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SubjectRe: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs

* Borislav Petkov <bp@alien8.de> wrote:

> plain 3.19:
>
> 234.681331200 seconds time elapsed ( +- 0.15% )
>
> eagerfpu=ENABLE
>
> 234.066525648 seconds time elapsed ( +- 0.19% )

hm, a win of more than 600 milliseconds - more than I'd
have expected.

I really want to believe this, but I worry about the
systematic boot-to-boot noise though, which cannot be
eliminated via --repeat 10.

Would it be possible to add a simple runtime debug switch
to switch between the two FPU modes dynamically via a
sysctl?

It should not crash tasks I think if it's flipped around on
a reasonably idle system, so should allow much better
apples-to-apples comparisons with the same kind of page
cache layout, etc.

Thanks,

Ingo


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