1 /* 2 * Copyright (c) 2019, 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_GC_G1_G1COLLECTIONSETCANDIDATES_HPP 26 #define SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP 27 28 #include "gc/g1/g1CollectionSetCandidates.hpp" 29 #include "gc/shared/workgroup.hpp" 30 #include "memory/allocation.hpp" 31 #include "runtime/globals.hpp" 32 33 class HeapRegion; 34 class HeapRegionClosure; 35 36 // Set of collection set candidates, i.e. all old gen regions we consider worth 37 // collecting in the remainder of the current mixed phase. Regions are sorted by decreasing 38 // gc efficiency. 39 // Maintains a cursor into the list that specifies the next collection set candidate 40 // to put into the current collection set. 41 class G1CollectionSetCandidates : public CHeapObj<mtGC> { 42 HeapRegion** _regions; 43 uint _num_regions; // Total number of regions in the collection set candidate set. 44 45 // The sum of bytes that can be reclaimed in the remaining set of collection 46 // set candidates. 47 size_t _remaining_reclaimable_bytes; 48 // The index of the next candidate old region to be considered for 49 // addition to the current collection set. 50 uint _front_idx; 51 52 public: 53 G1CollectionSetCandidates(HeapRegion** regions, uint num_regions, size_t remaining_reclaimable_bytes) : 54 _regions(regions), 55 _num_regions(num_regions), 56 _remaining_reclaimable_bytes(remaining_reclaimable_bytes), 57 _front_idx(0) { } 58 59 ~G1CollectionSetCandidates() { 60 FREE_C_HEAP_ARRAY(HeapRegion*, _regions); 61 } 62 63 // Returns the total number of collection set candidate old regions added. 64 uint num_regions() { return _num_regions; } 65 66 // Return the candidate region at the cursor position to be considered for collection without 67 // removing it. 68 HeapRegion* peek_front() { 69 HeapRegion* res = NULL; 70 if (_front_idx < _num_regions) { 71 res = _regions[_front_idx]; 72 assert(res != NULL, "Unexpected NULL HeapRegion at index %u", _front_idx); 73 } 74 return res; 75 } 76 77 // Remove the given region from the candidates set and move the cursor to the next one. 78 HeapRegion* pop_front(); 79 80 // Add the given HeapRegion to the front of the collection set candidate set again. 81 void push_front(HeapRegion* hr); 82 83 // Iterate over all remaining collection set candidate regions. 84 void iterate(HeapRegionClosure* cl); 85 86 // Return the number of candidate regions remaining. 87 uint num_remaining() { return _num_regions - _front_idx; } 88 89 bool is_empty() { return num_remaining() == 0; } 90 91 // Return the amount of reclaimable bytes that may be collected by the remaining 92 // candidate regions. 93 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; } 94 95 void verify() const PRODUCT_RETURN; 96 }; 97 98 #endif /* SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP */ 99