e90cdc2dae
Summary: Even if hard limit hits, flushing more memtable may not help cap the memory usage if already more than half data is scheduled for flush. Not triggering flush instead. Closes https://github.com/facebook/rocksdb/pull/2469 Differential Revision: D5284249 Pulled By: siying fbshipit-source-id: 8ab7ba1aba56a634dbe72b318fcab2093063972e
127 lines
4.9 KiB
C++
127 lines
4.9 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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// This source code is also licensed under the GPLv2 license found in the
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// COPYING file in the root directory of this source tree.
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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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#include "rocksdb/write_buffer_manager.h"
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#include <mutex>
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#include "util/coding.h"
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namespace rocksdb {
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#ifndef ROCKSDB_LITE
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namespace {
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const size_t kSizeDummyEntry = 1024 * 1024;
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// The key will be longer than keys for blocks in SST files so they won't
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// conflict.
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const size_t kCacheKeyPrefix = kMaxVarint64Length * 4 + 1;
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} // namespace
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struct WriteBufferManager::CacheRep {
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std::shared_ptr<Cache> cache_;
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std::mutex cache_mutex_;
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std::atomic<size_t> cache_allocated_size_;
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// The non-prefix part will be updated according to the ID to use.
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char cache_key_[kCacheKeyPrefix + kMaxVarint64Length];
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uint64_t next_cache_key_id_ = 0;
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std::vector<Cache::Handle*> dummy_handles_;
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explicit CacheRep(std::shared_ptr<Cache> cache)
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: cache_(cache), cache_allocated_size_(0) {
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memset(cache_key_, 0, kCacheKeyPrefix);
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size_t pointer_size = sizeof(const void*);
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assert(pointer_size <= kCacheKeyPrefix);
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memcpy(cache_key_, static_cast<const void*>(this), pointer_size);
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}
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Slice GetNextCacheKey() {
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memset(cache_key_ + kCacheKeyPrefix, 0, kMaxVarint64Length);
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char* end =
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EncodeVarint64(cache_key_ + kCacheKeyPrefix, next_cache_key_id_++);
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return Slice(cache_key_, static_cast<size_t>(end - cache_key_));
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}
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};
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#else
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struct WriteBufferManager::CacheRep {};
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#endif // ROCKSDB_LITE
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WriteBufferManager::WriteBufferManager(size_t _buffer_size,
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std::shared_ptr<Cache> cache)
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: buffer_size_(_buffer_size),
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mutable_limit_(buffer_size_ * 7 / 8),
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memory_used_(0),
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memory_active_(0),
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cache_rep_(nullptr) {
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#ifndef ROCKSDB_LITE
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if (cache) {
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// Construct the cache key using the pointer to this.
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cache_rep_.reset(new CacheRep(cache));
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}
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#endif // ROCKSDB_LITE
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}
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WriteBufferManager::~WriteBufferManager() {
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#ifndef ROCKSDB_LITE
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if (cache_rep_) {
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for (auto* handle : cache_rep_->dummy_handles_) {
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cache_rep_->cache_->Release(handle, true);
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}
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}
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#endif // ROCKSDB_LITE
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}
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// Should only be called from write thread
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void WriteBufferManager::ReserveMemWithCache(size_t mem) {
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#ifndef ROCKSDB_LITE
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assert(cache_rep_ != nullptr);
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// Use a mutex to protect various data structures. Can be optimzied to a
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// lock-free solution if it ends up with a performance bottleneck.
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std::lock_guard<std::mutex> lock(cache_rep_->cache_mutex_);
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size_t new_mem_used = memory_used_.load(std::memory_order_relaxed) + mem;
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memory_used_.store(new_mem_used, std::memory_order_relaxed);
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while (new_mem_used > cache_rep_->cache_allocated_size_) {
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// Expand size by at least 1MB.
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// Add a dummy record to the cache
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Cache::Handle* handle;
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cache_rep_->cache_->Insert(cache_rep_->GetNextCacheKey(), nullptr,
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kSizeDummyEntry, nullptr, &handle);
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cache_rep_->dummy_handles_.push_back(handle);
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cache_rep_->cache_allocated_size_ += kSizeDummyEntry;
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}
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#endif // ROCKSDB_LITE
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}
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void WriteBufferManager::FreeMemWithCache(size_t mem) {
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#ifndef ROCKSDB_LITE
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assert(cache_rep_ != nullptr);
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// Use a mutex to protect various data structures. Can be optimzied to a
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// lock-free solution if it ends up with a performance bottleneck.
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std::lock_guard<std::mutex> lock(cache_rep_->cache_mutex_);
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size_t new_mem_used = memory_used_.load(std::memory_order_relaxed) - mem;
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memory_used_.store(new_mem_used, std::memory_order_relaxed);
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// Gradually shrink memory costed in the block cache if the actual
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// usage is less than 3/4 of what we reserve from the block cache.
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// We do this becausse:
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// 1. we don't pay the cost of the block cache immediately a memtable is
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// freed, as block cache insert is expensive;
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// 2. eventually, if we walk away from a temporary memtable size increase,
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// we make sure shrink the memory costed in block cache over time.
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// In this way, we only shrink costed memory showly even there is enough
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// margin.
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if (new_mem_used < cache_rep_->cache_allocated_size_ / 4 * 3 &&
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cache_rep_->cache_allocated_size_ - kSizeDummyEntry > new_mem_used) {
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assert(!cache_rep_->dummy_handles_.empty());
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cache_rep_->cache_->Release(cache_rep_->dummy_handles_.back(), true);
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cache_rep_->dummy_handles_.pop_back();
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cache_rep_->cache_allocated_size_ -= kSizeDummyEntry;
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}
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#endif // ROCKSDB_LITE
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}
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} // namespace rocksdb
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