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_CMS_COMPACTIBLEFREELISTSPACE_HPP
26 #define SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP
27
28 #include "gc/cms/adaptiveFreeList.hpp"
29 #include "gc/cms/promotionInfo.hpp"
30 #include "gc/shared/blockOffsetTable.hpp"
31 #include "gc/shared/space.hpp"
32 #include "memory/binaryTreeDictionary.hpp"
33 #include "memory/freeList.hpp"
34
35 // Classes in support of keeping track of promotions into a non-Contiguous
36 // space, in this case a CompactibleFreeListSpace.
37
38 // Forward declarations
39 class CMSCollector;
40 class CompactibleFreeListSpace;
41 class ConcurrentMarkSweepGeneration;
42 class BlkClosure;
43 class BlkClosureCareful;
44 class FreeChunk;
45 class UpwardsObjectClosure;
46 class ObjectClosureCareful;
47 class Klass;
48
49 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
50 public:
51 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
52 _allocation_size_limit(0) {}
53 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
54 size_t allocation_size_limit) {
55 _ptr = ptr;
56 _word_size = word_size;
57 _refillSize = refill_size;
58 _allocation_size_limit = allocation_size_limit;
59 }
60 HeapWord* _ptr;
61 size_t _word_size;
62 size_t _refillSize;
63 size_t _allocation_size_limit; // Largest size that will be allocated
64
65 void print_on(outputStream* st) const;
66 };
67
68 // Concrete subclass of CompactibleSpace that implements
69 // a free list space, such as used in the concurrent mark sweep
70 // generation.
71
72 class CompactibleFreeListSpace: public CompactibleSpace {
73 friend class VMStructs;
74 friend class ConcurrentMarkSweepGeneration;
75 friend class CMSCollector;
76 // Local alloc buffer for promotion into this space.
77 friend class CFLS_LAB;
78 // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class
79 template <typename SpaceType>
80 friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
81 template <typename SpaceType>
82 friend void CompactibleSpace::scan_and_compact(SpaceType* space);
83 template <typename SpaceType>
84 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
85
86 // "Size" of chunks of work (executed during parallel remark phases
87 // of CMS collection); this probably belongs in CMSCollector, although
88 // it's cached here because it's used in
89 // initialize_sequential_subtasks_for_rescan() which modifies
90 // par_seq_tasks which also lives in Space. XXX
91 const size_t _rescan_task_size;
92 const size_t _marking_task_size;
93
94 // Yet another sequential tasks done structure. This supports
95 // CMS GC, where we have threads dynamically
96 // claiming sub-tasks from a larger parallel task.
97 SequentialSubTasksDone _conc_par_seq_tasks;
98
99 BlockOffsetArrayNonContigSpace _bt;
100
101 CMSCollector* _collector;
102 ConcurrentMarkSweepGeneration* _gen;
103
104 // Data structures for free blocks (used during allocation/sweeping)
105
106 // Allocation is done linearly from two different blocks depending on
107 // whether the request is small or large, in an effort to reduce
108 // fragmentation. We assume that any locking for allocation is done
109 // by the containing generation. Thus, none of the methods in this
110 // space are re-entrant.
111 enum SomeConstants {
112 SmallForLinearAlloc = 16, // size < this then use _sLAB
113 SmallForDictionary = 257, // size < this then use _indexedFreeList
114 IndexSetSize = SmallForDictionary // keep this odd-sized
115 };
116 static size_t IndexSetStart;
117 static size_t IndexSetStride;
118
119 private:
120 enum FitStrategyOptions {
121 FreeBlockStrategyNone = 0,
122 FreeBlockBestFitFirst
123 };
124
125 PromotionInfo _promoInfo;
126
127 // Helps to impose a global total order on freelistLock ranks;
128 // assumes that CFLSpace's are allocated in global total order
129 static int _lockRank;
130
131 // A lock protecting the free lists and free blocks;
132 // mutable because of ubiquity of locking even for otherwise const methods
133 mutable Mutex _freelistLock;
134 // Locking verifier convenience function
135 void assert_locked() const PRODUCT_RETURN;
136 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
137
138 // Linear allocation blocks
139 LinearAllocBlock _smallLinearAllocBlock;
140
141 FreeBlockDictionary<FreeChunk>::DictionaryChoice _dictionaryChoice;
142 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks
143
144 // Indexed array for small size blocks
145 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
146
147 // Allocation strategy
148 bool _fitStrategy; // Use best fit strategy
149 bool _adaptive_freelists; // Use adaptive freelists
150
151 // This is an address close to the largest free chunk in the heap.
152 // It is currently assumed to be at the end of the heap. Free
153 // chunks with addresses greater than nearLargestChunk are coalesced
154 // in an effort to maintain a large chunk at the end of the heap.
155 HeapWord* _nearLargestChunk;
156
157 // Used to keep track of limit of sweep for the space
158 HeapWord* _sweep_limit;
159
160 // Used to make the young collector update the mod union table
161 MemRegionClosure* _preconsumptionDirtyCardClosure;
162
163 // Support for compacting cms
164 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
165 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
166
167 // Initialization helpers.
168 void initializeIndexedFreeListArray();
169
170 // Extra stuff to manage promotion parallelism.
171
172 // A lock protecting the dictionary during par promotion allocation.
173 mutable Mutex _parDictionaryAllocLock;
174 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
175
176 // Locks protecting the exact lists during par promotion allocation.
177 Mutex* _indexedFreeListParLocks[IndexSetSize];
178
179 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
180 // required to be smaller than "IndexSetSize".) If successful,
181 // adds them to "fl", which is required to be an empty free list.
182 // If the count of "fl" is negative, it's absolute value indicates a
183 // number of free chunks that had been previously "borrowed" from global
184 // list of size "word_sz", and must now be decremented.
185 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
186
187 // Used by par_get_chunk_of_blocks() for the chunks from the
188 // indexed_free_lists.
189 bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
190
191 // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
192 // evenly splittable into "n" "word_sz" chunks. Returns that
193 // evenly splittable chunk. May split a larger chunk to get the
194 // evenly splittable chunk.
195 FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
196
197 // Used by par_get_chunk_of_blocks() for the chunks from the
198 // dictionary.
199 void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
200
201 // Allocation helper functions
202 // Allocate using a strategy that takes from the indexed free lists
203 // first. This allocation strategy assumes a companion sweeping
204 // strategy that attempts to keep the needed number of chunks in each
205 // indexed free lists.
206 HeapWord* allocate_adaptive_freelists(size_t size);
207 // Allocate from the linear allocation buffers first. This allocation
208 // strategy assumes maximal coalescing can maintain chunks large enough
209 // to be used as linear allocation buffers.
210 HeapWord* allocate_non_adaptive_freelists(size_t size);
211
212 // Gets a chunk from the linear allocation block (LinAB). If there
213 // is not enough space in the LinAB, refills it.
214 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
215 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
216 // Get a chunk from the space remaining in the linear allocation block. Do
217 // not attempt to refill if the space is not available, return NULL. Do the
218 // repairs on the linear allocation block as appropriate.
219 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
220 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
221
222 // Helper function for getChunkFromIndexedFreeList.
223 // Replenish the indexed free list for this "size". Do not take from an
224 // underpopulated size.
225 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
226
227 // Get a chunk from the indexed free list. If the indexed free list
228 // does not have a free chunk, try to replenish the indexed free list
229 // then get the free chunk from the replenished indexed free list.
230 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
231
232 // The returned chunk may be larger than requested (or null).
233 FreeChunk* getChunkFromDictionary(size_t size);
234 // The returned chunk is the exact size requested (or null).
235 FreeChunk* getChunkFromDictionaryExact(size_t size);
236
237 // Find a chunk in the indexed free list that is the best
238 // fit for size "numWords".
239 FreeChunk* bestFitSmall(size_t numWords);
240 // For free list "fl" of chunks of size > numWords,
241 // remove a chunk, split off a chunk of size numWords
242 // and return it. The split off remainder is returned to
243 // the free lists. The old name for getFromListGreater
244 // was lookInListGreater.
245 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
246 // Get a chunk in the indexed free list or dictionary,
247 // by considering a larger chunk and splitting it.
248 FreeChunk* getChunkFromGreater(size_t numWords);
249 // Verify that the given chunk is in the indexed free lists.
250 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
251 // Remove the specified chunk from the indexed free lists.
252 void removeChunkFromIndexedFreeList(FreeChunk* fc);
253 // Remove the specified chunk from the dictionary.
254 void removeChunkFromDictionary(FreeChunk* fc);
255 // Split a free chunk into a smaller free chunk of size "new_size".
256 // Return the smaller free chunk and return the remainder to the
257 // free lists.
258 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
259 // Add a chunk to the free lists.
260 void addChunkToFreeLists(HeapWord* chunk, size_t size);
261 // Add a chunk to the free lists, preferring to suffix it
262 // to the last free chunk at end of space if possible, and
263 // updating the block census stats as well as block offset table.
264 // Take any locks as appropriate if we are multithreaded.
265 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
266 // Add a free chunk to the indexed free lists.
267 void returnChunkToFreeList(FreeChunk* chunk);
268 // Add a free chunk to the dictionary.
269 void returnChunkToDictionary(FreeChunk* chunk);
270
271 // Functions for maintaining the linear allocation buffers (LinAB).
272 // Repairing a linear allocation block refers to operations
273 // performed on the remainder of a LinAB after an allocation
274 // has been made from it.
275 void repairLinearAllocationBlocks();
276 void repairLinearAllocBlock(LinearAllocBlock* blk);
277 void refillLinearAllocBlock(LinearAllocBlock* blk);
278 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
279 void refillLinearAllocBlocksIfNeeded();
280
281 void verify_objects_initialized() const;
282
283 // Statistics reporting helper functions
284 void reportFreeListStatistics() const;
285 void reportIndexedFreeListStatistics() const;
286 size_t maxChunkSizeInIndexedFreeLists() const;
287 size_t numFreeBlocksInIndexedFreeLists() const;
288 // Accessor
289 HeapWord* unallocated_block() const {
290 if (BlockOffsetArrayUseUnallocatedBlock) {
291 HeapWord* ub = _bt.unallocated_block();
292 assert(ub >= bottom() &&
293 ub <= end(), "space invariant");
294 return ub;
295 } else {
296 return end();
297 }
298 }
299 void freed(HeapWord* start, size_t size) {
300 _bt.freed(start, size);
301 }
302
303 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
304 // See comments for CompactibleSpace for more information.
305 inline HeapWord* scan_limit() const {
306 return end();
307 }
308
309 inline bool scanned_block_is_obj(const HeapWord* addr) const {
310 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
311 }
312
313 inline size_t scanned_block_size(const HeapWord* addr) const {
314 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
315 }
316
317 inline size_t adjust_obj_size(size_t size) const {
318 return adjustObjectSize(size);
319 }
320
321 inline size_t obj_size(const HeapWord* addr) const {
322 return adjustObjectSize(oop(addr)->size());
323 }
324
325 protected:
326 // Reset the indexed free list to its initial empty condition.
327 void resetIndexedFreeListArray();
328 // Reset to an initial state with a single free block described
329 // by the MemRegion parameter.
330 void reset(MemRegion mr);
331 // Return the total number of words in the indexed free lists.
332 size_t totalSizeInIndexedFreeLists() const;
333
334 public:
335 // Constructor
336 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
337 bool use_adaptive_freelists,
338 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
339 // Accessors
340 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
341 FreeBlockDictionary<FreeChunk>* dictionary() const { return _dictionary; }
342 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
343 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
344
345 // Set CMS global values.
346 static void set_cms_values();
347
348 // Return the free chunk at the end of the space. If no such
349 // chunk exists, return NULL.
350 FreeChunk* find_chunk_at_end();
351
352 bool adaptive_freelists() const { return _adaptive_freelists; }
353
354 void set_collector(CMSCollector* collector) { _collector = collector; }
355
356 // Support for parallelization of rescan and marking.
357 const size_t rescan_task_size() const { return _rescan_task_size; }
358 const size_t marking_task_size() const { return _marking_task_size; }
359 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
360 void initialize_sequential_subtasks_for_rescan(int n_threads);
361 void initialize_sequential_subtasks_for_marking(int n_threads,
362 HeapWord* low = NULL);
363
364 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
365 return _preconsumptionDirtyCardClosure;
366 }
367
368 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
369 _preconsumptionDirtyCardClosure = cl;
370 }
371
372 // Space enquiries
373 size_t used() const;
374 size_t free() const;
375 size_t max_alloc_in_words() const;
376 // XXX: should have a less conservative used_region() than that of
377 // Space; we could consider keeping track of highest allocated
378 // address and correcting that at each sweep, as the sweeper
379 // goes through the entire allocated part of the generation. We
380 // could also use that information to keep the sweeper from
381 // sweeping more than is necessary. The allocator and sweeper will
382 // of course need to synchronize on this, since the sweeper will
383 // try to bump down the address and the allocator will try to bump it up.
384 // For now, however, we'll just use the default used_region()
385 // which overestimates the region by returning the entire
386 // committed region (this is safe, but inefficient).
387
388 // Returns a subregion of the space containing all the objects in
389 // the space.
390 MemRegion used_region() const {
391 return MemRegion(bottom(),
392 BlockOffsetArrayUseUnallocatedBlock ?
393 unallocated_block() : end());
394 }
395
396 virtual bool is_free_block(const HeapWord* p) const;
397
398 // Resizing support
399 void set_end(HeapWord* value); // override
400
401 // Never mangle CompactibleFreeListSpace
402 void mangle_unused_area() {}
403 void mangle_unused_area_complete() {}
404
405 // Mutual exclusion support
406 Mutex* freelistLock() const { return &_freelistLock; }
407
408 // Iteration support
409 void oop_iterate(ExtendedOopClosure* cl);
410
411 void object_iterate(ObjectClosure* blk);
412 // Apply the closure to each object in the space whose references
413 // point to objects in the heap. The usage of CompactibleFreeListSpace
414 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
415 // objects in the space with references to objects that are no longer
416 // valid. For example, an object may reference another object
417 // that has already been sweep up (collected). This method uses
418 // obj_is_alive() to determine whether it is safe to iterate of
419 // an object.
420 void safe_object_iterate(ObjectClosure* blk);
421
422 // Iterate over all objects that intersect with mr, calling "cl->do_object"
423 // on each. There is an exception to this: if this closure has already
424 // been invoked on an object, it may skip such objects in some cases. This is
425 // Most likely to happen in an "upwards" (ascending address) iteration of
426 // MemRegions.
427 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
428
429 // Requires that "mr" be entirely within the space.
430 // Apply "cl->do_object" to all objects that intersect with "mr".
431 // If the iteration encounters an unparseable portion of the region,
432 // terminate the iteration and return the address of the start of the
433 // subregion that isn't done. Return of "NULL" indicates that the
434 // iteration completed.
435 HeapWord* object_iterate_careful_m(MemRegion mr,
436 ObjectClosureCareful* cl);
437
438 // Override: provides a DCTO_CL specific to this kind of space.
439 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
440 CardTableModRefBS::PrecisionStyle precision,
441 HeapWord* boundary,
442 bool parallel);
443
444 void blk_iterate(BlkClosure* cl);
445 void blk_iterate_careful(BlkClosureCareful* cl);
446 HeapWord* block_start_const(const void* p) const;
447 HeapWord* block_start_careful(const void* p) const;
448 size_t block_size(const HeapWord* p) const;
449 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
450 bool block_is_obj(const HeapWord* p) const;
451 bool obj_is_alive(const HeapWord* p) const;
452 size_t block_size_nopar(const HeapWord* p) const;
453 bool block_is_obj_nopar(const HeapWord* p) const;
454
455 // Iteration support for promotion
456 void save_marks();
457 bool no_allocs_since_save_marks();
458
459 // Iteration support for sweeping
460 void save_sweep_limit() {
461 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
462 unallocated_block() : end();
463 if (CMSTraceSweeper) {
464 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
465 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
466 p2i(_sweep_limit), p2i(bottom()), p2i(end()));
467 }
468 }
469 NOT_PRODUCT(
470 void clear_sweep_limit() { _sweep_limit = NULL; }
471 )
472 HeapWord* sweep_limit() { return _sweep_limit; }
473
474 // Apply "blk->do_oop" to the addresses of all reference fields in objects
475 // promoted into this generation since the most recent save_marks() call.
476 // Fields in objects allocated by applications of the closure
477 // *are* included in the iteration. Thus, when the iteration completes
478 // there should be no further such objects remaining.
479 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
480 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
481 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
482 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
483
484 // Allocation support
485 HeapWord* allocate(size_t size);
486 HeapWord* par_allocate(size_t size);
487
488 oop promote(oop obj, size_t obj_size);
489 void gc_prologue();
490 void gc_epilogue();
491
492 // This call is used by a containing CMS generation / collector
493 // to inform the CFLS space that a sweep has been completed
494 // and that the space can do any related house-keeping functions.
495 void sweep_completed();
496
497 // For an object in this space, the mark-word's two
498 // LSB's having the value [11] indicates that it has been
499 // promoted since the most recent call to save_marks() on
500 // this generation and has not subsequently been iterated
501 // over (using oop_since_save_marks_iterate() above).
502 // This property holds only for single-threaded collections,
503 // and is typically used for Cheney scans; for MT scavenges,
504 // the property holds for all objects promoted during that
505 // scavenge for the duration of the scavenge and is used
506 // by card-scanning to avoid scanning objects (being) promoted
507 // during that scavenge.
508 bool obj_allocated_since_save_marks(const oop obj) const {
509 assert(is_in_reserved(obj), "Wrong space?");
510 return ((PromotedObject*)obj)->hasPromotedMark();
511 }
512
513 // A worst-case estimate of the space required (in HeapWords) to expand the
514 // heap when promoting an obj of size obj_size.
515 size_t expansionSpaceRequired(size_t obj_size) const;
516
517 FreeChunk* allocateScratch(size_t size);
518
519 // Returns true if either the small or large linear allocation buffer is empty.
520 bool linearAllocationWouldFail() const;
521
522 // Adjust the chunk for the minimum size. This version is called in
523 // most cases in CompactibleFreeListSpace methods.
524 inline static size_t adjustObjectSize(size_t size) {
525 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
526 }
527 // This is a virtual version of adjustObjectSize() that is called
528 // only occasionally when the compaction space changes and the type
529 // of the new compaction space is is only known to be CompactibleSpace.
530 size_t adjust_object_size_v(size_t size) const {
531 return adjustObjectSize(size);
532 }
533 // Minimum size of a free block.
534 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
535 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
536 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
537 bool coalesced);
538
539 // Support for decisions regarding concurrent collection policy.
540 bool should_concurrent_collect() const;
541
542 // Support for compaction.
543 void prepare_for_compaction(CompactPoint* cp);
544 void adjust_pointers();
545 void compact();
546 // Reset the space to reflect the fact that a compaction of the
547 // space has been done.
548 virtual void reset_after_compaction();
549
550 // Debugging support.
551 void print() const;
552 void print_on(outputStream* st) const;
553 void prepare_for_verify();
554 void verify() const;
555 void verifyFreeLists() const PRODUCT_RETURN;
556 void verifyIndexedFreeLists() const;
557 void verifyIndexedFreeList(size_t size) const;
558 // Verify that the given chunk is in the free lists:
559 // i.e. either the binary tree dictionary, the indexed free lists
560 // or the linear allocation block.
561 bool verify_chunk_in_free_list(FreeChunk* fc) const;
562 // Verify that the given chunk is the linear allocation block.
563 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
564 // Do some basic checks on the the free lists.
565 void check_free_list_consistency() const PRODUCT_RETURN;
566
567 // Printing support
568 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
569 void print_indexed_free_lists(outputStream* st) const;
570 void print_dictionary_free_lists(outputStream* st) const;
571 void print_promo_info_blocks(outputStream* st) const;
572
573 NOT_PRODUCT (
574 void initializeIndexedFreeListArrayReturnedBytes();
575 size_t sumIndexedFreeListArrayReturnedBytes();
576 // Return the total number of chunks in the indexed free lists.
577 size_t totalCountInIndexedFreeLists() const;
578 // Return the total number of chunks in the space.
579 size_t totalCount();
580 )
581
582 // The census consists of counts of the quantities such as
583 // the current count of the free chunks, number of chunks
584 // created as a result of the split of a larger chunk or
585 // coalescing of smaller chucks, etc. The counts in the
586 // census is used to make decisions on splitting and
587 // coalescing of chunks during the sweep of garbage.
588
589 // Print the statistics for the free lists.
590 void printFLCensus(size_t sweep_count) const;
591
592 // Statistics functions
593 // Initialize census for lists before the sweep.
594 void beginSweepFLCensus(float inter_sweep_current,
595 float inter_sweep_estimate,
596 float intra_sweep_estimate);
597 // Set the surplus for each of the free lists.
598 void setFLSurplus();
599 // Set the hint for each of the free lists.
600 void setFLHints();
601 // Clear the census for each of the free lists.
602 void clearFLCensus();
603 // Perform functions for the census after the end of the sweep.
604 void endSweepFLCensus(size_t sweep_count);
605 // Return true if the count of free chunks is greater
606 // than the desired number of free chunks.
607 bool coalOverPopulated(size_t size);
608
609 // Record (for each size):
610 //
611 // split-births = #chunks added due to splits in (prev-sweep-end,
612 // this-sweep-start)
613 // split-deaths = #chunks removed for splits in (prev-sweep-end,
614 // this-sweep-start)
615 // num-curr = #chunks at start of this sweep
616 // num-prev = #chunks at end of previous sweep
617 //
618 // The above are quantities that are measured. Now define:
619 //
620 // num-desired := num-prev + split-births - split-deaths - num-curr
621 //
622 // Roughly, num-prev + split-births is the supply,
623 // split-deaths is demand due to other sizes
624 // and num-curr is what we have left.
625 //
626 // Thus, num-desired is roughly speaking the "legitimate demand"
627 // for blocks of this size and what we are striving to reach at the
628 // end of the current sweep.
629 //
630 // For a given list, let num-len be its current population.
631 // Define, for a free list of a given size:
632 //
633 // coal-overpopulated := num-len >= num-desired * coal-surplus
634 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
635 // coalescing -- we do not coalesce unless we think that the current
636 // supply has exceeded the estimated demand by more than 5%).
637 //
638 // For the set of sizes in the binary tree, which is neither dense nor
639 // closed, it may be the case that for a particular size we have never
640 // had, or do not now have, or did not have at the previous sweep,
641 // chunks of that size. We need to extend the definition of
642 // coal-overpopulated to such sizes as well:
643 //
644 // For a chunk in/not in the binary tree, extend coal-overpopulated
645 // defined above to include all sizes as follows:
646 //
647 // . a size that is non-existent is coal-overpopulated
648 // . a size that has a num-desired <= 0 as defined above is
649 // coal-overpopulated.
650 //
651 // Also define, for a chunk heap-offset C and mountain heap-offset M:
652 //
653 // close-to-mountain := C >= 0.99 * M
654 //
655 // Now, the coalescing strategy is:
656 //
657 // Coalesce left-hand chunk with right-hand chunk if and
658 // only if:
659 //
660 // EITHER
661 // . left-hand chunk is of a size that is coal-overpopulated
662 // OR
663 // . right-hand chunk is close-to-mountain
664 void smallCoalBirth(size_t size);
665 void smallCoalDeath(size_t size);
666 void coalBirth(size_t size);
667 void coalDeath(size_t size);
668 void smallSplitBirth(size_t size);
669 void smallSplitDeath(size_t size);
670 void split_birth(size_t size);
671 void splitDeath(size_t size);
672 void split(size_t from, size_t to1);
673
674 double flsFrag() const;
675 };
676
677 // A parallel-GC-thread-local allocation buffer for allocation into a
678 // CompactibleFreeListSpace.
679 class CFLS_LAB : public CHeapObj<mtGC> {
680 // The space that this buffer allocates into.
681 CompactibleFreeListSpace* _cfls;
682
683 // Our local free lists.
684 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
685
686 // Initialized from a command-line arg.
687
688 // Allocation statistics in support of dynamic adjustment of
689 // #blocks to claim per get_from_global_pool() call below.
690 static AdaptiveWeightedAverage
691 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
692 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
693 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
694 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
695
696 // Internal work method
697 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
698
699 public:
700 static const int _default_dynamic_old_plab_size = 16;
701 static const int _default_static_old_plab_size = 50;
702
703 CFLS_LAB(CompactibleFreeListSpace* cfls);
704
705 // Allocate and return a block of the given size, or else return NULL.
706 HeapWord* alloc(size_t word_sz);
707
708 // Return any unused portions of the buffer to the global pool.
709 void retire(int tid);
710
711 // Dynamic OldPLABSize sizing
712 static void compute_desired_plab_size();
713 // When the settings are modified from default static initialization
714 static void modify_initialization(size_t n, unsigned wt);
715 };
716
717 size_t PromotionInfo::refillSize() const {
718 const size_t CMSSpoolBlockSize = 256;
719 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
720 * CMSSpoolBlockSize);
721 return CompactibleFreeListSpace::adjustObjectSize(sz);
722 }
723
724 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP