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// 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 "rocksdb/cache.h"
#include "rocksdb/slice.h"
#include "rocksdb/status.h"
#include "table/block_based/reader_common.h"
#include "util/coding.h"
namespace ROCKSDB_NAMESPACE {
template <CacheEntryRole R>
CacheReservationManagerImpl<R>::CacheReservationHandle::CacheReservationHandle(
std::size_t incremental_memory_used,
std::shared_ptr<CacheReservationManagerImpl> cache_res_mgr)
: incremental_memory_used_(incremental_memory_used) {
assert(cache_res_mgr);
cache_res_mgr_ = cache_res_mgr;
}
template <CacheEntryRole R>
CacheReservationManagerImpl<
R>::CacheReservationHandle::~CacheReservationHandle() {
Status s = cache_res_mgr_->ReleaseCacheReservation(incremental_memory_used_);
s.PermitUncheckedError();
}
template <CacheEntryRole R>
CacheReservationManagerImpl<R>::CacheReservationManagerImpl(
std::shared_ptr<Cache> cache, bool delayed_decrease)
: cache_(cache),
delayed_decrease_(delayed_decrease),
cache_allocated_size_(0),
memory_used_(0) {
assert(cache != nullptr);
}
template <CacheEntryRole R>
CacheReservationManagerImpl<R>::~CacheReservationManagerImpl() {
for (auto* handle : dummy_handles_) {
cache_.ReleaseAndEraseIfLastRef(handle);
}
}
template <CacheEntryRole R>
Status CacheReservationManagerImpl<R>::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(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;
}
}
}
template <CacheEntryRole R>
Status CacheReservationManagerImpl<R>::MakeCacheReservation(
std::size_t incremental_memory_used,
std::unique_ptr<CacheReservationManager::CacheReservationHandle>* handle) {
assert(handle);
Status s =
UpdateCacheReservation(GetTotalMemoryUsed() + incremental_memory_used);
(*handle).reset(new CacheReservationManagerImpl::CacheReservationHandle(
incremental_memory_used,
std::enable_shared_from_this<
CacheReservationManagerImpl<R>>::shared_from_this()));
return s;
}
template <CacheEntryRole R>
Status CacheReservationManagerImpl<R>::ReleaseCacheReservation(
std::size_t incremental_memory_used) {
assert(GetTotalMemoryUsed() >= incremental_memory_used);
std::size_t updated_total_mem_used =
GetTotalMemoryUsed() - incremental_memory_used;
Status s = UpdateCacheReservation(updated_total_mem_used);
return s;
}
template <CacheEntryRole R>
Status CacheReservationManagerImpl<R>::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(), kSizeDummyEntry, &handle);
if (return_status != Status::OK()) {
return return_status;
}
dummy_handles_.push_back(handle);
cache_allocated_size_ += kSizeDummyEntry;
}
return return_status;
}
template <CacheEntryRole R>
Status CacheReservationManagerImpl<R>::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_.ReleaseAndEraseIfLastRef(handle);
dummy_handles_.pop_back();
cache_allocated_size_ -= kSizeDummyEntry;
}
return return_status;
}
template <CacheEntryRole R>
std::size_t CacheReservationManagerImpl<R>::GetTotalReservedCacheSize() {
return cache_allocated_size_.load(std::memory_order_relaxed);
}
template <CacheEntryRole R>
std::size_t CacheReservationManagerImpl<R>::GetTotalMemoryUsed() {
return memory_used_;
}
template <CacheEntryRole R>
Slice CacheReservationManagerImpl<R>::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.
cache_key_ = CacheKey::CreateUniqueForCacheLifetime(cache_.get());
return cache_key_.AsSlice();
}
template <CacheEntryRole R>
const Cache::CacheItemHelper*
CacheReservationManagerImpl<R>::TEST_GetCacheItemHelperForRole() {
return CacheInterface::GetHelper();
}
template class CacheReservationManagerImpl<
CacheEntryRole::kBlockBasedTableReader>;
template class CacheReservationManagerImpl<
CacheEntryRole::kCompressionDictionaryBuildingBuffer>;
template class CacheReservationManagerImpl<CacheEntryRole::kFilterConstruction>;
template class CacheReservationManagerImpl<CacheEntryRole::kMisc>;
template class CacheReservationManagerImpl<CacheEntryRole::kWriteBuffer>;
template class CacheReservationManagerImpl<CacheEntryRole::kFileMetadata>;
template class CacheReservationManagerImpl<CacheEntryRole::kBlobCache>;
} // namespace ROCKSDB_NAMESPACE
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