Wed, 14 Dec 2011 12:15:26 +0100
7121373: Clean up CollectedHeap::is_in
Summary: Fixed G1CollectedHeap::is_in, added tests, cleaned up comments and made Space::is_in pure virtual.
Reviewed-by: brutisso, tonyp, jcoomes
1 /*
2 * Copyright (c) 2001, 2011, 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 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
28 #include "gc_implementation/concurrentMarkSweep/binaryTreeDictionary.hpp"
29 #include "gc_implementation/concurrentMarkSweep/freeList.hpp"
30 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp"
31 #include "memory/blockOffsetTable.inline.hpp"
32 #include "memory/space.hpp"
34 // Classes in support of keeping track of promotions into a non-Contiguous
35 // space, in this case a CompactibleFreeListSpace.
37 // Forward declarations
38 class CompactibleFreeListSpace;
39 class BlkClosure;
40 class BlkClosureCareful;
41 class UpwardsObjectClosure;
42 class ObjectClosureCareful;
43 class Klass;
45 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
46 public:
47 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
48 _allocation_size_limit(0) {}
49 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
50 size_t allocation_size_limit) {
51 _ptr = ptr;
52 _word_size = word_size;
53 _refillSize = refill_size;
54 _allocation_size_limit = allocation_size_limit;
55 }
56 HeapWord* _ptr;
57 size_t _word_size;
58 size_t _refillSize;
59 size_t _allocation_size_limit; // largest size that will be allocated
61 void print_on(outputStream* st) const;
62 };
64 // Concrete subclass of CompactibleSpace that implements
65 // a free list space, such as used in the concurrent mark sweep
66 // generation.
68 class CompactibleFreeListSpace: public CompactibleSpace {
69 friend class VMStructs;
70 friend class ConcurrentMarkSweepGeneration;
71 friend class ASConcurrentMarkSweepGeneration;
72 friend class CMSCollector;
73 friend class CMSPermGenGen;
74 // Local alloc buffer for promotion into this space.
75 friend class CFLS_LAB;
77 // "Size" of chunks of work (executed during parallel remark phases
78 // of CMS collection); this probably belongs in CMSCollector, although
79 // it's cached here because it's used in
80 // initialize_sequential_subtasks_for_rescan() which modifies
81 // par_seq_tasks which also lives in Space. XXX
82 const size_t _rescan_task_size;
83 const size_t _marking_task_size;
85 // Yet another sequential tasks done structure. This supports
86 // CMS GC, where we have threads dynamically
87 // claiming sub-tasks from a larger parallel task.
88 SequentialSubTasksDone _conc_par_seq_tasks;
90 BlockOffsetArrayNonContigSpace _bt;
92 CMSCollector* _collector;
93 ConcurrentMarkSweepGeneration* _gen;
95 // Data structures for free blocks (used during allocation/sweeping)
97 // Allocation is done linearly from two different blocks depending on
98 // whether the request is small or large, in an effort to reduce
99 // fragmentation. We assume that any locking for allocation is done
100 // by the containing generation. Thus, none of the methods in this
101 // space are re-entrant.
102 enum SomeConstants {
103 SmallForLinearAlloc = 16, // size < this then use _sLAB
104 SmallForDictionary = 257, // size < this then use _indexedFreeList
105 IndexSetSize = SmallForDictionary // keep this odd-sized
106 };
107 static size_t IndexSetStart;
108 static size_t IndexSetStride;
110 private:
111 enum FitStrategyOptions {
112 FreeBlockStrategyNone = 0,
113 FreeBlockBestFitFirst
114 };
116 PromotionInfo _promoInfo;
118 // helps to impose a global total order on freelistLock ranks;
119 // assumes that CFLSpace's are allocated in global total order
120 static int _lockRank;
122 // a lock protecting the free lists and free blocks;
123 // mutable because of ubiquity of locking even for otherwise const methods
124 mutable Mutex _freelistLock;
125 // locking verifier convenience function
126 void assert_locked() const PRODUCT_RETURN;
127 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
129 // Linear allocation blocks
130 LinearAllocBlock _smallLinearAllocBlock;
132 FreeBlockDictionary::DictionaryChoice _dictionaryChoice;
133 FreeBlockDictionary* _dictionary; // ptr to dictionary for large size blocks
135 FreeList _indexedFreeList[IndexSetSize];
136 // indexed array for small size blocks
137 // allocation stategy
138 bool _fitStrategy; // Use best fit strategy.
139 bool _adaptive_freelists; // Use adaptive freelists
141 // This is an address close to the largest free chunk in the heap.
142 // It is currently assumed to be at the end of the heap. Free
143 // chunks with addresses greater than nearLargestChunk are coalesced
144 // in an effort to maintain a large chunk at the end of the heap.
145 HeapWord* _nearLargestChunk;
147 // Used to keep track of limit of sweep for the space
148 HeapWord* _sweep_limit;
150 // Support for compacting cms
151 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
152 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
154 // Initialization helpers.
155 void initializeIndexedFreeListArray();
157 // Extra stuff to manage promotion parallelism.
159 // a lock protecting the dictionary during par promotion allocation.
160 mutable Mutex _parDictionaryAllocLock;
161 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
163 // Locks protecting the exact lists during par promotion allocation.
164 Mutex* _indexedFreeListParLocks[IndexSetSize];
166 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
167 // required to be smaller than "IndexSetSize".) If successful,
168 // adds them to "fl", which is required to be an empty free list.
169 // If the count of "fl" is negative, it's absolute value indicates a
170 // number of free chunks that had been previously "borrowed" from global
171 // list of size "word_sz", and must now be decremented.
172 void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl);
174 // Allocation helper functions
175 // Allocate using a strategy that takes from the indexed free lists
176 // first. This allocation strategy assumes a companion sweeping
177 // strategy that attempts to keep the needed number of chunks in each
178 // indexed free lists.
179 HeapWord* allocate_adaptive_freelists(size_t size);
180 // Allocate from the linear allocation buffers first. This allocation
181 // strategy assumes maximal coalescing can maintain chunks large enough
182 // to be used as linear allocation buffers.
183 HeapWord* allocate_non_adaptive_freelists(size_t size);
185 // Gets a chunk from the linear allocation block (LinAB). If there
186 // is not enough space in the LinAB, refills it.
187 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
188 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
189 // Get a chunk from the space remaining in the linear allocation block. Do
190 // not attempt to refill if the space is not available, return NULL. Do the
191 // repairs on the linear allocation block as appropriate.
192 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
193 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
195 // Helper function for getChunkFromIndexedFreeList.
196 // Replenish the indexed free list for this "size". Do not take from an
197 // underpopulated size.
198 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
200 // Get a chunk from the indexed free list. If the indexed free list
201 // does not have a free chunk, try to replenish the indexed free list
202 // then get the free chunk from the replenished indexed free list.
203 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
205 // The returned chunk may be larger than requested (or null).
206 FreeChunk* getChunkFromDictionary(size_t size);
207 // The returned chunk is the exact size requested (or null).
208 FreeChunk* getChunkFromDictionaryExact(size_t size);
210 // Find a chunk in the indexed free list that is the best
211 // fit for size "numWords".
212 FreeChunk* bestFitSmall(size_t numWords);
213 // For free list "fl" of chunks of size > numWords,
214 // remove a chunk, split off a chunk of size numWords
215 // and return it. The split off remainder is returned to
216 // the free lists. The old name for getFromListGreater
217 // was lookInListGreater.
218 FreeChunk* getFromListGreater(FreeList* fl, size_t numWords);
219 // Get a chunk in the indexed free list or dictionary,
220 // by considering a larger chunk and splitting it.
221 FreeChunk* getChunkFromGreater(size_t numWords);
222 // Verify that the given chunk is in the indexed free lists.
223 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
224 // Remove the specified chunk from the indexed free lists.
225 void removeChunkFromIndexedFreeList(FreeChunk* fc);
226 // Remove the specified chunk from the dictionary.
227 void removeChunkFromDictionary(FreeChunk* fc);
228 // Split a free chunk into a smaller free chunk of size "new_size".
229 // Return the smaller free chunk and return the remainder to the
230 // free lists.
231 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
232 // Add a chunk to the free lists.
233 void addChunkToFreeLists(HeapWord* chunk, size_t size);
234 // Add a chunk to the free lists, preferring to suffix it
235 // to the last free chunk at end of space if possible, and
236 // updating the block census stats as well as block offset table.
237 // Take any locks as appropriate if we are multithreaded.
238 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
239 // Add a free chunk to the indexed free lists.
240 void returnChunkToFreeList(FreeChunk* chunk);
241 // Add a free chunk to the dictionary.
242 void returnChunkToDictionary(FreeChunk* chunk);
244 // Functions for maintaining the linear allocation buffers (LinAB).
245 // Repairing a linear allocation block refers to operations
246 // performed on the remainder of a LinAB after an allocation
247 // has been made from it.
248 void repairLinearAllocationBlocks();
249 void repairLinearAllocBlock(LinearAllocBlock* blk);
250 void refillLinearAllocBlock(LinearAllocBlock* blk);
251 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
252 void refillLinearAllocBlocksIfNeeded();
254 void verify_objects_initialized() const;
256 // Statistics reporting helper functions
257 void reportFreeListStatistics() const;
258 void reportIndexedFreeListStatistics() const;
259 size_t maxChunkSizeInIndexedFreeLists() const;
260 size_t numFreeBlocksInIndexedFreeLists() const;
261 // Accessor
262 HeapWord* unallocated_block() const {
263 if (BlockOffsetArrayUseUnallocatedBlock) {
264 HeapWord* ub = _bt.unallocated_block();
265 assert(ub >= bottom() &&
266 ub <= end(), "space invariant");
267 return ub;
268 } else {
269 return end();
270 }
271 }
272 void freed(HeapWord* start, size_t size) {
273 _bt.freed(start, size);
274 }
276 protected:
277 // reset the indexed free list to its initial empty condition.
278 void resetIndexedFreeListArray();
279 // reset to an initial state with a single free block described
280 // by the MemRegion parameter.
281 void reset(MemRegion mr);
282 // Return the total number of words in the indexed free lists.
283 size_t totalSizeInIndexedFreeLists() const;
285 public:
286 // Constructor...
287 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
288 bool use_adaptive_freelists,
289 FreeBlockDictionary::DictionaryChoice);
290 // accessors
291 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
292 FreeBlockDictionary* dictionary() const { return _dictionary; }
293 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
294 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
296 // Set CMS global values
297 static void set_cms_values();
299 // Return the free chunk at the end of the space. If no such
300 // chunk exists, return NULL.
301 FreeChunk* find_chunk_at_end();
303 bool adaptive_freelists() const { return _adaptive_freelists; }
305 void set_collector(CMSCollector* collector) { _collector = collector; }
307 // Support for parallelization of rescan and marking
308 const size_t rescan_task_size() const { return _rescan_task_size; }
309 const size_t marking_task_size() const { return _marking_task_size; }
310 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
311 void initialize_sequential_subtasks_for_rescan(int n_threads);
312 void initialize_sequential_subtasks_for_marking(int n_threads,
313 HeapWord* low = NULL);
315 // Space enquiries
316 size_t used() const;
317 size_t free() const;
318 size_t max_alloc_in_words() const;
319 // XXX: should have a less conservative used_region() than that of
320 // Space; we could consider keeping track of highest allocated
321 // address and correcting that at each sweep, as the sweeper
322 // goes through the entire allocated part of the generation. We
323 // could also use that information to keep the sweeper from
324 // sweeping more than is necessary. The allocator and sweeper will
325 // of course need to synchronize on this, since the sweeper will
326 // try to bump down the address and the allocator will try to bump it up.
327 // For now, however, we'll just use the default used_region()
328 // which overestimates the region by returning the entire
329 // committed region (this is safe, but inefficient).
331 // Returns a subregion of the space containing all the objects in
332 // the space.
333 MemRegion used_region() const {
334 return MemRegion(bottom(),
335 BlockOffsetArrayUseUnallocatedBlock ?
336 unallocated_block() : end());
337 }
339 bool is_in(const void* p) const {
340 return used_region().contains(p);
341 }
343 virtual bool is_free_block(const HeapWord* p) const;
345 // Resizing support
346 void set_end(HeapWord* value); // override
348 // mutual exclusion support
349 Mutex* freelistLock() const { return &_freelistLock; }
351 // Iteration support
352 void oop_iterate(MemRegion mr, OopClosure* cl);
353 void oop_iterate(OopClosure* cl);
355 void object_iterate(ObjectClosure* blk);
356 // Apply the closure to each object in the space whose references
357 // point to objects in the heap. The usage of CompactibleFreeListSpace
358 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
359 // objects in the space with references to objects that are no longer
360 // valid. For example, an object may reference another object
361 // that has already been sweep up (collected). This method uses
362 // obj_is_alive() to determine whether it is safe to iterate of
363 // an object.
364 void safe_object_iterate(ObjectClosure* blk);
365 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
367 // Requires that "mr" be entirely within the space.
368 // Apply "cl->do_object" to all objects that intersect with "mr".
369 // If the iteration encounters an unparseable portion of the region,
370 // terminate the iteration and return the address of the start of the
371 // subregion that isn't done. Return of "NULL" indicates that the
372 // interation completed.
373 virtual HeapWord*
374 object_iterate_careful_m(MemRegion mr,
375 ObjectClosureCareful* cl);
376 virtual HeapWord*
377 object_iterate_careful(ObjectClosureCareful* cl);
379 // Override: provides a DCTO_CL specific to this kind of space.
380 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
381 CardTableModRefBS::PrecisionStyle precision,
382 HeapWord* boundary);
384 void blk_iterate(BlkClosure* cl);
385 void blk_iterate_careful(BlkClosureCareful* cl);
386 HeapWord* block_start_const(const void* p) const;
387 HeapWord* block_start_careful(const void* p) const;
388 size_t block_size(const HeapWord* p) const;
389 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
390 bool block_is_obj(const HeapWord* p) const;
391 bool obj_is_alive(const HeapWord* p) const;
392 size_t block_size_nopar(const HeapWord* p) const;
393 bool block_is_obj_nopar(const HeapWord* p) const;
395 // iteration support for promotion
396 void save_marks();
397 bool no_allocs_since_save_marks();
398 void object_iterate_since_last_GC(ObjectClosure* cl);
400 // iteration support for sweeping
401 void save_sweep_limit() {
402 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
403 unallocated_block() : end();
404 if (CMSTraceSweeper) {
405 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
406 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
407 _sweep_limit, bottom(), end());
408 }
409 }
410 NOT_PRODUCT(
411 void clear_sweep_limit() { _sweep_limit = NULL; }
412 )
413 HeapWord* sweep_limit() { return _sweep_limit; }
415 // Apply "blk->do_oop" to the addresses of all reference fields in objects
416 // promoted into this generation since the most recent save_marks() call.
417 // Fields in objects allocated by applications of the closure
418 // *are* included in the iteration. Thus, when the iteration completes
419 // there should be no further such objects remaining.
420 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
421 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
422 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
423 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
425 // Allocation support
426 HeapWord* allocate(size_t size);
427 HeapWord* par_allocate(size_t size);
429 oop promote(oop obj, size_t obj_size);
430 void gc_prologue();
431 void gc_epilogue();
433 // This call is used by a containing CMS generation / collector
434 // to inform the CFLS space that a sweep has been completed
435 // and that the space can do any related house-keeping functions.
436 void sweep_completed();
438 // For an object in this space, the mark-word's two
439 // LSB's having the value [11] indicates that it has been
440 // promoted since the most recent call to save_marks() on
441 // this generation and has not subsequently been iterated
442 // over (using oop_since_save_marks_iterate() above).
443 // This property holds only for single-threaded collections,
444 // and is typically used for Cheney scans; for MT scavenges,
445 // the property holds for all objects promoted during that
446 // scavenge for the duration of the scavenge and is used
447 // by card-scanning to avoid scanning objects (being) promoted
448 // during that scavenge.
449 bool obj_allocated_since_save_marks(const oop obj) const {
450 assert(is_in_reserved(obj), "Wrong space?");
451 return ((PromotedObject*)obj)->hasPromotedMark();
452 }
454 // A worst-case estimate of the space required (in HeapWords) to expand the
455 // heap when promoting an obj of size obj_size.
456 size_t expansionSpaceRequired(size_t obj_size) const;
458 FreeChunk* allocateScratch(size_t size);
460 // returns true if either the small or large linear allocation buffer is empty.
461 bool linearAllocationWouldFail() const;
463 // Adjust the chunk for the minimum size. This version is called in
464 // most cases in CompactibleFreeListSpace methods.
465 inline static size_t adjustObjectSize(size_t size) {
466 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
467 }
468 // This is a virtual version of adjustObjectSize() that is called
469 // only occasionally when the compaction space changes and the type
470 // of the new compaction space is is only known to be CompactibleSpace.
471 size_t adjust_object_size_v(size_t size) const {
472 return adjustObjectSize(size);
473 }
474 // Minimum size of a free block.
475 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
476 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
477 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
478 bool coalesced);
480 // Support for decisions regarding concurrent collection policy
481 bool should_concurrent_collect() const;
483 // Support for compaction
484 void prepare_for_compaction(CompactPoint* cp);
485 void adjust_pointers();
486 void compact();
487 // reset the space to reflect the fact that a compaction of the
488 // space has been done.
489 virtual void reset_after_compaction();
491 // Debugging support
492 void print() const;
493 void print_on(outputStream* st) const;
494 void prepare_for_verify();
495 void verify(bool allow_dirty) const;
496 void verifyFreeLists() const PRODUCT_RETURN;
497 void verifyIndexedFreeLists() const;
498 void verifyIndexedFreeList(size_t size) const;
499 // Verify that the given chunk is in the free lists:
500 // i.e. either the binary tree dictionary, the indexed free lists
501 // or the linear allocation block.
502 bool verifyChunkInFreeLists(FreeChunk* fc) const;
503 // Verify that the given chunk is the linear allocation block
504 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
505 // Do some basic checks on the the free lists.
506 void check_free_list_consistency() const PRODUCT_RETURN;
508 // Printing support
509 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
510 void print_indexed_free_lists(outputStream* st) const;
511 void print_dictionary_free_lists(outputStream* st) const;
512 void print_promo_info_blocks(outputStream* st) const;
514 NOT_PRODUCT (
515 void initializeIndexedFreeListArrayReturnedBytes();
516 size_t sumIndexedFreeListArrayReturnedBytes();
517 // Return the total number of chunks in the indexed free lists.
518 size_t totalCountInIndexedFreeLists() const;
519 // Return the total numberof chunks in the space.
520 size_t totalCount();
521 )
523 // The census consists of counts of the quantities such as
524 // the current count of the free chunks, number of chunks
525 // created as a result of the split of a larger chunk or
526 // coalescing of smaller chucks, etc. The counts in the
527 // census is used to make decisions on splitting and
528 // coalescing of chunks during the sweep of garbage.
530 // Print the statistics for the free lists.
531 void printFLCensus(size_t sweep_count) const;
533 // Statistics functions
534 // Initialize census for lists before the sweep.
535 void beginSweepFLCensus(float inter_sweep_current,
536 float inter_sweep_estimate,
537 float intra_sweep_estimate);
538 // Set the surplus for each of the free lists.
539 void setFLSurplus();
540 // Set the hint for each of the free lists.
541 void setFLHints();
542 // Clear the census for each of the free lists.
543 void clearFLCensus();
544 // Perform functions for the census after the end of the sweep.
545 void endSweepFLCensus(size_t sweep_count);
546 // Return true if the count of free chunks is greater
547 // than the desired number of free chunks.
548 bool coalOverPopulated(size_t size);
550 // Record (for each size):
551 //
552 // split-births = #chunks added due to splits in (prev-sweep-end,
553 // this-sweep-start)
554 // split-deaths = #chunks removed for splits in (prev-sweep-end,
555 // this-sweep-start)
556 // num-curr = #chunks at start of this sweep
557 // num-prev = #chunks at end of previous sweep
558 //
559 // The above are quantities that are measured. Now define:
560 //
561 // num-desired := num-prev + split-births - split-deaths - num-curr
562 //
563 // Roughly, num-prev + split-births is the supply,
564 // split-deaths is demand due to other sizes
565 // and num-curr is what we have left.
566 //
567 // Thus, num-desired is roughly speaking the "legitimate demand"
568 // for blocks of this size and what we are striving to reach at the
569 // end of the current sweep.
570 //
571 // For a given list, let num-len be its current population.
572 // Define, for a free list of a given size:
573 //
574 // coal-overpopulated := num-len >= num-desired * coal-surplus
575 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
576 // coalescing -- we do not coalesce unless we think that the current
577 // supply has exceeded the estimated demand by more than 5%).
578 //
579 // For the set of sizes in the binary tree, which is neither dense nor
580 // closed, it may be the case that for a particular size we have never
581 // had, or do not now have, or did not have at the previous sweep,
582 // chunks of that size. We need to extend the definition of
583 // coal-overpopulated to such sizes as well:
584 //
585 // For a chunk in/not in the binary tree, extend coal-overpopulated
586 // defined above to include all sizes as follows:
587 //
588 // . a size that is non-existent is coal-overpopulated
589 // . a size that has a num-desired <= 0 as defined above is
590 // coal-overpopulated.
591 //
592 // Also define, for a chunk heap-offset C and mountain heap-offset M:
593 //
594 // close-to-mountain := C >= 0.99 * M
595 //
596 // Now, the coalescing strategy is:
597 //
598 // Coalesce left-hand chunk with right-hand chunk if and
599 // only if:
600 //
601 // EITHER
602 // . left-hand chunk is of a size that is coal-overpopulated
603 // OR
604 // . right-hand chunk is close-to-mountain
605 void smallCoalBirth(size_t size);
606 void smallCoalDeath(size_t size);
607 void coalBirth(size_t size);
608 void coalDeath(size_t size);
609 void smallSplitBirth(size_t size);
610 void smallSplitDeath(size_t size);
611 void splitBirth(size_t size);
612 void splitDeath(size_t size);
613 void split(size_t from, size_t to1);
615 double flsFrag() const;
616 };
618 // A parallel-GC-thread-local allocation buffer for allocation into a
619 // CompactibleFreeListSpace.
620 class CFLS_LAB : public CHeapObj {
621 // The space that this buffer allocates into.
622 CompactibleFreeListSpace* _cfls;
624 // Our local free lists.
625 FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
627 // Initialized from a command-line arg.
629 // Allocation statistics in support of dynamic adjustment of
630 // #blocks to claim per get_from_global_pool() call below.
631 static AdaptiveWeightedAverage
632 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
633 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
634 static int _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
635 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
637 // Internal work method
638 void get_from_global_pool(size_t word_sz, FreeList* fl);
640 public:
641 CFLS_LAB(CompactibleFreeListSpace* cfls);
643 // Allocate and return a block of the given size, or else return NULL.
644 HeapWord* alloc(size_t word_sz);
646 // Return any unused portions of the buffer to the global pool.
647 void retire(int tid);
649 // Dynamic OldPLABSize sizing
650 static void compute_desired_plab_size();
651 // When the settings are modified from default static initialization
652 static void modify_initialization(size_t n, unsigned wt);
653 };
655 size_t PromotionInfo::refillSize() const {
656 const size_t CMSSpoolBlockSize = 256;
657 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
658 * CMSSpoolBlockSize);
659 return CompactibleFreeListSpace::adjustObjectSize(sz);
660 }
662 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP