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