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
118 lines
2.8 KiB
C++
118 lines
2.8 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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#include <list>
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#include <memory>
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#include <string>
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#include "include/rocksdb/comparator.h"
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#include "util/arena.h"
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#include "util/mutexlock.h"
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namespace rocksdb {
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//
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// CacheWriteBuffer
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//
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// Buffer abstraction that can be manipulated via append
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// (not thread safe)
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class CacheWriteBuffer {
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public:
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explicit CacheWriteBuffer(const size_t size) : size_(size), pos_(0) {
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buf_.reset(new char[size_]);
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assert(!pos_);
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assert(size_);
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}
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virtual ~CacheWriteBuffer() {}
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void Append(const char* buf, const size_t size) {
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assert(pos_ + size <= size_);
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memcpy(buf_.get() + pos_, buf, size);
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pos_ += size;
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assert(pos_ <= size_);
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}
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void FillTrailingZeros() {
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assert(pos_ <= size_);
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memset(buf_.get() + pos_, '0', size_ - pos_);
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pos_ = size_;
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}
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void Reset() { pos_ = 0; }
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size_t Free() const { return size_ - pos_; }
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size_t Capacity() const { return size_; }
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size_t Used() const { return pos_; }
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char* Data() const { return buf_.get(); }
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private:
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std::unique_ptr<char[]> buf_;
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const size_t size_;
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size_t pos_;
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};
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//
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// CacheWriteBufferAllocator
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//
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// Buffer pool abstraction(not thread safe)
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//
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class CacheWriteBufferAllocator {
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public:
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explicit CacheWriteBufferAllocator(const uint32_t buffer_size,
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const uint32_t buffer_count)
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: buffer_size_(buffer_size) {
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MutexLock _(&lock_);
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buffer_size_ = buffer_size;
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for (uint32_t i = 0; i < buffer_count; i++) {
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auto* buf = new CacheWriteBuffer(buffer_size_);
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assert(buf);
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if (buf) {
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bufs_.push_back(buf);
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}
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}
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}
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virtual ~CacheWriteBufferAllocator() {
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MutexLock _(&lock_);
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assert(bufs_.size() * buffer_size_ == Capacity());
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for (auto* buf : bufs_) {
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delete buf;
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}
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bufs_.clear();
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}
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CacheWriteBuffer* Allocate() {
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MutexLock _(&lock_);
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if (bufs_.empty()) {
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return nullptr;
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}
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assert(!bufs_.empty());
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CacheWriteBuffer* const buf = bufs_.front();
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bufs_.pop_front();
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return buf;
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}
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void Deallocate(CacheWriteBuffer* const buf) {
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assert(buf);
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MutexLock _(&lock_);
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buf->Reset();
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bufs_.push_back(buf);
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}
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size_t Capacity() const { return bufs_.size() * buffer_size_; }
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size_t Free() const { return bufs_.size() * buffer_size_; }
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size_t BufferSize() const { return buffer_size_; }
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private:
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port::Mutex lock_; // Sync lock
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size_t buffer_size_; // Size of each buffer
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std::list<CacheWriteBuffer*> bufs_; // Buffer stash
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};
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} // namespace rocksdb
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