Re: -mm seems significanty slower than mainline on kernbench

[Peter Williams]

Martin J. Bligh wrote:
> > > Thanks, but I have that. What do you think those vertical bars on the 
> > > graph are for? ;-) They're deviation of 5 runs. I throw away the best 
> > > and worst first.
> >
> >
> >
> > Not very good scientific practice :-)
>
>
>
> Bollocks to scientific practice ;-) It works, it produces very stable 
> results, has done for a few years now. Things like cron or sunspots can 
> kick in. Yes, yes, I did stats at University ... but the real world 
> doesn't work like that. The visuals in the graph speak for it.
>
> > Looking at the other 6 kernbench graphs, I see that it also occurs for 
> > elm3b70 but no others (including elm3b6 and elm3b67).  Are there any 
> > differences between the various elm3b systems that could explain this?
> Yes. They're all completely different architectures - there's a brief 
> description at the top of the main page. elm3b67 should be ignored, nay 
> thrown out of the window. It's an unstable POS that randomly loses 
> processors. I've removed it from the pages.
>
> elm3b70 is PPC64 (8 cpu)
> elm3b6 is x86_64.
> elm3b132 is a 4x SMP ia32 Pentium 3.
> moe is 16x NUMA-Q (ia32).
> gekko-lp1 is a 2x PPC blade.
>
> > > Use the visuals in the graph .. it's very telling. -mm is *broken*.
> > > It may well not be the same issue as last time though, I shouldn't
> > > have jumped to that conclusion.
> >
> >
> >
> > It's very hard to understand how it could be an issue on a system that 
> > doesn't have a lot of abnormally niced (i.e. non zero) tasks that are 
> > fairly active as it's now mathematically equivalent to the original in 
> > the absence of such tasks.  Do these two systems have many such tasks 
> > running?
> >
> > Would it be possible to get a run with the following patches backed out:
> >
> > +sched-modified-nice-support-for-smp-load-balancing-fix.patch
> > +sched-modified-nice-support-for-smp-load-balancing-fix-fix.patch
>
>
>
> Yup, that should prove or disprove it. It's probably something 
> completely un-scheduler-related ;-)
>
> M.

Looking at the latest results for 2.6.16-rc1-mm3, it appears to me that 
this is no longer an issue.  Do you agree?

Peter
--
Peter Williams                                   pwil3058@xxxxxxxxxxxxxx

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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