(size_t size);
605 void coalDeath(size_t size);
606 void smallSplitBirth(size_t size);
607 void smallSplitDeath(size_t size);
608 void splitBirth(size_t size);
609 void splitDeath(size_t size);
610 void split(size_t from, size_t to1);
611
612 double flsFrag() const;
613 };
614
615 // A parallel-GC-thread-local allocation buffer for allocation into a
616 // CompactibleFreeListSpace.
617 class CFLS_LAB : public CHeapObj {
618 // The space that this buffer allocates into.
619 CompactibleFreeListSpace* _cfls;
620
621 // Our local free lists.
622 FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
623
624 // Initialized from a command-line arg.
625
626 // Allocation statistics in support of dynamic adjustment of
627 // #blocks to claim per get_from_global_pool() call below.
628 static AdaptiveWeightedAverage
629 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
630 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
631 static int _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
632 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
633
634 // Internal work method
635 void get_from_global_pool(size_t word_sz, FreeList* fl);
636
637 public:
638 CFLS_LAB(CompactibleFreeListSpace* cfls);
639
640 // Allocate and return a block of the given size, or else return NULL.
641 HeapWord* alloc(size_t word_sz);
642
643 // Return any unused portions of the buffer to the global pool.
644 void retire(int tid);
645
646 // Dynamic OldPLABSize sizing
647 static void compute_desired_plab_size();
648 // When the settings are modified from default static initialization
649 static void modify_initialization(size_t n, unsigned wt);
650 };
651
652 size_t PromotionInfo::refillSize() const {
653 const size_t CMSSpoolBlockSize = 256;
654 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
655 * CMSSpoolBlockSize);
656 return CompactibleFreeListSpace::adjustObjectSize(sz);
657 }
658
659 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP