lkml.org 
[lkml]   [2016]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement
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.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

\
 
 \ /
  Last update: 2016-09-17 09:57    [W:0.073 / U:2.752 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site