1 /* 2 * Copyright (c) 2001, 2015, 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_G1_COLLECTIONSETCHOOSER_HPP 26 #define SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP 27 28 #include "gc/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 _front; 52 53 // The index of the last candidate old region 54 uint _end; 55 56 // Keeps track of the start of the next array chunk to be claimed by 57 // parallel GC workers. 58 uint _first_par_unreserved_idx; 59 60 // If a region has more live bytes than this threshold, it will not 61 // be added to the CSet chooser and will not be a candidate for 62 // collection. 63 size_t _region_live_threshold_bytes; 64 65 // The sum of reclaimable bytes over all the regions in the CSet chooser. 66 size_t _remaining_reclaimable_bytes; 67 68 public: 69 70 // Return the current candidate region to be considered for 71 // collection without removing it from the CSet chooser. 72 HeapRegion* peek() { 73 HeapRegion* res = NULL; 74 if (_front < _end) { 75 res = regions_at(_front); 76 assert(res != NULL, "Unexpected NULL hr in _regions at index %u", _front); 77 } 78 return res; 79 } 80 81 // Remove the given region from the CSet chooser and move to the 82 // next one. 83 HeapRegion* pop() { 84 HeapRegion* hr = regions_at(_front); 85 assert(hr != NULL, "pre-condition"); 86 assert(_front < _end, "pre-condition"); 87 regions_at_put(_front, NULL); 88 assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes, 89 "remaining reclaimable bytes inconsistent " 90 "from region: " SIZE_FORMAT " remaining: " SIZE_FORMAT, 91 hr->reclaimable_bytes(), _remaining_reclaimable_bytes); 92 _remaining_reclaimable_bytes -= hr->reclaimable_bytes(); 93 _front += 1; 94 return hr; 95 } 96 97 void push(HeapRegion* hr); 98 99 CollectionSetChooser(); 100 101 void sort_regions(); 102 103 // Determine whether to add the given region to the CSet chooser or 104 // not. Currently, we skip pinned regions and regions whose live 105 // bytes are over the threshold. Humongous regions may be reclaimed during cleanup. 106 bool should_add(HeapRegion* hr) { 107 assert(hr->is_marked(), "pre-condition"); 108 assert(!hr->is_young(), "should never consider young regions"); 109 return !hr->is_pinned() && 110 hr->live_bytes() < _region_live_threshold_bytes; 111 } 112 113 // Returns the number candidate old regions added 114 uint length() { return _end; } 115 116 // Serial version. 117 void add_region(HeapRegion *hr); 118 119 // Must be called before calls to claim_array_chunk(). 120 // n_regions is the number of regions, chunk_size the chunk size. 121 void prepare_for_par_region_addition(uint n_threads, uint n_regions, uint chunk_size); 122 // Returns the first index in a contiguous chunk of chunk_size indexes 123 // that the calling thread has reserved. These must be set by the 124 // calling thread using set_region() (to NULL if necessary). 125 uint claim_array_chunk(uint chunk_size); 126 // Set the marked array entry at index to hr. Careful to claim the index 127 // first if in parallel. 128 void set_region(uint index, HeapRegion* hr); 129 // Atomically increment the number of added regions by region_num 130 // and the amount of reclaimable bytes by reclaimable_bytes. 131 void update_totals(uint region_num, size_t reclaimable_bytes); 132 133 void clear(); 134 135 // Return the number of candidate regions that remain to be collected. 136 uint remaining_regions() { return _end - _front; } 137 138 // Determine whether the CSet chooser has more candidate regions or not. 139 bool is_empty() { return remaining_regions() == 0; } 140 141 // Return the reclaimable bytes that remain to be collected on 142 // all the candidate regions in the CSet chooser. 143 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; } 144 145 // Returns true if the used portion of "_regions" is properly 146 // sorted, otherwise asserts false. 147 void verify() PRODUCT_RETURN; 148 }; 149 150 class CSetChooserParUpdater : public StackObj { 151 private: 152 CollectionSetChooser* _chooser; 153 bool _parallel; 154 uint _chunk_size; 155 uint _cur_chunk_idx; 156 uint _cur_chunk_end; 157 uint _regions_added; 158 size_t _reclaimable_bytes_added; 159 160 public: 161 CSetChooserParUpdater(CollectionSetChooser* chooser, 162 bool parallel, uint chunk_size) : 163 _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size), 164 _cur_chunk_idx(0), _cur_chunk_end(0), 165 _regions_added(0), _reclaimable_bytes_added(0) { } 166 167 ~CSetChooserParUpdater() { 168 if (_parallel && _regions_added > 0) { 169 _chooser->update_totals(_regions_added, _reclaimable_bytes_added); 170 } 171 } 172 173 void add_region(HeapRegion* hr) { 174 if (_parallel) { 175 if (_cur_chunk_idx == _cur_chunk_end) { 176 _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size); 177 _cur_chunk_end = _cur_chunk_idx + _chunk_size; 178 } 179 assert(_cur_chunk_idx < _cur_chunk_end, "invariant"); 180 _chooser->set_region(_cur_chunk_idx, hr); 181 _cur_chunk_idx += 1; 182 } else { 183 _chooser->add_region(hr); 184 } 185 _regions_added += 1; 186 _reclaimable_bytes_added += hr->reclaimable_bytes(); 187 } 188 189 bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); } 190 }; 191 192 #endif // SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP 193