Introduce a dedicated class to represent blob values (#10571)
Summary: The patch introduces a new class called `BlobContents`, which represents a single uncompressed blob value. We currently use `std::string` for this purpose; `BlobContents` is somewhat smaller but the primary reason for a dedicated class is that it enables certain improvements and optimizations like eliding a copy when inserting a blob into the cache, using custom allocators, or more control over and better accounting of the memory usage of cached blobs (see https://github.com/facebook/rocksdb/issues/10484). (We plan to implement these in subsequent PRs.) Pull Request resolved: https://github.com/facebook/rocksdb/pull/10571 Test Plan: `make check` Reviewed By: riversand963 Differential Revision: D39000965 Pulled By: ltamasi fbshipit-source-id: f296eddf9dec4fc3e11cad525b462bdf63c78f96main
Levi Tamasi
2 years ago
committed by
Facebook GitHub Bot
parent
418b36a9bc
commit
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// Copyright (c) Meta Platforms, Inc. and affiliates.
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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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#include "db/blob/blob_contents.h" |
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#include <cassert> |
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#include "cache/cache_helpers.h" |
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namespace ROCKSDB_NAMESPACE { |
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std::unique_ptr<BlobContents> BlobContents::Create( |
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CacheAllocationPtr&& allocation, size_t size) { |
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return std::unique_ptr<BlobContents>( |
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new BlobContents(std::move(allocation), size)); |
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} |
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size_t BlobContents::SizeCallback(void* obj) { |
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assert(obj); |
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return static_cast<const BlobContents*>(obj)->size(); |
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} |
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Status BlobContents::SaveToCallback(void* from_obj, size_t from_offset, |
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size_t length, void* out) { |
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assert(from_obj); |
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const BlobContents* buf = static_cast<const BlobContents*>(from_obj); |
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assert(buf->size() >= from_offset + length); |
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memcpy(out, buf->data().data() + from_offset, length); |
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return Status::OK(); |
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} |
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void BlobContents::DeleteCallback(const Slice& key, void* value) { |
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DeleteCacheEntry<BlobContents>(key, value); |
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} |
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Cache::CacheItemHelper* BlobContents::GetCacheItemHelper() { |
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static Cache::CacheItemHelper cache_helper(&SizeCallback, &SaveToCallback, |
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&DeleteCallback); |
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return &cache_helper; |
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} |
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Status BlobContents::CreateCallback(const void* buf, size_t size, |
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void** out_obj, size_t* charge) { |
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CacheAllocationPtr allocation(new char[size]); |
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memcpy(allocation.get(), buf, size); |
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std::unique_ptr<BlobContents> obj = Create(std::move(allocation), size); |
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BlobContents* const contents = obj.release(); |
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*out_obj = contents; |
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*charge = contents->size(); |
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return Status::OK(); |
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} |
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} // namespace ROCKSDB_NAMESPACE
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// Copyright (c) Meta Platforms, Inc. and affiliates.
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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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#pragma once |
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#include <memory> |
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#include "memory/memory_allocator.h" |
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#include "rocksdb/cache.h" |
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#include "rocksdb/rocksdb_namespace.h" |
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#include "rocksdb/slice.h" |
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#include "rocksdb/status.h" |
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namespace ROCKSDB_NAMESPACE { |
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// A class representing a single uncompressed value read from a blob file.
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class BlobContents { |
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public: |
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static std::unique_ptr<BlobContents> Create(CacheAllocationPtr&& allocation, |
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size_t size); |
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BlobContents(const BlobContents&) = delete; |
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BlobContents& operator=(const BlobContents&) = delete; |
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BlobContents(BlobContents&&) = default; |
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BlobContents& operator=(BlobContents&&) = default; |
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~BlobContents() = default; |
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const Slice& data() const { return data_; } |
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size_t size() const { return data_.size(); } |
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// Callbacks for secondary cache
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static size_t SizeCallback(void* obj); |
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static Status SaveToCallback(void* from_obj, size_t from_offset, |
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size_t length, void* out); |
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static void DeleteCallback(const Slice& key, void* value); |
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static Cache::CacheItemHelper* GetCacheItemHelper(); |
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static Status CreateCallback(const void* buf, size_t size, void** out_obj, |
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size_t* charge); |
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private: |
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BlobContents(CacheAllocationPtr&& allocation, size_t size) |
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: allocation_(std::move(allocation)), data_(allocation_.get(), size) {} |
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CacheAllocationPtr allocation_; |
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Slice data_; |
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}; |
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} // namespace ROCKSDB_NAMESPACE
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