如何快速是无可争议的锁？ [英] How fast is an uncontested lock?

问题描述

和多少快/慢它比一个无可争议的原子变量（如原子c为C的> ++）操作。此外，慢多少是有争议的原子变量相对于无争议的锁？我工作的体系结构的x86-64。

And how much faster/slower it is as compared to an uncontested atomic variable (such as atomic<> of C++) operation. Also, how much slower are contested atomic variables relative to the uncontested lock? The architecture I'm working on is x86-64.

推荐答案

有GitHub上一个项目，此测量的目的的在不同的平台。不幸的是，我的硕士论文后，我从来没有真正跟进这一点，但至少基本的code是那里的时候。

There’s a project on GitHub with the purpose of measuring this on different platforms. Unfortunately, after my master thesis I never really had the time to follow up on this but at least the rudimentary code is there.

它衡量的pthreads和OpenMP锁，相比于 __ sync_fetch_and_add 内在的。

It measures pthreads and OpenMP locks, compared to the __sync_fetch_and_add intrinsic.

从我记得，我们期待锁和原子操作之间的pretty大的差别（〜一个数量级），但真正的区别竟然是非常小的。

From what I remember, we were expecting a pretty big difference between locks and atomic operations (~ an order of magnitude) but the real difference turned out to be very small.

不过，在我的系统产生的结果反映我原来的猜测，现在测即（无论是否pthreads的或使用的OpenMP）原子操作要快五倍，和一个锁定的增值业务需要大约为35ns（包括获取锁，进行增量，并且解除锁定）。

However, measuring now on my system yields results which reflect my original guess, namely that (regardless of whether pthreads or OpenMP is used) atomic operations are about five times faster, and a single locked increment operation takes about 35ns (this includes acquiring the lock, performing the increment, and releasing the lock).

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