Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptiblekernel and CPU hotplug

[H. Peter Anvin]

Mathieu Desnoyers wrote:
> I can't argue about the benefit of using VM CPU pinning to manage
> resources because I don't use it myself, but I ran some tests out of
> curiosity to find if uncontended locks were that cheap, and it turns out
> they aren't. Here are the results :
>
> Xeon 2.0GHz
>
> Summary
>
> make -j1 kernel/      33.94 +/- 0.07         34.91 +/- 0.27      2.8 %
> hackbench 50           2.99 +/- 0.01          3.74 +/- 0.01     25.1 %
>
> 1 CPU, replace smp lock prefixes with DS segment selector prefixes
> 1 CPU, noreplace-smp

For reference, could you also compare replace smp lock with NOPs?

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/