Message-Id: <5.2.1.1.2.20030822065336.019d58b8@pop.gmx.net>
Date: Fri, 22 Aug 2003 07:11:26 +0200
To: Con Kolivas <kernel@kolivas.org>
From: Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH] O17int
Cc: Voluspa <lista1@comhem.se>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
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At 09:59 AM 8/22/2003 +1000, Con Kolivas wrote:
>Quoting Mike Galbraith <efault@gmx.de>:
>
> > > > The most generally effective form of the "down-shift" anti-starvation
> > > > tactic that I've tried, is to periodically check the head of all queues
> > > > below current position (can do very quickly), and actively select the
> > > > oldest task who hasn't run since some defined deadline.  Queues are
> > > > serviced based upon priority most of the time, and based upon age some
> > of
> > > > the time.
> > >
> > >Hmm also sounds fudgy.
> >
> > Yeah.  I crossbred it with a ~deadline scheduler, and created a mutt.
>
>But how did this mutt perform?

At the time, I was more concerned by the very long semaphore hold times I 
was seeing than anything else.  That it helped quite a lot.  It didn't hurt 
throughput in any way I could see, and it improved irman's latency 
numbers.  (process load was routinely hitting ~1.5 seconds max latency at 
the time, that tree cut it to roughly 400-500ms iirc)  Just like anything 
else that increases fairness though, it hurt X feel somewhat in the 
presence of load.

         -Mike 

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