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