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rocksdb/cache/sharded_cache.h

135 lines
6.1 KiB

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include <atomic>
#include <string>
#include "port/port.h"
#include "rocksdb/cache.h"
namespace ROCKSDB_NAMESPACE {
// Single cache shard interface.
class CacheShard {
public:
explicit CacheShard(CacheMetadataChargePolicy metadata_charge_policy)
: metadata_charge_policy_(metadata_charge_policy) {}
virtual ~CacheShard() = default;
using DeleterFn = Cache::DeleterFn;
virtual Status Insert(const Slice& key, uint32_t hash, void* value,
size_t charge, DeleterFn deleter,
Cache::Handle** handle, Cache::Priority priority) = 0;
virtual Status Insert(const Slice& key, uint32_t hash, void* value,
const Cache::CacheItemHelper* helper, size_t charge,
Cache::Handle** handle, Cache::Priority priority) = 0;
virtual Cache::Handle* Lookup(const Slice& key, uint32_t hash) = 0;
virtual Cache::Handle* Lookup(const Slice& key, uint32_t hash,
const Cache::CacheItemHelper* helper,
const Cache::CreateCallback& create_cb,
Cache::Priority priority, bool wait,
Statistics* stats) = 0;
virtual bool Release(Cache::Handle* handle, bool useful,
bool erase_if_last_ref) = 0;
virtual bool IsReady(Cache::Handle* handle) = 0;
virtual void Wait(Cache::Handle* handle) = 0;
virtual bool Ref(Cache::Handle* handle) = 0;
virtual bool Release(Cache::Handle* handle, bool erase_if_last_ref) = 0;
virtual void Erase(const Slice& key, uint32_t hash) = 0;
virtual void SetCapacity(size_t capacity) = 0;
virtual void SetStrictCapacityLimit(bool strict_capacity_limit) = 0;
virtual size_t GetUsage() const = 0;
virtual size_t GetPinnedUsage() const = 0;
virtual size_t GetOccupancyCount() const = 0;
virtual size_t GetTableAddressCount() const = 0;
// Handles iterating over roughly `average_entries_per_lock` entries, using
// `state` to somehow record where it last ended up. Caller initially uses
// *state == 0 and implementation sets *state = UINT32_MAX to indicate
// completion.
virtual void ApplyToSomeEntries(
const std::function<void(const Slice& key, void* value, size_t charge,
DeleterFn deleter)>& callback,
uint32_t average_entries_per_lock, uint32_t* state) = 0;
virtual void EraseUnRefEntries() = 0;
virtual std::string GetPrintableOptions() const { return ""; }
protected:
const CacheMetadataChargePolicy metadata_charge_policy_;
};
// Generic cache interface which shards cache by hash of keys. 2^num_shard_bits
// shards will be created, with capacity split evenly to each of the shards.
// Keys are sharded by the highest num_shard_bits bits of hash value.
class ShardedCache : public Cache {
public:
ShardedCache(size_t capacity, int num_shard_bits, bool strict_capacity_limit,
std::shared_ptr<MemoryAllocator> memory_allocator = nullptr);
virtual ~ShardedCache() = default;
virtual CacheShard* GetShard(uint32_t shard) = 0;
virtual const CacheShard* GetShard(uint32_t shard) const = 0;
virtual uint32_t GetHash(Handle* handle) const = 0;
virtual void SetCapacity(size_t capacity) override;
virtual void SetStrictCapacityLimit(bool strict_capacity_limit) override;
virtual Status Insert(const Slice& key, void* value, size_t charge,
DeleterFn deleter, Handle** handle,
Priority priority) override;
virtual Status Insert(const Slice& key, void* value,
const CacheItemHelper* helper, size_t charge,
Handle** handle = nullptr,
Priority priority = Priority::LOW) override;
virtual Handle* Lookup(const Slice& key, Statistics* stats) override;
virtual Handle* Lookup(const Slice& key, const CacheItemHelper* helper,
const CreateCallback& create_cb, Priority priority,
bool wait, Statistics* stats = nullptr) override;
virtual bool Release(Handle* handle, bool useful,
bool erase_if_last_ref = false) override;
virtual bool IsReady(Handle* handle) override;
virtual void Wait(Handle* handle) override;
virtual bool Ref(Handle* handle) override;
virtual bool Release(Handle* handle, bool erase_if_last_ref = false) override;
virtual void Erase(const Slice& key) override;
virtual uint64_t NewId() override;
virtual size_t GetCapacity() const override;
virtual bool HasStrictCapacityLimit() const override;
virtual size_t GetUsage() const override;
virtual size_t GetUsage(Handle* handle) const override;
virtual size_t GetPinnedUsage() const override;
virtual size_t GetOccupancyCount() const override;
virtual size_t GetTableAddressCount() const override;
virtual void ApplyToAllEntries(
const std::function<void(const Slice& key, void* value, size_t charge,
DeleterFn deleter)>& callback,
const ApplyToAllEntriesOptions& opts) override;
virtual void EraseUnRefEntries() override;
virtual std::string GetPrintableOptions() const override;
int GetNumShardBits() const;
uint32_t GetNumShards() const;
protected:
inline uint32_t Shard(uint32_t hash) { return hash & shard_mask_; }
private:
const uint32_t shard_mask_;
mutable port::Mutex capacity_mutex_;
size_t capacity_;
bool strict_capacity_limit_;
std::atomic<uint64_t> last_id_;
};
// 512KB is traditional minimum shard size.
int GetDefaultCacheShardBits(size_t capacity,
size_t min_shard_size = 512U * 1024U);
} // namespace ROCKSDB_NAMESPACE