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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP
26 #define SHARE_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 AFLBinaryTreeDictionary : public BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> > {
52 public:
53 AFLBinaryTreeDictionary(MemRegion mr)
54 : BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> >(mr) {}
55
56 // Find the list with size "size" in the binary tree and update
57 // the statistics in the list according to "split" (chunk was
58 // split or coalesce) and "birth" (chunk was added or removed).
59 void dict_census_update(size_t size, bool split, bool birth);
60 // Return true if the dictionary is overpopulated (more chunks of
61 // this size than desired) for size "size".
62 bool coal_dict_over_populated(size_t size);
63 // Methods called at the beginning of a sweep to prepare the
64 // statistics for the sweep.
65 void begin_sweep_dict_census(double coalSurplusPercent,
66 float inter_sweep_current,
67 float inter_sweep_estimate,
68 float intra_sweep_estimate);
69 // Methods called after the end of a sweep to modify the
70 // statistics for the sweep.
71 void end_sweep_dict_census(double splitSurplusPercent);
72 // Accessors for statistics
73 void set_tree_surplus(double splitSurplusPercent);
74 void set_tree_hints(void);
75 // Reset statistics for all the lists in the tree.
76 void clear_tree_census(void);
77 // Print the statistics for all the lists in the tree. Also may
78 // print out summaries.
79 void print_dict_census(outputStream* st) const;
80 };
81
82 class LinearAllocBlock {
83 public:
84 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
85 _allocation_size_limit(0) {}
86 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
87 size_t allocation_size_limit) {
88 _ptr = ptr;
89 _word_size = word_size;
90 _refillSize = refill_size;
91 _allocation_size_limit = allocation_size_limit;
92 }
93 HeapWord* _ptr;
94 size_t _word_size;
95 size_t _refillSize;
96 size_t _allocation_size_limit; // Largest size that will be allocated
97
98 void print_on(outputStream* st) const;
99 };
100
101 // Concrete subclass of CompactibleSpace that implements
102 // a free list space, such as used in the concurrent mark sweep
103 // generation.
104
105 class CompactibleFreeListSpace: public CompactibleSpace {
106 friend class VMStructs;
107 friend class ConcurrentMarkSweepGeneration;
108 friend class CMSCollector;
109 // Local alloc buffer for promotion into this space.
110 friend class CompactibleFreeListSpaceLAB;
111 // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class
112 template <typename SpaceType>
113 friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
114 template <typename SpaceType>
115 friend void CompactibleSpace::scan_and_compact(SpaceType* space);
116 template <typename SpaceType>
117 friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);
118 template <typename SpaceType>
119 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
120
121 // "Size" of chunks of work (executed during parallel remark phases
122 // of CMS collection); this probably belongs in CMSCollector, although
123 // it's cached here because it's used in
124 // initialize_sequential_subtasks_for_rescan() which modifies
125 // par_seq_tasks which also lives in Space. XXX
126 const size_t _rescan_task_size;
127 const size_t _marking_task_size;
128
129 // Yet another sequential tasks done structure. This supports
130 // CMS GC, where we have threads dynamically
131 // claiming sub-tasks from a larger parallel task.
132 SequentialSubTasksDone _conc_par_seq_tasks;
133
134 BlockOffsetArrayNonContigSpace _bt;
135
136 CMSCollector* _collector;
137 ConcurrentMarkSweepGeneration* _old_gen;
138
139 // Data structures for free blocks (used during allocation/sweeping)
140
141 // Allocation is done linearly from two different blocks depending on
142 // whether the request is small or large, in an effort to reduce
143 // fragmentation. We assume that any locking for allocation is done
144 // by the containing generation. Thus, none of the methods in this
145 // space are re-entrant.
146 enum SomeConstants {
147 SmallForLinearAlloc = 16, // size < this then use _sLAB
148 SmallForDictionary = 257, // size < this then use _indexedFreeList
149 IndexSetSize = SmallForDictionary // keep this odd-sized
150 };
151 static size_t IndexSetStart;
152 static size_t IndexSetStride;
153 static size_t _min_chunk_size_in_bytes;
154
155 private:
156 enum FitStrategyOptions {
157 FreeBlockStrategyNone = 0,
158 FreeBlockBestFitFirst
159 };
160
161 PromotionInfo _promoInfo;
162
163 // Helps to impose a global total order on freelistLock ranks;
164 // assumes that CFLSpace's are allocated in global total order
165 static int _lockRank;
166
167 // A lock protecting the free lists and free blocks;
168 // mutable because of ubiquity of locking even for otherwise const methods
169 mutable Mutex _freelistLock;
170
171 // Locking verifier convenience function
172 void assert_locked() const PRODUCT_RETURN;
173 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
174
175 // Linear allocation blocks
176 LinearAllocBlock _smallLinearAllocBlock;
177
178 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks
179
180 // Indexed array for small size blocks
181 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
182
183 // Allocation strategy
184 bool _fitStrategy; // Use best fit strategy
185
186 // This is an address close to the largest free chunk in the heap.
187 // It is currently assumed to be at the end of the heap. Free
188 // chunks with addresses greater than nearLargestChunk are coalesced
189 // in an effort to maintain a large chunk at the end of the heap.
190 HeapWord* _nearLargestChunk;
191
192 // Used to keep track of limit of sweep for the space
193 HeapWord* _sweep_limit;
194
195 // Stable value of used().
196 size_t _used_stable;
197
198 // Used to make the young collector update the mod union table
199 MemRegionClosure* _preconsumptionDirtyCardClosure;
200
201 // Support for compacting cms
202 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
203 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
204
205 // Initialization helpers.
206 void initializeIndexedFreeListArray();
207
208 // Extra stuff to manage promotion parallelism.
209
210 // A lock protecting the dictionary during par promotion allocation.
211 mutable Mutex _parDictionaryAllocLock;
212 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
213
214 // Locks protecting the exact lists during par promotion allocation.
215 Mutex* _indexedFreeListParLocks[IndexSetSize];
216
217 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
218 // required to be smaller than "IndexSetSize".) If successful,
219 // adds them to "fl", which is required to be an empty free list.
220 // If the count of "fl" is negative, it's absolute value indicates a
221 // number of free chunks that had been previously "borrowed" from global
222 // list of size "word_sz", and must now be decremented.
223 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
224
225 // Used by par_get_chunk_of_blocks() for the chunks from the
226 // indexed_free_lists.
227 bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
228
229 // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
230 // evenly splittable into "n" "word_sz" chunks. Returns that
231 // evenly splittable chunk. May split a larger chunk to get the
232 // evenly splittable chunk.
233 FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
234
235 // Used by par_get_chunk_of_blocks() for the chunks from the
236 // dictionary.
237 void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
238
239 // Allocation helper functions
240 // Allocate using a strategy that takes from the indexed free lists
241 // first. This allocation strategy assumes a companion sweeping
242 // strategy that attempts to keep the needed number of chunks in each
243 // indexed free lists.
244 HeapWord* allocate_adaptive_freelists(size_t size);
245
246 // Gets a chunk from the linear allocation block (LinAB). If there
247 // is not enough space in the LinAB, refills it.
248 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
249 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
250 // Get a chunk from the space remaining in the linear allocation block. Do
251 // not attempt to refill if the space is not available, return NULL. Do the
252 // repairs on the linear allocation block as appropriate.
253 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
254 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
255
256 // Helper function for getChunkFromIndexedFreeList.
257 // Replenish the indexed free list for this "size". Do not take from an
258 // underpopulated size.
259 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
260
261 // Get a chunk from the indexed free list. If the indexed free list
262 // does not have a free chunk, try to replenish the indexed free list
263 // then get the free chunk from the replenished indexed free list.
264 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
265
266 // The returned chunk may be larger than requested (or null).
267 FreeChunk* getChunkFromDictionary(size_t size);
268 // The returned chunk is the exact size requested (or null).
269 FreeChunk* getChunkFromDictionaryExact(size_t size);
270
271 // Find a chunk in the indexed free list that is the best
272 // fit for size "numWords".
273 FreeChunk* bestFitSmall(size_t numWords);
274 // For free list "fl" of chunks of size > numWords,
275 // remove a chunk, split off a chunk of size numWords
276 // and return it. The split off remainder is returned to
277 // the free lists. The old name for getFromListGreater
278 // was lookInListGreater.
279 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
280 // Get a chunk in the indexed free list or dictionary,
281 // by considering a larger chunk and splitting it.
282 FreeChunk* getChunkFromGreater(size_t numWords);
283 // Verify that the given chunk is in the indexed free lists.
284 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
285 // Remove the specified chunk from the indexed free lists.
286 void removeChunkFromIndexedFreeList(FreeChunk* fc);
287 // Remove the specified chunk from the dictionary.
288 void removeChunkFromDictionary(FreeChunk* fc);
289 // Split a free chunk into a smaller free chunk of size "new_size".
290 // Return the smaller free chunk and return the remainder to the
291 // free lists.
292 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
293 // Add a chunk to the free lists.
294 void addChunkToFreeLists(HeapWord* chunk, size_t size);
295 // Add a chunk to the free lists, preferring to suffix it
296 // to the last free chunk at end of space if possible, and
297 // updating the block census stats as well as block offset table.
298 // Take any locks as appropriate if we are multithreaded.
299 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
300 // Add a free chunk to the indexed free lists.
301 void returnChunkToFreeList(FreeChunk* chunk);
302 // Add a free chunk to the dictionary.
303 void returnChunkToDictionary(FreeChunk* chunk);
304
305 // Functions for maintaining the linear allocation buffers (LinAB).
306 // Repairing a linear allocation block refers to operations
307 // performed on the remainder of a LinAB after an allocation
308 // has been made from it.
309 void repairLinearAllocationBlocks();
310 void repairLinearAllocBlock(LinearAllocBlock* blk);
311 void refillLinearAllocBlock(LinearAllocBlock* blk);
312 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
313 void refillLinearAllocBlocksIfNeeded();
314
315 void verify_objects_initialized() const;
316
317 // Statistics reporting helper functions
318 void reportFreeListStatistics(const char* title) const;
319 void reportIndexedFreeListStatistics(outputStream* st) const;
320 size_t maxChunkSizeInIndexedFreeLists() const;
321 size_t numFreeBlocksInIndexedFreeLists() const;
322 // Accessor
323 HeapWord* unallocated_block() const {
324 if (BlockOffsetArrayUseUnallocatedBlock) {
325 HeapWord* ub = _bt.unallocated_block();
326 assert(ub >= bottom() &&
327 ub <= end(), "space invariant");
328 return ub;
329 } else {
330 return end();
331 }
332 }
333 void freed(HeapWord* start, size_t size) {
334 _bt.freed(start, size);
335 }
336
337 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
338 // See comments for CompactibleSpace for more information.
339 inline HeapWord* scan_limit() const {
340 return end();
341 }
342
343 inline bool scanned_block_is_obj(const HeapWord* addr) const {
344 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
345 }
346
347 inline size_t scanned_block_size(const HeapWord* addr) const {
348 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
349 }
350
351 inline size_t adjust_obj_size(size_t size) const {
352 return adjustObjectSize(size);
353 }
354
355 inline size_t obj_size(const HeapWord* addr) const;
356
357 protected:
358 // Reset the indexed free list to its initial empty condition.
359 void resetIndexedFreeListArray();
360 // Reset to an initial state with a single free block described
361 // by the MemRegion parameter.
362 void reset(MemRegion mr);
363 // Return the total number of words in the indexed free lists.
364 size_t totalSizeInIndexedFreeLists() const;
365
366 public:
367 // Constructor
368 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);
369 // Accessors
370 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
371 AFLBinaryTreeDictionary* dictionary() const { return _dictionary; }
372 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
373 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
374
375 // Set CMS global values.
376 static void set_cms_values();
377
378 // Return the free chunk at the end of the space. If no such
379 // chunk exists, return NULL.
380 FreeChunk* find_chunk_at_end();
381
382 void set_collector(CMSCollector* collector) { _collector = collector; }
383
384 // Support for parallelization of rescan and marking.
385 const size_t rescan_task_size() const { return _rescan_task_size; }
386 const size_t marking_task_size() const { return _marking_task_size; }
387 // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple.
388 const size_t max_flag_size_for_task_size() const;
389 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
390 void initialize_sequential_subtasks_for_rescan(int n_threads);
391 void initialize_sequential_subtasks_for_marking(int n_threads,
392 HeapWord* low = NULL);
393
394 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
395 return _preconsumptionDirtyCardClosure;
396 }
397
398 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
399 _preconsumptionDirtyCardClosure = cl;
400 }
401
402 // Space enquiries
403 size_t used() const;
404 size_t free() const;
405 size_t max_alloc_in_words() const;
406 // XXX: should have a less conservative used_region() than that of
407 // Space; we could consider keeping track of highest allocated
408 // address and correcting that at each sweep, as the sweeper
409 // goes through the entire allocated part of the generation. We
410 // could also use that information to keep the sweeper from
411 // sweeping more than is necessary. The allocator and sweeper will
412 // of course need to synchronize on this, since the sweeper will
413 // try to bump down the address and the allocator will try to bump it up.
414 // For now, however, we'll just use the default used_region()
415 // which overestimates the region by returning the entire
416 // committed region (this is safe, but inefficient).
417
418 // Returns monotonically increasing stable used space bytes for CMS.
419 // This is required for jhat and other memory monitoring tools
420 // that might otherwise see inconsistent used space values during a garbage
421 // collection, promotion or allocation into compactibleFreeListSpace.
422 // The value returned by this function might be smaller than the
423 // actual value.
424 size_t used_stable() const;
425 // Recalculate and cache the current stable used() value. Only to be called
426 // in places where we can be sure that the result is stable.
427 void recalculate_used_stable();
428
429 // Returns a subregion of the space containing all the objects in
430 // the space.
431 MemRegion used_region() const {
432 return MemRegion(bottom(),
433 BlockOffsetArrayUseUnallocatedBlock ?
434 unallocated_block() : end());
435 }
436
437 virtual bool is_free_block(const HeapWord* p) const;
438
439 // Resizing support
440 void set_end(HeapWord* value); // override
441
442 // Never mangle CompactibleFreeListSpace
443 void mangle_unused_area() {}
444 void mangle_unused_area_complete() {}
445
446 // Mutual exclusion support
447 Mutex* freelistLock() const { return &_freelistLock; }
448
449 // Iteration support
450 void oop_iterate(OopIterateClosure* cl);
451
452 void object_iterate(ObjectClosure* blk);
453 // Apply the closure to each object in the space whose references
454 // point to objects in the heap. The usage of CompactibleFreeListSpace
455 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
456 // objects in the space with references to objects that are no longer
457 // valid. For example, an object may reference another object
458 // that has already been sweep up (collected). This method uses
459 // obj_is_alive() to determine whether it is safe to iterate of
460 // an object.
461 void safe_object_iterate(ObjectClosure* blk);
462
463 // Iterate over all objects that intersect with mr, calling "cl->do_object"
464 // on each. There is an exception to this: if this closure has already
465 // been invoked on an object, it may skip such objects in some cases. This is
466 // Most likely to happen in an "upwards" (ascending address) iteration of
467 // MemRegions.
468 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
469
470 // Requires that "mr" be entirely within the space.
471 // Apply "cl->do_object" to all objects that intersect with "mr".
472 // If the iteration encounters an unparseable portion of the region,
473 // terminate the iteration and return the address of the start of the
474 // subregion that isn't done. Return of "NULL" indicates that the
475 // iteration completed.
476 HeapWord* object_iterate_careful_m(MemRegion mr,
477 ObjectClosureCareful* cl);
478
479 // Override: provides a DCTO_CL specific to this kind of space.
480 DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
481 CardTable::PrecisionStyle precision,
482 HeapWord* boundary,
483 bool parallel);
484
485 void blk_iterate(BlkClosure* cl);
486 void blk_iterate_careful(BlkClosureCareful* cl);
487 HeapWord* block_start_const(const void* p) const;
488 HeapWord* block_start_careful(const void* p) const;
489 size_t block_size(const HeapWord* p) const;
490 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
491 bool block_is_obj(const HeapWord* p) const;
492 bool obj_is_alive(const HeapWord* p) const;
493 size_t block_size_nopar(const HeapWord* p) const;
494 bool block_is_obj_nopar(const HeapWord* p) const;
495
496 // Iteration support for promotion
497 void save_marks();
498 bool no_allocs_since_save_marks();
499
500 // Iteration support for sweeping
501 void save_sweep_limit() {
502 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
503 unallocated_block() : end();
504 log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT
505 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
506 p2i(_sweep_limit), p2i(bottom()), p2i(end()));
507 }
508 NOT_PRODUCT(
509 void clear_sweep_limit() { _sweep_limit = NULL; }
510 )
511 HeapWord* sweep_limit() { return _sweep_limit; }
512
513 // Apply "blk->do_oop" to the addresses of all reference fields in objects
514 // promoted into this generation since the most recent save_marks() call.
515 // Fields in objects allocated by applications of the closure
516 // *are* included in the iteration. Thus, when the iteration completes
517 // there should be no further such objects remaining.
518 template <typename OopClosureType>
519 void oop_since_save_marks_iterate(OopClosureType* blk);
520
521 // Allocation support
522 HeapWord* allocate(size_t size);
523 HeapWord* par_allocate(size_t size);
524
525 oop promote(oop obj, size_t obj_size);
526 void gc_prologue();
527 void gc_epilogue();
528
529 // This call is used by a containing CMS generation / collector
530 // to inform the CFLS space that a sweep has been completed
531 // and that the space can do any related house-keeping functions.
532 void sweep_completed();
533
534 // For an object in this space, the mark-word's two
535 // LSB's having the value [11] indicates that it has been
536 // promoted since the most recent call to save_marks() on
537 // this generation and has not subsequently been iterated
538 // over (using oop_since_save_marks_iterate() above).
539 // This property holds only for single-threaded collections,
540 // and is typically used for Cheney scans; for MT scavenges,
541 // the property holds for all objects promoted during that
542 // scavenge for the duration of the scavenge and is used
543 // by card-scanning to avoid scanning objects (being) promoted
544 // during that scavenge.
545 bool obj_allocated_since_save_marks(const oop obj) const {
546 assert(is_in_reserved(obj), "Wrong space?");
547 return ((PromotedObject*)obj)->hasPromotedMark();
548 }
549
550 // A worst-case estimate of the space required (in HeapWords) to expand the
551 // heap when promoting an obj of size obj_size.
552 size_t expansionSpaceRequired(size_t obj_size) const;
553
554 FreeChunk* allocateScratch(size_t size);
555
556 // Returns true if either the small or large linear allocation buffer is empty.
557 bool linearAllocationWouldFail() const;
558
559 // Adjust the chunk for the minimum size. This version is called in
560 // most cases in CompactibleFreeListSpace methods.
561 inline static size_t adjustObjectSize(size_t size) {
562 return align_object_size(MAX2(size, (size_t)MinChunkSize));
563 }
564 // This is a virtual version of adjustObjectSize() that is called
565 // only occasionally when the compaction space changes and the type
566 // of the new compaction space is is only known to be CompactibleSpace.
567 size_t adjust_object_size_v(size_t size) const {
568 return adjustObjectSize(size);
569 }
570 // Minimum size of a free block.
571 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
572 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
573 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
574 bool coalesced);
575
576 // Support for compaction.
577 void prepare_for_compaction(CompactPoint* cp);
578 void adjust_pointers();
579 void compact();
580 // Reset the space to reflect the fact that a compaction of the
581 // space has been done.
582 virtual void reset_after_compaction();
583
584 // Debugging support.
585 void print() const;
586 void print_on(outputStream* st) const;
587 void prepare_for_verify();
588 void verify() const;
589 void verifyFreeLists() const PRODUCT_RETURN;
590 void verifyIndexedFreeLists() const;
591 void verifyIndexedFreeList(size_t size) const;
592 // Verify that the given chunk is in the free lists:
593 // i.e. either the binary tree dictionary, the indexed free lists
594 // or the linear allocation block.
595 bool verify_chunk_in_free_list(FreeChunk* fc) const;
596 // Verify that the given chunk is the linear allocation block.
597 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
598 // Do some basic checks on the the free lists.
599 void check_free_list_consistency() const PRODUCT_RETURN;
600
601 // Printing support
602 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
603 void print_indexed_free_lists(outputStream* st) const;
604 void print_dictionary_free_lists(outputStream* st) const;
605 void print_promo_info_blocks(outputStream* st) const;
606
607 NOT_PRODUCT (
608 void initializeIndexedFreeListArrayReturnedBytes();
609 size_t sumIndexedFreeListArrayReturnedBytes();
610 // Return the total number of chunks in the indexed free lists.
611 size_t totalCountInIndexedFreeLists() const;
612 // Return the total number of chunks in the space.
613 size_t totalCount();
614 )
615
616 // The census consists of counts of the quantities such as
617 // the current count of the free chunks, number of chunks
618 // created as a result of the split of a larger chunk or
619 // coalescing of smaller chucks, etc. The counts in the
620 // census is used to make decisions on splitting and
621 // coalescing of chunks during the sweep of garbage.
622
623 // Print the statistics for the free lists.
624 void printFLCensus(size_t sweep_count) const;
625
626 // Statistics functions
627 // Initialize census for lists before the sweep.
628 void beginSweepFLCensus(float inter_sweep_current,
629 float inter_sweep_estimate,
630 float intra_sweep_estimate);
631 // Set the surplus for each of the free lists.
632 void setFLSurplus();
633 // Set the hint for each of the free lists.
634 void setFLHints();
635 // Clear the census for each of the free lists.
636 void clearFLCensus();
637 // Perform functions for the census after the end of the sweep.
638 void endSweepFLCensus(size_t sweep_count);
639 // Return true if the count of free chunks is greater
640 // than the desired number of free chunks.
641 bool coalOverPopulated(size_t size);
642
643 // Record (for each size):
644 //
645 // split-births = #chunks added due to splits in (prev-sweep-end,
646 // this-sweep-start)
647 // split-deaths = #chunks removed for splits in (prev-sweep-end,
648 // this-sweep-start)
649 // num-curr = #chunks at start of this sweep
650 // num-prev = #chunks at end of previous sweep
651 //
652 // The above are quantities that are measured. Now define:
653 //
654 // num-desired := num-prev + split-births - split-deaths - num-curr
655 //
656 // Roughly, num-prev + split-births is the supply,
657 // split-deaths is demand due to other sizes
658 // and num-curr is what we have left.
659 //
660 // Thus, num-desired is roughly speaking the "legitimate demand"
661 // for blocks of this size and what we are striving to reach at the
662 // end of the current sweep.
663 //
664 // For a given list, let num-len be its current population.
665 // Define, for a free list of a given size:
666 //
667 // coal-overpopulated := num-len >= num-desired * coal-surplus
668 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
669 // coalescing -- we do not coalesce unless we think that the current
670 // supply has exceeded the estimated demand by more than 5%).
671 //
672 // For the set of sizes in the binary tree, which is neither dense nor
673 // closed, it may be the case that for a particular size we have never
674 // had, or do not now have, or did not have at the previous sweep,
675 // chunks of that size. We need to extend the definition of
676 // coal-overpopulated to such sizes as well:
677 //
678 // For a chunk in/not in the binary tree, extend coal-overpopulated
679 // defined above to include all sizes as follows:
680 //
681 // . a size that is non-existent is coal-overpopulated
682 // . a size that has a num-desired <= 0 as defined above is
683 // coal-overpopulated.
684 //
685 // Also define, for a chunk heap-offset C and mountain heap-offset M:
686 //
687 // close-to-mountain := C >= 0.99 * M
688 //
689 // Now, the coalescing strategy is:
690 //
691 // Coalesce left-hand chunk with right-hand chunk if and
692 // only if:
693 //
694 // EITHER
695 // . left-hand chunk is of a size that is coal-overpopulated
696 // OR
697 // . right-hand chunk is close-to-mountain
698 void smallCoalBirth(size_t size);
699 void smallCoalDeath(size_t size);
700 void coalBirth(size_t size);
701 void coalDeath(size_t size);
702 void smallSplitBirth(size_t size);
703 void smallSplitDeath(size_t size);
704 void split_birth(size_t size);
705 void splitDeath(size_t size);
706 void split(size_t from, size_t to1);
707
708 double flsFrag() const;
709 };
710
711 // A parallel-GC-thread-local allocation buffer for allocation into a
712 // CompactibleFreeListSpace.
713 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> {
714 // The space that this buffer allocates into.
715 CompactibleFreeListSpace* _cfls;
716
717 // Our local free lists.
718 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
719
720 // Initialized from a command-line arg.
721
722 // Allocation statistics in support of dynamic adjustment of
723 // #blocks to claim per get_from_global_pool() call below.
724 static AdaptiveWeightedAverage
725 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
726 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
727 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
728 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
729
730 // Internal work method
731 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
732
733 public:
734 static const int _default_dynamic_old_plab_size = 16;
735 static const int _default_static_old_plab_size = 50;
736
737 CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls);
738
739 // Allocate and return a block of the given size, or else return NULL.
740 HeapWord* alloc(size_t word_sz);
741
742 // Return any unused portions of the buffer to the global pool.
743 void retire(int tid);
744
745 // Dynamic OldPLABSize sizing
746 static void compute_desired_plab_size();
747 // When the settings are modified from default static initialization
748 static void modify_initialization(size_t n, unsigned wt);
749 };
750
751 size_t PromotionInfo::refillSize() const {
752 const size_t CMSSpoolBlockSize = 256;
753 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
754 * CMSSpoolBlockSize);
755 return CompactibleFreeListSpace::adjustObjectSize(sz);
756 }
757
758 #endif // SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP