jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp@7ae4e26cb1e0 (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp@7ae4e26cb1e0 (annotated)

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

Thu, 12 Oct 2017 21:27:07 +0800

author: aoqi
date: Thu, 12 Oct 2017 21:27:07 +0800
changeset 7535: 7ae4e26cb1e0
parent 7476: c2844108a708
parent 6876: 710a3c8b516e
child 9806: 758c07667682
permissions: -rw-r--r--

merge

 /*
  * Copyright (c) 2001, 2014, 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.
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  */
 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
 #include "gc_implementation/concurrentMarkSweep/adaptiveFreeList.hpp"
 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp"
 #include "memory/binaryTreeDictionary.hpp"
 #include "memory/blockOffsetTable.inline.hpp"
 #include "memory/freeList.hpp"
 #include "memory/space.hpp"
 // 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 FreeChunk;
 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;
   // 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 size_t IndexSetStart;
   static size_t 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<FreeChunk>::DictionaryChoice _dictionaryChoice;
   AFLBinaryTreeDictionary* _dictionary;    // ptr to dictionary for large size blocks
   AdaptiveFreeList<FreeChunk> _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, AdaptiveFreeList<FreeChunk>* fl);
   // Used by par_get_chunk_of_blocks() for the chunks from the
   // indexed_free_lists.
   bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
   // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
   // evenly splittable into "n" "word_sz" chunks.  Returns that
   // evenly splittable chunk.  May split a larger chunk to get the
   // evenly splittable chunk.
   FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
   // Used by par_get_chunk_of_blocks() for the chunks from the
   // dictionary.
   void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* 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(AdaptiveFreeList<FreeChunk>* 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<FreeChunk>::DictionaryChoice);
   // accessors
   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
   FreeBlockDictionary<FreeChunk>* 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());
   }
   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(ExtendedOopClosure* 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);
   // Iterate over all objects that intersect with mr, calling "cl->do_object"
   // on each.  There is an exception to this: if this closure has already
   // been invoked on an object, it may skip such objects in some cases.  This is
   // Most likely to happen in an "upwards" (ascending address) iteration of
   // MemRegions.
   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.
  HeapWord* object_iterate_careful_m(MemRegion mr,
                                     ObjectClosureCareful* cl);
   // Override: provides a DCTO_CL specific to this kind of space.
   DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* 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();
   // iteration support for sweeping
   void save_sweep_limit() {
     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
                    unallocated_block() : end();
     if (CMSTraceSweeper) {
       gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
                              "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
                              p2i(_sweep_limit), p2i(bottom()), p2i(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()                           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:
   // i.e. either the binary tree dictionary, the indexed free lists
   // or the linear allocation block.
   bool verify_chunk_in_free_list(FreeChunk* fc) const;
   // Verify that the given chunk is the linear allocation block
   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
   // Do some basic checks on the the free lists.
   void check_free_list_consistency()      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 split_birth(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<mtGC> {
   // The space that this buffer allocates into.
   CompactibleFreeListSpace* _cfls;
   // Our local free lists.
   AdaptiveFreeList<FreeChunk> _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 uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
   // Internal work method
   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* 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);
 }
 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp@7ae4e26cb1e0 (annotated)

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