1 /* 2 * Copyright (c) 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_G1HOTCARDCACHE_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP 27 28 #include "gc_implementation/g1/g1_globals.hpp" 29 #include "gc_implementation/g1/g1CardCounts.hpp" 30 #include "memory/allocation.hpp" 31 #include "runtime/safepoint.hpp" 32 #include "runtime/thread.inline.hpp" 33 #include "utilities/globalDefinitions.hpp" 34 35 class DirtyCardQueue; 36 class G1CollectedHeap; 37 class G1RemSet; 38 class HeapRegion; 39 40 // An evicting cache of cards that have been logged by the G1 post 41 // write barrier. Placing a card in the cache delays the refinement 42 // of the card until the card is evicted, or the cache is drained 43 // during the next evacuation pause. 44 // 45 // The first thing the G1 post write barrier does is to check whether 46 // the card containing the updated pointer is already dirty and, if 47 // so, skips the remaining code in the barrier. 48 // 49 // Delaying the refinement of a card will make the card fail the 50 // first is_dirty check in the write barrier, skipping the remainder 51 // of the write barrier. 52 // 53 // This can significantly reduce the overhead of the write barrier 54 // code, increasing throughput. 55 56 class G1HotCardCache: public CHeapObj<mtGC> { 57 G1CollectedHeap* _g1h; 58 59 // The card cache table 60 jbyte** _hot_cache; 61 62 int _hot_cache_size; 63 int _n_hot; 64 int _hot_cache_idx; 65 66 int _hot_cache_par_chunk_size; 67 volatile int _hot_cache_par_claimed_idx; 68 69 bool _use_cache; 70 71 G1CardCounts _card_counts; 72 73 bool default_use_cache() const { 74 return (G1ConcRSLogCacheSize > 0); 75 } 76 77 public: 78 G1HotCardCache(G1CollectedHeap* g1h); 79 ~G1HotCardCache(); 80 81 void initialize(); 82 83 bool use_cache() { return _use_cache; } 84 85 void set_use_cache(bool b) { 86 _use_cache = (b ? default_use_cache() : false); 87 } 88 89 // Returns the card to be refined or NULL. 90 // 91 // Increments the count for given the card. if the card is not 'hot', 92 // it is returned for immediate refining. Otherwise the card is 93 // added to the hot card cache. 94 // If there is enough room in the hot card cache for the card we're 95 // adding, NULL is returned and no further action in needed. 96 // If we evict a card from the cache to make room for the new card, 97 // the evicted card is then returned for refinement. 98 jbyte* insert(jbyte* card_ptr); 99 100 // Refine the cards that have delayed as a result of 101 // being in the cache. 102 void drain(int worker_i, G1RemSet* g1rs, DirtyCardQueue* into_cset_dcq); 103 104 // Set up for parallel processing of the cards in the hot cache 105 void reset_hot_cache_claimed_index() { 106 _hot_cache_par_claimed_idx = 0; 107 } 108 109 // Resets the hot card cache and discards the entries. 110 void reset_hot_cache() { 111 assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint"); 112 assert(Thread::current()->is_VM_thread(), "Current thread should be the VMthread"); 113 _hot_cache_idx = 0; _n_hot = 0; 114 } 115 116 bool hot_cache_is_empty() { return _n_hot == 0; } 117 118 // Resizes the card counts table to match the given capacity 119 void resize_card_counts(size_t heap_capacity); 120 121 // Zeros the values in the card counts table for entire committed heap 122 void reset_card_counts(); 123 124 // Zeros the values in the card counts table for the given region 125 void reset_card_counts(HeapRegion* hr); 126 }; 127 128 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP