diff options
author | Benoit Steiner <benoit.steiner.goog@gmail.com> | 2016-03-22 15:24:23 -0700 |
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committer | Benoit Steiner <benoit.steiner.goog@gmail.com> | 2016-03-22 15:24:23 -0700 |
commit | 002cf0d1c979857e057879d8c84b92439dbcc90d (patch) | |
tree | 0a317243eb0b125176826f704ddf7c68168ecb43 /unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h | |
parent | 65a7113a36f70aeca34eac29f32b24ef865cb6e4 (diff) |
Use a single Barrier instead of a collection of Notifications to reduce the thread synchronization overhead
Diffstat (limited to 'unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h')
-rw-r--r-- | unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h | 75 |
1 files changed, 60 insertions, 15 deletions
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h b/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h index dcbef5b03..e4165bbf8 100644 --- a/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h +++ b/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h @@ -118,47 +118,82 @@ class ThreadPool : public ThreadPoolInterface { }; -// Notification is an object that allows a user to to wait for another -// thread to signal a notification that an event has occurred. -// -// Multiple threads can wait on the same Notification object. -// but only one caller must call Notify() on the object. -class Notification { +// Barrier is an object that allows one or more threads to wait until +// Notify has been called a specified number of times. +class Barrier { public: - Notification() : notified_(false) {} - ~Notification() {} + Barrier(unsigned int count) : state_(count << 1), notified_(false) { + eigen_assert(((count << 1) >> 1) == count); + } + ~Barrier() { + eigen_assert((state_>>1) == 0); + } void Notify() { + unsigned int v = state_.fetch_sub(2, std::memory_order_acq_rel) - 2; + if (v != 1) { + eigen_assert(((v + 2) & ~1) != 0); + return; // either count has not dropped to 0, or waiter is not waiting + } std::unique_lock<std::mutex> l(mu_); eigen_assert(!notified_); notified_ = true; cv_.notify_all(); } - void WaitForNotification() { + void Wait() { + unsigned int v = state_.fetch_or(1, std::memory_order_acq_rel); + if ((v >> 1) == 0) return; std::unique_lock<std::mutex> l(mu_); - cv_.wait(l, [this]() { return notified_; } ); + while (!notified_) { + cv_.wait(l); + } } private: std::mutex mu_; std::condition_variable cv_; + std::atomic<unsigned int> state_; // low bit is waiter flag bool notified_; }; + +// Notification is an object that allows a user to to wait for another +// thread to signal a notification that an event has occurred. +// +// Multiple threads can wait on the same Notification object, +// but only one caller must call Notify() on the object. +struct Notification : Barrier { + Notification() : Barrier(1) {}; +}; + + // Runs an arbitrary function and then calls Notify() on the passed in // Notification. -template <typename Function, typename... Args> struct FunctionWrapper +template <typename Function, typename... Args> struct FunctionWrapperWithNotification { static void run(Notification* n, Function f, Args... args) { f(args...); - n->Notify(); + if (n) { + n->Notify(); + } + } +}; + +template <typename Function, typename... Args> struct FunctionWrapperWithBarrier +{ + static void run(Barrier* b, Function f, Args... args) { + f(args...); + if (b) { + b->Notify(); + } } }; -static EIGEN_STRONG_INLINE void wait_until_ready(Notification* n) { +template <typename SyncType> +static EIGEN_STRONG_INLINE void wait_until_ready(SyncType* n) { if (n) { - n->WaitForNotification(); + n->Wait(); } } @@ -203,10 +238,20 @@ struct ThreadPoolDevice { EIGEN_STRONG_INLINE Notification* enqueue(Function&& f, Args&&... args) const { Notification* n = new Notification(); std::function<void()> func = - std::bind(&FunctionWrapper<Function, Args...>::run, n, f, args...); + std::bind(&FunctionWrapperWithNotification<Function, Args...>::run, n, f, args...); pool_->Schedule(func); return n; } + + template <class Function, class... Args> + EIGEN_STRONG_INLINE void enqueue_with_barrier(Barrier* b, + Function&& f, + Args&&... args) const { + std::function<void()> func = std::bind( + &FunctionWrapperWithBarrier<Function, Args...>::run, b, f, args...); + pool_->Schedule(func); + } + template <class Function, class... Args> EIGEN_STRONG_INLINE void enqueueNoNotification(Function&& f, Args&&... args) const { std::function<void()> func = std::bind(f, args...); |