1 /* 2 * Copyright (c) 2013, 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 #include "precompiled.hpp" 26 #include "gc/g1/dirtyCardQueue.hpp" 27 #include "gc/g1/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/g1HotCardCache.hpp" 29 #include "gc/g1/g1RemSet.hpp" 30 #include "runtime/atomic.inline.hpp" 31 32 G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h): 33 _g1h(g1h), _hot_cache(NULL), _use_cache(false), _card_counts(g1h) {} 34 35 void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) { 36 if (default_use_cache()) { 37 _use_cache = true; 38 39 _hot_cache_size = (size_t)1 << G1ConcRSLogCacheSize; 40 _hot_cache = _hot_cache_memory.allocate(_hot_cache_size); 41 42 reset_hot_cache_internal(); 43 44 // For refining the cards in the hot cache in parallel 45 _hot_cache_par_chunk_size = ClaimChunkSize; 46 _hot_cache_par_claimed_idx = 0; 47 48 _card_counts.initialize(card_counts_storage); 49 } 50 } 51 52 G1HotCardCache::~G1HotCardCache() { 53 if (default_use_cache()) { 54 assert(_hot_cache != NULL, "Logic"); 55 _hot_cache_memory.free(); 56 _hot_cache = NULL; 57 } 58 } 59 60 jbyte* G1HotCardCache::insert(jbyte* card_ptr) { 61 uint count = _card_counts.add_card_count(card_ptr); 62 if (!_card_counts.is_hot(count)) { 63 // The card is not hot so do not store it in the cache; 64 // return it for immediate refining. 65 return card_ptr; 66 } 67 // Otherwise, the card is hot. 68 size_t index = Atomic::add(1, &_hot_cache_idx) - 1; 69 size_t masked_index = index & (_hot_cache_size - 1); 70 jbyte* current_ptr = _hot_cache[masked_index]; 71 72 // Try to store the new card pointer into the cache. Compare-and-swap to guard 73 // against the unlikely event of a race resulting in another card pointer to 74 // have already been written to the cache. In this case we will return 75 // card_ptr in favor of the other option, which would be starting over. This 76 // should be OK since card_ptr will likely be the older card already when/if 77 // this ever happens. 78 jbyte* previous_ptr = (jbyte*)Atomic::cmpxchg_ptr(card_ptr, 79 &_hot_cache[masked_index], 80 current_ptr); 81 return (previous_ptr == current_ptr) ? previous_ptr : card_ptr; 82 } 83 84 void G1HotCardCache::drain(uint worker_i, 85 G1RemSet* g1rs, 86 DirtyCardQueue* into_cset_dcq) { 87 if (!default_use_cache()) { 88 assert(_hot_cache == NULL, "Logic"); 89 return; 90 } 91 92 assert(_hot_cache != NULL, "Logic"); 93 assert(!use_cache(), "cache should be disabled"); 94 95 while (_hot_cache_par_claimed_idx < _hot_cache_size) { 96 size_t end_idx = Atomic::add(_hot_cache_par_chunk_size, 97 &_hot_cache_par_claimed_idx); 98 size_t start_idx = end_idx - _hot_cache_par_chunk_size; 99 // The current worker has successfully claimed the chunk [start_idx..end_idx) 100 end_idx = MIN2(end_idx, _hot_cache_size); 101 for (size_t i = start_idx; i < end_idx; i++) { 102 jbyte* card_ptr = _hot_cache[i]; 103 if (card_ptr != NULL) { 104 if (g1rs->refine_card(card_ptr, worker_i, true)) { 105 // The part of the heap spanned by the card contains references 106 // that point into the current collection set. 107 // We need to record the card pointer in the DirtyCardQueueSet 108 // that we use for such cards. 109 // 110 // The only time we care about recording cards that contain 111 // references that point into the collection set is during 112 // RSet updating while within an evacuation pause. 113 // In this case worker_i should be the id of a GC worker thread 114 assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint"); 115 assert(worker_i < ParallelGCThreads, 116 err_msg("incorrect worker id: %u", worker_i)); 117 118 into_cset_dcq->enqueue(card_ptr); 119 } 120 } else { 121 break; 122 } 123 } 124 } 125 126 // The existing entries in the hot card cache, which were just refined 127 // above, are discarded prior to re-enabling the cache near the end of the GC. 128 } 129 130 void G1HotCardCache::reset_card_counts(HeapRegion* hr) { 131 _card_counts.clear_region(hr); 132 } 133 134 void G1HotCardCache::reset_card_counts() { 135 _card_counts.clear_all(); 136 }