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* _old_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 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks
142
143 // Indexed array for small size blocks
144 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
145
146 // Allocation strategy
147 bool _fitStrategy; // Use best fit strategy
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
206 // Gets a chunk from the linear allocation block (LinAB). If there
207 // is not enough space in the LinAB, refills it.
208 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
209 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
210 // Get a chunk from the space remaining in the linear allocation block. Do
211 // not attempt to refill if the space is not available, return NULL. Do the
212 // repairs on the linear allocation block as appropriate.
213 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
214 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
215
216 // Helper function for getChunkFromIndexedFreeList.
217 // Replenish the indexed free list for this "size". Do not take from an
218 // underpopulated size.
219 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
220
221 // Get a chunk from the indexed free list. If the indexed free list
222 // does not have a free chunk, try to replenish the indexed free list
223 // then get the free chunk from the replenished indexed free list.
224 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
225
226 // The returned chunk may be larger than requested (or null).
227 FreeChunk* getChunkFromDictionary(size_t size);
228 // The returned chunk is the exact size requested (or null).
229 FreeChunk* getChunkFromDictionaryExact(size_t size);
230
231 // Find a chunk in the indexed free list that is the best
232 // fit for size "numWords".
233 FreeChunk* bestFitSmall(size_t numWords);
234 // For free list "fl" of chunks of size > numWords,
235 // remove a chunk, split off a chunk of size numWords
236 // and return it. The split off remainder is returned to
237 // the free lists. The old name for getFromListGreater
238 // was lookInListGreater.
239 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
240 // Get a chunk in the indexed free list or dictionary,
241 // by considering a larger chunk and splitting it.
242 FreeChunk* getChunkFromGreater(size_t numWords);
243 // Verify that the given chunk is in the indexed free lists.
244 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
245 // Remove the specified chunk from the indexed free lists.
246 void removeChunkFromIndexedFreeList(FreeChunk* fc);
247 // Remove the specified chunk from the dictionary.
248 void removeChunkFromDictionary(FreeChunk* fc);
249 // Split a free chunk into a smaller free chunk of size "new_size".
250 // Return the smaller free chunk and return the remainder to the
251 // free lists.
252 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
253 // Add a chunk to the free lists.
254 void addChunkToFreeLists(HeapWord* chunk, size_t size);
255 // Add a chunk to the free lists, preferring to suffix it
256 // to the last free chunk at end of space if possible, and
257 // updating the block census stats as well as block offset table.
258 // Take any locks as appropriate if we are multithreaded.
259 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
260 // Add a free chunk to the indexed free lists.
261 void returnChunkToFreeList(FreeChunk* chunk);
262 // Add a free chunk to the dictionary.
263 void returnChunkToDictionary(FreeChunk* chunk);
264
265 // Functions for maintaining the linear allocation buffers (LinAB).
266 // Repairing a linear allocation block refers to operations
267 // performed on the remainder of a LinAB after an allocation
268 // has been made from it.
269 void repairLinearAllocationBlocks();
270 void repairLinearAllocBlock(LinearAllocBlock* blk);
271 void refillLinearAllocBlock(LinearAllocBlock* blk);
272 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
273 void refillLinearAllocBlocksIfNeeded();
274
275 void verify_objects_initialized() const;
276
277 // Statistics reporting helper functions
278 void reportFreeListStatistics() const;
279 void reportIndexedFreeListStatistics() const;
280 size_t maxChunkSizeInIndexedFreeLists() const;
281 size_t numFreeBlocksInIndexedFreeLists() const;
282 // Accessor
283 HeapWord* unallocated_block() const {
284 if (BlockOffsetArrayUseUnallocatedBlock) {
285 HeapWord* ub = _bt.unallocated_block();
286 assert(ub >= bottom() &&
287 ub <= end(), "space invariant");
288 return ub;
289 } else {
290 return end();
291 }
292 }
293 void freed(HeapWord* start, size_t size) {
294 _bt.freed(start, size);
295 }
296
297 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
298 // See comments for CompactibleSpace for more information.
299 inline HeapWord* scan_limit() const {
300 return end();
301 }
302
303 inline bool scanned_block_is_obj(const HeapWord* addr) const {
304 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
305 }
306
307 inline size_t scanned_block_size(const HeapWord* addr) const {
308 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
309 }
310
311 inline size_t adjust_obj_size(size_t size) const {
312 return adjustObjectSize(size);
313 }
314
315 inline size_t obj_size(const HeapWord* addr) const {
316 return adjustObjectSize(oop(addr)->size());
317 }
318
319 protected:
320 // Reset the indexed free list to its initial empty condition.
321 void resetIndexedFreeListArray();
322 // Reset to an initial state with a single free block described
323 // by the MemRegion parameter.
324 void reset(MemRegion mr);
325 // Return the total number of words in the indexed free lists.
326 size_t totalSizeInIndexedFreeLists() const;
327
328 public:
329 // Constructor
330 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);
331 // Accessors
332 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
333 FreeBlockDictionary<FreeChunk>* dictionary() const { return _dictionary; }
334 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
335 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
336
337 // Set CMS global values.
338 static void set_cms_values();
339
340 // Return the free chunk at the end of the space. If no such
341 // chunk exists, return NULL.
342 FreeChunk* find_chunk_at_end();
343
344 void set_collector(CMSCollector* collector) { _collector = collector; }
345
346 // Support for parallelization of rescan and marking.
347 const size_t rescan_task_size() const { return _rescan_task_size; }
348 const size_t marking_task_size() const { return _marking_task_size; }
349 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
350 void initialize_sequential_subtasks_for_rescan(int n_threads);
351 void initialize_sequential_subtasks_for_marking(int n_threads,
352 HeapWord* low = NULL);
353
354 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
355 return _preconsumptionDirtyCardClosure;
356 }
357
358 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
359 _preconsumptionDirtyCardClosure = cl;
360 }
361
362 // Space enquiries
363 size_t used() const;
364 size_t free() const;
365 size_t max_alloc_in_words() const;
366 // XXX: should have a less conservative used_region() than that of
367 // Space; we could consider keeping track of highest allocated
368 // address and correcting that at each sweep, as the sweeper
369 // goes through the entire allocated part of the generation. We
370 // could also use that information to keep the sweeper from
371 // sweeping more than is necessary. The allocator and sweeper will
372 // of course need to synchronize on this, since the sweeper will
373 // try to bump down the address and the allocator will try to bump it up.
374 // For now, however, we'll just use the default used_region()
375 // which overestimates the region by returning the entire
376 // committed region (this is safe, but inefficient).
377
378 // Returns a subregion of the space containing all the objects in
379 // the space.
380 MemRegion used_region() const {
381 return MemRegion(bottom(),
382 BlockOffsetArrayUseUnallocatedBlock ?
383 unallocated_block() : end());
384 }
385
386 virtual bool is_free_block(const HeapWord* p) const;
387
388 // Resizing support
389 void set_end(HeapWord* value); // override
390
391 // Never mangle CompactibleFreeListSpace
392 void mangle_unused_area() {}
393 void mangle_unused_area_complete() {}
394
395 // Mutual exclusion support
396 Mutex* freelistLock() const { return &_freelistLock; }
397
398 // Iteration support
399 void oop_iterate(ExtendedOopClosure* cl);
400
401 void object_iterate(ObjectClosure* blk);
402 // Apply the closure to each object in the space whose references
403 // point to objects in the heap. The usage of CompactibleFreeListSpace
404 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
405 // objects in the space with references to objects that are no longer
406 // valid. For example, an object may reference another object
407 // that has already been sweep up (collected). This method uses
408 // obj_is_alive() to determine whether it is safe to iterate of
409 // an object.
410 void safe_object_iterate(ObjectClosure* blk);
411
412 // Iterate over all objects that intersect with mr, calling "cl->do_object"
413 // on each. There is an exception to this: if this closure has already
414 // been invoked on an object, it may skip such objects in some cases. This is
415 // Most likely to happen in an "upwards" (ascending address) iteration of
416 // MemRegions.
417 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
418
419 // Requires that "mr" be entirely within the space.
420 // Apply "cl->do_object" to all objects that intersect with "mr".
421 // If the iteration encounters an unparseable portion of the region,
422 // terminate the iteration and return the address of the start of the
423 // subregion that isn't done. Return of "NULL" indicates that the
424 // iteration completed.
425 HeapWord* object_iterate_careful_m(MemRegion mr,
426 ObjectClosureCareful* cl);
427
428 // Override: provides a DCTO_CL specific to this kind of space.
429 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
430 CardTableModRefBS::PrecisionStyle precision,
431 HeapWord* boundary,
432 bool parallel);
433
434 void blk_iterate(BlkClosure* cl);
435 void blk_iterate_careful(BlkClosureCareful* cl);
436 HeapWord* block_start_const(const void* p) const;
437 HeapWord* block_start_careful(const void* p) const;
438 size_t block_size(const HeapWord* p) const;
439 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
440 bool block_is_obj(const HeapWord* p) const;
441 bool obj_is_alive(const HeapWord* p) const;
442 size_t block_size_nopar(const HeapWord* p) const;
443 bool block_is_obj_nopar(const HeapWord* p) const;
444
445 // Iteration support for promotion
446 void save_marks();
447 bool no_allocs_since_save_marks();
448
449 // Iteration support for sweeping
450 void save_sweep_limit() {
451 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
452 unallocated_block() : end();
453 if (CMSTraceSweeper) {
454 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
455 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
456 p2i(_sweep_limit), p2i(bottom()), p2i(end()));
457 }
458 }
459 NOT_PRODUCT(
460 void clear_sweep_limit() { _sweep_limit = NULL; }
461 )
462 HeapWord* sweep_limit() { return _sweep_limit; }
463
464 // Apply "blk->do_oop" to the addresses of all reference fields in objects
465 // promoted into this generation since the most recent save_marks() call.
466 // Fields in objects allocated by applications of the closure
467 // *are* included in the iteration. Thus, when the iteration completes
468 // there should be no further such objects remaining.
469 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
470 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
471 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
472 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
473
474 // Allocation support
475 HeapWord* allocate(size_t size);
476 HeapWord* par_allocate(size_t size);
477
478 oop promote(oop obj, size_t obj_size);
479 void gc_prologue();
480 void gc_epilogue();
481
482 // This call is used by a containing CMS generation / collector
483 // to inform the CFLS space that a sweep has been completed
484 // and that the space can do any related house-keeping functions.
485 void sweep_completed();
486
487 // For an object in this space, the mark-word's two
488 // LSB's having the value [11] indicates that it has been
489 // promoted since the most recent call to save_marks() on
490 // this generation and has not subsequently been iterated
491 // over (using oop_since_save_marks_iterate() above).
492 // This property holds only for single-threaded collections,
493 // and is typically used for Cheney scans; for MT scavenges,
494 // the property holds for all objects promoted during that
495 // scavenge for the duration of the scavenge and is used
496 // by card-scanning to avoid scanning objects (being) promoted
497 // during that scavenge.
498 bool obj_allocated_since_save_marks(const oop obj) const {
499 assert(is_in_reserved(obj), "Wrong space?");
500 return ((PromotedObject*)obj)->hasPromotedMark();
501 }
502
503 // A worst-case estimate of the space required (in HeapWords) to expand the
504 // heap when promoting an obj of size obj_size.
505 size_t expansionSpaceRequired(size_t obj_size) const;
506
507 FreeChunk* allocateScratch(size_t size);
508
509 // Returns true if either the small or large linear allocation buffer is empty.
510 bool linearAllocationWouldFail() const;
511
512 // Adjust the chunk for the minimum size. This version is called in
513 // most cases in CompactibleFreeListSpace methods.
514 inline static size_t adjustObjectSize(size_t size) {
515 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
516 }
517 // This is a virtual version of adjustObjectSize() that is called
518 // only occasionally when the compaction space changes and the type
519 // of the new compaction space is is only known to be CompactibleSpace.
520 size_t adjust_object_size_v(size_t size) const {
521 return adjustObjectSize(size);
522 }
523 // Minimum size of a free block.
524 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
525 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
526 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
527 bool coalesced);
528
529 // Support for compaction.
530 void prepare_for_compaction(CompactPoint* cp);
531 void adjust_pointers();
532 void compact();
533 // Reset the space to reflect the fact that a compaction of the
534 // space has been done.
535 virtual void reset_after_compaction();
536
537 // Debugging support.
538 void print() const;
539 void print_on(outputStream* st) const;
540 void prepare_for_verify();
541 void verify() const;
542 void verifyFreeLists() const PRODUCT_RETURN;
543 void verifyIndexedFreeLists() const;
544 void verifyIndexedFreeList(size_t size) const;
545 // Verify that the given chunk is in the free lists:
546 // i.e. either the binary tree dictionary, the indexed free lists
547 // or the linear allocation block.
548 bool verify_chunk_in_free_list(FreeChunk* fc) const;
549 // Verify that the given chunk is the linear allocation block.
550 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
551 // Do some basic checks on the the free lists.
552 void check_free_list_consistency() const PRODUCT_RETURN;
553
554 // Printing support
555 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
556 void print_indexed_free_lists(outputStream* st) const;
557 void print_dictionary_free_lists(outputStream* st) const;
558 void print_promo_info_blocks(outputStream* st) const;
559
560 NOT_PRODUCT (
561 void initializeIndexedFreeListArrayReturnedBytes();
562 size_t sumIndexedFreeListArrayReturnedBytes();
563 // Return the total number of chunks in the indexed free lists.
564 size_t totalCountInIndexedFreeLists() const;
565 // Return the total number of chunks in the space.
566 size_t totalCount();
567 )
568
569 // The census consists of counts of the quantities such as
570 // the current count of the free chunks, number of chunks
571 // created as a result of the split of a larger chunk or
572 // coalescing of smaller chucks, etc. The counts in the
573 // census is used to make decisions on splitting and
574 // coalescing of chunks during the sweep of garbage.
575
576 // Print the statistics for the free lists.
577 void printFLCensus(size_t sweep_count) const;
578
579 // Statistics functions
580 // Initialize census for lists before the sweep.
581 void beginSweepFLCensus(float inter_sweep_current,
582 float inter_sweep_estimate,
583 float intra_sweep_estimate);
584 // Set the surplus for each of the free lists.
585 void setFLSurplus();
586 // Set the hint for each of the free lists.
587 void setFLHints();
588 // Clear the census for each of the free lists.
589 void clearFLCensus();
590 // Perform functions for the census after the end of the sweep.
591 void endSweepFLCensus(size_t sweep_count);
592 // Return true if the count of free chunks is greater
593 // than the desired number of free chunks.
594 bool coalOverPopulated(size_t size);
595
596 // Record (for each size):
597 //
598 // split-births = #chunks added due to splits in (prev-sweep-end,
599 // this-sweep-start)
600 // split-deaths = #chunks removed for splits in (prev-sweep-end,
601 // this-sweep-start)
602 // num-curr = #chunks at start of this sweep
603 // num-prev = #chunks at end of previous sweep
604 //
605 // The above are quantities that are measured. Now define:
606 //
607 // num-desired := num-prev + split-births - split-deaths - num-curr
608 //
609 // Roughly, num-prev + split-births is the supply,
610 // split-deaths is demand due to other sizes
611 // and num-curr is what we have left.
612 //
613 // Thus, num-desired is roughly speaking the "legitimate demand"
614 // for blocks of this size and what we are striving to reach at the
615 // end of the current sweep.
616 //
617 // For a given list, let num-len be its current population.
618 // Define, for a free list of a given size:
619 //
620 // coal-overpopulated := num-len >= num-desired * coal-surplus
621 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
622 // coalescing -- we do not coalesce unless we think that the current
623 // supply has exceeded the estimated demand by more than 5%).
624 //
625 // For the set of sizes in the binary tree, which is neither dense nor
626 // closed, it may be the case that for a particular size we have never
627 // had, or do not now have, or did not have at the previous sweep,
628 // chunks of that size. We need to extend the definition of
629 // coal-overpopulated to such sizes as well:
630 //
631 // For a chunk in/not in the binary tree, extend coal-overpopulated
632 // defined above to include all sizes as follows:
633 //
634 // . a size that is non-existent is coal-overpopulated
635 // . a size that has a num-desired <= 0 as defined above is
636 // coal-overpopulated.
637 //
638 // Also define, for a chunk heap-offset C and mountain heap-offset M:
639 //
640 // close-to-mountain := C >= 0.99 * M
641 //
642 // Now, the coalescing strategy is:
643 //
644 // Coalesce left-hand chunk with right-hand chunk if and
645 // only if:
646 //
647 // EITHER
648 // . left-hand chunk is of a size that is coal-overpopulated
649 // OR
650 // . right-hand chunk is close-to-mountain
651 void smallCoalBirth(size_t size);
652 void smallCoalDeath(size_t size);
653 void coalBirth(size_t size);
654 void coalDeath(size_t size);
655 void smallSplitBirth(size_t size);
656 void smallSplitDeath(size_t size);
657 void split_birth(size_t size);
658 void splitDeath(size_t size);
659 void split(size_t from, size_t to1);
660
661 double flsFrag() const;
662 };
663
664 // A parallel-GC-thread-local allocation buffer for allocation into a
665 // CompactibleFreeListSpace.
666 class CFLS_LAB : public CHeapObj<mtGC> {
667 // The space that this buffer allocates into.
668 CompactibleFreeListSpace* _cfls;
669
670 // Our local free lists.
671 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
672
673 // Initialized from a command-line arg.
674
675 // Allocation statistics in support of dynamic adjustment of
676 // #blocks to claim per get_from_global_pool() call below.
677 static AdaptiveWeightedAverage
678 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
679 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
680 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
681 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
682
683 // Internal work method
684 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
685
686 public:
687 static const int _default_dynamic_old_plab_size = 16;
688 static const int _default_static_old_plab_size = 50;
689
690 CFLS_LAB(CompactibleFreeListSpace* cfls);
691
692 // Allocate and return a block of the given size, or else return NULL.
693 HeapWord* alloc(size_t word_sz);
694
695 // Return any unused portions of the buffer to the global pool.
696 void retire(int tid);
697
698 // Dynamic OldPLABSize sizing
699 static void compute_desired_plab_size();
700 // When the settings are modified from default static initialization
701 static void modify_initialization(size_t n, unsigned wt);
702 };
703
704 size_t PromotionInfo::refillSize() const {
705 const size_t CMSSpoolBlockSize = 256;
706 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
707 * CMSSpoolBlockSize);
708 return CompactibleFreeListSpace::adjustObjectSize(sz);
709 }
710
711 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP