rocksdb/db/writebuffer.h
2016-02-09 15:12:00 -08:00

53 lines
1.5 KiB
C++

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same 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.
//
// WriteBuffer is for managing memory allocation for one or more MemTables.
#pragma once
#include <atomic>
namespace rocksdb {
class WriteBuffer {
public:
explicit WriteBuffer(size_t _buffer_size)
: buffer_size_(_buffer_size), memory_used_(0) {}
~WriteBuffer() {}
size_t memory_usage() const {
return memory_used_.load(std::memory_order_relaxed);
}
size_t buffer_size() const { return buffer_size_; }
// Should only be called from write thread
bool ShouldFlush() const {
return buffer_size() > 0 && memory_usage() >= buffer_size();
}
// Should only be called from write thread
void ReserveMem(size_t mem) {
memory_used_.fetch_add(mem, std::memory_order_relaxed);
}
void FreeMem(size_t mem) {
memory_used_.fetch_sub(mem, std::memory_order_relaxed);
}
private:
const size_t buffer_size_;
std::atomic<size_t> memory_used_;
// No copying allowed
WriteBuffer(const WriteBuffer&);
void operator=(const WriteBuffer&);
};
} // namespace rocksdb