1 /* 2 * Copyright (c) 2001, 2013, 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_COLLECTIONSETCHOOSER_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP 27 28 #include "gc_implementation/g1/heapRegion.hpp" 29 #include "utilities/growableArray.hpp" 30 31 class CollectionSetChooser: public CHeapObj<mtGC> { 32 33 GrowableArray<HeapRegion*> _regions; 34 35 // Unfortunately, GrowableArray uses ints for length and indexes. To 36 // avoid excessive casting in the rest of the class the following 37 // wrapper methods are provided that use uints. 38 39 uint regions_length() { return (uint) _regions.length(); } 40 HeapRegion* regions_at(uint i) { return _regions.at((int) i); } 41 void regions_at_put(uint i, HeapRegion* hr) { 42 _regions.at_put((int) i, hr); 43 } 44 void regions_at_put_grow(uint i, HeapRegion* hr) { 45 _regions.at_put_grow((int) i, hr); 46 } 47 void regions_trunc_to(uint i) { _regions.trunc_to((uint) i); } 48 49 // The index of the next candidate old region to be considered for 50 // addition to the CSet. 51 uint _curr_index; 52 53 // The number of candidate old regions added to the CSet chooser. 54 // Note: this is not updated when removing a region using 55 // remove_and_move_to_next() below. 56 uint _length; 57 58 // Keeps track of the start of the next array chunk to be claimed by 59 // parallel GC workers. 60 uint _first_par_unreserved_idx; 61 62 // If a region has more live bytes than this threshold, it will not 63 // be added to the CSet chooser and will not be a candidate for 64 // collection. 65 size_t _region_live_threshold_bytes; 66 67 // The sum of reclaimable bytes over all the regions in the CSet chooser. 68 size_t _remaining_reclaimable_bytes; 69 70 public: 71 72 // Return the current candidate region to be considered for 73 // collection without removing it from the CSet chooser. 74 HeapRegion* peek() { 75 HeapRegion* res = NULL; 76 if (_curr_index < _length) { 77 res = regions_at(_curr_index); 78 assert(res != NULL, 79 err_msg("Unexpected NULL hr in _regions at index %u", 80 _curr_index)); 81 } 82 return res; 83 } 84 85 // Remove the given region from the CSet chooser and move to the 86 // next one. The given region should be the current candidate region 87 // in the CSet chooser. 88 void remove_and_move_to_next(HeapRegion* hr) { 89 assert(hr != NULL, "pre-condition"); 90 assert(_curr_index < _length, "pre-condition"); 91 assert(regions_at(_curr_index) == hr, "pre-condition"); 92 regions_at_put(_curr_index, NULL); 93 assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes, 94 err_msg("remaining reclaimable bytes inconsistent " 95 "from region: "SIZE_FORMAT" remaining: "SIZE_FORMAT, 96 hr->reclaimable_bytes(), _remaining_reclaimable_bytes)); 97 _remaining_reclaimable_bytes -= hr->reclaimable_bytes(); 98 _curr_index += 1; 99 } 100 101 CollectionSetChooser(); 102 103 void sort_regions(); 104 105 // Determine whether to add the given region to the CSet chooser or 106 // not. Currently, we skip humongous regions (we never add them to 107 // the CSet, we only reclaim them during cleanup) and regions whose 108 // live bytes are over the threshold. 109 bool should_add(HeapRegion* hr) { 110 assert(hr->is_marked(), "pre-condition"); 111 assert(!hr->is_young(), "should never consider young regions"); 112 return !hr->is_humongous() && 113 hr->live_bytes() < _region_live_threshold_bytes; 114 } 115 116 // Returns the number candidate old regions added 117 uint length() { return _length; } 118 119 // Serial version. 120 void add_region(HeapRegion *hr); 121 122 // Must be called before calls to claim_array_chunk(). 123 // n_regions is the number of regions, chunk_size the chunk size. 124 void prepare_for_par_region_addition(uint n_regions, uint chunk_size); 125 // Returns the first index in a contiguous chunk of chunk_size indexes 126 // that the calling thread has reserved. These must be set by the 127 // calling thread using set_region() (to NULL if necessary). 128 uint claim_array_chunk(uint chunk_size); 129 // Set the marked array entry at index to hr. Careful to claim the index 130 // first if in parallel. 131 void set_region(uint index, HeapRegion* hr); 132 // Atomically increment the number of added regions by region_num 133 // and the amount of reclaimable bytes by reclaimable_bytes. 134 void update_totals(uint region_num, size_t reclaimable_bytes); 135 136 void clear(); 137 138 // Return the number of candidate regions that remain to be collected. 139 uint remaining_regions() { return _length - _curr_index; } 140 141 // Determine whether the CSet chooser has more candidate regions or not. 142 bool is_empty() { return remaining_regions() == 0; } 143 144 // Return the reclaimable bytes that remain to be collected on 145 // all the candidate regions in the CSet chooser. 146 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; } 147 148 // Returns true if the used portion of "_regions" is properly 149 // sorted, otherwise asserts false. 150 void verify() PRODUCT_RETURN; 151 }; 152 153 class CSetChooserParUpdater : public StackObj { 154 private: 155 CollectionSetChooser* _chooser; 156 bool _parallel; 157 uint _chunk_size; 158 uint _cur_chunk_idx; 159 uint _cur_chunk_end; 160 uint _regions_added; 161 size_t _reclaimable_bytes_added; 162 163 public: 164 CSetChooserParUpdater(CollectionSetChooser* chooser, 165 bool parallel, uint chunk_size) : 166 _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size), 167 _cur_chunk_idx(0), _cur_chunk_end(0), 168 _regions_added(0), _reclaimable_bytes_added(0) { } 169 170 ~CSetChooserParUpdater() { 171 if (_parallel && _regions_added > 0) { 172 _chooser->update_totals(_regions_added, _reclaimable_bytes_added); 173 } 174 } 175 176 void add_region(HeapRegion* hr) { 177 if (_parallel) { 178 if (_cur_chunk_idx == _cur_chunk_end) { 179 _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size); 180 _cur_chunk_end = _cur_chunk_idx + _chunk_size; 181 } 182 assert(_cur_chunk_idx < _cur_chunk_end, "invariant"); 183 _chooser->set_region(_cur_chunk_idx, hr); 184 _cur_chunk_idx += 1; 185 } else { 186 _chooser->add_region(hr); 187 } 188 _regions_added += 1; 189 _reclaimable_bytes_added += hr->reclaimable_bytes(); 190 } 191 192 bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); } 193 }; 194 195 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP 196