1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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 "memory/binaryTreeDictionary.hpp"
31 #include "memory/blockOffsetTable.inline.hpp"
32 #include "memory/freeList.hpp"
33 #include "memory/space.hpp"
34
35 // Classes in support of keeping track of promotions into a non-Contiguous
36 // space, in this case a CompactibleFreeListSpace.
37
38 // Forward declarations
39 class CompactibleFreeListSpace;
40 class BlkClosure;
41 class BlkClosureCareful;
42 class FreeChunk;
43 class UpwardsObjectClosure;
44 class ObjectClosureCareful;
45 class Klass;
46
47 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
48 public:
49 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
50 _allocation_size_limit(0) {}
51 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
52 size_t allocation_size_limit) {
53 _ptr = ptr;
54 _word_size = word_size;
55 _refillSize = refill_size;
56 _allocation_size_limit = allocation_size_limit;
57 }
58 HeapWord* _ptr;
59 size_t _word_size;
60 size_t _refillSize;
61 size_t _allocation_size_limit; // Largest size that will be allocated
62
63 void print_on(outputStream* st) const;
64 };
65
66 // Concrete subclass of CompactibleSpace that implements
67 // a free list space, such as used in the concurrent mark sweep
68 // generation.
69
70 class CompactibleFreeListSpace: public CompactibleSpace {
71 friend class VMStructs;
72 friend class ConcurrentMarkSweepGeneration;
73 friend class ASConcurrentMarkSweepGeneration;
74 friend class CMSCollector;
75 // Local alloc buffer for promotion into this space.
76 friend class CFLS_LAB;
77
78 // "Size" of chunks of work (executed during parallel remark phases
79 // of CMS collection); this probably belongs in CMSCollector, although
80 // it's cached here because it's used in
81 // initialize_sequential_subtasks_for_rescan() which modifies
82 // par_seq_tasks which also lives in Space. XXX
83 const size_t _rescan_task_size;
84 const size_t _marking_task_size;
85
86 // Yet another sequential tasks done structure. This supports
87 // CMS GC, where we have threads dynamically
88 // claiming sub-tasks from a larger parallel task.
89 SequentialSubTasksDone _conc_par_seq_tasks;
90
91 BlockOffsetArrayNonContigSpace _bt;
92
93 CMSCollector* _collector;
94 ConcurrentMarkSweepGeneration* _gen;
95
96 // Data structures for free blocks (used during allocation/sweeping)
97
98 // Allocation is done linearly from two different blocks depending on
99 // whether the request is small or large, in an effort to reduce
100 // fragmentation. We assume that any locking for allocation is done
101 // by the containing generation. Thus, none of the methods in this
102 // space are re-entrant.
103 enum SomeConstants {
104 SmallForLinearAlloc = 16, // size < this then use _sLAB
105 SmallForDictionary = 257, // size < this then use _indexedFreeList
106 IndexSetSize = SmallForDictionary // keep this odd-sized
107 };
108 static size_t IndexSetStart;
109 static size_t IndexSetStride;
110
111 private:
112 enum FitStrategyOptions {
113 FreeBlockStrategyNone = 0,
114 FreeBlockBestFitFirst
115 };
116
117 PromotionInfo _promoInfo;
118
119 // Helps to impose a global total order on freelistLock ranks;
120 // assumes that CFLSpace's are allocated in global total order
121 static int _lockRank;
122
123 // A lock protecting the free lists and free blocks;
124 // mutable because of ubiquity of locking even for otherwise const methods
125 mutable Mutex _freelistLock;
126 // Locking verifier convenience function
127 void assert_locked() const PRODUCT_RETURN;
128 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
129
130 // Linear allocation blocks
131 LinearAllocBlock _smallLinearAllocBlock;
132
133 FreeBlockDictionary<FreeChunk>::DictionaryChoice _dictionaryChoice;
134 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks
135
136 // Indexed array for small size blocks
137 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
138
139 // Allocation strategy
140 bool _fitStrategy; // Use best fit strategy
141 bool _adaptive_freelists; // Use adaptive freelists
142
143 // This is an address close to the largest free chunk in the heap.
144 // It is currently assumed to be at the end of the heap. Free
145 // chunks with addresses greater than nearLargestChunk are coalesced
146 // in an effort to maintain a large chunk at the end of the heap.
147 HeapWord* _nearLargestChunk;
148
149 // Used to keep track of limit of sweep for the space
150 HeapWord* _sweep_limit;
151
152 // Support for compacting cms
153 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
154 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
155
156 // Initialization helpers.
157 void initializeIndexedFreeListArray();
158
159 // Extra stuff to manage promotion parallelism.
160
161 // A lock protecting the dictionary during par promotion allocation.
162 mutable Mutex _parDictionaryAllocLock;
163 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
164
165 // Locks protecting the exact lists during par promotion allocation.
166 Mutex* _indexedFreeListParLocks[IndexSetSize];
167
168 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
169 // required to be smaller than "IndexSetSize".) If successful,
170 // adds them to "fl", which is required to be an empty free list.
171 // If the count of "fl" is negative, it's absolute value indicates a
172 // number of free chunks that had been previously "borrowed" from global
173 // list of size "word_sz", and must now be decremented.
174 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
175
176 // Allocation helper functions
177 // Allocate using a strategy that takes from the indexed free lists
178 // first. This allocation strategy assumes a companion sweeping
179 // strategy that attempts to keep the needed number of chunks in each
180 // indexed free lists.
181 HeapWord* allocate_adaptive_freelists(size_t size);
182 // Allocate from the linear allocation buffers first. This allocation
183 // strategy assumes maximal coalescing can maintain chunks large enough
184 // to be used as linear allocation buffers.
185 HeapWord* allocate_non_adaptive_freelists(size_t size);
186
187 // Gets a chunk from the linear allocation block (LinAB). If there
188 // is not enough space in the LinAB, refills it.
189 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
190 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
191 // Get a chunk from the space remaining in the linear allocation block. Do
192 // not attempt to refill if the space is not available, return NULL. Do the
193 // repairs on the linear allocation block as appropriate.
194 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
195 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
196
197 // Helper function for getChunkFromIndexedFreeList.
198 // Replenish the indexed free list for this "size". Do not take from an
199 // underpopulated size.
200 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
201
202 // Get a chunk from the indexed free list. If the indexed free list
203 // does not have a free chunk, try to replenish the indexed free list
204 // then get the free chunk from the replenished indexed free list.
205 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
206
207 // The returned chunk may be larger than requested (or null).
208 FreeChunk* getChunkFromDictionary(size_t size);
209 // The returned chunk is the exact size requested (or null).
210 FreeChunk* getChunkFromDictionaryExact(size_t size);
211
212 // Find a chunk in the indexed free list that is the best
213 // fit for size "numWords".
214 FreeChunk* bestFitSmall(size_t numWords);
215 // For free list "fl" of chunks of size > numWords,
216 // remove a chunk, split off a chunk of size numWords
217 // and return it. The split off remainder is returned to
218 // the free lists. The old name for getFromListGreater
219 // was lookInListGreater.
220 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
221 // Get a chunk in the indexed free list or dictionary,
222 // by considering a larger chunk and splitting it.
223 FreeChunk* getChunkFromGreater(size_t numWords);
224 // Verify that the given chunk is in the indexed free lists.
225 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
226 // Remove the specified chunk from the indexed free lists.
227 void removeChunkFromIndexedFreeList(FreeChunk* fc);
228 // Remove the specified chunk from the dictionary.
229 void removeChunkFromDictionary(FreeChunk* fc);
230 // Split a free chunk into a smaller free chunk of size "new_size".
231 // Return the smaller free chunk and return the remainder to the
232 // free lists.
233 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
234 // Add a chunk to the free lists.
235 void addChunkToFreeLists(HeapWord* chunk, size_t size);
236 // Add a chunk to the free lists, preferring to suffix it
237 // to the last free chunk at end of space if possible, and
238 // updating the block census stats as well as block offset table.
239 // Take any locks as appropriate if we are multithreaded.
240 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
241 // Add a free chunk to the indexed free lists.
242 void returnChunkToFreeList(FreeChunk* chunk);
243 // Add a free chunk to the dictionary.
244 void returnChunkToDictionary(FreeChunk* chunk);
245
246 // Functions for maintaining the linear allocation buffers (LinAB).
247 // Repairing a linear allocation block refers to operations
248 // performed on the remainder of a LinAB after an allocation
249 // has been made from it.
250 void repairLinearAllocationBlocks();
251 void repairLinearAllocBlock(LinearAllocBlock* blk);
252 void refillLinearAllocBlock(LinearAllocBlock* blk);
253 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
254 void refillLinearAllocBlocksIfNeeded();
255
256 void verify_objects_initialized() const;
257
258 // Statistics reporting helper functions
259 void reportFreeListStatistics() const;
260 void reportIndexedFreeListStatistics() const;
261 size_t maxChunkSizeInIndexedFreeLists() const;
262 size_t numFreeBlocksInIndexedFreeLists() const;
263 // Accessor
264 HeapWord* unallocated_block() const {
265 if (BlockOffsetArrayUseUnallocatedBlock) {
266 HeapWord* ub = _bt.unallocated_block();
267 assert(ub >= bottom() &&
268 ub <= end(), "space invariant");
269 return ub;
270 } else {
271 return end();
272 }
273 }
274 void freed(HeapWord* start, size_t size) {
275 _bt.freed(start, size);
276 }
277
278 protected:
279 // Reset the indexed free list to its initial empty condition.
280 void resetIndexedFreeListArray();
281 // Reset to an initial state with a single free block described
282 // by the MemRegion parameter.
283 void reset(MemRegion mr);
284 // Return the total number of words in the indexed free lists.
285 size_t totalSizeInIndexedFreeLists() const;
286
287 public:
288 // Constructor
289 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
290 bool use_adaptive_freelists,
291 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
292 // Accessors
293 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
294 FreeBlockDictionary<FreeChunk>* dictionary() const { return _dictionary; }
295 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
296 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
297
298 // Set CMS global values.
299 static void set_cms_values();
300
301 // Return the free chunk at the end of the space. If no such
302 // chunk exists, return NULL.
303 FreeChunk* find_chunk_at_end();
304
305 bool adaptive_freelists() const { return _adaptive_freelists; }
306
307 void set_collector(CMSCollector* collector) { _collector = collector; }
308
309 // Support for parallelization of rescan and marking.
310 const size_t rescan_task_size() const { return _rescan_task_size; }
311 const size_t marking_task_size() const { return _marking_task_size; }
312 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
313 void initialize_sequential_subtasks_for_rescan(int n_threads);
314 void initialize_sequential_subtasks_for_marking(int n_threads,
315 HeapWord* low = NULL);
316
317 // Space enquiries
318 size_t used() const;
319 size_t free() const;
320 size_t max_alloc_in_words() const;
321 // XXX: should have a less conservative used_region() than that of
322 // Space; we could consider keeping track of highest allocated
323 // address and correcting that at each sweep, as the sweeper
324 // goes through the entire allocated part of the generation. We
325 // could also use that information to keep the sweeper from
326 // sweeping more than is necessary. The allocator and sweeper will
327 // of course need to synchronize on this, since the sweeper will
328 // try to bump down the address and the allocator will try to bump it up.
329 // For now, however, we'll just use the default used_region()
330 // which overestimates the region by returning the entire
331 // committed region (this is safe, but inefficient).
332
333 // Returns a subregion of the space containing all the objects in
334 // the space.
335 MemRegion used_region() const {
336 return MemRegion(bottom(),
337 BlockOffsetArrayUseUnallocatedBlock ?
338 unallocated_block() : end());
339 }
340
341 bool is_in(const void* p) const {
342 return used_region().contains(p);
343 }
344
345 virtual bool is_free_block(const HeapWord* p) const;
346
347 // Resizing support
348 void set_end(HeapWord* value); // override
349
350 // Mutual exclusion support
351 Mutex* freelistLock() const { return &_freelistLock; }
352
353 // Iteration support
354 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
355 void oop_iterate(ExtendedOopClosure* cl);
356
357 void object_iterate(ObjectClosure* blk);
358 // Apply the closure to each object in the space whose references
359 // point to objects in the heap. The usage of CompactibleFreeListSpace
360 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
361 // objects in the space with references to objects that are no longer
362 // valid. For example, an object may reference another object
363 // that has already been sweep up (collected). This method uses
364 // obj_is_alive() to determine whether it is safe to iterate of
365 // an object.
366 void safe_object_iterate(ObjectClosure* blk);
367 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
368
369 // Requires that "mr" be entirely within the space.
370 // Apply "cl->do_object" to all objects that intersect with "mr".
371 // If the iteration encounters an unparseable portion of the region,
372 // terminate the iteration and return the address of the start of the
373 // subregion that isn't done. Return of "NULL" indicates that the
374 // iteration completed.
375 virtual HeapWord*
376 object_iterate_careful_m(MemRegion mr,
377 ObjectClosureCareful* cl);
378 virtual HeapWord*
379 object_iterate_careful(ObjectClosureCareful* cl);
380
381 // Override: provides a DCTO_CL specific to this kind of space.
382 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
383 CardTableModRefBS::PrecisionStyle precision,
384 HeapWord* boundary);
385
386 void blk_iterate(BlkClosure* cl);
387 void blk_iterate_careful(BlkClosureCareful* cl);
388 HeapWord* block_start_const(const void* p) const;
389 HeapWord* block_start_careful(const void* p) const;
390 size_t block_size(const HeapWord* p) const;
391 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
392 bool block_is_obj(const HeapWord* p) const;
393 bool obj_is_alive(const HeapWord* p) const;
394 size_t block_size_nopar(const HeapWord* p) const;
395 bool block_is_obj_nopar(const HeapWord* p) const;
396
397 // Iteration support for promotion
398 void save_marks();
399 bool no_allocs_since_save_marks();
400
401 // Iteration support for sweeping
402 void save_sweep_limit() {
403 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
404 unallocated_block() : end();
405 if (CMSTraceSweeper) {
406 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
407 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
408 _sweep_limit, bottom(), end());
409 }
410 }
411 NOT_PRODUCT(
412 void clear_sweep_limit() { _sweep_limit = NULL; }
413 )
414 HeapWord* sweep_limit() { return _sweep_limit; }
415
416 // Apply "blk->do_oop" to the addresses of all reference fields in objects
417 // promoted into this generation since the most recent save_marks() call.
418 // Fields in objects allocated by applications of the closure
419 // *are* included in the iteration. Thus, when the iteration completes
420 // there should be no further such objects remaining.
421 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
422 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
423 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
424 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
425
426 // Allocation support
427 HeapWord* allocate(size_t size);
428 HeapWord* par_allocate(size_t size);
429
430 oop promote(oop obj, size_t obj_size);
431 void gc_prologue();
432 void gc_epilogue();
433
434 // This call is used by a containing CMS generation / collector
435 // to inform the CFLS space that a sweep has been completed
436 // and that the space can do any related house-keeping functions.
437 void sweep_completed();
438
439 // For an object in this space, the mark-word's two
440 // LSB's having the value [11] indicates that it has been
441 // promoted since the most recent call to save_marks() on
442 // this generation and has not subsequently been iterated
443 // over (using oop_since_save_marks_iterate() above).
444 // This property holds only for single-threaded collections,
445 // and is typically used for Cheney scans; for MT scavenges,
446 // the property holds for all objects promoted during that
447 // scavenge for the duration of the scavenge and is used
448 // by card-scanning to avoid scanning objects (being) promoted
449 // during that scavenge.
450 bool obj_allocated_since_save_marks(const oop obj) const {
451 assert(is_in_reserved(obj), "Wrong space?");
452 return ((PromotedObject*)obj)->hasPromotedMark();
453 }
454
455 // A worst-case estimate of the space required (in HeapWords) to expand the
456 // heap when promoting an obj of size obj_size.
457 size_t expansionSpaceRequired(size_t obj_size) const;
458
459 FreeChunk* allocateScratch(size_t size);
460
461 // Returns true if either the small or large linear allocation buffer is empty.
462 bool linearAllocationWouldFail() const;
463
464 // Adjust the chunk for the minimum size. This version is called in
465 // most cases in CompactibleFreeListSpace methods.
466 inline static size_t adjustObjectSize(size_t size) {
467 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
468 }
469 // This is a virtual version of adjustObjectSize() that is called
470 // only occasionally when the compaction space changes and the type
471 // of the new compaction space is is only known to be CompactibleSpace.
472 size_t adjust_object_size_v(size_t size) const {
473 return adjustObjectSize(size);
474 }
475 // Minimum size of a free block.
476 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
477 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
478 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
479 bool coalesced);
480
481 // Support for decisions regarding concurrent collection policy.
482 bool should_concurrent_collect() const;
483
484 // Support for compaction.
485 void prepare_for_compaction(CompactPoint* cp);
486 void adjust_pointers();
487 void compact();
488 // Reset the space to reflect the fact that a compaction of the
489 // space has been done.
490 virtual void reset_after_compaction();
491
492 // Debugging support.
493 void print() const;
494 void print_on(outputStream* st) const;
495 void prepare_for_verify();
496 void verify() const;
497 void verifyFreeLists() const PRODUCT_RETURN;
498 void verifyIndexedFreeLists() const;
499 void verifyIndexedFreeList(size_t size) const;
500 // Verify that the given chunk is in the free lists:
501 // i.e. either the binary tree dictionary, the indexed free lists
502 // or the linear allocation block.
503 bool verify_chunk_in_free_list(FreeChunk* fc) const;
504 // Verify that the given chunk is the linear allocation block.
505 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
506 // Do some basic checks on the the free lists.
507 void check_free_list_consistency() const PRODUCT_RETURN;
508
509 // Printing support
510 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
511 void print_indexed_free_lists(outputStream* st) const;
512 void print_dictionary_free_lists(outputStream* st) const;
513 void print_promo_info_blocks(outputStream* st) const;
514
515 NOT_PRODUCT (
516 void initializeIndexedFreeListArrayReturnedBytes();
517 size_t sumIndexedFreeListArrayReturnedBytes();
518 // Return the total number of chunks in the indexed free lists.
519 size_t totalCountInIndexedFreeLists() const;
520 // Return the total number of chunks in the space.
521 size_t totalCount();
522 )
523
524 // The census consists of counts of the quantities such as
525 // the current count of the free chunks, number of chunks
526 // created as a result of the split of a larger chunk or
527 // coalescing of smaller chucks, etc. The counts in the
528 // census is used to make decisions on splitting and
529 // coalescing of chunks during the sweep of garbage.
530
531 // Print the statistics for the free lists.
532 void printFLCensus(size_t sweep_count) const;
533
534 // Statistics functions
535 // Initialize census for lists before the sweep.
536 void beginSweepFLCensus(float inter_sweep_current,
537 float inter_sweep_estimate,
538 float intra_sweep_estimate);
539 // Set the surplus for each of the free lists.
540 void setFLSurplus();
541 // Set the hint for each of the free lists.
542 void setFLHints();
543 // Clear the census for each of the free lists.
544 void clearFLCensus();
545 // Perform functions for the census after the end of the sweep.
546 void endSweepFLCensus(size_t sweep_count);
547 // Return true if the count of free chunks is greater
548 // than the desired number of free chunks.
549 bool coalOverPopulated(size_t size);
550
551 // Record (for each size):
552 //
553 // split-births = #chunks added due to splits in (prev-sweep-end,
554 // this-sweep-start)
555 // split-deaths = #chunks removed for splits in (prev-sweep-end,
556 // this-sweep-start)
557 // num-curr = #chunks at start of this sweep
558 // num-prev = #chunks at end of previous sweep
559 //
560 // The above are quantities that are measured. Now define:
561 //
562 // num-desired := num-prev + split-births - split-deaths - num-curr
563 //
564 // Roughly, num-prev + split-births is the supply,
565 // split-deaths is demand due to other sizes
566 // and num-curr is what we have left.
567 //
568 // Thus, num-desired is roughly speaking the "legitimate demand"
569 // for blocks of this size and what we are striving to reach at the
570 // end of the current sweep.
571 //
572 // For a given list, let num-len be its current population.
573 // Define, for a free list of a given size:
574 //
575 // coal-overpopulated := num-len >= num-desired * coal-surplus
576 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
577 // coalescing -- we do not coalesce unless we think that the current
578 // supply has exceeded the estimated demand by more than 5%).
579 //
580 // For the set of sizes in the binary tree, which is neither dense nor
581 // closed, it may be the case that for a particular size we have never
582 // had, or do not now have, or did not have at the previous sweep,
583 // chunks of that size. We need to extend the definition of
584 // coal-overpopulated to such sizes as well:
585 //
586 // For a chunk in/not in the binary tree, extend coal-overpopulated
587 // defined above to include all sizes as follows:
588 //
589 // . a size that is non-existent is coal-overpopulated
590 // . a size that has a num-desired <= 0 as defined above is
591 // coal-overpopulated.
592 //
593 // Also define, for a chunk heap-offset C and mountain heap-offset M:
594 //
595 // close-to-mountain := C >= 0.99 * M
596 //
597 // Now, the coalescing strategy is:
598 //
599 // Coalesce left-hand chunk with right-hand chunk if and
600 // only if:
601 //
602 // EITHER
603 // . left-hand chunk is of a size that is coal-overpopulated
604 // OR
605 // . right-hand chunk is close-to-mountain
606 void smallCoalBirth(size_t size);
607 void smallCoalDeath(size_t size);
608 void coalBirth(size_t size);
609 void coalDeath(size_t size);
610 void smallSplitBirth(size_t size);
611 void smallSplitDeath(size_t size);
612 void split_birth(size_t size);
613 void splitDeath(size_t size);
614 void split(size_t from, size_t to1);
615
616 double flsFrag() const;
617 };
618
619 // A parallel-GC-thread-local allocation buffer for allocation into a
620 // CompactibleFreeListSpace.
621 class CFLS_LAB : public CHeapObj<mtGC> {
622 // The space that this buffer allocates into.
623 CompactibleFreeListSpace* _cfls;
624
625 // Our local free lists.
626 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
627
628 // Initialized from a command-line arg.
629
630 // Allocation statistics in support of dynamic adjustment of
631 // #blocks to claim per get_from_global_pool() call below.
632 static AdaptiveWeightedAverage
633 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
634 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
635 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
636 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
637
638 // Internal work method
639 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
640
641 public:
642 CFLS_LAB(CompactibleFreeListSpace* cfls);
643
644 // Allocate and return a block of the given size, or else return NULL.
645 HeapWord* alloc(size_t word_sz);
646
647 // Return any unused portions of the buffer to the global pool.
648 void retire(int tid);
649
650 // Dynamic OldPLABSize sizing
651 static void compute_desired_plab_size();
652 // When the settings are modified from default static initialization
653 static void modify_initialization(size_t n, unsigned wt);
654 };
655
656 size_t PromotionInfo::refillSize() const {
657 const size_t CMSSpoolBlockSize = 256;
658 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
659 * CMSSpoolBlockSize);
660 return CompactibleFreeListSpace::adjustObjectSize(sz);
661 }
662
663 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP