Mon, 03 May 2010 10:24:51 -0700
6948537: CMS: BOT walkers observe out-of-thin-air zeros on sun4v sparc/CMT
Summary: On sun4v/CMT avoid use of memset() in BOT updates so as to prevent concurrent BOT readers from seeing the phantom zeros arising from memset()'s use of BIS.
Reviewed-by: jmasa, johnc, minqi, poonam, tonyp
1 /*
2 * Copyright 2001-2009 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
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22 *
23 */
25 // Classes in support of keeping track of promotions into a non-Contiguous
26 // space, in this case a CompactibleFreeListSpace.
28 // Forward declarations
29 class CompactibleFreeListSpace;
30 class BlkClosure;
31 class BlkClosureCareful;
32 class UpwardsObjectClosure;
33 class ObjectClosureCareful;
34 class Klass;
36 class PromotedObject VALUE_OBJ_CLASS_SPEC {
37 private:
38 enum {
39 promoted_mask = right_n_bits(2), // i.e. 0x3
40 displaced_mark = nth_bit(2), // i.e. 0x4
41 next_mask = ~(right_n_bits(3)) // i.e. ~(0x7)
42 };
43 intptr_t _next;
44 public:
45 inline PromotedObject* next() const {
46 return (PromotedObject*)(_next & next_mask);
47 }
48 inline void setNext(PromotedObject* x) {
49 assert(((intptr_t)x & ~next_mask) == 0,
50 "Conflict in bit usage, "
51 " or insufficient alignment of objects");
52 _next |= (intptr_t)x;
53 }
54 inline void setPromotedMark() {
55 _next |= promoted_mask;
56 }
57 inline bool hasPromotedMark() const {
58 return (_next & promoted_mask) == promoted_mask;
59 }
60 inline void setDisplacedMark() {
61 _next |= displaced_mark;
62 }
63 inline bool hasDisplacedMark() const {
64 return (_next & displaced_mark) != 0;
65 }
66 inline void clearNext() { _next = 0; }
67 debug_only(void *next_addr() { return (void *) &_next; })
68 };
70 class SpoolBlock: public FreeChunk {
71 friend class PromotionInfo;
72 protected:
73 SpoolBlock* nextSpoolBlock;
74 size_t bufferSize; // number of usable words in this block
75 markOop* displacedHdr; // the displaced headers start here
77 // Note about bufferSize: it denotes the number of entries available plus 1;
78 // legal indices range from 1 through BufferSize - 1. See the verification
79 // code verify() that counts the number of displaced headers spooled.
80 size_t computeBufferSize() {
81 return (size() * sizeof(HeapWord) - sizeof(*this)) / sizeof(markOop);
82 }
84 public:
85 void init() {
86 bufferSize = computeBufferSize();
87 displacedHdr = (markOop*)&displacedHdr;
88 nextSpoolBlock = NULL;
89 }
91 void print_on(outputStream* st) const;
92 void print() const { print_on(gclog_or_tty); }
93 };
95 class PromotionInfo VALUE_OBJ_CLASS_SPEC {
96 bool _tracking; // set if tracking
97 CompactibleFreeListSpace* _space; // the space to which this belongs
98 PromotedObject* _promoHead; // head of list of promoted objects
99 PromotedObject* _promoTail; // tail of list of promoted objects
100 SpoolBlock* _spoolHead; // first spooling block
101 SpoolBlock* _spoolTail; // last non-full spooling block or null
102 SpoolBlock* _splice_point; // when _spoolTail is null, holds list tail
103 SpoolBlock* _spareSpool; // free spool buffer
104 size_t _firstIndex; // first active index in
105 // first spooling block (_spoolHead)
106 size_t _nextIndex; // last active index + 1 in last
107 // spooling block (_spoolTail)
108 private:
109 // ensure that spooling space exists; return true if there is spooling space
110 bool ensure_spooling_space_work();
112 public:
113 PromotionInfo() :
114 _tracking(0), _space(NULL),
115 _promoHead(NULL), _promoTail(NULL),
116 _spoolHead(NULL), _spoolTail(NULL),
117 _spareSpool(NULL), _firstIndex(1),
118 _nextIndex(1) {}
120 bool noPromotions() const {
121 assert(_promoHead != NULL || _promoTail == NULL, "list inconsistency");
122 return _promoHead == NULL;
123 }
124 void startTrackingPromotions();
125 void stopTrackingPromotions(uint worker_id = 0);
126 bool tracking() const { return _tracking; }
127 void track(PromotedObject* trackOop); // keep track of a promoted oop
128 // The following variant must be used when trackOop is not fully
129 // initialized and has a NULL klass:
130 void track(PromotedObject* trackOop, klassOop klassOfOop); // keep track of a promoted oop
131 void setSpace(CompactibleFreeListSpace* sp) { _space = sp; }
132 CompactibleFreeListSpace* space() const { return _space; }
133 markOop nextDisplacedHeader(); // get next header & forward spool pointer
134 void saveDisplacedHeader(markOop hdr);
135 // save header and forward spool
137 inline size_t refillSize() const;
139 SpoolBlock* getSpoolBlock(); // return a free spooling block
140 inline bool has_spooling_space() {
141 return _spoolTail != NULL && _spoolTail->bufferSize > _nextIndex;
142 }
143 // ensure that spooling space exists
144 bool ensure_spooling_space() {
145 return has_spooling_space() || ensure_spooling_space_work();
146 }
147 #define PROMOTED_OOPS_ITERATE_DECL(OopClosureType, nv_suffix) \
148 void promoted_oops_iterate##nv_suffix(OopClosureType* cl);
149 ALL_SINCE_SAVE_MARKS_CLOSURES(PROMOTED_OOPS_ITERATE_DECL)
150 #undef PROMOTED_OOPS_ITERATE_DECL
151 void promoted_oops_iterate(OopsInGenClosure* cl) {
152 promoted_oops_iterate_v(cl);
153 }
154 void verify() const;
155 void reset() {
156 _promoHead = NULL;
157 _promoTail = NULL;
158 _spoolHead = NULL;
159 _spoolTail = NULL;
160 _spareSpool = NULL;
161 _firstIndex = 0;
162 _nextIndex = 0;
164 }
166 void print_on(outputStream* st) const;
167 void print_statistics(uint worker_id) const;
168 };
170 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
171 public:
172 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
173 _allocation_size_limit(0) {}
174 void set(HeapWord* ptr, size_t word_size, size_t refill_size,
175 size_t allocation_size_limit) {
176 _ptr = ptr;
177 _word_size = word_size;
178 _refillSize = refill_size;
179 _allocation_size_limit = allocation_size_limit;
180 }
181 HeapWord* _ptr;
182 size_t _word_size;
183 size_t _refillSize;
184 size_t _allocation_size_limit; // largest size that will be allocated
185 };
187 // Concrete subclass of CompactibleSpace that implements
188 // a free list space, such as used in the concurrent mark sweep
189 // generation.
191 class CompactibleFreeListSpace: public CompactibleSpace {
192 friend class VMStructs;
193 friend class ConcurrentMarkSweepGeneration;
194 friend class ASConcurrentMarkSweepGeneration;
195 friend class CMSCollector;
196 friend class CMSPermGenGen;
197 // Local alloc buffer for promotion into this space.
198 friend class CFLS_LAB;
200 // "Size" of chunks of work (executed during parallel remark phases
201 // of CMS collection); this probably belongs in CMSCollector, although
202 // it's cached here because it's used in
203 // initialize_sequential_subtasks_for_rescan() which modifies
204 // par_seq_tasks which also lives in Space. XXX
205 const size_t _rescan_task_size;
206 const size_t _marking_task_size;
208 // Yet another sequential tasks done structure. This supports
209 // CMS GC, where we have threads dynamically
210 // claiming sub-tasks from a larger parallel task.
211 SequentialSubTasksDone _conc_par_seq_tasks;
213 BlockOffsetArrayNonContigSpace _bt;
215 CMSCollector* _collector;
216 ConcurrentMarkSweepGeneration* _gen;
218 // Data structures for free blocks (used during allocation/sweeping)
220 // Allocation is done linearly from two different blocks depending on
221 // whether the request is small or large, in an effort to reduce
222 // fragmentation. We assume that any locking for allocation is done
223 // by the containing generation. Thus, none of the methods in this
224 // space are re-entrant.
225 enum SomeConstants {
226 SmallForLinearAlloc = 16, // size < this then use _sLAB
227 SmallForDictionary = 257, // size < this then use _indexedFreeList
228 IndexSetSize = SmallForDictionary, // keep this odd-sized
229 IndexSetStart = MinObjAlignment,
230 IndexSetStride = MinObjAlignment
231 };
233 private:
234 enum FitStrategyOptions {
235 FreeBlockStrategyNone = 0,
236 FreeBlockBestFitFirst
237 };
239 PromotionInfo _promoInfo;
241 // helps to impose a global total order on freelistLock ranks;
242 // assumes that CFLSpace's are allocated in global total order
243 static int _lockRank;
245 // a lock protecting the free lists and free blocks;
246 // mutable because of ubiquity of locking even for otherwise const methods
247 mutable Mutex _freelistLock;
248 // locking verifier convenience function
249 void assert_locked() const PRODUCT_RETURN;
250 void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
252 // Linear allocation blocks
253 LinearAllocBlock _smallLinearAllocBlock;
255 FreeBlockDictionary::DictionaryChoice _dictionaryChoice;
256 FreeBlockDictionary* _dictionary; // ptr to dictionary for large size blocks
258 FreeList _indexedFreeList[IndexSetSize];
259 // indexed array for small size blocks
260 // allocation stategy
261 bool _fitStrategy; // Use best fit strategy.
262 bool _adaptive_freelists; // Use adaptive freelists
264 // This is an address close to the largest free chunk in the heap.
265 // It is currently assumed to be at the end of the heap. Free
266 // chunks with addresses greater than nearLargestChunk are coalesced
267 // in an effort to maintain a large chunk at the end of the heap.
268 HeapWord* _nearLargestChunk;
270 // Used to keep track of limit of sweep for the space
271 HeapWord* _sweep_limit;
273 // Support for compacting cms
274 HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
275 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
277 // Initialization helpers.
278 void initializeIndexedFreeListArray();
280 // Extra stuff to manage promotion parallelism.
282 // a lock protecting the dictionary during par promotion allocation.
283 mutable Mutex _parDictionaryAllocLock;
284 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
286 // Locks protecting the exact lists during par promotion allocation.
287 Mutex* _indexedFreeListParLocks[IndexSetSize];
289 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
290 // required to be smaller than "IndexSetSize".) If successful,
291 // adds them to "fl", which is required to be an empty free list.
292 // If the count of "fl" is negative, it's absolute value indicates a
293 // number of free chunks that had been previously "borrowed" from global
294 // list of size "word_sz", and must now be decremented.
295 void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl);
297 // Allocation helper functions
298 // Allocate using a strategy that takes from the indexed free lists
299 // first. This allocation strategy assumes a companion sweeping
300 // strategy that attempts to keep the needed number of chunks in each
301 // indexed free lists.
302 HeapWord* allocate_adaptive_freelists(size_t size);
303 // Allocate from the linear allocation buffers first. This allocation
304 // strategy assumes maximal coalescing can maintain chunks large enough
305 // to be used as linear allocation buffers.
306 HeapWord* allocate_non_adaptive_freelists(size_t size);
308 // Gets a chunk from the linear allocation block (LinAB). If there
309 // is not enough space in the LinAB, refills it.
310 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
311 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size);
312 // Get a chunk from the space remaining in the linear allocation block. Do
313 // not attempt to refill if the space is not available, return NULL. Do the
314 // repairs on the linear allocation block as appropriate.
315 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
316 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size);
318 // Helper function for getChunkFromIndexedFreeList.
319 // Replenish the indexed free list for this "size". Do not take from an
320 // underpopulated size.
321 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
323 // Get a chunk from the indexed free list. If the indexed free list
324 // does not have a free chunk, try to replenish the indexed free list
325 // then get the free chunk from the replenished indexed free list.
326 inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
328 // The returned chunk may be larger than requested (or null).
329 FreeChunk* getChunkFromDictionary(size_t size);
330 // The returned chunk is the exact size requested (or null).
331 FreeChunk* getChunkFromDictionaryExact(size_t size);
333 // Find a chunk in the indexed free list that is the best
334 // fit for size "numWords".
335 FreeChunk* bestFitSmall(size_t numWords);
336 // For free list "fl" of chunks of size > numWords,
337 // remove a chunk, split off a chunk of size numWords
338 // and return it. The split off remainder is returned to
339 // the free lists. The old name for getFromListGreater
340 // was lookInListGreater.
341 FreeChunk* getFromListGreater(FreeList* fl, size_t numWords);
342 // Get a chunk in the indexed free list or dictionary,
343 // by considering a larger chunk and splitting it.
344 FreeChunk* getChunkFromGreater(size_t numWords);
345 // Verify that the given chunk is in the indexed free lists.
346 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
347 // Remove the specified chunk from the indexed free lists.
348 void removeChunkFromIndexedFreeList(FreeChunk* fc);
349 // Remove the specified chunk from the dictionary.
350 void removeChunkFromDictionary(FreeChunk* fc);
351 // Split a free chunk into a smaller free chunk of size "new_size".
352 // Return the smaller free chunk and return the remainder to the
353 // free lists.
354 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
355 // Add a chunk to the free lists.
356 void addChunkToFreeLists(HeapWord* chunk, size_t size);
357 // Add a chunk to the free lists, preferring to suffix it
358 // to the last free chunk at end of space if possible, and
359 // updating the block census stats as well as block offset table.
360 // Take any locks as appropriate if we are multithreaded.
361 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
362 // Add a free chunk to the indexed free lists.
363 void returnChunkToFreeList(FreeChunk* chunk);
364 // Add a free chunk to the dictionary.
365 void returnChunkToDictionary(FreeChunk* chunk);
367 // Functions for maintaining the linear allocation buffers (LinAB).
368 // Repairing a linear allocation block refers to operations
369 // performed on the remainder of a LinAB after an allocation
370 // has been made from it.
371 void repairLinearAllocationBlocks();
372 void repairLinearAllocBlock(LinearAllocBlock* blk);
373 void refillLinearAllocBlock(LinearAllocBlock* blk);
374 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
375 void refillLinearAllocBlocksIfNeeded();
377 void verify_objects_initialized() const;
379 // Statistics reporting helper functions
380 void reportFreeListStatistics() const;
381 void reportIndexedFreeListStatistics() const;
382 size_t maxChunkSizeInIndexedFreeLists() const;
383 size_t numFreeBlocksInIndexedFreeLists() const;
384 // Accessor
385 HeapWord* unallocated_block() const {
386 HeapWord* ub = _bt.unallocated_block();
387 assert(ub >= bottom() &&
388 ub <= end(), "space invariant");
389 return ub;
390 }
391 void freed(HeapWord* start, size_t size) {
392 _bt.freed(start, size);
393 }
395 protected:
396 // reset the indexed free list to its initial empty condition.
397 void resetIndexedFreeListArray();
398 // reset to an initial state with a single free block described
399 // by the MemRegion parameter.
400 void reset(MemRegion mr);
401 // Return the total number of words in the indexed free lists.
402 size_t totalSizeInIndexedFreeLists() const;
404 public:
405 // Constructor...
406 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
407 bool use_adaptive_freelists,
408 FreeBlockDictionary::DictionaryChoice);
409 // accessors
410 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
411 FreeBlockDictionary* dictionary() const { return _dictionary; }
412 HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
413 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
415 // Return the free chunk at the end of the space. If no such
416 // chunk exists, return NULL.
417 FreeChunk* find_chunk_at_end();
419 bool adaptive_freelists() const { return _adaptive_freelists; }
421 void set_collector(CMSCollector* collector) { _collector = collector; }
423 // Support for parallelization of rescan and marking
424 const size_t rescan_task_size() const { return _rescan_task_size; }
425 const size_t marking_task_size() const { return _marking_task_size; }
426 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
427 void initialize_sequential_subtasks_for_rescan(int n_threads);
428 void initialize_sequential_subtasks_for_marking(int n_threads,
429 HeapWord* low = NULL);
431 // Space enquiries
432 size_t used() const;
433 size_t free() const;
434 size_t max_alloc_in_words() const;
435 // XXX: should have a less conservative used_region() than that of
436 // Space; we could consider keeping track of highest allocated
437 // address and correcting that at each sweep, as the sweeper
438 // goes through the entire allocated part of the generation. We
439 // could also use that information to keep the sweeper from
440 // sweeping more than is necessary. The allocator and sweeper will
441 // of course need to synchronize on this, since the sweeper will
442 // try to bump down the address and the allocator will try to bump it up.
443 // For now, however, we'll just use the default used_region()
444 // which overestimates the region by returning the entire
445 // committed region (this is safe, but inefficient).
447 // Returns a subregion of the space containing all the objects in
448 // the space.
449 MemRegion used_region() const {
450 return MemRegion(bottom(),
451 BlockOffsetArrayUseUnallocatedBlock ?
452 unallocated_block() : end());
453 }
455 // This is needed because the default implementation uses block_start()
456 // which can;t be used at certain times (for example phase 3 of mark-sweep).
457 // A better fix is to change the assertions in phase 3 of mark-sweep to
458 // use is_in_reserved(), but that is deferred since the is_in() assertions
459 // are buried through several layers of callers and are used elsewhere
460 // as well.
461 bool is_in(const void* p) const {
462 return used_region().contains(p);
463 }
465 virtual bool is_free_block(const HeapWord* p) const;
467 // Resizing support
468 void set_end(HeapWord* value); // override
470 // mutual exclusion support
471 Mutex* freelistLock() const { return &_freelistLock; }
473 // Iteration support
474 void oop_iterate(MemRegion mr, OopClosure* cl);
475 void oop_iterate(OopClosure* cl);
477 void object_iterate(ObjectClosure* blk);
478 // Apply the closure to each object in the space whose references
479 // point to objects in the heap. The usage of CompactibleFreeListSpace
480 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
481 // objects in the space with references to objects that are no longer
482 // valid. For example, an object may reference another object
483 // that has already been sweep up (collected). This method uses
484 // obj_is_alive() to determine whether it is safe to iterate of
485 // an object.
486 void safe_object_iterate(ObjectClosure* blk);
487 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
489 // Requires that "mr" be entirely within the space.
490 // Apply "cl->do_object" to all objects that intersect with "mr".
491 // If the iteration encounters an unparseable portion of the region,
492 // terminate the iteration and return the address of the start of the
493 // subregion that isn't done. Return of "NULL" indicates that the
494 // interation completed.
495 virtual HeapWord*
496 object_iterate_careful_m(MemRegion mr,
497 ObjectClosureCareful* cl);
498 virtual HeapWord*
499 object_iterate_careful(ObjectClosureCareful* cl);
501 // Override: provides a DCTO_CL specific to this kind of space.
502 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
503 CardTableModRefBS::PrecisionStyle precision,
504 HeapWord* boundary);
506 void blk_iterate(BlkClosure* cl);
507 void blk_iterate_careful(BlkClosureCareful* cl);
508 HeapWord* block_start_const(const void* p) const;
509 HeapWord* block_start_careful(const void* p) const;
510 size_t block_size(const HeapWord* p) const;
511 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
512 bool block_is_obj(const HeapWord* p) const;
513 bool obj_is_alive(const HeapWord* p) const;
514 size_t block_size_nopar(const HeapWord* p) const;
515 bool block_is_obj_nopar(const HeapWord* p) const;
517 // iteration support for promotion
518 void save_marks();
519 bool no_allocs_since_save_marks();
520 void object_iterate_since_last_GC(ObjectClosure* cl);
522 // iteration support for sweeping
523 void save_sweep_limit() {
524 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
525 unallocated_block() : end();
526 }
527 NOT_PRODUCT(
528 void clear_sweep_limit() { _sweep_limit = NULL; }
529 )
530 HeapWord* sweep_limit() { return _sweep_limit; }
532 // Apply "blk->do_oop" to the addresses of all reference fields in objects
533 // promoted into this generation since the most recent save_marks() call.
534 // Fields in objects allocated by applications of the closure
535 // *are* included in the iteration. Thus, when the iteration completes
536 // there should be no further such objects remaining.
537 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
538 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
539 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
540 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
542 // Allocation support
543 HeapWord* allocate(size_t size);
544 HeapWord* par_allocate(size_t size);
546 oop promote(oop obj, size_t obj_size);
547 void gc_prologue();
548 void gc_epilogue();
550 // This call is used by a containing CMS generation / collector
551 // to inform the CFLS space that a sweep has been completed
552 // and that the space can do any related house-keeping functions.
553 void sweep_completed();
555 // For an object in this space, the mark-word's two
556 // LSB's having the value [11] indicates that it has been
557 // promoted since the most recent call to save_marks() on
558 // this generation and has not subsequently been iterated
559 // over (using oop_since_save_marks_iterate() above).
560 bool obj_allocated_since_save_marks(const oop obj) const {
561 assert(is_in_reserved(obj), "Wrong space?");
562 return ((PromotedObject*)obj)->hasPromotedMark();
563 }
565 // A worst-case estimate of the space required (in HeapWords) to expand the
566 // heap when promoting an obj of size obj_size.
567 size_t expansionSpaceRequired(size_t obj_size) const;
569 FreeChunk* allocateScratch(size_t size);
571 // returns true if either the small or large linear allocation buffer is empty.
572 bool linearAllocationWouldFail() const;
574 // Adjust the chunk for the minimum size. This version is called in
575 // most cases in CompactibleFreeListSpace methods.
576 inline static size_t adjustObjectSize(size_t size) {
577 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
578 }
579 // This is a virtual version of adjustObjectSize() that is called
580 // only occasionally when the compaction space changes and the type
581 // of the new compaction space is is only known to be CompactibleSpace.
582 size_t adjust_object_size_v(size_t size) const {
583 return adjustObjectSize(size);
584 }
585 // Minimum size of a free block.
586 virtual size_t minimum_free_block_size() const { return MinChunkSize; }
587 void removeFreeChunkFromFreeLists(FreeChunk* chunk);
588 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
589 bool coalesced);
591 // Support for decisions regarding concurrent collection policy
592 bool should_concurrent_collect() const;
594 // Support for compaction
595 void prepare_for_compaction(CompactPoint* cp);
596 void adjust_pointers();
597 void compact();
598 // reset the space to reflect the fact that a compaction of the
599 // space has been done.
600 virtual void reset_after_compaction();
602 // Debugging support
603 void print() const;
604 void prepare_for_verify();
605 void verify(bool allow_dirty) const;
606 void verifyFreeLists() const PRODUCT_RETURN;
607 void verifyIndexedFreeLists() const;
608 void verifyIndexedFreeList(size_t size) const;
609 // verify that the given chunk is in the free lists.
610 bool verifyChunkInFreeLists(FreeChunk* fc) const;
611 // Do some basic checks on the the free lists.
612 void checkFreeListConsistency() const PRODUCT_RETURN;
614 // Printing support
615 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
616 void print_indexed_free_lists(outputStream* st) const;
617 void print_dictionary_free_lists(outputStream* st) const;
618 void print_promo_info_blocks(outputStream* st) const;
620 NOT_PRODUCT (
621 void initializeIndexedFreeListArrayReturnedBytes();
622 size_t sumIndexedFreeListArrayReturnedBytes();
623 // Return the total number of chunks in the indexed free lists.
624 size_t totalCountInIndexedFreeLists() const;
625 // Return the total numberof chunks in the space.
626 size_t totalCount();
627 )
629 // The census consists of counts of the quantities such as
630 // the current count of the free chunks, number of chunks
631 // created as a result of the split of a larger chunk or
632 // coalescing of smaller chucks, etc. The counts in the
633 // census is used to make decisions on splitting and
634 // coalescing of chunks during the sweep of garbage.
636 // Print the statistics for the free lists.
637 void printFLCensus(size_t sweep_count) const;
639 // Statistics functions
640 // Initialize census for lists before the sweep.
641 void beginSweepFLCensus(float inter_sweep_current,
642 float inter_sweep_estimate,
643 float intra_sweep_estimate);
644 // Set the surplus for each of the free lists.
645 void setFLSurplus();
646 // Set the hint for each of the free lists.
647 void setFLHints();
648 // Clear the census for each of the free lists.
649 void clearFLCensus();
650 // Perform functions for the census after the end of the sweep.
651 void endSweepFLCensus(size_t sweep_count);
652 // Return true if the count of free chunks is greater
653 // than the desired number of free chunks.
654 bool coalOverPopulated(size_t size);
656 // Record (for each size):
657 //
658 // split-births = #chunks added due to splits in (prev-sweep-end,
659 // this-sweep-start)
660 // split-deaths = #chunks removed for splits in (prev-sweep-end,
661 // this-sweep-start)
662 // num-curr = #chunks at start of this sweep
663 // num-prev = #chunks at end of previous sweep
664 //
665 // The above are quantities that are measured. Now define:
666 //
667 // num-desired := num-prev + split-births - split-deaths - num-curr
668 //
669 // Roughly, num-prev + split-births is the supply,
670 // split-deaths is demand due to other sizes
671 // and num-curr is what we have left.
672 //
673 // Thus, num-desired is roughly speaking the "legitimate demand"
674 // for blocks of this size and what we are striving to reach at the
675 // end of the current sweep.
676 //
677 // For a given list, let num-len be its current population.
678 // Define, for a free list of a given size:
679 //
680 // coal-overpopulated := num-len >= num-desired * coal-surplus
681 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
682 // coalescing -- we do not coalesce unless we think that the current
683 // supply has exceeded the estimated demand by more than 5%).
684 //
685 // For the set of sizes in the binary tree, which is neither dense nor
686 // closed, it may be the case that for a particular size we have never
687 // had, or do not now have, or did not have at the previous sweep,
688 // chunks of that size. We need to extend the definition of
689 // coal-overpopulated to such sizes as well:
690 //
691 // For a chunk in/not in the binary tree, extend coal-overpopulated
692 // defined above to include all sizes as follows:
693 //
694 // . a size that is non-existent is coal-overpopulated
695 // . a size that has a num-desired <= 0 as defined above is
696 // coal-overpopulated.
697 //
698 // Also define, for a chunk heap-offset C and mountain heap-offset M:
699 //
700 // close-to-mountain := C >= 0.99 * M
701 //
702 // Now, the coalescing strategy is:
703 //
704 // Coalesce left-hand chunk with right-hand chunk if and
705 // only if:
706 //
707 // EITHER
708 // . left-hand chunk is of a size that is coal-overpopulated
709 // OR
710 // . right-hand chunk is close-to-mountain
711 void smallCoalBirth(size_t size);
712 void smallCoalDeath(size_t size);
713 void coalBirth(size_t size);
714 void coalDeath(size_t size);
715 void smallSplitBirth(size_t size);
716 void smallSplitDeath(size_t size);
717 void splitBirth(size_t size);
718 void splitDeath(size_t size);
719 void split(size_t from, size_t to1);
721 double flsFrag() const;
722 };
724 // A parallel-GC-thread-local allocation buffer for allocation into a
725 // CompactibleFreeListSpace.
726 class CFLS_LAB : public CHeapObj {
727 // The space that this buffer allocates into.
728 CompactibleFreeListSpace* _cfls;
730 // Our local free lists.
731 FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
733 // Initialized from a command-line arg.
735 // Allocation statistics in support of dynamic adjustment of
736 // #blocks to claim per get_from_global_pool() call below.
737 static AdaptiveWeightedAverage
738 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize];
739 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
740 static int _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
741 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize];
743 // Internal work method
744 void get_from_global_pool(size_t word_sz, FreeList* fl);
746 public:
747 CFLS_LAB(CompactibleFreeListSpace* cfls);
749 // Allocate and return a block of the given size, or else return NULL.
750 HeapWord* alloc(size_t word_sz);
752 // Return any unused portions of the buffer to the global pool.
753 void retire(int tid);
755 // Dynamic OldPLABSize sizing
756 static void compute_desired_plab_size();
757 // When the settings are modified from default static initialization
758 static void modify_initialization(size_t n, unsigned wt);
759 };
761 size_t PromotionInfo::refillSize() const {
762 const size_t CMSSpoolBlockSize = 256;
763 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
764 * CMSSpoolBlockSize);
765 return CompactibleFreeListSpace::adjustObjectSize(sz);
766 }