4118e13330
Summary: Exposing persistent cache stats (counters) to the user via public API. Closes https://github.com/facebook/rocksdb/pull/1485 Differential Revision: D4155274 Pulled By: siying fbshipit-source-id: 30a9f50
139 lines
3.7 KiB
C++
139 lines
3.7 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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#pragma once
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#ifndef ROCKSDB_LITE
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#include <atomic>
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#include <limits>
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#include <sstream>
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#include <string>
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#include <vector>
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#include "rocksdb/cache.h"
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#include "utilities/persistent_cache/hash_table.h"
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#include "utilities/persistent_cache/hash_table_evictable.h"
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#include "utilities/persistent_cache/persistent_cache_tier.h"
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// VolatileCacheTier
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//
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// This file provides persistent cache tier implementation for caching
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// key/values in RAM.
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//
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// key/values
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// |
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// V
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// +-------------------+
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// | VolatileCacheTier | Store in an evictable hash table
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// +-------------------+
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// |
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// V
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// on eviction
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// pushed to next tier
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//
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// The implementation is designed to be concurrent. The evictable hash table
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// implementation is not concurrent at this point though.
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//
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// The eviction algorithm is LRU
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namespace rocksdb {
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class VolatileCacheTier : public PersistentCacheTier {
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public:
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explicit VolatileCacheTier(
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const bool is_compressed = true,
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const size_t max_size = std::numeric_limits<size_t>::max())
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: is_compressed_(is_compressed), max_size_(max_size) {}
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virtual ~VolatileCacheTier();
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// insert to cache
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Status Insert(const Slice& page_key, const char* data,
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const size_t size) override;
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// lookup key in cache
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Status Lookup(const Slice& page_key, std::unique_ptr<char[]>* data,
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size_t* size) override;
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// is compressed cache ?
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bool IsCompressed() override { return is_compressed_; }
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// erase key from cache
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bool Erase(const Slice& key) override;
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// Expose stats as map
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PersistentCache::StatsType Stats() override;
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private:
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//
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// Cache data abstraction
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//
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struct CacheData : LRUElement<CacheData> {
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explicit CacheData(CacheData&& rhs) ROCKSDB_NOEXCEPT
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: key(std::move(rhs.key)),
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value(std::move(rhs.value)) {}
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explicit CacheData(const std::string& _key, const std::string& _value = "")
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: key(_key), value(_value) {}
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virtual ~CacheData() {}
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const std::string key;
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const std::string value;
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};
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static void DeleteCacheData(CacheData* data);
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//
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// Index and LRU definition
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//
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struct CacheDataHash {
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uint64_t operator()(const CacheData* obj) const {
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assert(obj);
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return std::hash<std::string>()(obj->key);
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}
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};
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struct CacheDataEqual {
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bool operator()(const CacheData* lhs, const CacheData* rhs) const {
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assert(lhs);
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assert(rhs);
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return lhs->key == rhs->key;
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}
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};
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struct Statistics {
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uint64_t cache_misses_ = 0;
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uint64_t cache_hits_ = 0;
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uint64_t cache_inserts_ = 0;
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uint64_t cache_evicts_ = 0;
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double CacheHitPct() const {
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auto lookups = cache_hits_ + cache_misses_;
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return lookups ? 100 * cache_hits_ / static_cast<double>(lookups) : 0.0;
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}
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double CacheMissPct() const {
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auto lookups = cache_hits_ + cache_misses_;
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return lookups ? 100 * cache_misses_ / static_cast<double>(lookups) : 0.0;
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}
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};
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typedef EvictableHashTable<CacheData, CacheDataHash, CacheDataEqual>
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IndexType;
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// Evict LRU tail
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bool Evict();
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const bool is_compressed_ = true; // does it store compressed data
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IndexType index_; // in-memory cache
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std::atomic<uint64_t> max_size_{0}; // Maximum size of the cache
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std::atomic<uint64_t> size_{0}; // Size of the cache
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Statistics stats_;
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};
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} // namespace rocksdb
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#endif
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