72f8cc703c
Summary: Add mid-point insertion functionality to LRU cache. Caller of `Cache::Insert()` can set an additional parameter to make a cache entry have higher priority. The LRU cache will reserve at most `capacity * high_pri_pool_pct` bytes for high-pri cache entries. If `high_pri_pool_pct` is zero, the cache degenerates to normal LRU cache. Context: If we are to put index and filter blocks into RocksDB block cache, index/filter block can be swap out too early. We want to add an option to RocksDB to reserve some capacity in block cache just for index/filter blocks, to mitigate the issue. In later diffs I'll update block based table reader to use the interface to cache index/filter blocks at high priority, and expose the option to `DBOptions` and make it dynamic changeable. Test Plan: unit test. Reviewers: IslamAbdelRahman, sdong, lightmark Reviewed By: lightmark Subscribers: andrewkr, dhruba, march, leveldb Differential Revision: https://reviews.facebook.net/D61977
94 lines
3.7 KiB
C++
94 lines
3.7 KiB
C++
// Copyright (c) 2011-present, 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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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include <atomic>
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#include "port/port.h"
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#include "rocksdb/cache.h"
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#include "util/hash.h"
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namespace rocksdb {
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// Single cache shard interface.
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class CacheShard {
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public:
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CacheShard() = default;
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virtual ~CacheShard() = default;
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virtual Status Insert(const Slice& key, uint32_t hash, void* value,
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size_t charge,
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void (*deleter)(const Slice& key, void* value),
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Cache::Handle** handle, Cache::Priority priority) = 0;
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virtual Cache::Handle* Lookup(const Slice& key, uint32_t hash) = 0;
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virtual void Release(Cache::Handle* handle) = 0;
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virtual void Erase(const Slice& key, uint32_t hash) = 0;
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virtual void SetCapacity(size_t capacity) = 0;
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virtual void SetStrictCapacityLimit(bool strict_capacity_limit) = 0;
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virtual size_t GetUsage() const = 0;
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virtual size_t GetPinnedUsage() const = 0;
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virtual void ApplyToAllCacheEntries(void (*callback)(void*, size_t),
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bool thread_safe) = 0;
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virtual void EraseUnRefEntries() = 0;
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};
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// Generic cache interface which shards cache by hash of keys. 2^num_shard_bits
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// shards will be created, with capacity split evenly to each of the shards.
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// Keys are sharded by the highest num_shard_bits bits of hash value.
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class ShardedCache : public Cache {
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public:
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ShardedCache(size_t capacity, int num_shard_bits, bool strict_capacity_limit);
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virtual ~ShardedCache() = default;
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virtual const char* Name() const override = 0;
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virtual CacheShard* GetShard(int shard) = 0;
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virtual const CacheShard* GetShard(int shard) const = 0;
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virtual void* Value(Handle* handle) override = 0;
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virtual size_t GetCharge(Handle* handle) const = 0;
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virtual uint32_t GetHash(Handle* handle) const = 0;
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virtual void DisownData() override = 0;
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virtual void SetCapacity(size_t capacity) override;
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virtual void SetStrictCapacityLimit(bool strict_capacity_limit) override;
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virtual Status Insert(const Slice& key, void* value, size_t charge,
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void (*deleter)(const Slice& key, void* value),
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Handle** handle, Priority priority) override;
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virtual Handle* Lookup(const Slice& key) override;
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virtual void Release(Handle* handle) override;
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virtual void Erase(const Slice& key) override;
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virtual uint64_t NewId() override;
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virtual size_t GetCapacity() const override;
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virtual bool HasStrictCapacityLimit() const override;
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virtual size_t GetUsage() const override;
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virtual size_t GetUsage(Handle* handle) const override;
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virtual size_t GetPinnedUsage() const override;
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virtual void ApplyToAllCacheEntries(void (*callback)(void*, size_t),
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bool thread_safe) override;
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virtual void EraseUnRefEntries() override;
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private:
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static inline uint32_t HashSlice(const Slice& s) {
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return Hash(s.data(), s.size(), 0);
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}
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uint32_t Shard(uint32_t hash) {
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// Note, hash >> 32 yields hash in gcc, not the zero we expect!
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return (num_shard_bits_ > 0) ? (hash >> (32 - num_shard_bits_)) : 0;
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}
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int num_shard_bits_;
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mutable port::Mutex capacity_mutex_;
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size_t capacity_;
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bool strict_capacity_limit_;
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std::atomic<uint64_t> last_id_;
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};
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} // namespace rocksdb
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