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/g1BiasedArray.hpp" 29 30 class HeapRegion; 31 class HeapRegionClosure; 32 class FreeRegionList; 33 34 class G1HeapRegionTable : public G1BiasedMappedArray<HeapRegion*> { 35 protected: 36 virtual HeapRegion* default_value() const { return NULL; } 37 }; 38 39 // This class keeps track of the region metadata (i.e., HeapRegion 40 // instances). They are kept in the _regions array in address 41 // order. A region's index in the array corresponds to its index in 42 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is 43 // the one after it, etc.). Two regions that are consecutive in the 44 // array should also be adjacent in the address space (i.e., 45 // region(i).end() == region(i+1).bottom(). 46 // 47 // We create a HeapRegion when we commit the region's address space 48 // for the first time. When we uncommit the address space of a 49 // region we retain the HeapRegion to be able to re-use it in the 50 // future (in case we recommit it). 51 // 52 // We keep track of three lengths: 53 // 54 // * _committed_length (returned by length()) is the number of currently 55 // committed regions. 56 // * _allocated_length (not exposed outside this class) is the 57 // number of regions for which we have HeapRegions. 58 // * max_length() returns the maximum number of regions the heap can have. 59 // 60 // and maintain that: _committed_length <= _allocated_length <= max_length() 61 62 class HeapRegionSeq: public CHeapObj<mtGC> { 63 friend class VMStructs; 64 65 G1HeapRegionTable _regions; 66 67 // The number of regions committed in the heap. 68 uint _committed_length; 69 70 // A hint for which index to start searching from for humongous 71 // allocations. 72 uint _next_search_index; 73 74 // The number of regions for which we have allocated HeapRegions for. 75 uint _allocated_length; 76 77 // Find a contiguous set of empty regions of length num, starting 78 // from the given index. 79 uint find_contiguous_from(uint from, uint num); 80 81 void increment_allocated_length() { 82 assert(_allocated_length < max_length(), "pre-condition"); 83 _allocated_length++; 84 } 85 86 void increment_length() { 87 assert(length() < max_length(), "pre-condition"); 88 _committed_length++; 89 } 90 91 void decrement_length() { 92 assert(length() > 0, "pre-condition"); 93 _committed_length--; 94 } 95 96 HeapWord* heap_bottom() const { return _regions.bottom_address_mapped(); } 97 HeapWord* heap_end() const {return _regions.end_address_mapped(); } 98 99 public: 100 // Empty contructor, we'll initialize it with the initialize() method. 101 HeapRegionSeq() : _regions(), _committed_length(0), _next_search_index(0), _allocated_length(0) { } 102 103 void initialize(HeapWord* bottom, HeapWord* end); 104 105 // Return the HeapRegion at the given index. Assume that the index 106 // is valid. 107 inline HeapRegion* at(uint index) const; 108 109 // If addr is within the committed space return its corresponding 110 // HeapRegion, otherwise return NULL. 111 inline HeapRegion* addr_to_region(HeapWord* addr) const; 112 113 // Return the HeapRegion that corresponds to the given 114 // address. Assume the address is valid. 115 inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const; 116 117 // Return the number of regions that have been committed in the heap. 118 uint length() const { return _committed_length; } 119 120 // Return the maximum number of regions in the heap. 121 uint max_length() const { return (uint)_regions.length(); } 122 123 // Expand the sequence to reflect that the heap has grown from 124 // old_end to new_end. Either create new HeapRegions, or re-use 125 // existing ones, and return them in the given list. Returns the 126 // memory region that covers the newly-created regions. If a 127 // HeapRegion allocation fails, the result memory region might be 128 // smaller than the desired one. 129 MemRegion expand_by(HeapWord* old_end, HeapWord* new_end, 130 FreeRegionList* list); 131 132 // Return the number of contiguous regions at the end of the sequence 133 // that are available for allocation. 134 uint free_suffix(); 135 136 // Find a contiguous set of empty regions of length num and return 137 // the index of the first region or G1_NULL_HRS_INDEX if the 138 // search was unsuccessful. 139 uint find_contiguous(uint num); 140 141 // Apply blk->doHeapRegion() on all committed regions in address order, 142 // terminating the iteration early if doHeapRegion() returns true. 143 void iterate(HeapRegionClosure* blk) const; 144 145 // As above, but start the iteration from hr and loop around. If hr 146 // is NULL, we start from the first region in the heap. 147 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const; 148 149 // Tag as uncommitted as many regions that are completely free as 150 // possible, up to num_regions_to_remove, from the suffix of the committed 151 // sequence. Return the actual number of removed regions. 152 uint shrink_by(uint num_regions_to_remove); 153 154 // Do some sanity checking. 155 void verify_optional() PRODUCT_RETURN; 156 }; 157 158 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP