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SubjectRe: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug
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


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