38b03c840e
Summary: This ports `folly::DistributedMutex` into RocksDB. The PR includes everything else needed to compile and use DistributedMutex as a component within folly. Most files are unchanged except for some portability stuff and includes. For now, I've put this under `rocksdb/third-party`, but if there is a better folder to put this under, let me know. I also am not sure how or where to put unit tests for third-party stuff like this. It seems like gtest is included already, but I need to link with it from another third-party folder. This also includes some other common components from folly - folly/Optional - folly/ScopeGuard (In particular `SCOPE_EXIT`) - folly/synchronization/ParkingLot (A portable futex-like interface) - folly/synchronization/AtomicNotification (The standard C++ interface for futexes) - folly/Indestructible (For singletons that don't get destroyed without allocations) Pull Request resolved: https://github.com/facebook/rocksdb/pull/5642 Differential Revision: D16544439 fbshipit-source-id: 179b98b5dcddc3075926d31a30f92fd064245731
39 lines
1.6 KiB
C++
39 lines
1.6 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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#pragma once
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#include <cstdint>
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namespace folly {
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// Memory locations within the same cache line are subject to destructive
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// interference, also known as false sharing, which is when concurrent
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// accesses to these different memory locations from different cores, where at
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// least one of the concurrent accesses is or involves a store operation,
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// induce contention and harm performance.
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//
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// Microbenchmarks indicate that pairs of cache lines also see destructive
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// interference under heavy use of atomic operations, as observed for atomic
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// increment on Sandy Bridge.
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//
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// We assume a cache line size of 64, so we use a cache line pair size of 128
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// to avoid destructive interference.
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//
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// mimic: std::hardware_destructive_interference_size, C++17
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constexpr std::size_t hardware_destructive_interference_size = 128;
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// Memory locations within the same cache line are subject to constructive
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// interference, also known as true sharing, which is when accesses to some
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// memory locations induce all memory locations within the same cache line to
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// be cached, benefiting subsequent accesses to different memory locations
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// within the same cache line and heping performance.
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//
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// mimic: std::hardware_constructive_interference_size, C++17
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constexpr std::size_t hardware_constructive_interference_size = 64;
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} // namespace folly
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