Messages in this thread | | | Date | Wed, 17 Aug 2016 07:46:05 +0200 | From | Borislav Petkov <> | Subject | Re: [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement |
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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 <bp@suse.de> 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?
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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