高效的内存屏障 [英] Efficient Memory Barriers

问题描述

我有一个多线程应用程序，其中每个线程都有一个整数类型的变量.这些变量在程序执行期间增加.在代码的某些点，一个线程将其计数变量与其他线程的计数变量进行比较.

I have a multithreaded application, where each thread has a variable of integer type. These variables are incremented during execution of the program. At certain points in the code, a thread compares its counting variable with those of the other threads.

现在，由于我们知道在多核上运行的线程可能会无序执行，因此一个线程可能无法读取其他线程的预期计数器值.为了解决这个问题，一种方法是使用原子变量，例如C ++ 11的std :: atomic<>.但是，在每个计数器增量处执行内存隔离会大大降低程序的速度.

Now since, we know that threads running on multicore might execute out of order, a thread might not read the expected counter values of the other threads. To solve this problem, one way is to use atomic variable, such as std::atomic<> of C++11. However, performing a memory fence at each increment of counters will significantly slow down the program.

现在我要做的是，当一个线程将要读取其他线程的计数器时，仅创建一个内存隔离，然后在内存中更新所有线程的计数器.如何用C ++做到这一点.我正在使用Linux和g ++.

Now what I want to do is that when a thread is about to read other thread's counter, only then a memory fence is created and counters of all the threads are updated in the memory at that point. How can this be done in C++. I am using Linux and g++.

推荐答案

C ++ 11标准库包括对<atomic>和std::atomic_thread_fence中的篱笆的支持.

The C++11 standard library includes support for fences in <atomic> with std::atomic_thread_fence.

调用此方法会调用完整的篱笆:

Calling this invokes a full fence:

std::atomic_thread_fence(std::memory_order_seq_cst);

如果您只想发射获取或释放栅栏，则可以使用std:memory_order_acquire和std::memory_order_release代替.

If you want to emit only an acquire or only a release fence, you can use std:memory_order_acquire and std::memory_order_release instead.

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