1/*
2 * Copyright (c) 2013, 2016, 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
31G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h):
32  _g1h(g1h), _hot_cache(NULL), _use_cache(false), _card_counts(g1h) {}
33
34void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) {
35  if (default_use_cache()) {
36    _use_cache = true;
37
38    _hot_cache_size = (size_t)1 << G1ConcRSLogCacheSize;
39    _hot_cache = ArrayAllocator<jbyte*, mtGC>::allocate(_hot_cache_size);
40
41    reset_hot_cache_internal();
42
43    // For refining the cards in the hot cache in parallel
44    _hot_cache_par_chunk_size = ClaimChunkSize;
45    _hot_cache_par_claimed_idx = 0;
46
47    _card_counts.initialize(card_counts_storage);
48  }
49}
50
51G1HotCardCache::~G1HotCardCache() {
52  if (default_use_cache()) {
53    assert(_hot_cache != NULL, "Logic");
54    ArrayAllocator<jbyte*, mtGC>::free(_hot_cache, _hot_cache_size);
55    _hot_cache = NULL;
56  }
57}
58
59jbyte* G1HotCardCache::insert(jbyte* card_ptr) {
60  uint count = _card_counts.add_card_count(card_ptr);
61  if (!_card_counts.is_hot(count)) {
62    // The card is not hot so do not store it in the cache;
63    // return it for immediate refining.
64    return card_ptr;
65  }
66  // Otherwise, the card is hot.
67  size_t index = Atomic::add(1, &_hot_cache_idx) - 1;
68  size_t masked_index = index & (_hot_cache_size - 1);
69  jbyte* current_ptr = _hot_cache[masked_index];
70
71  // Try to store the new card pointer into the cache. Compare-and-swap to guard
72  // against the unlikely event of a race resulting in another card pointer to
73  // have already been written to the cache. In this case we will return
74  // card_ptr in favor of the other option, which would be starting over. This
75  // should be OK since card_ptr will likely be the older card already when/if
76  // this ever happens.
77  jbyte* previous_ptr = (jbyte*)Atomic::cmpxchg_ptr(card_ptr,
78                                                    &_hot_cache[masked_index],
79                                                    current_ptr);
80  return (previous_ptr == current_ptr) ? previous_ptr : card_ptr;
81}
82
83void G1HotCardCache::drain(CardTableEntryClosure* cl, uint worker_i) {
84  assert(default_use_cache(), "Drain only necessary if we use the hot card cache.");
85
86  assert(_hot_cache != NULL, "Logic");
87  assert(!use_cache(), "cache should be disabled");
88
89  while (_hot_cache_par_claimed_idx < _hot_cache_size) {
90    size_t end_idx = Atomic::add(_hot_cache_par_chunk_size,
91                                 &_hot_cache_par_claimed_idx);
92    size_t start_idx = end_idx - _hot_cache_par_chunk_size;
93    // The current worker has successfully claimed the chunk [start_idx..end_idx)
94    end_idx = MIN2(end_idx, _hot_cache_size);
95    for (size_t i = start_idx; i < end_idx; i++) {
96      jbyte* card_ptr = _hot_cache[i];
97      if (card_ptr != NULL) {
98        bool result = cl->do_card_ptr(card_ptr, worker_i);
99        assert(result, "Closure should always return true");
100      } else {
101        break;
102      }
103    }
104  }
105
106  // The existing entries in the hot card cache, which were just refined
107  // above, are discarded prior to re-enabling the cache near the end of the GC.
108}
109
110void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
111  _card_counts.clear_region(hr);
112}
113
114void G1HotCardCache::reset_card_counts() {
115  _card_counts.clear_all();
116}
117