1 /*
2 * Copyright (c) 2013, 2014, 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_implementation/g1/dirtyCardQueue.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1HotCardCache.hpp"
29 #include "gc_implementation/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 = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size, mtGC);
41 for (size_t i = 0; i < _hot_cache_size; i++) {
42 _hot_cache[i] = NULL;
43 }
44
45 _hot_cache_idx = 0;
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 FREE_C_HEAP_ARRAY(jbyte*, _hot_cache);
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(1, &_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 = (jbyte*)Atomic::cmpxchg_ptr(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(uint worker_i,
87 G1RemSet* g1rs,
88 DirtyCardQueue* into_cset_dcq) {
89 if (!default_use_cache()) {
90 assert(_hot_cache == NULL, "Logic");
91 return;
92 }
93
94 assert(_hot_cache != NULL, "Logic");
95 assert(!use_cache(), "cache should be disabled");
96
97 while (_hot_cache_par_claimed_idx < _hot_cache_size) { // read once
98 size_t end_idx = Atomic::add(_hot_cache_par_chunk_size, &_hot_cache_par_claimed_idx);
99 size_t start_idx = end_idx - _hot_cache_par_chunk_size;
100 // The current worker has successfully claimed the chunk [start_idx..end_idx)
101 end_idx = MIN2(end_idx, _hot_cache_size);
102 for (size_t i = start_idx; i < end_idx; i++) {
103 jbyte* card_ptr = _hot_cache[i];
104 if (card_ptr != NULL) {
105 if (g1rs->refine_card(card_ptr, worker_i, true)) {
106 // The part of the heap spanned by the card contains references
107 // that point into the current collection set.
108 // We need to record the card pointer in the DirtyCardQueueSet
109 // that we use for such cards.
110 //
111 // The only time we care about recording cards that contain
112 // references that point into the collection set is during
113 // RSet updating while within an evacuation pause.
114 // In this case worker_i should be the id of a GC worker thread
115 assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
116 assert(worker_i < ParallelGCThreads,
117 err_msg("incorrect worker id: %u", worker_i));
118
119 into_cset_dcq->enqueue(card_ptr);
120 }
121 } else {
122 break;
123 }
124 }
125 }
126
127 // The existing entries in the hot card cache, which were just refined
128 // above, are discarded prior to re-enabling the cache near the end of the GC.
129 }
130
131 void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
132 _card_counts.clear_region(hr);
133 }
134
135 void G1HotCardCache::reset_card_counts() {
136 _card_counts.clear_all();
137 }