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From: Con Kolivas <kernel@kolivas.org>
To: ck@vds.kolivas.org
Subject: Re: [ck] Re: [REPORT] cfs-v6-rc2 vs sd-0.46 vs 2.6.21-rc7
Date: Fri, 27 Apr 2007 08:59:36 +1000
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Cc: Ingo Molnar <mingo@elte.hu>, Michael Gerdau <mgd@technosis.de>,
       Nick Piggin <npiggin@suse.de>, Bill Davidsen <davidsen@tmr.com>,
       Juliusz Chroboczek <jch@pps.jussieu.fr>, Mike Galbraith <efault@gmx.de>,
       linux-kernel@vger.kernel.org,
       William Lee Irwin III <wli@holomorphy.com>,
       Peter Williams <pwil3058@bigpond.net.au>,
       Gene Heskett <gene.heskett@gmail.com>, Willy Tarreau <w@1wt.eu>,
       Thomas Gleixner <tglx@linutronix.de>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Arjan van de Ven <arjan@infradead.org>
References: <200704261312.25571.mgd@technosis.de> <20070426120723.GA4092@elte.hu>
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On Thursday 26 April 2007 22:07, Ingo Molnar wrote:
> * Michael Gerdau <mgd@technosis.de> wrote:
> > Hi list,
> >
> > find below a test comparing
> >     2.6.21-rc7 (mainline)
> >     2.6.21-rc7-sd046
> >     2.6.21-rc7-cfs-v6-rc2(*) (X @ nice 0)
> >     2.6.21-rc7-cfs-v6-rc2(*) (X @ nice -10)
> > running on a dualcore x86_64.
>
> thanks for the testing!

Very interesting indeed but fairly complicated as well.

> as a summary: i think your numbers demonstrate it nicely that the
> shorter 'timeslice length' that both CFS and SD utilizes does not have a
> measurable negative impact on your workload. To measure the total impact
> of 'timeslicing' you might want to try the exact same workload with a
> much higher 'timeslice length' of say 400 msecs, via:
>
>     echo 400000000 > /proc/sys/kernel/sched_granularity_ns  # on CFS
>     echo 400 > /proc/sys/kernel/rr_interval                 # on SD

I thought that the effective "timeslice" on CFS was double the 
sched_granularity_ns so wouldn't this make the effective timeslice double 
that of what you're setting SD to? Anyway the difference between 400 and 
800ms timeslices is unlikely to be significant so I don't mind.

-- 
-ck