On Tue, Aug 16, 2016 at 04:09:19PM -0700, H. Peter Anvin wrote:
> On August 16, 2016 10:16:35 AM PDT, Borislav Petkov <[email protected]> wrote:
> >On Tue, Aug 16, 2016 at 09:59:00AM -0700, H. Peter Anvin wrote:
> >> Dang...
> >
> >Isn't 9.3% improvement a good thing(tm) ?
>
> Yes, it's huge. The only explanation I could imagine is that scrambling %rdi
> caused the scheduler to do completely the wrong thing.
I'm questioning the validity, actually. Report says test machine was
Sandy Bridge-EP and I'd bet good money this one has POPCNT support so
how are we even hitting that __sw_hweight64() path, at all?
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Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284
(AG Nürnberg)
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