1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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 "gc_implementation/shared/gcTrace.hpp"
31 #include "memory/binaryTreeDictionary.hpp"
32 #include "memory/blockOffsetTable.inline.hpp"
33 #include "memory/freeList.hpp"
34 #include "memory/space.hpp"
35
36 // Classes in support of keeping track of promotions into a non-Contiguous
37 // space, in this case a CompactibleFreeListSpace.
38
39 // Forward declarations
40 class CompactibleFreeListSpace;
41 class BlkClosure;
42 class BlkClosureCareful;
43 class FreeChunk;
44 class UpwardsObjectClosure;
45 class ObjectClosureCareful;
46 class Klass;
47
48 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
49 public:
50 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
51 _allocation_size_limit(0) {}
52 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
53 size_t allocation_size_limit) {
54 _ptr = ptr;
55 _word_size = word_size;
56 _refillSize = refill_size;
57 _allocation_size_limit = allocation_size_limit;
58 }
59 HeapWord* _ptr;
60 size_t _word_size;
61 size_t _refillSize;
62 size_t _allocation_size_limit; // Largest size that will be allocated
63
64 void print_on(outputStream* st) const;
65 };
66
67 // Concrete subclass of CompactibleSpace that implements
68 // a free list space, such as used in the concurrent mark sweep
69 // generation.
70
71 class CompactibleFreeListSpace: public CompactibleSpace {
72 friend class VMStructs;
73 friend class ConcurrentMarkSweepGeneration;
74 friend class CMSCollector;
75 // Local alloc buffer for promotion into this space.
76 friend class CFLS_LAB;
77 // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class
78 template <typename SpaceType>
79 friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
80 template <typename SpaceType>
81 friend void CompactibleSpace::scan_and_compact(SpaceType* space);
82 template <typename SpaceType>
83 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
84
85 // "Size" of chunks of work (executed during parallel remark phases
86 // of CMS collection); this probably belongs in CMSCollector, although
87 // it's cached here because it's used in
88 // initialize_sequential_subtasks_for_rescan() which modifies
89 // par_seq_tasks which also lives in Space. XXX
90 const size_t _rescan_task_size;
91 const size_t _marking_task_size;
92
93 // Yet another sequential tasks done structure. This supports
94 // CMS GC, where we have threads dynamically
95 // claiming sub-tasks from a larger parallel task.
96 SequentialSubTasksDone _conc_par_seq_tasks;
97
98 BlockOffsetArrayNonContigSpace _bt;
99
100 CMSCollector* _collector;
101 ConcurrentMarkSweepGeneration* _gen;
102
103 // Data structures for free blocks (used during allocation/sweeping)
104
105 // Allocation is done linearly from two different blocks depending on
106 // whether the request is small or large, in an effort to reduce
107 // fragmentation. We assume that any locking for allocation is done
108 // by the containing generation. Thus, none of the methods in this
109 // space are re-entrant.
110 enum SomeConstants {
111 SmallForLinearAlloc = 16, // size < this then use _sLAB
112 SmallForDictionary = 257, // size < this then use _indexedFreeList
113 IndexSetSize = SmallForDictionary // keep this odd-sized
114 };
115 static size_t IndexSetStart;
116 static size_t IndexSetStride;
117
118 private:
119 enum FitStrategyOptions {
120 FreeBlockStrategyNone = 0,
121 FreeBlockBestFitFirst
122 };
123
124 PromotionInfo _promoInfo;
125
126 // Helps to impose a global total order on freelistLock ranks;
127 // assumes that CFLSpace's are allocated in global total order
128 static int _lockRank;
129
130 // A lock protecting the free lists and free blocks;
131 // mutable because of ubiquity of locking even for otherwise const methods
132 mutable Mutex _freelistLock;
133 // Locking verifier convenience function
134 void assert_locked() const PRODUCT_RETURN;
135 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
136
137 // Linear allocation blocks
138 LinearAllocBlock _smallLinearAllocBlock;
139
140 FreeBlockDictionary<FreeChunk>::DictionaryChoice _dictionaryChoice;
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 bool _adaptive_freelists; // Use adaptive freelists
149
150 // This is an address close to the largest free chunk in the heap.
151 // It is currently assumed to be at the end of the heap. Free
152 // chunks with addresses greater than nearLargestChunk are coalesced
153 // in an effort to maintain a large chunk at the end of the heap.
154 HeapWord* _nearLargestChunk;
155
156 // Used to keep track of limit of sweep for the space
157 HeapWord* _sweep_limit;
158
159 // Support for compacting cms
160 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
161 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
162
163 // Initialization helpers.
164 void initializeIndexedFreeListArray();
165
166 // Extra stuff to manage promotion parallelism.
167
168 // A lock protecting the dictionary during par promotion allocation.
169 mutable Mutex _parDictionaryAllocLock;
170 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
171
172 // Locks protecting the exact lists during par promotion allocation.
173 Mutex* _indexedFreeListParLocks[IndexSetSize];
174
175 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
176 // required to be smaller than "IndexSetSize".) If successful,
177 // adds them to "fl", which is required to be an empty free list.
178 // If the count of "fl" is negative, it's absolute value indicates a
179 // number of free chunks that had been previously "borrowed" from global
180 // list of size "word_sz", and must now be decremented.
181 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
182
183 // Used by par_get_chunk_of_blocks() for the chunks from the
184 // indexed_free_lists.
185 bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
186
187 // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
188 // evenly splittable into "n" "word_sz" chunks. Returns that
189 // evenly splittable chunk. May split a larger chunk to get the
190 // evenly splittable chunk.
191 FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
192
193 // Used by par_get_chunk_of_blocks() for the chunks from the
194 // dictionary.
195 void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
196
197 // Allocation helper functions
198 // Allocate using a strategy that takes from the indexed free lists
199 // first. This allocation strategy assumes a companion sweeping
200 // strategy that attempts to keep the needed number of chunks in each
201 // indexed free lists.
202 HeapWord* allocate_adaptive_freelists(size_t size);
203 // Allocate from the linear allocation buffers first. This allocation
204 // strategy assumes maximal coalescing can maintain chunks large enough
205 // to be used as linear allocation buffers.
206 HeapWord* allocate_non_adaptive_freelists(size_t size);
207
208 // Gets a chunk from the linear allocation block (LinAB). If there
209 // is not enough space in the LinAB, refills it.
210 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
211 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
212 // Get a chunk from the space remaining in the linear allocation block. Do
213 // not attempt to refill if the space is not available, return NULL. Do the
214 // repairs on the linear allocation block as appropriate.
215 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
216 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
217
218 // Helper function for getChunkFromIndexedFreeList.
219 // Replenish the indexed free list for this "size". Do not take from an
220 // underpopulated size.
221 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
222
223 // Get a chunk from the indexed free list. If the indexed free list
224 // does not have a free chunk, try to replenish the indexed free list
225 // then get the free chunk from the replenished indexed free list.
226 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
227
228 // The returned chunk may be larger than requested (or null).
229 FreeChunk* getChunkFromDictionary(size_t size);
230 // The returned chunk is the exact size requested (or null).
231 FreeChunk* getChunkFromDictionaryExact(size_t size);
232
233 // Find a chunk in the indexed free list that is the best
234 // fit for size "numWords".
235 FreeChunk* bestFitSmall(size_t numWords);
236 // For free list "fl" of chunks of size > numWords,
237 // remove a chunk, split off a chunk of size numWords
238 // and return it. The split off remainder is returned to
239 // the free lists. The old name for getFromListGreater
240 // was lookInListGreater.
241 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
242 // Get a chunk in the indexed free list or dictionary,
243 // by considering a larger chunk and splitting it.
244 FreeChunk* getChunkFromGreater(size_t numWords);
245 // Verify that the given chunk is in the indexed free lists.
246 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
247 // Remove the specified chunk from the indexed free lists.
248 void removeChunkFromIndexedFreeList(FreeChunk* fc);
249 // Remove the specified chunk from the dictionary.
250 void removeChunkFromDictionary(FreeChunk* fc);
251 // Split a free chunk into a smaller free chunk of size "new_size".
252 // Return the smaller free chunk and return the remainder to the
253 // free lists.
254 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
255 // Add a chunk to the free lists.
256 void addChunkToFreeLists(HeapWord* chunk, size_t size);
257 // Add a chunk to the free lists, preferring to suffix it
258 // to the last free chunk at end of space if possible, and
259 // updating the block census stats as well as block offset table.
260 // Take any locks as appropriate if we are multithreaded.
261 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
262 // Add a free chunk to the indexed free lists.
263 void returnChunkToFreeList(FreeChunk* chunk);
264 // Add a free chunk to the dictionary.
265 void returnChunkToDictionary(FreeChunk* chunk);
266
267 // Functions for maintaining the linear allocation buffers (LinAB).
268 // Repairing a linear allocation block refers to operations
269 // performed on the remainder of a LinAB after an allocation
270 // has been made from it.
271 void repairLinearAllocationBlocks();
272 void repairLinearAllocBlock(LinearAllocBlock* blk);
273 void refillLinearAllocBlock(LinearAllocBlock* blk);
274 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
275 void refillLinearAllocBlocksIfNeeded();
276
277 void verify_objects_initialized() const;
278
279 // Statistics reporting helper functions
280 void reportFreeListStatistics() const;
281 void reportIndexedFreeListStatistics() const;
282 size_t maxChunkSizeInIndexedFreeLists() const;
283 size_t numFreeBlocksInIndexedFreeLists() const;
284 // Accessor
285 HeapWord* unallocated_block() const {
286 if (BlockOffsetArrayUseUnallocatedBlock) {
287 HeapWord* ub = _bt.unallocated_block();
288 assert(ub >= bottom() &&
289 ub <= end(), "space invariant");
290 return ub;
291 } else {
292 return end();
293 }
294 }
295 void freed(HeapWord* start, size_t size) {
296 _bt.freed(start, size);
297 }
298
299 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
300 // See comments for CompactibleSpace for more information.
301 inline HeapWord* scan_limit() const {
302 return end();
303 }
304
305 inline bool scanned_block_is_obj(const HeapWord* addr) const {
306 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
307 }
308
309 inline size_t scanned_block_size(const HeapWord* addr) const {
310 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
311 }
312
313 inline size_t adjust_obj_size(size_t size) const {
314 return adjustObjectSize(size);
315 }
316
317 inline size_t obj_size(const HeapWord* addr) const {
318 return adjustObjectSize(oop(addr)->size());
319 }
320
321 protected:
322 // Reset the indexed free list to its initial empty condition.
323 void resetIndexedFreeListArray();
324 // Reset to an initial state with a single free block described
325 // by the MemRegion parameter.
326 void reset(MemRegion mr);
327 // Return the total number of words in the indexed free lists.
328 size_t totalSizeInIndexedFreeLists() const;
329
330 public:
331 // Constructor
332 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
333 bool use_adaptive_freelists,
334 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
335 // Accessors
336 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
337 FreeBlockDictionary<FreeChunk>* dictionary() const { return _dictionary; }
338 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
339 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
340
341 // Set CMS global values.
342 static void set_cms_values();
343
344 // Return the free chunk at the end of the space. If no such
345 // chunk exists, return NULL.
346 FreeChunk* find_chunk_at_end();
347
348 bool adaptive_freelists() const { return _adaptive_freelists; }
349
350 void set_collector(CMSCollector* collector) { _collector = collector; }
351
352 // Support for parallelization of rescan and marking.
353 const size_t rescan_task_size() const { return _rescan_task_size; }
354 const size_t marking_task_size() const { return _marking_task_size; }
355 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
356 void initialize_sequential_subtasks_for_rescan(int n_threads);
357 void initialize_sequential_subtasks_for_marking(int n_threads,
358 HeapWord* low = NULL);
359
360 // Space enquiries
361 size_t used() const;
362 size_t free() const;
363 size_t max_alloc_in_words() const;
364 // XXX: should have a less conservative used_region() than that of
365 // Space; we could consider keeping track of highest allocated
366 // address and correcting that at each sweep, as the sweeper
367 // goes through the entire allocated part of the generation. We
368 // could also use that information to keep the sweeper from
369 // sweeping more than is necessary. The allocator and sweeper will
370 // of course need to synchronize on this, since the sweeper will
371 // try to bump down the address and the allocator will try to bump it up.
372 // For now, however, we'll just use the default used_region()
373 // which overestimates the region by returning the entire
374 // committed region (this is safe, but inefficient).
375
376 // Returns a subregion of the space containing all the objects in
377 // the space.
378 MemRegion used_region() const {
379 return MemRegion(bottom(),
380 BlockOffsetArrayUseUnallocatedBlock ?
381 unallocated_block() : end());
382 }
383
384 virtual bool is_free_block(const HeapWord* p) const;
385
386 // Resizing support
387 void set_end(HeapWord* value); // override
388
389 // Mutual exclusion support
390 Mutex* freelistLock() const { return &_freelistLock; }
391
392 // Iteration support
393 void oop_iterate(ExtendedOopClosure* cl);
394
395 void object_iterate(ObjectClosure* blk);
396 // Apply the closure to each object in the space whose references
397 // point to objects in the heap. The usage of CompactibleFreeListSpace
398 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
399 // objects in the space with references to objects that are no longer
400 // valid. For example, an object may reference another object
401 // that has already been sweep up (collected). This method uses
402 // obj_is_alive() to determine whether it is safe to iterate of
403 // an object.
404 void safe_object_iterate(ObjectClosure* blk);
405
406 // Iterate over all objects that intersect with mr, calling "cl->do_object"
407 // on each. There is an exception to this: if this closure has already
408 // been invoked on an object, it may skip such objects in some cases. This is
409 // Most likely to happen in an "upwards" (ascending address) iteration of
410 // MemRegions.
411 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
412
413 // Requires that "mr" be entirely within the space.
414 // Apply "cl->do_object" to all objects that intersect with "mr".
415 // If the iteration encounters an unparseable portion of the region,
416 // terminate the iteration and return the address of the start of the
417 // subregion that isn't done. Return of "NULL" indicates that the
418 // iteration completed.
419 HeapWord* object_iterate_careful_m(MemRegion mr,
420 ObjectClosureCareful* cl);
421
422 // Override: provides a DCTO_CL specific to this kind of space.
423 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
424 CardTableModRefBS::PrecisionStyle precision,
425 HeapWord* boundary);
426
427 void blk_iterate(BlkClosure* cl);
428 void blk_iterate_careful(BlkClosureCareful* cl);
429 HeapWord* block_start_const(const void* p) const;
430 HeapWord* block_start_careful(const void* p) const;
431 size_t block_size(const HeapWord* p) const;
432 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
433 bool block_is_obj(const HeapWord* p) const;
434 bool obj_is_alive(const HeapWord* p) const;
435 size_t block_size_nopar(const HeapWord* p) const;
436 bool block_is_obj_nopar(const HeapWord* p) const;
437
438 // Iteration support for promotion
439 void save_marks();
440 bool no_allocs_since_save_marks();
441
442 // Iteration support for sweeping
443 void save_sweep_limit() {
444 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
445 unallocated_block() : end();
446 if (CMSTraceSweeper) {
447 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
448 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
449 p2i(_sweep_limit), p2i(bottom()), p2i(end()));
450 }
451 }
452 NOT_PRODUCT(
453 void clear_sweep_limit() { _sweep_limit = NULL; }
454 )
455 HeapWord* sweep_limit() { return _sweep_limit; }
456
457 // Apply "blk->do_oop" to the addresses of all reference fields in objects
458 // promoted into this generation since the most recent save_marks() call.
459 // Fields in objects allocated by applications of the closure
460 // *are* included in the iteration. Thus, when the iteration completes
461 // there should be no further such objects remaining.
462 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
463 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
464 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
465 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
466
467 // Allocation support
468 HeapWord* allocate(size_t size);
469 HeapWord* par_allocate(size_t size);
470
471 oop promote(oop obj, size_t obj_size);
472 void gc_prologue();
473 void gc_epilogue();
474
475 // This call is used by a containing CMS generation / collector
476 // to inform the CFLS space that a sweep has been completed
477 // and that the space can do any related house-keeping functions.
478 void sweep_completed();
479
480 // For an object in this space, the mark-word's two
481 // LSB's having the value [11] indicates that it has been
482 // promoted since the most recent call to save_marks() on
483 // this generation and has not subsequently been iterated
484 // over (using oop_since_save_marks_iterate() above).
485 // This property holds only for single-threaded collections,
486 // and is typically used for Cheney scans; for MT scavenges,
487 // the property holds for all objects promoted during that
488 // scavenge for the duration of the scavenge and is used
489 // by card-scanning to avoid scanning objects (being) promoted
490 // during that scavenge.
491 bool obj_allocated_since_save_marks(const oop obj) const {
492 assert(is_in_reserved(obj), "Wrong space?");
493 return ((PromotedObject*)obj)->hasPromotedMark();
494 }
495
496 // A worst-case estimate of the space required (in HeapWords) to expand the
497 // heap when promoting an obj of size obj_size.
498 size_t expansionSpaceRequired(size_t obj_size) const;
499
500 FreeChunk* allocateScratch(size_t size);
501
502 // Returns true if either the small or large linear allocation buffer is empty.
503 bool linearAllocationWouldFail() const;
504
505 // Adjust the chunk for the minimum size. This version is called in
506 // most cases in CompactibleFreeListSpace methods.
507 inline static size_t adjustObjectSize(size_t size) {
508 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
509 }
510 // This is a virtual version of adjustObjectSize() that is called
511 // only occasionally when the compaction space changes and the type
512 // of the new compaction space is is only known to be CompactibleSpace.
513 size_t adjust_object_size_v(size_t size) const {
514 return adjustObjectSize(size);
515 }
516 // Minimum size of a free block.
517 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
518 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
519 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
520 bool coalesced);
521
522 // Support for decisions regarding concurrent collection policy.
523 bool should_concurrent_collect() const;
524
525 // Support for compaction.
526 void prepare_for_compaction(CompactPoint* cp);
527 void adjust_pointers();
528 void compact();
529 // Reset the space to reflect the fact that a compaction of the
530 // space has been done.
531 virtual void reset_after_compaction();
532
533 // Debugging support.
534 void print() const;
535 void print_on(outputStream* st) const;
536 void prepare_for_verify();
537 void verify() const;
538 void verifyFreeLists() const PRODUCT_RETURN;
539 void verifyIndexedFreeLists() const;
540 void verifyIndexedFreeList(size_t size) const;
541 // Verify that the given chunk is in the free lists:
542 // i.e. either the binary tree dictionary, the indexed free lists
543 // or the linear allocation block.
544 bool verify_chunk_in_free_list(FreeChunk* fc) const;
545 // Verify that the given chunk is the linear allocation block.
546 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
547 // Do some basic checks on the the free lists.
548 void check_free_list_consistency() const PRODUCT_RETURN;
549
550 // Printing support
551 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
552 void print_indexed_free_lists(outputStream* st) const;
553 void print_dictionary_free_lists(outputStream* st) const;
554 void print_promo_info_blocks(outputStream* st) const;
555
556 NOT_PRODUCT (
557 void initializeIndexedFreeListArrayReturnedBytes();
558 size_t sumIndexedFreeListArrayReturnedBytes();
559 // Return the total number of chunks in the indexed free lists.
560 size_t totalCountInIndexedFreeLists() const;
561 // Return the total number of chunks in the space.
562 size_t totalCount();
563 )
564
565 // The census consists of counts of the quantities such as
566 // the current count of the free chunks, number of chunks
567 // created as a result of the split of a larger chunk or
568 // coalescing of smaller chucks, etc. The counts in the
569 // census is used to make decisions on splitting and
570 // coalescing of chunks during the sweep of garbage.
571
572 // Print the statistics for the free lists.
573 void printFLCensus(size_t sweep_count) const;
574
575 // Statistics functions
576 // Initialize census for lists before the sweep.
577 void beginSweepFLCensus(float inter_sweep_current,
578 float inter_sweep_estimate,
579 float intra_sweep_estimate);
580 // Set the surplus for each of the free lists.
581 void setFLSurplus();
582 // Set the hint for each of the free lists.
583 void setFLHints();
584 // Clear the census for each of the free lists.
585 void clearFLCensus();
586 // Perform functions for the census after the end of the sweep.
587 void endSweepFLCensus(size_t sweep_count);
588 // Return true if the count of free chunks is greater
589 // than the desired number of free chunks.
590 bool coalOverPopulated(size_t size);
591
592 // Record (for each size):
593 //
594 // split-births = #chunks added due to splits in (prev-sweep-end,
595 // this-sweep-start)
596 // split-deaths = #chunks removed for splits in (prev-sweep-end,
597 // this-sweep-start)
598 // num-curr = #chunks at start of this sweep
599 // num-prev = #chunks at end of previous sweep
600 //
601 // The above are quantities that are measured. Now define:
602 //
603 // num-desired := num-prev + split-births - split-deaths - num-curr
604 //
605 // Roughly, num-prev + split-births is the supply,
606 // split-deaths is demand due to other sizes
607 // and num-curr is what we have left.
608 //
609 // Thus, num-desired is roughly speaking the "legitimate demand"
610 // for blocks of this size and what we are striving to reach at the
611 // end of the current sweep.
612 //
613 // For a given list, let num-len be its current population.
614 // Define, for a free list of a given size:
615 //
616 // coal-overpopulated := num-len >= num-desired * coal-surplus
617 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
618 // coalescing -- we do not coalesce unless we think that the current
619 // supply has exceeded the estimated demand by more than 5%).
620 //
621 // For the set of sizes in the binary tree, which is neither dense nor
622 // closed, it may be the case that for a particular size we have never
623 // had, or do not now have, or did not have at the previous sweep,
624 // chunks of that size. We need to extend the definition of
625 // coal-overpopulated to such sizes as well:
626 //
627 // For a chunk in/not in the binary tree, extend coal-overpopulated
628 // defined above to include all sizes as follows:
629 //
630 // . a size that is non-existent is coal-overpopulated
631 // . a size that has a num-desired <= 0 as defined above is
632 // coal-overpopulated.
633 //
634 // Also define, for a chunk heap-offset C and mountain heap-offset M:
635 //
636 // close-to-mountain := C >= 0.99 * M
637 //
638 // Now, the coalescing strategy is:
639 //
640 // Coalesce left-hand chunk with right-hand chunk if and
641 // only if:
642 //
643 // EITHER
644 // . left-hand chunk is of a size that is coal-overpopulated
645 // OR
646 // . right-hand chunk is close-to-mountain
647 void smallCoalBirth(size_t size);
648 void smallCoalDeath(size_t size);
649 void coalBirth(size_t size);
650 void coalDeath(size_t size);
651 void smallSplitBirth(size_t size);
652 void smallSplitDeath(size_t size);
653 void split_birth(size_t size);
654 void splitDeath(size_t size);
655 void split(size_t from, size_t to1);
656
657 double flsFrag() const;
658 };
659
660 // A parallel-GC-thread-local allocation buffer for allocation into a
661 // CompactibleFreeListSpace.
662 class CFLS_LAB : public CHeapObj<mtGC> {
663 // The space that this buffer allocates into.
664 CompactibleFreeListSpace* _cfls;
665
666 // Our local free lists.
667 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
668
669 // Initialized from a command-line arg.
670
671 // Allocation statistics in support of dynamic adjustment of
672 // #blocks to claim per get_from_global_pool() call below.
673 static AdaptiveWeightedAverage
674 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
675 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
676 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
677 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
678
679 // Internal work method
680 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
681
682 public:
683 CFLS_LAB(CompactibleFreeListSpace* cfls);
684
685 // Allocate and return a block of the given size, or else return NULL.
686 // The oop (old) is used to extract information for promotion trace event
687 HeapWord* alloc(const ParNewTracer* gc_tracer, size_t word_sz,
688 const oop old, const markOop m);
689
690 // Return any unused portions of the buffer to the global pool.
691 void retire(int tid);
692
693 // Dynamic OldPLABSize sizing
694 static void compute_desired_plab_size();
695 // When the settings are modified from default static initialization
696 static void modify_initialization(size_t n, unsigned wt);
697 };
698
699 size_t PromotionInfo::refillSize() const {
700 const size_t CMSSpoolBlockSize = 256;
701 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
702 * CMSSpoolBlockSize);
703 return CompactibleFreeListSpace::adjustObjectSize(sz);
704 }
705
706 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP