fc9d4071f0
Summary: Fixes a major performance regression in 6.26, where extra CPU is spent in SliceTransform::AsString when reads involve a prefix_extractor (Get, MultiGet, Seek). Common case performance is now better than 6.25. This change creates a "fast path" for verifying that the current prefix extractor is unchanged and compatible with what was used to generate a table file. This fast path detects the common case by pointer comparison on the current prefix_extractor and a "known good" prefix extractor (if applicable) that is saved at the time the table reader is opened. The "known good" prefix extractor is saved as another shared_ptr copy (in an existing field, however) to ensure the pointer is not recycled. When the prefix_extractor has changed to a different instance but same compatible configuration (rare, odd), performance is still a regression compared to 6.25, but this is likely acceptable because of the oddity of such a case. The performance of incompatible prefix_extractor is essentially unchanged. Also fixed a minor case (ForwardIterator) where a prefix_extractor could be used via a raw pointer after being freed as a shared_ptr, if replaced via SetOptions. Pull Request resolved: https://github.com/facebook/rocksdb/pull/9407 Test Plan: ## Performance Populate DB with `TEST_TMPDIR=/dev/shm/rocksdb ./db_bench -benchmarks=fillrandom -num=10000000 -disable_wal=1 -write_buffer_size=10000000 -bloom_bits=16 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -prefix_size=12` Running head-to-head comparisons simultaneously with `TEST_TMPDIR=/dev/shm/rocksdb ./db_bench -use_existing_db -readonly -benchmarks=seekrandom -num=10000000 -duration=20 -disable_wal=1 -bloom_bits=16 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -prefix_size=12` Below each is compared by ops/sec vs. baseline which is version 6.25 (multiple baseline runs because of variable machine load) v6.26: 4833 vs. 6698 (<- major regression!) v6.27: 4737 vs. 6397 (still) New: 6704 vs. 6461 (better than baseline in common case) Disabled fastpath: 4843 vs. 6389 (e.g. if prefix extractor instance changes but is still compatible) Changed prefix size (no usable filter) in new: 787 vs. 5927 Changed prefix size (no usable filter) in new & baseline: 773 vs. 784 Reviewed By: mrambacher Differential Revision: D33677812 Pulled By: pdillinger fbshipit-source-id: 571d9711c461fb97f957378a061b7e7dbc4d6a76
70 lines
2.3 KiB
C++
70 lines
2.3 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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#pragma once
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#include <memory>
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#include "rocksdb/file_system.h"
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#include "rocksdb/slice_transform.h"
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namespace ROCKSDB_NAMESPACE {
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struct ImmutableCFOptions;
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class TableCache;
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class VersionStorageInfo;
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class VersionEdit;
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struct FileMetaData;
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class InternalStats;
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class Version;
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class VersionSet;
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class ColumnFamilyData;
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// A helper class so we can efficiently apply a whole sequence
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// of edits to a particular state without creating intermediate
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// Versions that contain full copies of the intermediate state.
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class VersionBuilder {
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public:
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VersionBuilder(const FileOptions& file_options,
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const ImmutableCFOptions* ioptions, TableCache* table_cache,
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VersionStorageInfo* base_vstorage, VersionSet* version_set);
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~VersionBuilder();
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bool CheckConsistencyForNumLevels();
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Status Apply(const VersionEdit* edit);
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Status SaveTo(VersionStorageInfo* vstorage) const;
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Status LoadTableHandlers(
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InternalStats* internal_stats, int max_threads,
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bool prefetch_index_and_filter_in_cache, bool is_initial_load,
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const std::shared_ptr<const SliceTransform>& prefix_extractor,
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size_t max_file_size_for_l0_meta_pin);
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uint64_t GetMinOldestBlobFileNumber() const;
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private:
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class Rep;
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std::unique_ptr<Rep> rep_;
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};
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// A wrapper of version builder which references the current version in
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// constructor and unref it in the destructor.
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// Both of the constructor and destructor need to be called inside DB Mutex.
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class BaseReferencedVersionBuilder {
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public:
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explicit BaseReferencedVersionBuilder(ColumnFamilyData* cfd);
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BaseReferencedVersionBuilder(ColumnFamilyData* cfd, Version* v);
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~BaseReferencedVersionBuilder();
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VersionBuilder* version_builder() const { return version_builder_.get(); }
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private:
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std::unique_ptr<VersionBuilder> version_builder_;
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Version* version_;
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};
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} // namespace ROCKSDB_NAMESPACE
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