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