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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 virtual bool isCompactibleFreeListSpace() { return true; }
346
347 // Set CMS global values.
348 static void set_cms_values();
349
350 // Return the free chunk at the end of the space. If no such
351 // chunk exists, return NULL.
352 FreeChunk* find_chunk_at_end();
353
354 bool adaptive_freelists() const { return _adaptive_freelists; }
355
356 void set_collector(CMSCollector* collector) { _collector = collector; }
357
358 // Support for parallelization of rescan and marking.
359 const size_t rescan_task_size() const { return _rescan_task_size; }
360 const size_t marking_task_size() const { return _marking_task_size; }
361 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
362 void initialize_sequential_subtasks_for_rescan(int n_threads);
363 void initialize_sequential_subtasks_for_marking(int n_threads,
364 HeapWord* low = NULL);
365
366 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
367 return _preconsumptionDirtyCardClosure;
368 }
369
370 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
371 _preconsumptionDirtyCardClosure = cl;
372 }
373
374 // Space enquiries
375 size_t used() const;
376 size_t free() const;
377 size_t max_alloc_in_words() const;
378 // XXX: should have a less conservative used_region() than that of
379 // Space; we could consider keeping track of highest allocated
380 // address and correcting that at each sweep, as the sweeper
381 // goes through the entire allocated part of the generation. We
382 // could also use that information to keep the sweeper from
383 // sweeping more than is necessary. The allocator and sweeper will
384 // of course need to synchronize on this, since the sweeper will
385 // try to bump down the address and the allocator will try to bump it up.
386 // For now, however, we'll just use the default used_region()
387 // which overestimates the region by returning the entire
388 // committed region (this is safe, but inefficient).
389
390 // Returns a subregion of the space containing all the objects in
391 // the space.
392 MemRegion used_region() const {
393 return MemRegion(bottom(),
394 BlockOffsetArrayUseUnallocatedBlock ?
395 unallocated_block() : end());
396 }
397
398 virtual bool is_free_block(const HeapWord* p) const;
399
400 // Resizing support
401 void set_end(HeapWord* value); // override
402
403 // Never mangle CompactibleFreeListSpace
404 void mangle_unused_area() {}
405 void mangle_unused_area_complete() {}
406
407 // Mutual exclusion support
408 Mutex* freelistLock() const { return &_freelistLock; }
409
410 // Iteration support
411 void oop_iterate(ExtendedOopClosure* cl);
412
413 void object_iterate(ObjectClosure* blk);
414 // Apply the closure to each object in the space whose references
415 // point to objects in the heap. The usage of CompactibleFreeListSpace
416 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
417 // objects in the space with references to objects that are no longer
418 // valid. For example, an object may reference another object
419 // that has already been sweep up (collected). This method uses
420 // obj_is_alive() to determine whether it is safe to iterate of
421 // an object.
422 void safe_object_iterate(ObjectClosure* blk);
423
424 // Iterate over all objects that intersect with mr, calling "cl->do_object"
425 // on each. There is an exception to this: if this closure has already
426 // been invoked on an object, it may skip such objects in some cases. This is
427 // Most likely to happen in an "upwards" (ascending address) iteration of
428 // MemRegions.
429 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
430
431 // Requires that "mr" be entirely within the space.
432 // Apply "cl->do_object" to all objects that intersect with "mr".
433 // If the iteration encounters an unparseable portion of the region,
434 // terminate the iteration and return the address of the start of the
435 // subregion that isn't done. Return of "NULL" indicates that the
436 // iteration completed.
437 HeapWord* object_iterate_careful_m(MemRegion mr,
438 ObjectClosureCareful* cl);
439
440 // Override: provides a DCTO_CL specific to this kind of space.
441 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
442 CardTableModRefBS::PrecisionStyle precision,
443 HeapWord* boundary,
444 bool parallel);
445
446 void blk_iterate(BlkClosure* cl);
447 void blk_iterate_careful(BlkClosureCareful* cl);
448 HeapWord* block_start_const(const void* p) const;
449 HeapWord* block_start_careful(const void* p) const;
450 size_t block_size(const HeapWord* p) const;
451 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
452 bool block_is_obj(const HeapWord* p) const;
453 bool obj_is_alive(const HeapWord* p) const;
454 size_t block_size_nopar(const HeapWord* p) const;
455 bool block_is_obj_nopar(const HeapWord* p) const;
456
457 // Iteration support for promotion
458 void save_marks();
459 bool no_allocs_since_save_marks();
460
461 // Iteration support for sweeping
462 void save_sweep_limit() {
463 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
464 unallocated_block() : end();
465 if (CMSTraceSweeper) {
466 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
467 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
468 p2i(_sweep_limit), p2i(bottom()), p2i(end()));
469 }
470 }
471 NOT_PRODUCT(
472 void clear_sweep_limit() { _sweep_limit = NULL; }
473 )
474 HeapWord* sweep_limit() { return _sweep_limit; }
475
476 // Apply "blk->do_oop" to the addresses of all reference fields in objects
477 // promoted into this generation since the most recent save_marks() call.
478 // Fields in objects allocated by applications of the closure
479 // *are* included in the iteration. Thus, when the iteration completes
480 // there should be no further such objects remaining.
481 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
482 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
483 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
484 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
485
486 // Allocation support
487 HeapWord* allocate(size_t size);
488 HeapWord* par_allocate(size_t size);
489
490 oop promote(oop obj, size_t obj_size);
491 void gc_prologue();
492 void gc_epilogue();
493
494 // This call is used by a containing CMS generation / collector
495 // to inform the CFLS space that a sweep has been completed
496 // and that the space can do any related house-keeping functions.
497 void sweep_completed();
498
499 // For an object in this space, the mark-word's two
500 // LSB's having the value [11] indicates that it has been
501 // promoted since the most recent call to save_marks() on
502 // this generation and has not subsequently been iterated
503 // over (using oop_since_save_marks_iterate() above).
504 // This property holds only for single-threaded collections,
505 // and is typically used for Cheney scans; for MT scavenges,
506 // the property holds for all objects promoted during that
507 // scavenge for the duration of the scavenge and is used
508 // by card-scanning to avoid scanning objects (being) promoted
509 // during that scavenge.
510 bool obj_allocated_since_save_marks(const oop obj) const {
511 assert(is_in_reserved(obj), "Wrong space?");
512 return ((PromotedObject*)obj)->hasPromotedMark();
513 }
514
515 // A worst-case estimate of the space required (in HeapWords) to expand the
516 // heap when promoting an obj of size obj_size.
517 size_t expansionSpaceRequired(size_t obj_size) const;
518
519 FreeChunk* allocateScratch(size_t size);
520
521 // Returns true if either the small or large linear allocation buffer is empty.
522 bool linearAllocationWouldFail() const;
523
524 // Adjust the chunk for the minimum size. This version is called in
525 // most cases in CompactibleFreeListSpace methods.
526 inline static size_t adjustObjectSize(size_t size) {
527 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
528 }
529 // This is a virtual version of adjustObjectSize() that is called
530 // only occasionally when the compaction space changes and the type
531 // of the new compaction space is is only known to be CompactibleSpace.
532 size_t adjust_object_size_v(size_t size) const {
533 return adjustObjectSize(size);
534 }
535 // Minimum size of a free block.
536 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
537 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
538 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
539 bool coalesced);
540
541 // Support for decisions regarding concurrent collection policy.
542 bool should_concurrent_collect() const;
543
544 // Support for compaction.
545 void prepare_for_compaction(CompactPoint* cp);
546 void pms_prepare_for_compaction_work(CompactPoint* cp);
547 void adjust_pointers();
548 void compact();
549 void pms_compact_work();
550 // Reset the space to reflect the fact that a compaction of the
551 // space has been done.
552 virtual void reset_after_compaction();
553
554 // Debugging support.
555 void print() const;
556 void print_on(outputStream* st) const;
557 void prepare_for_verify();
558 void verify() const;
559 void verifyFreeLists() const PRODUCT_RETURN;
560 void verifyIndexedFreeLists() const;
561 void verifyIndexedFreeList(size_t size) const;
562 // Verify that the given chunk is in the free lists:
563 // i.e. either the binary tree dictionary, the indexed free lists
564 // or the linear allocation block.
565 bool verify_chunk_in_free_list(FreeChunk* fc) const;
566 // Verify that the given chunk is the linear allocation block.
567 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
568 // Do some basic checks on the the free lists.
569 void check_free_list_consistency() const PRODUCT_RETURN;
570
571 // Printing support
572 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
573 void print_indexed_free_lists(outputStream* st) const;
574 void print_dictionary_free_lists(outputStream* st) const;
575 void print_promo_info_blocks(outputStream* st) const;
576
577 NOT_PRODUCT (
578 void initializeIndexedFreeListArrayReturnedBytes();
579 size_t sumIndexedFreeListArrayReturnedBytes();
580 // Return the total number of chunks in the indexed free lists.
581 size_t totalCountInIndexedFreeLists() const;
582 // Return the total number of chunks in the space.
583 size_t totalCount();
584 )
585
586 // The census consists of counts of the quantities such as
587 // the current count of the free chunks, number of chunks
588 // created as a result of the split of a larger chunk or
589 // coalescing of smaller chucks, etc. The counts in the
590 // census is used to make decisions on splitting and
591 // coalescing of chunks during the sweep of garbage.
592
593 // Print the statistics for the free lists.
594 void printFLCensus(size_t sweep_count) const;
595
596 // Statistics functions
597 // Initialize census for lists before the sweep.
598 void beginSweepFLCensus(float inter_sweep_current,
599 float inter_sweep_estimate,
600 float intra_sweep_estimate);
601 // Set the surplus for each of the free lists.
602 void setFLSurplus();
603 // Set the hint for each of the free lists.
604 void setFLHints();
605 // Clear the census for each of the free lists.
606 void clearFLCensus();
607 // Perform functions for the census after the end of the sweep.
608 void endSweepFLCensus(size_t sweep_count);
609 // Return true if the count of free chunks is greater
610 // than the desired number of free chunks.
611 bool coalOverPopulated(size_t size);
612
613 // Record (for each size):
614 //
615 // split-births = #chunks added due to splits in (prev-sweep-end,
616 // this-sweep-start)
617 // split-deaths = #chunks removed for splits in (prev-sweep-end,
618 // this-sweep-start)
619 // num-curr = #chunks at start of this sweep
620 // num-prev = #chunks at end of previous sweep
621 //
622 // The above are quantities that are measured. Now define:
623 //
624 // num-desired := num-prev + split-births - split-deaths - num-curr
625 //
626 // Roughly, num-prev + split-births is the supply,
627 // split-deaths is demand due to other sizes
628 // and num-curr is what we have left.
629 //
630 // Thus, num-desired is roughly speaking the "legitimate demand"
631 // for blocks of this size and what we are striving to reach at the
632 // end of the current sweep.
633 //
634 // For a given list, let num-len be its current population.
635 // Define, for a free list of a given size:
636 //
637 // coal-overpopulated := num-len >= num-desired * coal-surplus
638 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
639 // coalescing -- we do not coalesce unless we think that the current
640 // supply has exceeded the estimated demand by more than 5%).
641 //
642 // For the set of sizes in the binary tree, which is neither dense nor
643 // closed, it may be the case that for a particular size we have never
644 // had, or do not now have, or did not have at the previous sweep,
645 // chunks of that size. We need to extend the definition of
646 // coal-overpopulated to such sizes as well:
647 //
648 // For a chunk in/not in the binary tree, extend coal-overpopulated
649 // defined above to include all sizes as follows:
650 //
651 // . a size that is non-existent is coal-overpopulated
652 // . a size that has a num-desired <= 0 as defined above is
653 // coal-overpopulated.
654 //
655 // Also define, for a chunk heap-offset C and mountain heap-offset M:
656 //
657 // close-to-mountain := C >= 0.99 * M
658 //
659 // Now, the coalescing strategy is:
660 //
661 // Coalesce left-hand chunk with right-hand chunk if and
662 // only if:
663 //
664 // EITHER
665 // . left-hand chunk is of a size that is coal-overpopulated
666 // OR
667 // . right-hand chunk is close-to-mountain
668 void smallCoalBirth(size_t size);
669 void smallCoalDeath(size_t size);
670 void coalBirth(size_t size);
671 void coalDeath(size_t size);
672 void smallSplitBirth(size_t size);
673 void smallSplitDeath(size_t size);
674 void split_birth(size_t size);
675 void splitDeath(size_t size);
676 void split(size_t from, size_t to1);
677
678 double flsFrag() const;
679 };
680
681 // A parallel-GC-thread-local allocation buffer for allocation into a
682 // CompactibleFreeListSpace.
683 class CFLS_LAB : public CHeapObj<mtGC> {
684 // The space that this buffer allocates into.
685 CompactibleFreeListSpace* _cfls;
686
687 // Our local free lists.
688 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
689
690 // Initialized from a command-line arg.
691
692 // Allocation statistics in support of dynamic adjustment of
693 // #blocks to claim per get_from_global_pool() call below.
694 static AdaptiveWeightedAverage
695 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
696 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
697 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
698 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
699
700 // Internal work method
701 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
702
703 public:
704 static const int _default_dynamic_old_plab_size = 16;
705 static const int _default_static_old_plab_size = 50;
706
707 CFLS_LAB(CompactibleFreeListSpace* cfls);
708
709 // Allocate and return a block of the given size, or else return NULL.
710 HeapWord* alloc(size_t word_sz);
711
712 // Return any unused portions of the buffer to the global pool.
713 void retire(int tid);
714
715 // Dynamic OldPLABSize sizing
716 static void compute_desired_plab_size();
717 // When the settings are modified from default static initialization
718 static void modify_initialization(size_t n, unsigned wt);
719 };
720
721 size_t PromotionInfo::refillSize() const {
722 const size_t CMSSpoolBlockSize = 256;
723 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
724 * CMSSpoolBlockSize);
725 return CompactibleFreeListSpace::adjustObjectSize(sz);
726 }
727
728 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP