1 /*
2 * Copyright (c) 2013, 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 #include "precompiled.hpp"
26 #include "gc/g1/g1CardTableEntryClosure.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1DirtyCardQueue.hpp"
29 #include "gc/g1/g1HotCardCache.hpp"
30 #include "runtime/atomic.hpp"
31
32 G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h):
33 _g1h(g1h), _use_cache(false), _card_counts(g1h),
34 _hot_cache(NULL), _hot_cache_size(0), _hot_cache_par_chunk_size(0),
35 _hot_cache_idx(0), _hot_cache_par_claimed_idx(0)
36 {}
37
38 void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) {
39 if (default_use_cache()) {
40 _use_cache = true;
41
42 _hot_cache_size = (size_t)1 << G1ConcRSLogCacheSize;
43 _hot_cache = ArrayAllocator<CardValue*>::allocate(_hot_cache_size, mtGC);
44
45 reset_hot_cache_internal();
46
47 // For refining the cards in the hot cache in parallel
48 _hot_cache_par_chunk_size = ClaimChunkSize;
49 _hot_cache_par_claimed_idx = 0;
50
51 _card_counts.initialize(card_counts_storage);
52 }
53 }
54
55 G1HotCardCache::~G1HotCardCache() {
56 if (default_use_cache()) {
57 assert(_hot_cache != NULL, "Logic");
58 ArrayAllocator<CardValue*>::free(_hot_cache, _hot_cache_size);
59 _hot_cache = NULL;
60 }
61 }
62
63 CardTable::CardValue* G1HotCardCache::insert(CardValue* card_ptr) {
64 uint count = _card_counts.add_card_count(card_ptr);
65 if (!_card_counts.is_hot(count)) {
66 // The card is not hot so do not store it in the cache;
67 // return it for immediate refining.
68 return card_ptr;
69 }
70 // Otherwise, the card is hot.
71 size_t index = Atomic::add(1u, &_hot_cache_idx) - 1;
72 size_t masked_index = index & (_hot_cache_size - 1);
73 CardValue* current_ptr = _hot_cache[masked_index];
74
75 // Try to store the new card pointer into the cache. Compare-and-swap to guard
76 // against the unlikely event of a race resulting in another card pointer to
77 // have already been written to the cache. In this case we will return
78 // card_ptr in favor of the other option, which would be starting over. This
79 // should be OK since card_ptr will likely be the older card already when/if
80 // this ever happens.
81 CardValue* previous_ptr = Atomic::cmpxchg(card_ptr,
82 &_hot_cache[masked_index],
83 current_ptr);
84 return (previous_ptr == current_ptr) ? previous_ptr : card_ptr;
85 }
86
87 void G1HotCardCache::drain(G1CardTableEntryClosure* cl, uint worker_i) {
88 assert(default_use_cache(), "Drain only necessary if we use the hot card cache.");
89
90 assert(_hot_cache != NULL, "Logic");
91 assert(!use_cache(), "cache should be disabled");
92
93 while (_hot_cache_par_claimed_idx < _hot_cache_size) {
94 size_t end_idx = Atomic::add(_hot_cache_par_chunk_size,
95 &_hot_cache_par_claimed_idx);
96 size_t start_idx = end_idx - _hot_cache_par_chunk_size;
97 // The current worker has successfully claimed the chunk [start_idx..end_idx)
98 end_idx = MIN2(end_idx, _hot_cache_size);
99 for (size_t i = start_idx; i < end_idx; i++) {
100 CardValue* card_ptr = _hot_cache[i];
101 if (card_ptr != NULL) {
102 bool result = cl->do_card_ptr(card_ptr, worker_i);
103 assert(result, "Closure should always return true");
104 } else {
105 break;
106 }
107 }
108 }
109
110 // The existing entries in the hot card cache, which were just refined
111 // above, are discarded prior to re-enabling the cache near the end of the GC.
112 }
113
114 void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
115 _card_counts.clear_region(hr);
116 }