Commit d5dd5107 authored by Yedidya Feldblum's avatar Yedidya Feldblum Committed by Facebook Github Bot

Move folly/MicroSpinLock.h to folly/synchronization/

Reviewed By: igorsugak

Differential Revision: D7078903

fbshipit-source-id: 13cdc49369f24cdadc3f9405d1ce609a79ff8988
parent 306be9f1
...@@ -33,8 +33,8 @@ ...@@ -33,8 +33,8 @@
#include <glog/logging.h> #include <glog/logging.h>
#include <folly/Memory.h> #include <folly/Memory.h>
#include <folly/MicroSpinLock.h>
#include <folly/ThreadLocal.h> #include <folly/ThreadLocal.h>
#include <folly/synchronization/MicroSpinLock.h>
namespace folly { namespace detail { namespace folly { namespace detail {
......
...@@ -131,7 +131,7 @@ Sample usage: ...@@ -131,7 +131,7 @@ Sample usage:
#include <folly/ConcurrentSkipList-inl.h> #include <folly/ConcurrentSkipList-inl.h>
#include <folly/Likely.h> #include <folly/Likely.h>
#include <folly/Memory.h> #include <folly/Memory.h>
#include <folly/MicroSpinLock.h> #include <folly/synchronization/MicroSpinLock.h>
namespace folly { namespace folly {
......
...@@ -438,6 +438,7 @@ nobase_follyinclude_HEADERS = \ ...@@ -438,6 +438,7 @@ nobase_follyinclude_HEADERS = \
synchronization/Baton.h \ synchronization/Baton.h \
synchronization/CallOnce.h \ synchronization/CallOnce.h \
synchronization/LifoSem.h \ synchronization/LifoSem.h \
synchronization/MicroSpinLock.h \
synchronization/ParkingLot.h \ synchronization/ParkingLot.h \
synchronization/PicoSpinLock.h \ synchronization/PicoSpinLock.h \
synchronization/RWSpinLock.h \ synchronization/RWSpinLock.h \
......
/* /*
* Copyright 2015-present Facebook, Inc. * Copyright 2011-present Facebook, Inc.
* *
* Licensed under the Apache License, Version 2.0 (the "License"); * Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License. * you may not use this file except in compliance with the License.
...@@ -14,145 +14,4 @@ ...@@ -14,145 +14,4 @@
* limitations under the License. * limitations under the License.
*/ */
/* #include <folly/synchronization/MicroSpinLock.h> // @shim
* N.B. You most likely do _not_ want to use MicroSpinLock or any
* other kind of spinlock. Consider MicroLock instead.
*
* In short, spinlocks in preemptive multi-tasking operating systems
* have serious problems and fast mutexes like std::mutex are almost
* certainly the better choice, because letting the OS scheduler put a
* thread to sleep is better for system responsiveness and throughput
* than wasting a timeslice repeatedly querying a lock held by a
* thread that's blocked, and you can't prevent userspace
* programs blocking.
*
* Spinlocks in an operating system kernel make much more sense than
* they do in userspace.
*/
#pragma once
/*
* @author Keith Adams <kma@fb.com>
* @author Jordan DeLong <delong.j@fb.com>
*/
#include <array>
#include <atomic>
#include <cassert>
#include <cstdint>
#include <mutex>
#include <type_traits>
#include <folly/Portability.h>
#include <folly/lang/Align.h>
#include <folly/synchronization/detail/Sleeper.h>
namespace folly {
/*
* A really, *really* small spinlock for fine-grained locking of lots
* of teeny-tiny data.
*
* Zero initializing these is guaranteed to be as good as calling
* init(), since the free state is guaranteed to be all-bits zero.
*
* This class should be kept a POD, so we can used it in other packed
* structs (gcc does not allow __attribute__((__packed__)) on structs that
* contain non-POD data). This means avoid adding a constructor, or
* making some members private, etc.
*/
struct MicroSpinLock {
enum { FREE = 0, LOCKED = 1 };
// lock_ can't be std::atomic<> to preserve POD-ness.
uint8_t lock_;
// Initialize this MSL. It is unnecessary to call this if you
// zero-initialize the MicroSpinLock.
void init() {
payload()->store(FREE);
}
bool try_lock() {
return cas(FREE, LOCKED);
}
void lock() {
detail::Sleeper sleeper;
do {
while (payload()->load() != FREE) {
sleeper.wait();
}
} while (!try_lock());
assert(payload()->load() == LOCKED);
}
void unlock() {
assert(payload()->load() == LOCKED);
payload()->store(FREE, std::memory_order_release);
}
private:
std::atomic<uint8_t>* payload() {
return reinterpret_cast<std::atomic<uint8_t>*>(&this->lock_);
}
bool cas(uint8_t compare, uint8_t newVal) {
return std::atomic_compare_exchange_strong_explicit(payload(), &compare, newVal,
std::memory_order_acquire,
std::memory_order_relaxed);
}
};
static_assert(
std::is_pod<MicroSpinLock>::value,
"MicroSpinLock must be kept a POD type.");
//////////////////////////////////////////////////////////////////////
/**
* Array of spinlocks where each one is padded to prevent false sharing.
* Useful for shard-based locking implementations in environments where
* contention is unlikely.
*/
// TODO: generate it from configure (`getconf LEVEL1_DCACHE_LINESIZE`)
#define FOLLY_CACHE_LINE_SIZE 64
template <class T, size_t N>
struct alignas(max_align_v) SpinLockArray {
T& operator[](size_t i) {
return data_[i].lock;
}
const T& operator[](size_t i) const {
return data_[i].lock;
}
constexpr size_t size() const { return N; }
private:
struct PaddedSpinLock {
PaddedSpinLock() : lock() {}
T lock;
char padding[FOLLY_CACHE_LINE_SIZE - sizeof(T)];
};
static_assert(sizeof(PaddedSpinLock) == FOLLY_CACHE_LINE_SIZE,
"Invalid size of PaddedSpinLock");
// Check if T can theoretically cross a cache line.
static_assert(
max_align_v > 0 && FOLLY_CACHE_LINE_SIZE % max_align_v == 0 &&
sizeof(T) <= max_align_v,
"T can cross cache line boundaries");
char padding_[FOLLY_CACHE_LINE_SIZE];
std::array<PaddedSpinLock, N> data_;
};
//////////////////////////////////////////////////////////////////////
typedef std::lock_guard<MicroSpinLock> MSLGuard;
//////////////////////////////////////////////////////////////////////
} // namespace folly
...@@ -28,7 +28,6 @@ ...@@ -28,7 +28,6 @@
#include <folly/Exception.h> #include <folly/Exception.h>
#include <folly/Function.h> #include <folly/Function.h>
#include <folly/MicroSpinLock.h>
#include <folly/Portability.h> #include <folly/Portability.h>
#include <folly/ScopeGuard.h> #include <folly/ScopeGuard.h>
#include <folly/SharedMutex.h> #include <folly/SharedMutex.h>
...@@ -36,6 +35,7 @@ ...@@ -36,6 +35,7 @@
#include <folly/detail/AtFork.h> #include <folly/detail/AtFork.h>
#include <folly/memory/Malloc.h> #include <folly/memory/Malloc.h>
#include <folly/portability/PThread.h> #include <folly/portability/PThread.h>
#include <folly/synchronization/MicroSpinLock.h>
#include <folly/detail/StaticSingletonManager.h> #include <folly/detail/StaticSingletonManager.h>
......
...@@ -24,7 +24,6 @@ ...@@ -24,7 +24,6 @@
#include <folly/Executor.h> #include <folly/Executor.h>
#include <folly/Function.h> #include <folly/Function.h>
#include <folly/MicroSpinLock.h>
#include <folly/Optional.h> #include <folly/Optional.h>
#include <folly/ScopeGuard.h> #include <folly/ScopeGuard.h>
#include <folly/Try.h> #include <folly/Try.h>
...@@ -32,6 +31,7 @@ ...@@ -32,6 +31,7 @@
#include <folly/futures/FutureException.h> #include <folly/futures/FutureException.h>
#include <folly/futures/detail/FSM.h> #include <folly/futures/detail/FSM.h>
#include <folly/lang/Exception.h> #include <folly/lang/Exception.h>
#include <folly/synchronization/MicroSpinLock.h>
#include <folly/io/async/Request.h> #include <folly/io/async/Request.h>
......
...@@ -19,7 +19,7 @@ ...@@ -19,7 +19,7 @@
#include <atomic> #include <atomic>
#include <mutex> #include <mutex>
#include <folly/MicroSpinLock.h> #include <folly/synchronization/MicroSpinLock.h>
namespace folly { namespace folly {
namespace futures { namespace futures {
......
/*
* Copyright 2015-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* N.B. You most likely do _not_ want to use MicroSpinLock or any
* other kind of spinlock. Consider MicroLock instead.
*
* In short, spinlocks in preemptive multi-tasking operating systems
* have serious problems and fast mutexes like std::mutex are almost
* certainly the better choice, because letting the OS scheduler put a
* thread to sleep is better for system responsiveness and throughput
* than wasting a timeslice repeatedly querying a lock held by a
* thread that's blocked, and you can't prevent userspace
* programs blocking.
*
* Spinlocks in an operating system kernel make much more sense than
* they do in userspace.
*/
#pragma once
/*
* @author Keith Adams <kma@fb.com>
* @author Jordan DeLong <delong.j@fb.com>
*/
#include <array>
#include <atomic>
#include <cassert>
#include <cstdint>
#include <mutex>
#include <type_traits>
#include <folly/Portability.h>
#include <folly/lang/Align.h>
#include <folly/synchronization/detail/Sleeper.h>
namespace folly {
/*
* A really, *really* small spinlock for fine-grained locking of lots
* of teeny-tiny data.
*
* Zero initializing these is guaranteed to be as good as calling
* init(), since the free state is guaranteed to be all-bits zero.
*
* This class should be kept a POD, so we can used it in other packed
* structs (gcc does not allow __attribute__((__packed__)) on structs that
* contain non-POD data). This means avoid adding a constructor, or
* making some members private, etc.
*/
struct MicroSpinLock {
enum { FREE = 0, LOCKED = 1 };
// lock_ can't be std::atomic<> to preserve POD-ness.
uint8_t lock_;
// Initialize this MSL. It is unnecessary to call this if you
// zero-initialize the MicroSpinLock.
void init() {
payload()->store(FREE);
}
bool try_lock() {
return cas(FREE, LOCKED);
}
void lock() {
detail::Sleeper sleeper;
do {
while (payload()->load() != FREE) {
sleeper.wait();
}
} while (!try_lock());
assert(payload()->load() == LOCKED);
}
void unlock() {
assert(payload()->load() == LOCKED);
payload()->store(FREE, std::memory_order_release);
}
private:
std::atomic<uint8_t>* payload() {
return reinterpret_cast<std::atomic<uint8_t>*>(&this->lock_);
}
bool cas(uint8_t compare, uint8_t newVal) {
return std::atomic_compare_exchange_strong_explicit(payload(), &compare, newVal,
std::memory_order_acquire,
std::memory_order_relaxed);
}
};
static_assert(
std::is_pod<MicroSpinLock>::value,
"MicroSpinLock must be kept a POD type.");
//////////////////////////////////////////////////////////////////////
/**
* Array of spinlocks where each one is padded to prevent false sharing.
* Useful for shard-based locking implementations in environments where
* contention is unlikely.
*/
// TODO: generate it from configure (`getconf LEVEL1_DCACHE_LINESIZE`)
#define FOLLY_CACHE_LINE_SIZE 64
template <class T, size_t N>
struct alignas(max_align_v) SpinLockArray {
T& operator[](size_t i) {
return data_[i].lock;
}
const T& operator[](size_t i) const {
return data_[i].lock;
}
constexpr size_t size() const { return N; }
private:
struct PaddedSpinLock {
PaddedSpinLock() : lock() {}
T lock;
char padding[FOLLY_CACHE_LINE_SIZE - sizeof(T)];
};
static_assert(sizeof(PaddedSpinLock) == FOLLY_CACHE_LINE_SIZE,
"Invalid size of PaddedSpinLock");
// Check if T can theoretically cross a cache line.
static_assert(
max_align_v > 0 && FOLLY_CACHE_LINE_SIZE % max_align_v == 0 &&
sizeof(T) <= max_align_v,
"T can cross cache line boundaries");
char padding_[FOLLY_CACHE_LINE_SIZE];
std::array<PaddedSpinLock, N> data_;
};
//////////////////////////////////////////////////////////////////////
typedef std::lock_guard<MicroSpinLock> MSLGuard;
//////////////////////////////////////////////////////////////////////
} // namespace folly
...@@ -34,7 +34,7 @@ ...@@ -34,7 +34,7 @@
*/ */
#include <folly/MicroLock.h> #include <folly/MicroLock.h>
#include <folly/MicroSpinLock.h> #include <folly/synchronization/MicroSpinLock.h>
#include <folly/Portability.h> #include <folly/Portability.h>
#if FOLLY_X64 || FOLLY_AARCH64 || FOLLY_PPC64 #if FOLLY_X64 || FOLLY_AARCH64 || FOLLY_PPC64
......
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