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), _cache_wrapped_around(false)
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 _cache_wrapped_around = false;
52
53 _card_counts.initialize(card_counts_storage);
54 }
55 }
56
57 G1HotCardCache::~G1HotCardCache() {
58 if (default_use_cache()) {
59 assert(_hot_cache != NULL, "Logic");
60 ArrayAllocator<CardValue*>::free(_hot_cache, _hot_cache_size);
61 _hot_cache = NULL;
62 }
63 }
64
65 CardTable::CardValue* G1HotCardCache::insert(CardValue* card_ptr) {
66 uint count = _card_counts.add_card_count(card_ptr);
67 if (!_card_counts.is_hot(count)) {
68 // The card is not hot so do not store it in the cache;
69 // return it for immediate refining.
70 return card_ptr;
71 }
72 // Otherwise, the card is hot.
73 size_t index = Atomic::add(1u, &_hot_cache_idx) - 1;
74 // This does not need an atomic update. Racing threads may at most write the
75 // same value.
76 if (index == _hot_cache_size) {
77 _cache_wrapped_around = true;
78 }
79 size_t masked_index = index & (_hot_cache_size - 1);
80 CardValue* current_ptr = _hot_cache[masked_index];
81
82 // Try to store the new card pointer into the cache. Compare-and-swap to guard
83 // against the unlikely event of a race resulting in another card pointer to
84 // have already been written to the cache. In this case we will return
85 // card_ptr in favor of the other option, which would be starting over. This
86 // should be OK since card_ptr will likely be the older card already when/if
87 // this ever happens.
88 CardValue* previous_ptr = Atomic::cmpxchg(card_ptr,
89 &_hot_cache[masked_index],
90 current_ptr);
91 return (previous_ptr == current_ptr) ? previous_ptr : card_ptr;
92 }
93
94 void G1HotCardCache::drain(G1CardTableEntryClosure* cl, uint worker_id) {
95 assert(default_use_cache(), "Drain only necessary if we use the hot card cache.");
96
97 assert(_hot_cache != NULL, "Logic");
98 assert(!use_cache(), "cache should be disabled");
99
100 while (_hot_cache_par_claimed_idx < _hot_cache_size) {
101 size_t end_idx = Atomic::add(_hot_cache_par_chunk_size,
102 &_hot_cache_par_claimed_idx);
103 size_t start_idx = end_idx - _hot_cache_par_chunk_size;
104 // The current worker has successfully claimed the chunk [start_idx..end_idx)
105 end_idx = MIN2(end_idx, _hot_cache_size);
106 for (size_t i = start_idx; i < end_idx; i++) {
107 CardValue* card_ptr = _hot_cache[i];
108 if (card_ptr != NULL) {
109 cl->do_card_ptr(card_ptr, worker_id);
110 } else {
111 break;
112 }
113 }
114 }
115
116 // The existing entries in the hot card cache, which were just refined
117 // above, are discarded prior to re-enabling the cache near the end of the GC.
118 }
119
120 void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
121 _card_counts.clear_region(hr);
122 }