jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp@be3f9c242c9d (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp@be3f9c242c9d (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp

Mon, 16 Aug 2010 15:58:42 -0700

author: ysr
date: Mon, 16 Aug 2010 15:58:42 -0700
changeset 2071: be3f9c242c9d
parent 1934: e9ff18c4ace7
child 2314: f95d63e2154a
permissions: -rw-r--r--

6948538: CMS: BOT walkers can fall into object allocation and initialization cracks
Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode.
Reviewed-by: chrisphi, johnc, poonam

 /*
  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 // Classes in support of keeping track of promotions into a non-Contiguous
 // space, in this case a CompactibleFreeListSpace.
 // Forward declarations
 class CompactibleFreeListSpace;
 class BlkClosure;
 class BlkClosureCareful;
 class UpwardsObjectClosure;
 class ObjectClosureCareful;
 class Klass;
 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
  public:
   LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
     _allocation_size_limit(0) {}
   void set(HeapWord* ptr, size_t word_size, size_t refill_size,
     size_t allocation_size_limit) {
     _ptr = ptr;
     _word_size = word_size;
     _refillSize = refill_size;
     _allocation_size_limit = allocation_size_limit;
   }
   HeapWord* _ptr;
   size_t    _word_size;
   size_t    _refillSize;
   size_t    _allocation_size_limit;  // largest size that will be allocated
   void print_on(outputStream* st) const;
 };
 // Concrete subclass of CompactibleSpace that implements
 // a free list space, such as used in the concurrent mark sweep
 // generation.
 class CompactibleFreeListSpace: public CompactibleSpace {
   friend class VMStructs;
   friend class ConcurrentMarkSweepGeneration;
   friend class ASConcurrentMarkSweepGeneration;
   friend class CMSCollector;
   friend class CMSPermGenGen;
   // Local alloc buffer for promotion into this space.
   friend class CFLS_LAB;
   // "Size" of chunks of work (executed during parallel remark phases
   // of CMS collection); this probably belongs in CMSCollector, although
   // it's cached here because it's used in
   // initialize_sequential_subtasks_for_rescan() which modifies
   // par_seq_tasks which also lives in Space. XXX
   const size_t _rescan_task_size;
   const size_t _marking_task_size;
   // Yet another sequential tasks done structure. This supports
   // CMS GC, where we have threads dynamically
   // claiming sub-tasks from a larger parallel task.
   SequentialSubTasksDone _conc_par_seq_tasks;
   BlockOffsetArrayNonContigSpace _bt;
   CMSCollector* _collector;
   ConcurrentMarkSweepGeneration* _gen;
   // Data structures for free blocks (used during allocation/sweeping)
   // Allocation is done linearly from two different blocks depending on
   // whether the request is small or large, in an effort to reduce
   // fragmentation. We assume that any locking for allocation is done
   // by the containing generation. Thus, none of the methods in this
   // space are re-entrant.
   enum SomeConstants {
     SmallForLinearAlloc = 16,        // size < this then use _sLAB
     SmallForDictionary  = 257,       // size < this then use _indexedFreeList
     IndexSetSize        = SmallForDictionary  // keep this odd-sized
   };
   static int IndexSetStart;
   static int IndexSetStride;
  private:
   enum FitStrategyOptions {
     FreeBlockStrategyNone = 0,
     FreeBlockBestFitFirst
   };
   PromotionInfo _promoInfo;
   // helps to impose a global total order on freelistLock ranks;
   // assumes that CFLSpace's are allocated in global total order
   static int   _lockRank;
   // a lock protecting the free lists and free blocks;
   // mutable because of ubiquity of locking even for otherwise const methods
   mutable Mutex _freelistLock;
   // locking verifier convenience function
   void assert_locked() const PRODUCT_RETURN;
   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
   // Linear allocation blocks
   LinearAllocBlock _smallLinearAllocBlock;
   FreeBlockDictionary::DictionaryChoice _dictionaryChoice;
   FreeBlockDictionary* _dictionary;    // ptr to dictionary for large size blocks
   FreeList _indexedFreeList[IndexSetSize];
                                        // indexed array for small size blocks
   // allocation stategy
   bool       _fitStrategy;      // Use best fit strategy.
   bool       _adaptive_freelists; // Use adaptive freelists
   // This is an address close to the largest free chunk in the heap.
   // It is currently assumed to be at the end of the heap.  Free
   // chunks with addresses greater than nearLargestChunk are coalesced
   // in an effort to maintain a large chunk at the end of the heap.
   HeapWord*  _nearLargestChunk;
   // Used to keep track of limit of sweep for the space
   HeapWord* _sweep_limit;
   // Support for compacting cms
   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
   // Initialization helpers.
   void initializeIndexedFreeListArray();
   // Extra stuff to manage promotion parallelism.
   // a lock protecting the dictionary during par promotion allocation.
   mutable Mutex _parDictionaryAllocLock;
   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
   // Locks protecting the exact lists during par promotion allocation.
   Mutex* _indexedFreeListParLocks[IndexSetSize];
   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
   // required to be smaller than "IndexSetSize".)  If successful,
   // adds them to "fl", which is required to be an empty free list.
   // If the count of "fl" is negative, it's absolute value indicates a
   // number of free chunks that had been previously "borrowed" from global
   // list of size "word_sz", and must now be decremented.
   void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl);
   // Allocation helper functions
   // Allocate using a strategy that takes from the indexed free lists
   // first.  This allocation strategy assumes a companion sweeping
   // strategy that attempts to keep the needed number of chunks in each
   // indexed free lists.
   HeapWord* allocate_adaptive_freelists(size_t size);
   // Allocate from the linear allocation buffers first.  This allocation
   // strategy assumes maximal coalescing can maintain chunks large enough
   // to be used as linear allocation buffers.
   HeapWord* allocate_non_adaptive_freelists(size_t size);
   // Gets a chunk from the linear allocation block (LinAB).  If there
   // is not enough space in the LinAB, refills it.
   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);
   // Get a chunk from the space remaining in the linear allocation block.  Do
   // not attempt to refill if the space is not available, return NULL.  Do the
   // repairs on the linear allocation block as appropriate.
   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);
   // Helper function for getChunkFromIndexedFreeList.
   // Replenish the indexed free list for this "size".  Do not take from an
   // underpopulated size.
   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
   // Get a chunk from the indexed free list.  If the indexed free list
   // does not have a free chunk, try to replenish the indexed free list
   // then get the free chunk from the replenished indexed free list.
   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
   // The returned chunk may be larger than requested (or null).
   FreeChunk* getChunkFromDictionary(size_t size);
   // The returned chunk is the exact size requested (or null).
   FreeChunk* getChunkFromDictionaryExact(size_t size);
   // Find a chunk in the indexed free list that is the best
   // fit for size "numWords".
   FreeChunk* bestFitSmall(size_t numWords);
   // For free list "fl" of chunks of size > numWords,
   // remove a chunk, split off a chunk of size numWords
   // and return it.  The split off remainder is returned to
   // the free lists.  The old name for getFromListGreater
   // was lookInListGreater.
   FreeChunk* getFromListGreater(FreeList* fl, size_t numWords);
   // Get a chunk in the indexed free list or dictionary,
   // by considering a larger chunk and splitting it.
   FreeChunk* getChunkFromGreater(size_t numWords);
   //  Verify that the given chunk is in the indexed free lists.
   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
   // Remove the specified chunk from the indexed free lists.
   void       removeChunkFromIndexedFreeList(FreeChunk* fc);
   // Remove the specified chunk from the dictionary.
   void       removeChunkFromDictionary(FreeChunk* fc);
   // Split a free chunk into a smaller free chunk of size "new_size".
   // Return the smaller free chunk and return the remainder to the
   // free lists.
   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
   // Add a chunk to the free lists.
   void       addChunkToFreeLists(HeapWord* chunk, size_t size);
   // Add a chunk to the free lists, preferring to suffix it
   // to the last free chunk at end of space if possible, and
   // updating the block census stats as well as block offset table.
   // Take any locks as appropriate if we are multithreaded.
   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
   // Add a free chunk to the indexed free lists.
   void       returnChunkToFreeList(FreeChunk* chunk);
   // Add a free chunk to the dictionary.
   void       returnChunkToDictionary(FreeChunk* chunk);
   // Functions for maintaining the linear allocation buffers (LinAB).
   // Repairing a linear allocation block refers to operations
   // performed on the remainder of a LinAB after an allocation
   // has been made from it.
   void       repairLinearAllocationBlocks();
   void       repairLinearAllocBlock(LinearAllocBlock* blk);
   void       refillLinearAllocBlock(LinearAllocBlock* blk);
   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
   void       refillLinearAllocBlocksIfNeeded();
   void       verify_objects_initialized() const;
   // Statistics reporting helper functions
   void       reportFreeListStatistics() const;
   void       reportIndexedFreeListStatistics() const;
   size_t     maxChunkSizeInIndexedFreeLists() const;
   size_t     numFreeBlocksInIndexedFreeLists() const;
   // Accessor
   HeapWord* unallocated_block() const {
     if (BlockOffsetArrayUseUnallocatedBlock) {
       HeapWord* ub = _bt.unallocated_block();
       assert(ub >= bottom() &&
              ub <= end(), "space invariant");
       return ub;
     } else {
       return end();
     }
   }
   void freed(HeapWord* start, size_t size) {
     _bt.freed(start, size);
   }
  protected:
   // reset the indexed free list to its initial empty condition.
   void resetIndexedFreeListArray();
   // reset to an initial state with a single free block described
   // by the MemRegion parameter.
   void reset(MemRegion mr);
   // Return the total number of words in the indexed free lists.
   size_t     totalSizeInIndexedFreeLists() const;
  public:
   // Constructor...
   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
                            bool use_adaptive_freelists,
                            FreeBlockDictionary::DictionaryChoice);
   // accessors
   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
   FreeBlockDictionary* dictionary() const { return _dictionary; }
   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
   // Set CMS global values
   static void set_cms_values();
   // Return the free chunk at the end of the space.  If no such
   // chunk exists, return NULL.
   FreeChunk* find_chunk_at_end();
   bool adaptive_freelists() const { return _adaptive_freelists; }
   void set_collector(CMSCollector* collector) { _collector = collector; }
   // Support for parallelization of rescan and marking
   const size_t rescan_task_size()  const { return _rescan_task_size;  }
   const size_t marking_task_size() const { return _marking_task_size; }
   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
   void initialize_sequential_subtasks_for_rescan(int n_threads);
   void initialize_sequential_subtasks_for_marking(int n_threads,
          HeapWord* low = NULL);
   // Space enquiries
   size_t used() const;
   size_t free() const;
   size_t max_alloc_in_words() const;
   // XXX: should have a less conservative used_region() than that of
   // Space; we could consider keeping track of highest allocated
   // address and correcting that at each sweep, as the sweeper
   // goes through the entire allocated part of the generation. We
   // could also use that information to keep the sweeper from
   // sweeping more than is necessary. The allocator and sweeper will
   // of course need to synchronize on this, since the sweeper will
   // try to bump down the address and the allocator will try to bump it up.
   // For now, however, we'll just use the default used_region()
   // which overestimates the region by returning the entire
   // committed region (this is safe, but inefficient).
   // Returns a subregion of the space containing all the objects in
   // the space.
   MemRegion used_region() const {
     return MemRegion(bottom(),
                      BlockOffsetArrayUseUnallocatedBlock ?
                      unallocated_block() : end());
   }
   // This is needed because the default implementation uses block_start()
   // which can;t be used at certain times (for example phase 3 of mark-sweep).
   // A better fix is to change the assertions in phase 3 of mark-sweep to
   // use is_in_reserved(), but that is deferred since the is_in() assertions
   // are buried through several layers of callers and are used elsewhere
   // as well.
   bool is_in(const void* p) const {
     return used_region().contains(p);
   }
   virtual bool is_free_block(const HeapWord* p) const;
   // Resizing support
   void set_end(HeapWord* value);  // override
   // mutual exclusion support
   Mutex* freelistLock() const { return &_freelistLock; }
   // Iteration support
   void oop_iterate(MemRegion mr, OopClosure* cl);
   void oop_iterate(OopClosure* cl);
   void object_iterate(ObjectClosure* blk);
   // Apply the closure to each object in the space whose references
   // point to objects in the heap.  The usage of CompactibleFreeListSpace
   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
   // objects in the space with references to objects that are no longer
   // valid.  For example, an object may reference another object
   // that has already been sweep up (collected).  This method uses
   // obj_is_alive() to determine whether it is safe to iterate of
   // an object.
   void safe_object_iterate(ObjectClosure* blk);
   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
   // Requires that "mr" be entirely within the space.
   // Apply "cl->do_object" to all objects that intersect with "mr".
   // If the iteration encounters an unparseable portion of the region,
   // terminate the iteration and return the address of the start of the
   // subregion that isn't done.  Return of "NULL" indicates that the
   // interation completed.
   virtual HeapWord*
        object_iterate_careful_m(MemRegion mr,
                                 ObjectClosureCareful* cl);
   virtual HeapWord*
        object_iterate_careful(ObjectClosureCareful* cl);
   // Override: provides a DCTO_CL specific to this kind of space.
   DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
                                      CardTableModRefBS::PrecisionStyle precision,
                                      HeapWord* boundary);
   void blk_iterate(BlkClosure* cl);
   void blk_iterate_careful(BlkClosureCareful* cl);
   HeapWord* block_start_const(const void* p) const;
   HeapWord* block_start_careful(const void* p) const;
   size_t block_size(const HeapWord* p) const;
   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
   bool block_is_obj(const HeapWord* p) const;
   bool obj_is_alive(const HeapWord* p) const;
   size_t block_size_nopar(const HeapWord* p) const;
   bool block_is_obj_nopar(const HeapWord* p) const;
   // iteration support for promotion
   void save_marks();
   bool no_allocs_since_save_marks();
   void object_iterate_since_last_GC(ObjectClosure* cl);
   // iteration support for sweeping
   void save_sweep_limit() {
     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
                    unallocated_block() : end();
   }
   NOT_PRODUCT(
     void clear_sweep_limit() { _sweep_limit = NULL; }
   )
   HeapWord* sweep_limit() { return _sweep_limit; }
   // Apply "blk->do_oop" to the addresses of all reference fields in objects
   // promoted into this generation since the most recent save_marks() call.
   // Fields in objects allocated by applications of the closure
   // *are* included in the iteration. Thus, when the iteration completes
   // there should be no further such objects remaining.
   #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
     void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
   ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
   #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
   // Allocation support
   HeapWord* allocate(size_t size);
   HeapWord* par_allocate(size_t size);
   oop       promote(oop obj, size_t obj_size);
   void      gc_prologue();
   void      gc_epilogue();
   // This call is used by a containing CMS generation / collector
   // to inform the CFLS space that a sweep has been completed
   // and that the space can do any related house-keeping functions.
   void      sweep_completed();
   // For an object in this space, the mark-word's two
   // LSB's having the value [11] indicates that it has been
   // promoted since the most recent call to save_marks() on
   // this generation and has not subsequently been iterated
   // over (using oop_since_save_marks_iterate() above).
   // This property holds only for single-threaded collections,
   // and is typically used for Cheney scans; for MT scavenges,
   // the property holds for all objects promoted during that
   // scavenge for the duration of the scavenge and is used
   // by card-scanning to avoid scanning objects (being) promoted
   // during that scavenge.
   bool obj_allocated_since_save_marks(const oop obj) const {
     assert(is_in_reserved(obj), "Wrong space?");
     return ((PromotedObject*)obj)->hasPromotedMark();
   }
   // A worst-case estimate of the space required (in HeapWords) to expand the
   // heap when promoting an obj of size obj_size.
   size_t expansionSpaceRequired(size_t obj_size) const;
   FreeChunk* allocateScratch(size_t size);
   // returns true if either the small or large linear allocation buffer is empty.
   bool       linearAllocationWouldFail() const;
   // Adjust the chunk for the minimum size.  This version is called in
   // most cases in CompactibleFreeListSpace methods.
   inline static size_t adjustObjectSize(size_t size) {
     return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
   }
   // This is a virtual version of adjustObjectSize() that is called
   // only occasionally when the compaction space changes and the type
   // of the new compaction space is is only known to be CompactibleSpace.
   size_t adjust_object_size_v(size_t size) const {
     return adjustObjectSize(size);
   }
   // Minimum size of a free block.
   virtual size_t minimum_free_block_size() const { return MinChunkSize; }
   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);
   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
               bool coalesced);
   // Support for decisions regarding concurrent collection policy
   bool should_concurrent_collect() const;
   // Support for compaction
   void prepare_for_compaction(CompactPoint* cp);
   void adjust_pointers();
   void compact();
   // reset the space to reflect the fact that a compaction of the
   // space has been done.
   virtual void reset_after_compaction();
   // Debugging support
   void print()                            const;
   void print_on(outputStream* st)         const;
   void prepare_for_verify();
   void verify(bool allow_dirty)           const;
   void verifyFreeLists()                  const PRODUCT_RETURN;
   void verifyIndexedFreeLists()           const;
   void verifyIndexedFreeList(size_t size) const;
   // verify that the given chunk is in the free lists.
   bool verifyChunkInFreeLists(FreeChunk* fc) const;
   // Do some basic checks on the the free lists.
   void checkFreeListConsistency()         const PRODUCT_RETURN;
   // Printing support
   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
   void print_indexed_free_lists(outputStream* st) const;
   void print_dictionary_free_lists(outputStream* st) const;
   void print_promo_info_blocks(outputStream* st) const;
   NOT_PRODUCT (
     void initializeIndexedFreeListArrayReturnedBytes();
     size_t sumIndexedFreeListArrayReturnedBytes();
     // Return the total number of chunks in the indexed free lists.
     size_t totalCountInIndexedFreeLists() const;
     // Return the total numberof chunks in the space.
     size_t totalCount();
   )
   // The census consists of counts of the quantities such as
   // the current count of the free chunks, number of chunks
   // created as a result of the split of a larger chunk or
   // coalescing of smaller chucks, etc.  The counts in the
   // census is used to make decisions on splitting and
   // coalescing of chunks during the sweep of garbage.
   // Print the statistics for the free lists.
   void printFLCensus(size_t sweep_count) const;
   // Statistics functions
   // Initialize census for lists before the sweep.
   void beginSweepFLCensus(float inter_sweep_current,
                           float inter_sweep_estimate,
                           float intra_sweep_estimate);
   // Set the surplus for each of the free lists.
   void setFLSurplus();
   // Set the hint for each of the free lists.
   void setFLHints();
   // Clear the census for each of the free lists.
   void clearFLCensus();
   // Perform functions for the census after the end of the sweep.
   void endSweepFLCensus(size_t sweep_count);
   // Return true if the count of free chunks is greater
   // than the desired number of free chunks.
   bool coalOverPopulated(size_t size);
 // Record (for each size):
 //
 //   split-births = #chunks added due to splits in (prev-sweep-end,
 //      this-sweep-start)
 //   split-deaths = #chunks removed for splits in (prev-sweep-end,
 //      this-sweep-start)
 //   num-curr     = #chunks at start of this sweep
 //   num-prev     = #chunks at end of previous sweep
 //
 // The above are quantities that are measured. Now define:
 //
 //   num-desired := num-prev + split-births - split-deaths - num-curr
 //
 // Roughly, num-prev + split-births is the supply,
 // split-deaths is demand due to other sizes
 // and num-curr is what we have left.
 //
 // Thus, num-desired is roughly speaking the "legitimate demand"
 // for blocks of this size and what we are striving to reach at the
 // end of the current sweep.
 //
 // For a given list, let num-len be its current population.
 // Define, for a free list of a given size:
 //
 //   coal-overpopulated := num-len >= num-desired * coal-surplus
 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
 // coalescing -- we do not coalesce unless we think that the current
 // supply has exceeded the estimated demand by more than 5%).
 //
 // For the set of sizes in the binary tree, which is neither dense nor
 // closed, it may be the case that for a particular size we have never
 // had, or do not now have, or did not have at the previous sweep,
 // chunks of that size. We need to extend the definition of
 // coal-overpopulated to such sizes as well:
 //
 //   For a chunk in/not in the binary tree, extend coal-overpopulated
 //   defined above to include all sizes as follows:
 //
 //   . a size that is non-existent is coal-overpopulated
 //   . a size that has a num-desired <= 0 as defined above is
 //     coal-overpopulated.
 //
 // Also define, for a chunk heap-offset C and mountain heap-offset M:
 //
 //   close-to-mountain := C >= 0.99 * M
 //
 // Now, the coalescing strategy is:
 //
 //    Coalesce left-hand chunk with right-hand chunk if and
 //    only if:
 //
 //      EITHER
 //        . left-hand chunk is of a size that is coal-overpopulated
 //      OR
 //        . right-hand chunk is close-to-mountain
   void smallCoalBirth(size_t size);
   void smallCoalDeath(size_t size);
   void coalBirth(size_t size);
   void coalDeath(size_t size);
   void smallSplitBirth(size_t size);
   void smallSplitDeath(size_t size);
   void splitBirth(size_t size);
   void splitDeath(size_t size);
   void split(size_t from, size_t to1);
   double flsFrag() const;
 };
 // A parallel-GC-thread-local allocation buffer for allocation into a
 // CompactibleFreeListSpace.
 class CFLS_LAB : public CHeapObj {
   // The space that this buffer allocates into.
   CompactibleFreeListSpace* _cfls;
   // Our local free lists.
   FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
   // Initialized from a command-line arg.
   // Allocation statistics in support of dynamic adjustment of
   // #blocks to claim per get_from_global_pool() call below.
   static AdaptiveWeightedAverage
                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];
   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
   static int    _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
   // Internal work method
   void get_from_global_pool(size_t word_sz, FreeList* fl);
 public:
   CFLS_LAB(CompactibleFreeListSpace* cfls);
   // Allocate and return a block of the given size, or else return NULL.
   HeapWord* alloc(size_t word_sz);
   // Return any unused portions of the buffer to the global pool.
   void retire(int tid);
   // Dynamic OldPLABSize sizing
   static void compute_desired_plab_size();
   // When the settings are modified from default static initialization
   static void modify_initialization(size_t n, unsigned wt);
 };
 size_t PromotionInfo::refillSize() const {
   const size_t CMSSpoolBlockSize = 256;
   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
                                    * CMSSpoolBlockSize);
   return CompactibleFreeListSpace::adjustObjectSize(sz);
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp@be3f9c242c9d (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp