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SubjectRe: [RFC 00/17] Pile o' entry stack changes

* Andy Lutomirski <luto@kernel.org> wrote:

> On Wed, Sep 6, 2017 at 3:16 PM, Andi Kleen <andi@firstfloor.org> wrote:
> > Andy Lutomirski <luto@kernel.org> writes:
> >>
> >> - Lots of people (Linus included) have asked to convert the entry
> >> code to pop registers on exit instead of movqing them off the
> >> stack. This makes a bunch of progress in that direction.
> >
> > You should benchmark it on Atoms. Likely it's a regression there
> > because they don't have the special PUSH/POP acceleration.
>
> I'm not entirely sure this is a worthwhile reason. Atom will lose a
> few cycles due to POP throughput, but there's a lot less decode
> bandwidth needed and we save a cache line or two.

I think we can also safely assume that Atom will eventually either join the
21st century or die out - mild Atom micro-costs are not a good reason to
complicate the entry code...

Thanks,

Ingo

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