d9cfaa2b16
Summary:
Persistent cache tier is the tier abstraction that can work for any block
device based device mounted on a file system. The design/implementation can
handle any generic block device.
Any generic block support is achieved by generalizing the access patten as
{io-size, q-depth, direct-io/buffered}.
We have specifically tested and adapted the IO path for NVM and SSD.
Persistent cache tier consists of there parts :
1) File layout
Provides the implementation for handling IO path for reading and writing data
(key/value pair).
2) Meta-data
Provides the implementation for handling the index for persistent read cache.
3) Implementation
It binds (1) and (2) and flushed out the PersistentCacheTier interface
This patch provides implementation for (1)(2). Follow up patch will provide (3)
and tests.
Test Plan: Compile and run check
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D57117
125 lines
3.3 KiB
C++
125 lines
3.3 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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#pragma once
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#ifndef ROCKSDB_LITE
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#include <functional>
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#include <string>
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#include <unordered_map>
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#include "rocksdb/slice.h"
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#include "utilities/persistent_cache/block_cache_tier_file.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/lrulist.h"
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namespace rocksdb {
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//
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// Block Cache Tier Metadata
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//
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// The BlockCacheTierMetadata holds all the metadata associated with block
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// cache. It
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// fundamentally contains 2 indexes and an LRU.
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//
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// Block Cache Index
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//
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// This is a forward index that maps a given key to a LBA (Logical Block
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// Address). LBA is a disk pointer that points to a record on the cache.
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//
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// LBA = { cache-id, offset, size }
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//
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// Cache File Index
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//
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// This is a forward index that maps a given cache-id to a cache file object.
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// Typically you would lookup using LBA and use the object to read or write
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struct BlockInfo {
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explicit BlockInfo(const Slice& key, const LBA& lba = LBA())
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: key_(key.ToString()), lba_(lba) {}
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std::string key_;
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LBA lba_;
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};
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class BlockCacheTierMetadata {
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public:
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explicit BlockCacheTierMetadata(const uint32_t blocks_capacity = 1024 * 1024,
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const uint32_t cachefile_capacity = 10 * 1024)
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: cache_file_index_(cachefile_capacity), block_index_(blocks_capacity) {}
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virtual ~BlockCacheTierMetadata() {}
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// Insert a given cache file
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bool Insert(BlockCacheFile* file);
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// Lookup cache file based on cache_id
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BlockCacheFile* Lookup(const uint32_t cache_id);
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// Insert block information to block index
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bool Insert(BlockInfo* binfo);
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// Lookup block information from block index
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bool Lookup(const Slice& key, LBA* lba);
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// Remove a given from the block index
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BlockInfo* Remove(const Slice& key);
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// Find and evict a cache file using LRU policy
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BlockCacheFile* Evict();
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// Clear the metadata contents
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virtual void Clear();
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protected:
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// Remove all block information from a given file
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virtual void RemoveAllKeys(BlockCacheFile* file);
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private:
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// Cache file index definition
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//
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// cache-id => BlockCacheFile
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struct BlockCacheFileHash {
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uint64_t operator()(const BlockCacheFile* rec) {
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return std::hash<uint32_t>()(rec->cacheid());
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}
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};
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struct BlockCacheFileEqual {
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uint64_t operator()(const BlockCacheFile* lhs, const BlockCacheFile* rhs) {
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return lhs->cacheid() == rhs->cacheid();
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}
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};
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typedef EvictableHashTable<BlockCacheFile, BlockCacheFileHash,
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BlockCacheFileEqual>
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CacheFileIndexType;
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// Block Lookup Index
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//
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// key => LBA
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struct Hash {
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size_t operator()(BlockInfo* node) const {
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return std::hash<std::string>()(node->key_);
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}
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};
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struct Equal {
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size_t operator()(BlockInfo* lhs, BlockInfo* rhs) const {
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return lhs->key_ == rhs->key_;
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}
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};
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typedef HashTable<BlockInfo*, Hash, Equal> BlockIndexType;
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CacheFileIndexType cache_file_index_;
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BlockIndexType block_index_;
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};
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} // namespace rocksdb
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#endif
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