Re: Interesting scheduling times - NOT
Rogier Wolff (R.E.Wolff@BitWizard.nl)
Thu, 24 Sep 1998 14:05:06 +0200 (MEST)
Richard Gooch wrote:
> Larry McVoy writes:
> > : As I've already said, you're probably not seeing the variance because
> > : you don't run with RT priority.
> >
> > Been there, tried it, the results have very low variance:
> >
> > RT: 5.42 (5.52 5.47 5.43 5.42 5.42 5.42 5.42 5.41 5.40 5.40 5.39)
> > !RT: 4.65 (4.86 4.85 4.84 4.83 4.66 4.65 4.61 4.55 4.55 4.54 4.54)
> >
> > With 10 background processes:
> >
> > RT: 11.04 (11.13 11.11 11.11 11.07 11.07 11.04 11.04 11.00 11.00 10.98 10.98)
> > !RT: 6.76 (6.99 6.80 6.79 6.79 6.76 6.76 6.75 6.51 6.49 6.48 6.47)
>
> Interesting.
>
> > : I'm left with variance (up to 50%) in the long run queue case. I can
> > : sometimes see this variance even with SCHED_OTHER. So there is still
> > : some other effect going on. Again, I don't see a variance this large
> > : with your test, so again there is something that my test is sensitive
> > : too.
> > : Using pipes and token passing doesn't change the variance, BTW.
> >
> > It does if you design the benchmark right. Look, you keep setting
> > yourself up to take a fall. You may be right about everything else,
> > but you're just dead wrong about the variance. There is no reason
> > for it to be there. It's not just my benchmark that doesn't see it,
> > every other variation of this benchmark is stable in the small
> > process case (where they are basically simulating or calling
> > sched_yield()).
>
> There is a *reason* the variance is there. The question is what is
> causing it. Glib replies like "your test is broken" don't answer the
> question. There is something different about my test that leaves it
Richard,
Could you please stop asking for other people to do a thorough analysis
of your results?
Your tests show significantly different results from the "industry
standard" lmbench benchmark. So, it is up to you to explain the
difference, if you want the linux kernel to be redesigned on the basis
of those results. You can post a message to the list, and ask if
anybody knows of any obvious explanations. The answer is 'No'.
You can hire me to do the analysis for $750 (US dollars).
Roger.
--
Actor asks a collegue: "To what do you owe your success in acting?"
Answer: "Honesty. Once you've learned how to fake that, you've got it made."
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Email: R.E.Wolff@BitWizard.nl || Tel: +31-15-2137555 || FAX: +31-15-2138217
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