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// 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,
Env::IOPriority rate_limiter_priority);
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 if underlying FS supports prefetching.
size_t readahead_size_;
size_t readahead_limit_ = 0;
// initial_auto_readahead_size_ is used 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
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