jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/heapRegionSeq.hpp@4dfb2df418f2 (annotated)

src/share/vm/gc_implementation/g1/heapRegionSeq.hpp@4dfb2df418f2 (annotated)

src/share/vm/gc_implementation/g1/heapRegionSeq.hpp

Thu, 22 Sep 2011 10:57:37 -0700

author: johnc
date: Thu, 22 Sep 2011 10:57:37 -0700
changeset 3175: 4dfb2df418f2
parent 3168: 4f93f0d00802
child 3713: 720b6a76dd9d
permissions: -rw-r--r--

6484982: G1: process references during evacuation pauses
Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate.
Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
 class HeapRegion;
 class HeapRegionClosure;
 class FreeRegionList;
 #define G1_NULL_HRS_INDEX ((size_t) -1)
 // This class keeps track of the region metadata (i.e., HeapRegion
 // instances). They are kept in the _regions array in address
 // order. A region's index in the array corresponds to its index in
 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is
 // the one after it, etc.). Two regions that are consecutive in the
 // array should also be adjacent in the address space (i.e.,
 // region(i).end() == region(i+1).bottom().
 //
 // We create a HeapRegion when we commit the region's address space
 // for the first time. When we uncommit the address space of a
 // region we retain the HeapRegion to be able to re-use it in the
 // future (in case we recommit it).
 //
 // We keep track of three lengths:
 //
 // * _length (returned by length()) is the number of currently
 //   committed regions.
 // * _allocated_length (not exposed outside this class) is the
 //   number of regions for which we have HeapRegions.
 // * _max_length (returned by max_length()) is the maximum number of
 //   regions the heap can have.
 //
 // and maintain that: _length <= _allocated_length <= _max_length
 class HeapRegionSeq: public CHeapObj {
   friend class VMStructs;
   // The array that holds the HeapRegions.
   HeapRegion** _regions;
   // Version of _regions biased to address 0
   HeapRegion** _regions_biased;
   // The number of regions committed in the heap.
   size_t _length;
   // The address of the first reserved word in the heap.
   HeapWord* _heap_bottom;
   // The address of the last reserved word in the heap - 1.
   HeapWord* _heap_end;
   // The log of the region byte size.
   size_t _region_shift;
   // A hint for which index to start searching from for humongous
   // allocations.
   size_t _next_search_index;
   // The number of regions for which we have allocated HeapRegions for.
   size_t _allocated_length;
   // The maximum number of regions in the heap.
   size_t _max_length;
   // Find a contiguous set of empty regions of length num, starting
   // from the given index.
   size_t find_contiguous_from(size_t from, size_t num);
   // Map a heap address to a biased region index. Assume that the
   // address is valid.
   inline size_t addr_to_index_biased(HeapWord* addr) const;
   void increment_length(size_t* length) {
     assert(*length < _max_length, "pre-condition");
     *length += 1;
   }
   void decrement_length(size_t* length) {
     assert(*length > 0, "pre-condition");
     *length -= 1;
   }
  public:
   // Empty contructor, we'll initialize it with the initialize() method.
   HeapRegionSeq() { }
   void initialize(HeapWord* bottom, HeapWord* end, size_t max_length);
   // Return the HeapRegion at the given index. Assume that the index
   // is valid.
   inline HeapRegion* at(size_t index) const;
   // If addr is within the committed space return its corresponding
   // HeapRegion, otherwise return NULL.
   inline HeapRegion* addr_to_region(HeapWord* addr) const;
   // Return the HeapRegion that corresponds to the given
   // address. Assume the address is valid.
   inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
   // Return the number of regions that have been committed in the heap.
   size_t length() const { return _length; }
   // Return the maximum number of regions in the heap.
   size_t max_length() const { return _max_length; }
   // Expand the sequence to reflect that the heap has grown from
   // old_end to new_end. Either create new HeapRegions, or re-use
   // existing ones, and return them in the given list. Returns the
   // memory region that covers the newly-created regions. If a
   // HeapRegion allocation fails, the result memory region might be
   // smaller than the desired one.
   MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
                       FreeRegionList* list);
   // Return the number of contiguous regions at the end of the sequence
   // that are available for allocation.
   size_t free_suffix();
   // Find a contiguous set of empty regions of length num and return
   // the index of the first region or G1_NULL_HRS_INDEX if the
   // search was unsuccessful.
   size_t find_contiguous(size_t num);
   // Apply blk->doHeapRegion() on all committed regions in address order,
   // terminating the iteration early if doHeapRegion() returns true.
   void iterate(HeapRegionClosure* blk) const;
   // As above, but start the iteration from hr and loop around. If hr
   // is NULL, we start from the first region in the heap.
   void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
   // Tag as uncommitted as many regions that are completely free as
   // possible, up to shrink_bytes, from the suffix of the committed
   // sequence. Return a MemRegion that corresponds to the address
   // range of the uncommitted regions. Assume shrink_bytes is page and
   // heap region aligned.
   MemRegion shrink_by(size_t shrink_bytes, size_t* num_regions_deleted);
   // Do some sanity checking.
   void verify_optional() PRODUCT_RETURN;
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP

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src/share/vm/gc_implementation/g1/heapRegionSeq.hpp@4dfb2df418f2 (annotated)

src/share/vm/gc_implementation/g1/heapRegionSeq.hpp