mirror of https://github.com/facebook/rocksdb.git
92 lines
3.0 KiB
C++
92 lines
3.0 KiB
C++
// Copyright (c) 2013, 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.
|
|
|
|
// Arena is an implementation of Arena class. For a request of small size,
|
|
// it allocates a block with pre-defined block size. For a request of big
|
|
// size, it uses malloc to directly get the requested size.
|
|
|
|
#pragma once
|
|
#include <cstddef>
|
|
#include <vector>
|
|
#include <assert.h>
|
|
#include <stdint.h>
|
|
#include "util/arena.h"
|
|
|
|
namespace rocksdb {
|
|
|
|
class Arena {
|
|
public:
|
|
// No copying allowed
|
|
Arena(const Arena&) = delete;
|
|
void operator=(const Arena&) = delete;
|
|
|
|
static const size_t kMinBlockSize;
|
|
static const size_t kMaxBlockSize;
|
|
|
|
explicit Arena(size_t block_size = kMinBlockSize);
|
|
~Arena();
|
|
|
|
char* Allocate(size_t bytes);
|
|
|
|
char* AllocateAligned(size_t bytes);
|
|
|
|
// Returns an estimate of the total memory usage of data allocated
|
|
// by the arena (exclude the space allocated but not yet used for future
|
|
// allocations).
|
|
size_t ApproximateMemoryUsage() const {
|
|
return blocks_memory_ + blocks_.capacity() * sizeof(char*) -
|
|
alloc_bytes_remaining_;
|
|
}
|
|
|
|
size_t MemoryAllocatedBytes() const { return blocks_memory_; }
|
|
|
|
private:
|
|
// Number of bytes allocated in one block
|
|
const size_t kBlockSize;
|
|
// Array of new[] allocated memory blocks
|
|
typedef std::vector<char*> Blocks;
|
|
Blocks blocks_;
|
|
|
|
// Stats for current active block.
|
|
// For each block, we allocate aligned memory chucks from one end and
|
|
// allocate unaligned memory chucks from the other end. Otherwise the
|
|
// memory waste for alignment will be higher if we allocate both types of
|
|
// memory from one direction.
|
|
char* unaligned_alloc_ptr_ = nullptr;
|
|
char* aligned_alloc_ptr_ = nullptr;
|
|
// How many bytes left in currently active block?
|
|
size_t alloc_bytes_remaining_ = 0;
|
|
|
|
char* AllocateFallback(size_t bytes, bool aligned);
|
|
char* AllocateNewBlock(size_t block_bytes);
|
|
|
|
// Bytes of memory in blocks allocated so far
|
|
size_t blocks_memory_ = 0;
|
|
};
|
|
|
|
inline char* Arena::Allocate(size_t bytes) {
|
|
// The semantics of what to return are a bit messy if we allow
|
|
// 0-byte allocations, so we disallow them here (we don't need
|
|
// them for our internal use).
|
|
assert(bytes > 0);
|
|
if (bytes <= alloc_bytes_remaining_) {
|
|
unaligned_alloc_ptr_ -= bytes;
|
|
alloc_bytes_remaining_ -= bytes;
|
|
return unaligned_alloc_ptr_;
|
|
}
|
|
return AllocateFallback(bytes, false /* unaligned */);
|
|
}
|
|
|
|
// check and adjust the block_size so that the return value is
|
|
// 1. in the range of [kMinBlockSize, kMaxBlockSize].
|
|
// 2. the multiple of align unit.
|
|
extern size_t OptimizeBlockSize(size_t block_size);
|
|
|
|
} // namespace rocksdb
|