1 /* 2 * Copyright (c) 2001, 2012, 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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP 27 28 #include "gc_implementation/g1/g1HeapSpanningTable.hpp" 29 30 class HeapRegion; 31 class HeapRegionClosure; 32 class FreeRegionList; 33 34 // This class keeps track of the region metadata (i.e., HeapRegion 35 // instances). They are kept in the _regions array in address 36 // order. A region's index in the array corresponds to its index in 37 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is 38 // the one after it, etc.). Two regions that are consecutive in the 39 // array should also be adjacent in the address space (i.e., 40 // region(i).end() == region(i+1).bottom(). 41 // 42 // We create a HeapRegion when we commit the region's address space 43 // for the first time. When we uncommit the address space of a 44 // region we retain the HeapRegion to be able to re-use it in the 45 // future (in case we recommit it). 46 // 47 // We keep track of three lengths (all three are maintained by the 48 // G1HeapSpanningTable superclass): 49 // 50 // * _length (returned by length()) is the number of currently 51 // committed regions. 52 // * _length_high_watermark is the number of regions for which we have 53 // already allocated HeapRegions. 54 // * _max_length (returned by max_length()) is the maximum number of 55 // regions the heap can have. 56 // 57 // and maintain that: _length <= _length_high_watermark <= _max_length 58 59 class HeapRegionSeq: public G1HeapSpanningTable<HeapRegion*> { 60 friend class VMStructs; 61 62 // The array that holds the HeapRegion instances. 63 HeapRegion** _regions; 64 65 // As above, but biased to address 0. 66 HeapRegion** _regions_biased; 67 68 // A hint for which index to start searching from for humongous 69 // allocations. 70 uint _next_search_index; 71 72 // Find a contiguous set of empty regions of length num, starting 73 // from the given index. 74 uint find_contiguous_from(uint from, uint num); 75 76 // Override 77 virtual HeapRegion* default_value() const { 78 return (HeapRegion*) NULL; 79 } 80 81 public: 82 83 // Return the HeapRegion at the given index. Assume that the index 84 // is valid. 85 inline HeapRegion* at(uint index) const; 86 87 // If addr is within the committed space return its corresponding 88 // HeapRegion, otherwise return NULL. 89 inline HeapRegion* at(HeapWord* addr) const; 90 91 // Return the HeapRegion that corresponds to the given address. 92 // Assume the address is valid. 93 inline HeapRegion* at_unsafe(HeapWord* addr) const; 94 95 // Return the number of contiguous regions at the end of the sequence 96 // that are available for allocation. 97 uint free_suffix(); 98 99 // Find a contiguous set of empty regions of length num and return 100 // the index of the first region or G1_NULL_HRS_INDEX if the 101 // search was unsuccessful. 102 uint find_contiguous(uint num); 103 104 // Apply blk->doHeapRegion() on all committed regions in address order, 105 // terminating the iteration early if doHeapRegion() returns true. 106 void iterate(HeapRegionClosure* blk) const; 107 108 // As above, but start the iteration from hr and loop around. If hr 109 // is NULL, we start from the first region in the heap. 110 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const; 111 112 // Expand the sequence to reflect that the heap has grown from 113 // old_end to new_end. Either create new HeapRegions, or re-use 114 // existing ones, and return them in the given list. Returns the 115 // memory region that covers the newly-created regions. If a 116 // HeapRegion allocation fails, the returned memory region might be 117 // smaller than the desired one. 118 MemRegion expand_to(HeapWord* new_end, FreeRegionList* list); 119 120 // Tag as uncommitted as many regions that are completely free as 121 // possible, up to new_end, from the suffix of the committed 122 // sequence. Return a MemRegion that corresponds to the address 123 // range of the uncommitted regions. 124 MemRegion shrink_to(HeapWord* new_end, uint* num_regions_deleted); 125 126 // Do sanity checking. 127 void verify_optional() PRODUCT_RETURN; 128 129 // Empty constructor, we'll do all initialization in the initialize() method. 130 HeapRegionSeq() { } 131 132 void initialize(HeapWord* bottom, HeapWord* max_end); 133 }; 134 135 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP