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rocksdb/cache/cache_reservation_manager.cc

178 lines
6.7 KiB

// 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.
#include "cache/cache_reservation_manager.h"
#include <cassert>
#include <cstddef>
#include <cstring>
#include <memory>
#include "cache/cache_entry_roles.h"
#include "rocksdb/cache.h"
#include "rocksdb/slice.h"
#include "rocksdb/status.h"
#include "table/block_based/block_based_table_reader.h"
#include "util/coding.h"
namespace ROCKSDB_NAMESPACE {
CacheReservationManager::CacheReservationManager(std::shared_ptr<Cache> cache,
bool delayed_decrease)
: delayed_decrease_(delayed_decrease),
cache_allocated_size_(0),
memory_used_(0) {
assert(cache != nullptr);
cache_ = cache;
std::memset(cache_key_, 0, kCacheKeyPrefixSize + kMaxVarint64Length);
EncodeVarint64(cache_key_, cache_->NewId());
}
CacheReservationManager::~CacheReservationManager() {
for (auto* handle : dummy_handles_) {
cache_->Release(handle, true);
}
}
template <CacheEntryRole R>
Status CacheReservationManager::UpdateCacheReservation(
std::size_t new_mem_used) {
memory_used_ = new_mem_used;
std::size_t cur_cache_allocated_size =
cache_allocated_size_.load(std::memory_order_relaxed);
if (new_mem_used == cur_cache_allocated_size) {
return Status::OK();
} else if (new_mem_used > cur_cache_allocated_size) {
Status s = IncreaseCacheReservation<R>(new_mem_used);
return s;
} else {
// In delayed decrease mode, we don't decrease cache reservation
// untill the memory usage is less than 3/4 of what we reserve
// in the cache.
// We do this because
// (1) Dummy entry insertion is expensive in block cache
// (2) Delayed releasing previously inserted dummy entries can save such
// expensive dummy entry insertion on memory increase in the near future,
// which is likely to happen when the memory usage is greater than or equal
// to 3/4 of what we reserve
if (delayed_decrease_ && new_mem_used >= cur_cache_allocated_size / 4 * 3) {
return Status::OK();
} else {
Status s = DecreaseCacheReservation(new_mem_used);
return s;
}
}
}
// Explicitly instantiate templates for "CacheEntryRole" values we use.
// This makes it possible to keep the template definitions in the .cc file.
template Status CacheReservationManager::UpdateCacheReservation<
CacheEntryRole::kWriteBuffer>(std::size_t new_mem_used);
template Status CacheReservationManager::UpdateCacheReservation<
CacheEntryRole::kCompressionDictionaryBuildingBuffer>(
std::size_t new_mem_used);
// For cache reservation manager unit tests
template Status CacheReservationManager::UpdateCacheReservation<
CacheEntryRole::kMisc>(std::size_t new_mem_used);
template <CacheEntryRole R>
Status CacheReservationManager::MakeCacheReservation(
std::size_t incremental_memory_used,
std::unique_ptr<CacheReservationHandle<R>>* handle) {
assert(handle != nullptr);
Status s =
UpdateCacheReservation<R>(GetTotalMemoryUsed() + incremental_memory_used);
(*handle).reset(new CacheReservationHandle<R>(incremental_memory_used,
shared_from_this()));
return s;
}
template Status
CacheReservationManager::MakeCacheReservation<CacheEntryRole::kMisc>(
std::size_t incremental_memory_used,
std::unique_ptr<CacheReservationHandle<CacheEntryRole::kMisc>>* handle);
template <CacheEntryRole R>
Status CacheReservationManager::IncreaseCacheReservation(
std::size_t new_mem_used) {
Status return_status = Status::OK();
while (new_mem_used > cache_allocated_size_.load(std::memory_order_relaxed)) {
Cache::Handle* handle = nullptr;
return_status = cache_->Insert(GetNextCacheKey(), nullptr, kSizeDummyEntry,
GetNoopDeleterForRole<R>(), &handle);
if (return_status != Status::OK()) {
return return_status;
}
dummy_handles_.push_back(handle);
cache_allocated_size_ += kSizeDummyEntry;
}
return return_status;
}
Status CacheReservationManager::DecreaseCacheReservation(
std::size_t new_mem_used) {
Status return_status = Status::OK();
// Decrease to the smallest multiple of kSizeDummyEntry that is greater than
// or equal to new_mem_used We do addition instead of new_mem_used <=
// cache_allocated_size_.load(std::memory_order_relaxed) - kSizeDummyEntry to
// avoid underflow of size_t when cache_allocated_size_ = 0
while (new_mem_used + kSizeDummyEntry <=
cache_allocated_size_.load(std::memory_order_relaxed)) {
assert(!dummy_handles_.empty());
auto* handle = dummy_handles_.back();
cache_->Release(handle, true);
dummy_handles_.pop_back();
cache_allocated_size_ -= kSizeDummyEntry;
}
return return_status;
}
std::size_t CacheReservationManager::GetTotalReservedCacheSize() {
return cache_allocated_size_.load(std::memory_order_relaxed);
}
std::size_t CacheReservationManager::GetTotalMemoryUsed() {
return memory_used_;
}
Slice CacheReservationManager::GetNextCacheKey() {
// Calling this function will have the side-effect of changing the
// underlying cache_key_ that is shared among other keys generated from this
// fucntion. Therefore please make sure the previous keys are saved/copied
// before calling this function.
std::memset(cache_key_ + kCacheKeyPrefixSize, 0, kMaxVarint64Length);
char* end =
EncodeVarint64(cache_key_ + kCacheKeyPrefixSize, next_cache_key_id_++);
return Slice(cache_key_, static_cast<std::size_t>(end - cache_key_));
}
template <CacheEntryRole R>
CacheReservationHandle<R>::CacheReservationHandle(
std::size_t incremental_memory_used,
std::shared_ptr<CacheReservationManager> cache_res_mgr)
: incremental_memory_used_(incremental_memory_used) {
assert(cache_res_mgr != nullptr);
cache_res_mgr_ = cache_res_mgr;
}
template <CacheEntryRole R>
CacheReservationHandle<R>::~CacheReservationHandle() {
assert(cache_res_mgr_ != nullptr);
assert(cache_res_mgr_->GetTotalMemoryUsed() >= incremental_memory_used_);
Status s = cache_res_mgr_->UpdateCacheReservation<R>(
cache_res_mgr_->GetTotalMemoryUsed() - incremental_memory_used_);
s.PermitUncheckedError();
}
// Explicitly instantiate templates for "CacheEntryRole" values we use.
// This makes it possible to keep the template definitions in the .cc file.
template class CacheReservationHandle<CacheEntryRole::kMisc>;
} // namespace ROCKSDB_NAMESPACE