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1 | // Copyright (c) 2011-present, Facebook, Inc. All rights reserved. |
2 | // This source code is licensed under both the GPLv2 (found in the | |
3 | // COPYING file in the root directory) and Apache 2.0 License | |
4 | // (found in the LICENSE.Apache file in the root directory). | |
5 | // Copyright (c) 2011 The LevelDB Authors. All rights reserved. | |
6 | // Use of this source code is governed by a BSD-style license that can be | |
7 | // found in the LICENSE file. See the AUTHORS file for names of contributors. | |
8 | // | |
9 | ||
10 | #include "util/compression_context_cache.h" | |
11 | ||
12 | #include "util/compression.h" | |
13 | #include "util/core_local.h" | |
14 | ||
15 | #include <atomic> | |
16 | ||
17 | namespace rocksdb { | |
18 | namespace compression_cache { | |
19 | ||
20 | void* const SentinelValue = nullptr; | |
21 | // Cache ZSTD uncompression contexts for reads | |
22 | // if needed we can add ZSTD compression context caching | |
23 | // which is currently is not done since BlockBasedTableBuilder | |
24 | // simply creates one compression context per new SST file. | |
25 | struct ZSTDCachedData { | |
26 | // We choose to cache the below structure instead of a ptr | |
27 | // because we want to avoid a) native types leak b) make | |
28 | // cache use transparent for the user | |
29 | ZSTDUncompressCachedData uncomp_cached_data_; | |
30 | std::atomic<void*> zstd_uncomp_sentinel_; | |
31 | ||
32 | char | |
33 | padding[(CACHE_LINE_SIZE - | |
34 | (sizeof(ZSTDUncompressCachedData) + sizeof(std::atomic<void*>)) % | |
35 | CACHE_LINE_SIZE)]; // unused padding field | |
36 | ||
37 | ZSTDCachedData() : zstd_uncomp_sentinel_(&uncomp_cached_data_) {} | |
38 | ZSTDCachedData(const ZSTDCachedData&) = delete; | |
39 | ZSTDCachedData& operator=(const ZSTDCachedData&) = delete; | |
40 | ||
41 | ZSTDUncompressCachedData GetUncompressData(int64_t idx) { | |
42 | ZSTDUncompressCachedData result; | |
43 | void* expected = &uncomp_cached_data_; | |
44 | if (zstd_uncomp_sentinel_.compare_exchange_strong(expected, | |
45 | SentinelValue)) { | |
46 | uncomp_cached_data_.CreateIfNeeded(); | |
47 | result.InitFromCache(uncomp_cached_data_, idx); | |
48 | } else { | |
49 | // Creates one time use data | |
50 | result.CreateIfNeeded(); | |
51 | } | |
52 | return result; | |
53 | } | |
54 | // Return the entry back into circulation | |
55 | // This is executed only when we successfully obtained | |
56 | // in the first place | |
57 | void ReturnUncompressData() { | |
58 | if (zstd_uncomp_sentinel_.exchange(&uncomp_cached_data_) != SentinelValue) { | |
59 | // Means we are returning while not having it acquired. | |
60 | assert(false); | |
61 | } | |
62 | } | |
63 | }; | |
64 | static_assert(sizeof(ZSTDCachedData) % CACHE_LINE_SIZE == 0, | |
65 | "Expected CACHE_LINE_SIZE alignment"); | |
66 | } // namespace compression_cache | |
67 | ||
68 | using namespace compression_cache; | |
69 | ||
70 | class CompressionContextCache::Rep { | |
71 | public: | |
72 | Rep() {} | |
73 | ZSTDUncompressCachedData GetZSTDUncompressData() { | |
74 | auto p = per_core_uncompr_.AccessElementAndIndex(); | |
75 | int64_t idx = static_cast<int64_t>(p.second); | |
76 | return p.first->GetUncompressData(idx); | |
77 | } | |
78 | void ReturnZSTDUncompressData(int64_t idx) { | |
79 | assert(idx >= 0); | |
80 | auto* cn = per_core_uncompr_.AccessAtCore(static_cast<size_t>(idx)); | |
81 | cn->ReturnUncompressData(); | |
82 | } | |
83 | ||
84 | private: | |
85 | CoreLocalArray<ZSTDCachedData> per_core_uncompr_; | |
86 | }; | |
87 | ||
88 | CompressionContextCache::CompressionContextCache() : rep_(new Rep()) {} | |
89 | ||
90 | CompressionContextCache* CompressionContextCache::Instance() { | |
91 | static CompressionContextCache instance; | |
92 | return &instance; | |
93 | } | |
94 | ||
95 | void CompressionContextCache::InitSingleton() { Instance(); } | |
96 | ||
97 | ZSTDUncompressCachedData | |
98 | CompressionContextCache::GetCachedZSTDUncompressData() { | |
99 | return rep_->GetZSTDUncompressData(); | |
100 | } | |
101 | ||
102 | void CompressionContextCache::ReturnCachedZSTDUncompressData(int64_t idx) { | |
103 | rep_->ReturnZSTDUncompressData(idx); | |
104 | } | |
105 | ||
106 | CompressionContextCache::~CompressionContextCache() { delete rep_; } | |
107 | ||
108 | } // namespace rocksdb |