1 /* 2 * Copyright (c) 2013, 2017, 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 "runtime/atomic.hpp" 30 31 G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h): 32 _g1h(g1h), _use_cache(false), _card_counts(g1h), 33 _hot_cache(NULL), _hot_cache_size(0), _hot_cache_par_chunk_size(0), 34 _hot_cache_idx(0), _hot_cache_par_claimed_idx(0) 35 {} 36 37 void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) { 38 if (default_use_cache()) { 39 _use_cache = true; 40 41 _hot_cache_size = (size_t)1 << G1ConcRSLogCacheSize; 42 _hot_cache = ArrayAllocator<jbyte*>::allocate(_hot_cache_size, mtGC); 43 44 reset_hot_cache_internal(); 45 46 // For refining the cards in the hot cache in parallel 47 _hot_cache_par_chunk_size = ClaimChunkSize; 48 _hot_cache_par_claimed_idx = 0; 49 50 _card_counts.initialize(card_counts_storage); 51 } 52 } 53 54 G1HotCardCache::~G1HotCardCache() { 55 if (default_use_cache()) { 56 assert(_hot_cache != NULL, "Logic"); 57 ArrayAllocator<jbyte*>::free(_hot_cache, _hot_cache_size); 58 _hot_cache = NULL; 59 } 60 } 61 62 jbyte* G1HotCardCache::insert(jbyte* card_ptr) { 63 uint count = _card_counts.add_card_count(card_ptr); 64 if (!_card_counts.is_hot(count)) { 65 // The card is not hot so do not store it in the cache; 66 // return it for immediate refining. 67 return card_ptr; 68 } 69 // Otherwise, the card is hot. 70 size_t index = Atomic::add(1u, &_hot_cache_idx) - 1; 71 size_t masked_index = index & (_hot_cache_size - 1); 72 jbyte* current_ptr = _hot_cache[masked_index]; 73 74 // Try to store the new card pointer into the cache. Compare-and-swap to guard 75 // against the unlikely event of a race resulting in another card pointer to 76 // have already been written to the cache. In this case we will return 77 // card_ptr in favor of the other option, which would be starting over. This 78 // should be OK since card_ptr will likely be the older card already when/if 79 // this ever happens. 80 jbyte* previous_ptr = Atomic::cmpxchg(card_ptr, 81 &_hot_cache[masked_index], 82 current_ptr); 83 return (previous_ptr == current_ptr) ? previous_ptr : card_ptr; 84 } 85 86 void G1HotCardCache::drain(CardTableEntryClosure* cl, uint worker_i) { 87 assert(default_use_cache(), "Drain only necessary if we use the hot card cache."); 88 89 assert(_hot_cache != NULL, "Logic"); 90 assert(!use_cache(), "cache should be disabled"); 91 92 while (_hot_cache_par_claimed_idx < _hot_cache_size) { 93 size_t end_idx = Atomic::add(_hot_cache_par_chunk_size, 94 &_hot_cache_par_claimed_idx); 95 size_t start_idx = end_idx - _hot_cache_par_chunk_size; 96 // The current worker has successfully claimed the chunk [start_idx..end_idx) 97 end_idx = MIN2(end_idx, _hot_cache_size); 98 for (size_t i = start_idx; i < end_idx; i++) { 99 jbyte* card_ptr = _hot_cache[i]; 100 if (card_ptr != NULL) { 101 bool result = cl->do_card_ptr(card_ptr, worker_i); 102 assert(result, "Closure should always return true"); 103 } else { 104 break; 105 } 106 } 107 } 108 109 // The existing entries in the hot card cache, which were just refined 110 // above, are discarded prior to re-enabling the cache near the end of the GC. 111 } 112 113 void G1HotCardCache::reset_card_counts(HeapRegion* hr) { 114 _card_counts.clear_region(hr); 115 }