Thu, 21 Aug 2008 23:36:31 -0400
Merge
1 /*
2 * Copyright 2001-2008 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // Classes in support of keeping track of promotions into a non-Contiguous
26 // space, in this case a CompactibleFreeListSpace.
28 #define CFLS_LAB_REFILL_STATS 0
30 // Forward declarations
31 class CompactibleFreeListSpace;
32 class BlkClosure;
33 class BlkClosureCareful;
34 class UpwardsObjectClosure;
35 class ObjectClosureCareful;
36 class Klass;
38 class PromotedObject VALUE_OBJ_CLASS_SPEC {
39 private:
40 enum {
41 promoted_mask = right_n_bits(2), // i.e. 0x3
42 displaced_mark = nth_bit(2), // i.e. 0x4
43 next_mask = ~(right_n_bits(3)) // i.e. ~(0x7)
44 };
45 intptr_t _next;
46 public:
47 inline PromotedObject* next() const {
48 return (PromotedObject*)(_next & next_mask);
49 }
50 inline void setNext(PromotedObject* x) {
51 assert(((intptr_t)x & ~next_mask) == 0,
52 "Conflict in bit usage, "
53 " or insufficient alignment of objects");
54 _next |= (intptr_t)x;
55 }
56 inline void setPromotedMark() {
57 _next |= promoted_mask;
58 }
59 inline bool hasPromotedMark() const {
60 return (_next & promoted_mask) == promoted_mask;
61 }
62 inline void setDisplacedMark() {
63 _next |= displaced_mark;
64 }
65 inline bool hasDisplacedMark() const {
66 return (_next & displaced_mark) != 0;
67 }
68 inline void clearNext() { _next = 0; }
69 debug_only(void *next_addr() { return (void *) &_next; })
70 };
72 class SpoolBlock: public FreeChunk {
73 friend class PromotionInfo;
74 protected:
75 SpoolBlock* nextSpoolBlock;
76 size_t bufferSize; // number of usable words in this block
77 markOop* displacedHdr; // the displaced headers start here
79 // Note about bufferSize: it denotes the number of entries available plus 1;
80 // legal indices range from 1 through BufferSize - 1. See the verification
81 // code verify() that counts the number of displaced headers spooled.
82 size_t computeBufferSize() {
83 return (size() * sizeof(HeapWord) - sizeof(*this)) / sizeof(markOop);
84 }
86 public:
87 void init() {
88 bufferSize = computeBufferSize();
89 displacedHdr = (markOop*)&displacedHdr;
90 nextSpoolBlock = NULL;
91 }
92 };
94 class PromotionInfo VALUE_OBJ_CLASS_SPEC {
95 bool _tracking; // set if tracking
96 CompactibleFreeListSpace* _space; // the space to which this belongs
97 PromotedObject* _promoHead; // head of list of promoted objects
98 PromotedObject* _promoTail; // tail of list of promoted objects
99 SpoolBlock* _spoolHead; // first spooling block
100 SpoolBlock* _spoolTail; // last non-full spooling block or null
101 SpoolBlock* _splice_point; // when _spoolTail is null, holds list tail
102 SpoolBlock* _spareSpool; // free spool buffer
103 size_t _firstIndex; // first active index in
104 // first spooling block (_spoolHead)
105 size_t _nextIndex; // last active index + 1 in last
106 // spooling block (_spoolTail)
107 private:
108 // ensure that spooling space exists; return true if there is spooling space
109 bool ensure_spooling_space_work();
111 public:
112 PromotionInfo() :
113 _tracking(0), _space(NULL),
114 _promoHead(NULL), _promoTail(NULL),
115 _spoolHead(NULL), _spoolTail(NULL),
116 _spareSpool(NULL), _firstIndex(1),
117 _nextIndex(1) {}
119 bool noPromotions() const {
120 assert(_promoHead != NULL || _promoTail == NULL, "list inconsistency");
121 return _promoHead == NULL;
122 }
123 void startTrackingPromotions();
124 void stopTrackingPromotions();
125 bool tracking() const { return _tracking; }
126 void track(PromotedObject* trackOop); // keep track of a promoted oop
127 // The following variant must be used when trackOop is not fully
128 // initialized and has a NULL klass:
129 void track(PromotedObject* trackOop, klassOop klassOfOop); // keep track of a promoted oop
130 void setSpace(CompactibleFreeListSpace* sp) { _space = sp; }
131 CompactibleFreeListSpace* space() const { return _space; }
132 markOop nextDisplacedHeader(); // get next header & forward spool pointer
133 void saveDisplacedHeader(markOop hdr);
134 // save header and forward spool
136 inline size_t refillSize() const;
138 SpoolBlock* getSpoolBlock(); // return a free spooling block
139 inline bool has_spooling_space() {
140 return _spoolTail != NULL && _spoolTail->bufferSize > _nextIndex;
141 }
142 // ensure that spooling space exists
143 bool ensure_spooling_space() {
144 return has_spooling_space() || ensure_spooling_space_work();
145 }
146 #define PROMOTED_OOPS_ITERATE_DECL(OopClosureType, nv_suffix) \
147 void promoted_oops_iterate##nv_suffix(OopClosureType* cl);
148 ALL_SINCE_SAVE_MARKS_CLOSURES(PROMOTED_OOPS_ITERATE_DECL)
149 #undef PROMOTED_OOPS_ITERATE_DECL
150 void promoted_oops_iterate(OopsInGenClosure* cl) {
151 promoted_oops_iterate_v(cl);
152 }
153 void verify() const;
154 void reset() {
155 _promoHead = NULL;
156 _promoTail = NULL;
157 _spoolHead = NULL;
158 _spoolTail = NULL;
159 _spareSpool = NULL;
160 _firstIndex = 0;
161 _nextIndex = 0;
163 }
164 };
166 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
167 public:
168 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
169 _allocation_size_limit(0) {}
170 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
171 size_t allocation_size_limit) {
172 _ptr = ptr;
173 _word_size = word_size;
174 _refillSize = refill_size;
175 _allocation_size_limit = allocation_size_limit;
176 }
177 HeapWord* _ptr;
178 size_t _word_size;
179 size_t _refillSize;
180 size_t _allocation_size_limit; // largest size that will be allocated
181 };
183 // Concrete subclass of CompactibleSpace that implements
184 // a free list space, such as used in the concurrent mark sweep
185 // generation.
187 class CompactibleFreeListSpace: public CompactibleSpace {
188 friend class VMStructs;
189 friend class ConcurrentMarkSweepGeneration;
190 friend class ASConcurrentMarkSweepGeneration;
191 friend class CMSCollector;
192 friend class CMSPermGenGen;
193 // Local alloc buffer for promotion into this space.
194 friend class CFLS_LAB;
196 // "Size" of chunks of work (executed during parallel remark phases
197 // of CMS collection); this probably belongs in CMSCollector, although
198 // it's cached here because it's used in
199 // initialize_sequential_subtasks_for_rescan() which modifies
200 // par_seq_tasks which also lives in Space. XXX
201 const size_t _rescan_task_size;
202 const size_t _marking_task_size;
204 // Yet another sequential tasks done structure. This supports
205 // CMS GC, where we have threads dynamically
206 // claiming sub-tasks from a larger parallel task.
207 SequentialSubTasksDone _conc_par_seq_tasks;
209 BlockOffsetArrayNonContigSpace _bt;
211 CMSCollector* _collector;
212 ConcurrentMarkSweepGeneration* _gen;
214 // Data structures for free blocks (used during allocation/sweeping)
216 // Allocation is done linearly from two different blocks depending on
217 // whether the request is small or large, in an effort to reduce
218 // fragmentation. We assume that any locking for allocation is done
219 // by the containing generation. Thus, none of the methods in this
220 // space are re-entrant.
221 enum SomeConstants {
222 SmallForLinearAlloc = 16, // size < this then use _sLAB
223 SmallForDictionary = 257, // size < this then use _indexedFreeList
224 IndexSetSize = SmallForDictionary, // keep this odd-sized
225 IndexSetStart = MinObjAlignment,
226 IndexSetStride = MinObjAlignment
227 };
229 private:
230 enum FitStrategyOptions {
231 FreeBlockStrategyNone = 0,
232 FreeBlockBestFitFirst
233 };
235 PromotionInfo _promoInfo;
237 // helps to impose a global total order on freelistLock ranks;
238 // assumes that CFLSpace's are allocated in global total order
239 static int _lockRank;
241 // a lock protecting the free lists and free blocks;
242 // mutable because of ubiquity of locking even for otherwise const methods
243 mutable Mutex _freelistLock;
244 // locking verifier convenience function
245 void assert_locked() const PRODUCT_RETURN;
247 // Linear allocation blocks
248 LinearAllocBlock _smallLinearAllocBlock;
250 FreeBlockDictionary::DictionaryChoice _dictionaryChoice;
251 FreeBlockDictionary* _dictionary; // ptr to dictionary for large size blocks
253 FreeList _indexedFreeList[IndexSetSize];
254 // indexed array for small size blocks
255 // allocation stategy
256 bool _fitStrategy; // Use best fit strategy.
257 bool _adaptive_freelists; // Use adaptive freelists
259 // This is an address close to the largest free chunk in the heap.
260 // It is currently assumed to be at the end of the heap. Free
261 // chunks with addresses greater than nearLargestChunk are coalesced
262 // in an effort to maintain a large chunk at the end of the heap.
263 HeapWord* _nearLargestChunk;
265 // Used to keep track of limit of sweep for the space
266 HeapWord* _sweep_limit;
268 // Support for compacting cms
269 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
270 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
272 // Initialization helpers.
273 void initializeIndexedFreeListArray();
275 // Extra stuff to manage promotion parallelism.
277 // a lock protecting the dictionary during par promotion allocation.
278 mutable Mutex _parDictionaryAllocLock;
279 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
281 // Locks protecting the exact lists during par promotion allocation.
282 Mutex* _indexedFreeListParLocks[IndexSetSize];
284 #if CFLS_LAB_REFILL_STATS
285 // Some statistics.
286 jint _par_get_chunk_from_small;
287 jint _par_get_chunk_from_large;
288 #endif
291 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
292 // required to be smaller than "IndexSetSize".) If successful,
293 // adds them to "fl", which is required to be an empty free list.
294 // If the count of "fl" is negative, it's absolute value indicates a
295 // number of free chunks that had been previously "borrowed" from global
296 // list of size "word_sz", and must now be decremented.
297 void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl);
299 // Allocation helper functions
300 // Allocate using a strategy that takes from the indexed free lists
301 // first. This allocation strategy assumes a companion sweeping
302 // strategy that attempts to keep the needed number of chunks in each
303 // indexed free lists.
304 HeapWord* allocate_adaptive_freelists(size_t size);
305 // Allocate from the linear allocation buffers first. This allocation
306 // strategy assumes maximal coalescing can maintain chunks large enough
307 // to be used as linear allocation buffers.
308 HeapWord* allocate_non_adaptive_freelists(size_t size);
310 // Gets a chunk from the linear allocation block (LinAB). If there
311 // is not enough space in the LinAB, refills it.
312 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
313 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
314 // Get a chunk from the space remaining in the linear allocation block. Do
315 // not attempt to refill if the space is not available, return NULL. Do the
316 // repairs on the linear allocation block as appropriate.
317 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
318 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
320 // Helper function for getChunkFromIndexedFreeList.
321 // Replenish the indexed free list for this "size". Do not take from an
322 // underpopulated size.
323 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size);
325 // Get a chunk from the indexed free list. If the indexed free list
326 // does not have a free chunk, try to replenish the indexed free list
327 // then get the free chunk from the replenished indexed free list.
328 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
330 // The returned chunk may be larger than requested (or null).
331 FreeChunk* getChunkFromDictionary(size_t size);
332 // The returned chunk is the exact size requested (or null).
333 FreeChunk* getChunkFromDictionaryExact(size_t size);
335 // Find a chunk in the indexed free list that is the best
336 // fit for size "numWords".
337 FreeChunk* bestFitSmall(size_t numWords);
338 // For free list "fl" of chunks of size > numWords,
339 // remove a chunk, split off a chunk of size numWords
340 // and return it. The split off remainder is returned to
341 // the free lists. The old name for getFromListGreater
342 // was lookInListGreater.
343 FreeChunk* getFromListGreater(FreeList* fl, size_t numWords);
344 // Get a chunk in the indexed free list or dictionary,
345 // by considering a larger chunk and splitting it.
346 FreeChunk* getChunkFromGreater(size_t numWords);
347 // Verify that the given chunk is in the indexed free lists.
348 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
349 // Remove the specified chunk from the indexed free lists.
350 void removeChunkFromIndexedFreeList(FreeChunk* fc);
351 // Remove the specified chunk from the dictionary.
352 void removeChunkFromDictionary(FreeChunk* fc);
353 // Split a free chunk into a smaller free chunk of size "new_size".
354 // Return the smaller free chunk and return the remainder to the
355 // free lists.
356 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
357 // Add a chunk to the free lists.
358 void addChunkToFreeLists(HeapWord* chunk, size_t size);
359 // Add a chunk to the free lists, preferring to suffix it
360 // to the last free chunk at end of space if possible, and
361 // updating the block census stats as well as block offset table.
362 // Take any locks as appropriate if we are multithreaded.
363 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
364 // Add a free chunk to the indexed free lists.
365 void returnChunkToFreeList(FreeChunk* chunk);
366 // Add a free chunk to the dictionary.
367 void returnChunkToDictionary(FreeChunk* chunk);
369 // Functions for maintaining the linear allocation buffers (LinAB).
370 // Repairing a linear allocation block refers to operations
371 // performed on the remainder of a LinAB after an allocation
372 // has been made from it.
373 void repairLinearAllocationBlocks();
374 void repairLinearAllocBlock(LinearAllocBlock* blk);
375 void refillLinearAllocBlock(LinearAllocBlock* blk);
376 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
377 void refillLinearAllocBlocksIfNeeded();
379 void verify_objects_initialized() const;
381 // Statistics reporting helper functions
382 void reportFreeListStatistics() const;
383 void reportIndexedFreeListStatistics() const;
384 size_t maxChunkSizeInIndexedFreeLists() const;
385 size_t numFreeBlocksInIndexedFreeLists() const;
386 // Accessor
387 HeapWord* unallocated_block() const {
388 HeapWord* ub = _bt.unallocated_block();
389 assert(ub >= bottom() &&
390 ub <= end(), "space invariant");
391 return ub;
392 }
393 void freed(HeapWord* start, size_t size) {
394 _bt.freed(start, size);
395 }
397 protected:
398 // reset the indexed free list to its initial empty condition.
399 void resetIndexedFreeListArray();
400 // reset to an initial state with a single free block described
401 // by the MemRegion parameter.
402 void reset(MemRegion mr);
403 // Return the total number of words in the indexed free lists.
404 size_t totalSizeInIndexedFreeLists() const;
406 public:
407 // Constructor...
408 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
409 bool use_adaptive_freelists,
410 FreeBlockDictionary::DictionaryChoice);
411 // accessors
412 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
413 FreeBlockDictionary* dictionary() const { return _dictionary; }
414 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
415 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
417 // Return the free chunk at the end of the space. If no such
418 // chunk exists, return NULL.
419 FreeChunk* find_chunk_at_end();
421 bool adaptive_freelists() const { return _adaptive_freelists; }
423 void set_collector(CMSCollector* collector) { _collector = collector; }
425 // Support for parallelization of rescan and marking
426 const size_t rescan_task_size() const { return _rescan_task_size; }
427 const size_t marking_task_size() const { return _marking_task_size; }
428 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
429 void initialize_sequential_subtasks_for_rescan(int n_threads);
430 void initialize_sequential_subtasks_for_marking(int n_threads,
431 HeapWord* low = NULL);
433 #if CFLS_LAB_REFILL_STATS
434 void print_par_alloc_stats();
435 #endif
437 // Space enquiries
438 size_t used() const;
439 size_t free() const;
440 size_t max_alloc_in_words() const;
441 // XXX: should have a less conservative used_region() than that of
442 // Space; we could consider keeping track of highest allocated
443 // address and correcting that at each sweep, as the sweeper
444 // goes through the entire allocated part of the generation. We
445 // could also use that information to keep the sweeper from
446 // sweeping more than is necessary. The allocator and sweeper will
447 // of course need to synchronize on this, since the sweeper will
448 // try to bump down the address and the allocator will try to bump it up.
449 // For now, however, we'll just use the default used_region()
450 // which overestimates the region by returning the entire
451 // committed region (this is safe, but inefficient).
453 // Returns a subregion of the space containing all the objects in
454 // the space.
455 MemRegion used_region() const {
456 return MemRegion(bottom(),
457 BlockOffsetArrayUseUnallocatedBlock ?
458 unallocated_block() : end());
459 }
461 // This is needed because the default implementation uses block_start()
462 // which can;t be used at certain times (for example phase 3 of mark-sweep).
463 // A better fix is to change the assertions in phase 3 of mark-sweep to
464 // use is_in_reserved(), but that is deferred since the is_in() assertions
465 // are buried through several layers of callers and are used elsewhere
466 // as well.
467 bool is_in(const void* p) const {
468 return used_region().contains(p);
469 }
471 virtual bool is_free_block(const HeapWord* p) const;
473 // Resizing support
474 void set_end(HeapWord* value); // override
476 // mutual exclusion support
477 Mutex* freelistLock() const { return &_freelistLock; }
479 // Iteration support
480 void oop_iterate(MemRegion mr, OopClosure* cl);
481 void oop_iterate(OopClosure* cl);
483 void object_iterate(ObjectClosure* blk);
484 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
486 // Requires that "mr" be entirely within the space.
487 // Apply "cl->do_object" to all objects that intersect with "mr".
488 // If the iteration encounters an unparseable portion of the region,
489 // terminate the iteration and return the address of the start of the
490 // subregion that isn't done. Return of "NULL" indicates that the
491 // interation completed.
492 virtual HeapWord*
493 object_iterate_careful_m(MemRegion mr,
494 ObjectClosureCareful* cl);
495 virtual HeapWord*
496 object_iterate_careful(ObjectClosureCareful* cl);
498 // Override: provides a DCTO_CL specific to this kind of space.
499 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
500 CardTableModRefBS::PrecisionStyle precision,
501 HeapWord* boundary);
503 void blk_iterate(BlkClosure* cl);
504 void blk_iterate_careful(BlkClosureCareful* cl);
505 HeapWord* block_start_const(const void* p) const;
506 HeapWord* block_start_careful(const void* p) const;
507 size_t block_size(const HeapWord* p) const;
508 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
509 bool block_is_obj(const HeapWord* p) const;
510 bool obj_is_alive(const HeapWord* p) const;
511 size_t block_size_nopar(const HeapWord* p) const;
512 bool block_is_obj_nopar(const HeapWord* p) const;
514 // iteration support for promotion
515 void save_marks();
516 bool no_allocs_since_save_marks();
517 void object_iterate_since_last_GC(ObjectClosure* cl);
519 // iteration support for sweeping
520 void save_sweep_limit() {
521 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
522 unallocated_block() : end();
523 }
524 NOT_PRODUCT(
525 void clear_sweep_limit() { _sweep_limit = NULL; }
526 )
527 HeapWord* sweep_limit() { return _sweep_limit; }
529 // Apply "blk->do_oop" to the addresses of all reference fields in objects
530 // promoted into this generation since the most recent save_marks() call.
531 // Fields in objects allocated by applications of the closure
532 // *are* included in the iteration. Thus, when the iteration completes
533 // there should be no further such objects remaining.
534 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
535 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
536 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
537 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
539 // Allocation support
540 HeapWord* allocate(size_t size);
541 HeapWord* par_allocate(size_t size);
543 oop promote(oop obj, size_t obj_size);
544 void gc_prologue();
545 void gc_epilogue();
547 // This call is used by a containing CMS generation / collector
548 // to inform the CFLS space that a sweep has been completed
549 // and that the space can do any related house-keeping functions.
550 void sweep_completed();
552 // For an object in this space, the mark-word's two
553 // LSB's having the value [11] indicates that it has been
554 // promoted since the most recent call to save_marks() on
555 // this generation and has not subsequently been iterated
556 // over (using oop_since_save_marks_iterate() above).
557 bool obj_allocated_since_save_marks(const oop obj) const {
558 assert(is_in_reserved(obj), "Wrong space?");
559 return ((PromotedObject*)obj)->hasPromotedMark();
560 }
562 // A worst-case estimate of the space required (in HeapWords) to expand the
563 // heap when promoting an obj of size obj_size.
564 size_t expansionSpaceRequired(size_t obj_size) const;
566 FreeChunk* allocateScratch(size_t size);
568 // returns true if either the small or large linear allocation buffer is empty.
569 bool linearAllocationWouldFail() const;
571 // Adjust the chunk for the minimum size. This version is called in
572 // most cases in CompactibleFreeListSpace methods.
573 inline static size_t adjustObjectSize(size_t size) {
574 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
575 }
576 // This is a virtual version of adjustObjectSize() that is called
577 // only occasionally when the compaction space changes and the type
578 // of the new compaction space is is only known to be CompactibleSpace.
579 size_t adjust_object_size_v(size_t size) const {
580 return adjustObjectSize(size);
581 }
582 // Minimum size of a free block.
583 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
584 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
585 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
586 bool coalesced);
588 // Support for decisions regarding concurrent collection policy
589 bool should_concurrent_collect() const;
591 // Support for compaction
592 void prepare_for_compaction(CompactPoint* cp);
593 void adjust_pointers();
594 void compact();
595 // reset the space to reflect the fact that a compaction of the
596 // space has been done.
597 virtual void reset_after_compaction();
599 // Debugging support
600 void print() const;
601 void prepare_for_verify();
602 void verify(bool allow_dirty) const;
603 void verifyFreeLists() const PRODUCT_RETURN;
604 void verifyIndexedFreeLists() const;
605 void verifyIndexedFreeList(size_t size) const;
606 // verify that the given chunk is in the free lists.
607 bool verifyChunkInFreeLists(FreeChunk* fc) const;
608 // Do some basic checks on the the free lists.
609 void checkFreeListConsistency() const PRODUCT_RETURN;
611 NOT_PRODUCT (
612 void initializeIndexedFreeListArrayReturnedBytes();
613 size_t sumIndexedFreeListArrayReturnedBytes();
614 // Return the total number of chunks in the indexed free lists.
615 size_t totalCountInIndexedFreeLists() const;
616 // Return the total numberof chunks in the space.
617 size_t totalCount();
618 )
620 // The census consists of counts of the quantities such as
621 // the current count of the free chunks, number of chunks
622 // created as a result of the split of a larger chunk or
623 // coalescing of smaller chucks, etc. The counts in the
624 // census is used to make decisions on splitting and
625 // coalescing of chunks during the sweep of garbage.
627 // Print the statistics for the free lists.
628 void printFLCensus(size_t sweep_count) const;
630 // Statistics functions
631 // Initialize census for lists before the sweep.
632 void beginSweepFLCensus(float sweep_current,
633 float sweep_estimate);
634 // Set the surplus for each of the free lists.
635 void setFLSurplus();
636 // Set the hint for each of the free lists.
637 void setFLHints();
638 // Clear the census for each of the free lists.
639 void clearFLCensus();
640 // Perform functions for the census after the end of the sweep.
641 void endSweepFLCensus(size_t sweep_count);
642 // Return true if the count of free chunks is greater
643 // than the desired number of free chunks.
644 bool coalOverPopulated(size_t size);
646 // Record (for each size):
647 //
648 // split-births = #chunks added due to splits in (prev-sweep-end,
649 // this-sweep-start)
650 // split-deaths = #chunks removed for splits in (prev-sweep-end,
651 // this-sweep-start)
652 // num-curr = #chunks at start of this sweep
653 // num-prev = #chunks at end of previous sweep
654 //
655 // The above are quantities that are measured. Now define:
656 //
657 // num-desired := num-prev + split-births - split-deaths - num-curr
658 //
659 // Roughly, num-prev + split-births is the supply,
660 // split-deaths is demand due to other sizes
661 // and num-curr is what we have left.
662 //
663 // Thus, num-desired is roughly speaking the "legitimate demand"
664 // for blocks of this size and what we are striving to reach at the
665 // end of the current sweep.
666 //
667 // For a given list, let num-len be its current population.
668 // Define, for a free list of a given size:
669 //
670 // coal-overpopulated := num-len >= num-desired * coal-surplus
671 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
672 // coalescing -- we do not coalesce unless we think that the current
673 // supply has exceeded the estimated demand by more than 5%).
674 //
675 // For the set of sizes in the binary tree, which is neither dense nor
676 // closed, it may be the case that for a particular size we have never
677 // had, or do not now have, or did not have at the previous sweep,
678 // chunks of that size. We need to extend the definition of
679 // coal-overpopulated to such sizes as well:
680 //
681 // For a chunk in/not in the binary tree, extend coal-overpopulated
682 // defined above to include all sizes as follows:
683 //
684 // . a size that is non-existent is coal-overpopulated
685 // . a size that has a num-desired <= 0 as defined above is
686 // coal-overpopulated.
687 //
688 // Also define, for a chunk heap-offset C and mountain heap-offset M:
689 //
690 // close-to-mountain := C >= 0.99 * M
691 //
692 // Now, the coalescing strategy is:
693 //
694 // Coalesce left-hand chunk with right-hand chunk if and
695 // only if:
696 //
697 // EITHER
698 // . left-hand chunk is of a size that is coal-overpopulated
699 // OR
700 // . right-hand chunk is close-to-mountain
701 void smallCoalBirth(size_t size);
702 void smallCoalDeath(size_t size);
703 void coalBirth(size_t size);
704 void coalDeath(size_t size);
705 void smallSplitBirth(size_t size);
706 void smallSplitDeath(size_t size);
707 void splitBirth(size_t size);
708 void splitDeath(size_t size);
709 void split(size_t from, size_t to1);
711 double flsFrag() const;
712 };
714 // A parallel-GC-thread-local allocation buffer for allocation into a
715 // CompactibleFreeListSpace.
716 class CFLS_LAB : public CHeapObj {
717 // The space that this buffer allocates into.
718 CompactibleFreeListSpace* _cfls;
720 // Our local free lists.
721 FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
723 // Initialized from a command-line arg.
724 size_t _blocks_to_claim;
726 #if CFLS_LAB_REFILL_STATS
727 // Some statistics.
728 int _refills;
729 int _blocksTaken;
730 static int _tot_refills;
731 static int _tot_blocksTaken;
732 static int _next_threshold;
733 #endif
735 public:
736 CFLS_LAB(CompactibleFreeListSpace* cfls);
738 // Allocate and return a block of the given size, or else return NULL.
739 HeapWord* alloc(size_t word_sz);
741 // Return any unused portions of the buffer to the global pool.
742 void retire();
743 };
745 size_t PromotionInfo::refillSize() const {
746 const size_t CMSSpoolBlockSize = 256;
747 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
748 * CMSSpoolBlockSize);
749 return CompactibleFreeListSpace::adjustObjectSize(sz);
750 }