8ed680bdb0
Summary: Add new API WriteBufferManager::dummy_entries_in_cache_usage() which reports the dummy entries size stored in cache to account for DataBlocks in WriteBufferManager. Pull Request resolved: https://github.com/facebook/rocksdb/pull/7837 Test Plan: Updated test ./write_buffer_manager_test Reviewed By: ajkr Differential Revision: D25794312 Pulled By: akankshamahajan15 fbshipit-source-id: 197f5e8701e3dc57a7df72dab1735624f90daf4b
107 lines
3.4 KiB
C++
107 lines
3.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// WriteBufferManager is for managing memory allocation for one or more
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// MemTables.
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#pragma once
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#include <atomic>
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#include <cstddef>
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#include "rocksdb/cache.h"
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namespace ROCKSDB_NAMESPACE {
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class WriteBufferManager {
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public:
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// _buffer_size = 0 indicates no limit. Memory won't be capped.
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// memory_usage() won't be valid and ShouldFlush() will always return true.
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// if `cache` is provided, we'll put dummy entries in the cache and cost
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// the memory allocated to the cache. It can be used even if _buffer_size = 0.
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explicit WriteBufferManager(size_t _buffer_size,
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std::shared_ptr<Cache> cache = {});
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// No copying allowed
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WriteBufferManager(const WriteBufferManager&) = delete;
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WriteBufferManager& operator=(const WriteBufferManager&) = delete;
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~WriteBufferManager();
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bool enabled() const { return buffer_size_ != 0; }
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bool cost_to_cache() const { return cache_rep_ != nullptr; }
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// Only valid if enabled()
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size_t memory_usage() const {
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return memory_used_.load(std::memory_order_relaxed);
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}
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size_t mutable_memtable_memory_usage() const {
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return memory_active_.load(std::memory_order_relaxed);
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}
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size_t dummy_entries_in_cache_usage() const {
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return dummy_size_.load(std::memory_order_relaxed);
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}
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size_t buffer_size() const { return buffer_size_; }
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// Should only be called from write thread
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bool ShouldFlush() const {
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if (enabled()) {
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if (mutable_memtable_memory_usage() > mutable_limit_) {
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return true;
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}
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if (memory_usage() >= buffer_size_ &&
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mutable_memtable_memory_usage() >= buffer_size_ / 2) {
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// If the memory exceeds the buffer size, we trigger more aggressive
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// flush. But if already more than half memory is being flushed,
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// triggering more flush may not help. We will hold it instead.
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return true;
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}
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}
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return false;
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}
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void ReserveMem(size_t mem) {
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if (cache_rep_ != nullptr) {
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ReserveMemWithCache(mem);
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} else if (enabled()) {
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memory_used_.fetch_add(mem, std::memory_order_relaxed);
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}
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if (enabled()) {
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memory_active_.fetch_add(mem, std::memory_order_relaxed);
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}
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}
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// We are in the process of freeing `mem` bytes, so it is not considered
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// when checking the soft limit.
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void ScheduleFreeMem(size_t mem) {
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if (enabled()) {
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memory_active_.fetch_sub(mem, std::memory_order_relaxed);
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}
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}
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void FreeMem(size_t mem) {
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if (cache_rep_ != nullptr) {
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FreeMemWithCache(mem);
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} else if (enabled()) {
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memory_used_.fetch_sub(mem, std::memory_order_relaxed);
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}
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}
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private:
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const size_t buffer_size_;
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const size_t mutable_limit_;
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std::atomic<size_t> memory_used_;
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// Memory that hasn't been scheduled to free.
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std::atomic<size_t> memory_active_;
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std::atomic<size_t> dummy_size_;
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struct CacheRep;
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std::unique_ptr<CacheRep> cache_rep_;
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void ReserveMemWithCache(size_t mem);
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void FreeMemWithCache(size_t mem);
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};
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} // namespace ROCKSDB_NAMESPACE
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