1 /*
   2  * Copyright (c) 2001, 2009, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 class HeapRegion;
  26 class HeapRegionClosure;
  27 
  28 class HeapRegionSeq: public CHeapObj {
  29 
  30   // _regions is kept sorted by start address order, and no two regions are
  31   // overlapping.
  32   GrowableArray<HeapRegion*> _regions;
  33 
  34   // The index in "_regions" at which to start the next allocation search.
  35   // (For efficiency only; private to obj_allocate after initialization.)
  36   int _alloc_search_start;
  37 
  38   // Attempts to allocate a block of the (assumed humongous) word_size,
  39   // starting at the region "ind".
  40   HeapWord* alloc_obj_from_region_index(int ind, size_t word_size);
  41 
  42   // Currently, we're choosing collection sets in a round-robin fashion,
  43   // starting here.
  44   int _next_rr_candidate;
  45 
  46   // The bottom address of the bottom-most region, or else NULL if there
  47   // are no regions in the sequence.
  48   char* _seq_bottom;
  49 
  50  public:
  51   // Initializes "this" to the empty sequence of regions.
  52   HeapRegionSeq(const size_t max_size);
  53 
  54   // Adds "hr" to "this" sequence.  Requires "hr" not to overlap with
  55   // any region already in "this".  (Will perform better if regions are
  56   // inserted in ascending address order.)
  57   void insert(HeapRegion* hr);
  58 
  59   // Given a HeapRegion*, returns its index within _regions,
  60   // or returns -1 if not found.
  61   int find(HeapRegion* hr);
  62 
  63   // Requires the index to be valid, and return the region at the index.
  64   HeapRegion* at(size_t i) { return _regions.at((int)i); }
  65 
  66   // Return the number of regions in the sequence.
  67   size_t length();
  68 
  69   // Returns the number of contiguous regions at the end of the sequence
  70   // that are available for allocation.
  71   size_t free_suffix();
  72 
  73   // Requires "word_size" to be humongous (in the technical sense).  If
  74   // possible, allocates a contiguous subsequence of the heap regions to
  75   // satisfy the allocation, and returns the address of the beginning of
  76   // that sequence, otherwise returns NULL.
  77   HeapWord* obj_allocate(size_t word_size);
  78 
  79   // Apply the "doHeapRegion" method of "blk" to all regions in "this",
  80   // in address order, terminating the iteration early
  81   // if the "doHeapRegion" method returns "true".
  82   void iterate(HeapRegionClosure* blk);
  83 
  84   // Apply the "doHeapRegion" method of "blk" to all regions in "this",
  85   // starting at "r" (or first region, if "r" is NULL), in a circular
  86   // manner, terminating the iteration early if the "doHeapRegion" method
  87   // returns "true".
  88   void iterate_from(HeapRegion* r, HeapRegionClosure* blk);
  89 
  90   // As above, but start from a given index in the sequence
  91   // instead of a given heap region.
  92   void iterate_from(int idx, HeapRegionClosure* blk);
  93 
  94   // Requires "shrink_bytes" to be a multiple of the page size and heap
  95   // region granularity.  Deletes as many "rightmost" completely free heap
  96   // regions from the sequence as comprise shrink_bytes bytes.  Returns the
  97   // MemRegion indicating the region those regions comprised, and sets
  98   // "num_regions_deleted" to the number of regions deleted.
  99   MemRegion shrink_by(size_t shrink_bytes, size_t& num_regions_deleted);
 100 
 101   // If "addr" falls within a region in the sequence, return that region,
 102   // or else NULL.
 103   HeapRegion* addr_to_region(const void* addr);
 104 
 105   void print();
 106 
 107   // Prints out runs of empty regions.
 108   void print_empty_runs();
 109 
 110 };