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

From: Ingo Molnar
Date: Sat Feb 21 2015 - 13:35:06 EST

* Borislav Petkov <bp@xxxxxxxxx> 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

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.


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