mirror of
https://github.com/facebook/rocksdb.git
synced 2024-12-03 14:52:53 +00:00
5cb2d09d47
Summary: Summary - Refactor FilePrefetchBuffer code - Implementation: FilePrefetchBuffer maintains a deque of free buffers (free_bufs_) of size num_buffers_ and buffers (bufs_) which contains the prefetched data. Whenever a buffer is consumed or is outdated (w.r.t. to requested offset), that buffer is cleared and returned to free_bufs_. If a buffer is available in free_bufs_, it's moved to bufs_ and is sent for prefetching. num_buffers_ defines how many buffers are maintained that contains prefetched data. If num_buffers_ == 1, it's a sequential read flow. Read API will be called on that one buffer whenever the data is requested and is not in the buffer. If num_buffers_ > 1, then the data is prefetched asynchronosuly in the buffers whenever the data is consumed from the buffers and that buffer is freed. If num_buffers > 1, then requested data can be overlapping between 2 buffers. To return the continuous buffer overlap_bufs_ is used. The requested data is copied from 2 buffers to the overlap_bufs_ and overlap_bufs_ is returned to the caller. - Merged Sync and Async code flow into one in FilePrefetchBuffer. Test Plan - - Crash test passed - Unit tests - Pending - Benchmarks Pull Request resolved: https://github.com/facebook/rocksdb/pull/12097 Reviewed By: ajkr Differential Revision: D51759552 Pulled By: akankshamahajan15 fbshipit-source-id: 69a352945affac2ed22be96048d55863e0168ad5
75 lines
3 KiB
C++
75 lines
3 KiB
C++
// 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 "table/block_based/block_based_table_reader.h"
|
|
|
|
namespace ROCKSDB_NAMESPACE {
|
|
class BlockPrefetcher {
|
|
public:
|
|
explicit BlockPrefetcher(size_t compaction_readahead_size,
|
|
size_t initial_auto_readahead_size)
|
|
: compaction_readahead_size_(compaction_readahead_size),
|
|
readahead_size_(initial_auto_readahead_size),
|
|
initial_auto_readahead_size_(initial_auto_readahead_size) {}
|
|
|
|
void PrefetchIfNeeded(
|
|
const BlockBasedTable::Rep* rep, const BlockHandle& handle,
|
|
size_t readahead_size, bool is_for_compaction,
|
|
const bool no_sequential_checking, const ReadOptions& read_options,
|
|
const std::function<void(bool, uint64_t&, uint64_t&)>& readaheadsize_cb,
|
|
bool is_async_io_prefetch);
|
|
FilePrefetchBuffer* prefetch_buffer() { return prefetch_buffer_.get(); }
|
|
|
|
void UpdateReadPattern(const uint64_t& offset, const size_t& len) {
|
|
prev_offset_ = offset;
|
|
prev_len_ = len;
|
|
}
|
|
|
|
bool IsBlockSequential(const uint64_t& offset) {
|
|
return (prev_len_ == 0 || (prev_offset_ + prev_len_ == offset));
|
|
}
|
|
|
|
void ResetValues(size_t initial_auto_readahead_size) {
|
|
num_file_reads_ = 1;
|
|
// Since initial_auto_readahead_size_ can be different from
|
|
// the value passed to BlockBasedTableOptions.initial_auto_readahead_size in
|
|
// case of adaptive_readahead, so fallback the readahead_size_ to that value
|
|
// in case of reset.
|
|
initial_auto_readahead_size_ = initial_auto_readahead_size;
|
|
readahead_size_ = initial_auto_readahead_size_;
|
|
readahead_limit_ = 0;
|
|
return;
|
|
}
|
|
|
|
void SetReadaheadState(ReadaheadFileInfo::ReadaheadInfo* readahead_info) {
|
|
num_file_reads_ = readahead_info->num_file_reads;
|
|
initial_auto_readahead_size_ = readahead_info->readahead_size;
|
|
TEST_SYNC_POINT_CALLBACK("BlockPrefetcher::SetReadaheadState",
|
|
&initial_auto_readahead_size_);
|
|
}
|
|
|
|
private:
|
|
// Readahead size used in compaction, its value is used only if
|
|
// lookup_context_.caller = kCompaction.
|
|
size_t compaction_readahead_size_;
|
|
|
|
// readahead_size_ is used in non-compaction read if underlying FS supports
|
|
// prefetching.
|
|
size_t readahead_size_;
|
|
size_t readahead_limit_ = 0;
|
|
// initial_auto_readahead_size_ is used in non-compaction read if RocksDB uses
|
|
// internal prefetch buffer.
|
|
uint64_t initial_auto_readahead_size_;
|
|
uint64_t num_file_reads_ = 0;
|
|
uint64_t prev_offset_ = 0;
|
|
size_t prev_len_ = 0;
|
|
std::unique_ptr<FilePrefetchBuffer> prefetch_buffer_;
|
|
};
|
|
} // namespace ROCKSDB_NAMESPACE
|