linux-kernel - Re: [patch] CFS scheduler, -v12

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Message-ID: <20070522201518.GC6113@elte.hu>
Date:	Tue, 22 May 2007 22:15:18 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Chris Friesen <cfriesen@...tel.com>
Cc:	William Lee Irwin III <wli@...omorphy.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Peter Williams <pwil3058@...pond.net.au>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] CFS scheduler, -v12


* Chris Friesen <cfriesen@...tel.com> wrote:

> Ingo Molnar wrote:
> 
> >CFS is fair even on SMP. Consider for example the worst-case 
> >3-tasks-on-2-CPUs workload on a 2-CPU box:
> >
> >  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> > 2658 mingo     20   0  1580  248  200 R   67  0.0   0:56.30 loop
> > 2656 mingo     20   0  1580  252  200 R   66  0.0   0:55.55 loop
> > 2657 mingo     20   0  1576  248  200 R   66  0.0   0:55.24 loop
> >
> >66% of CPU time for each task. The 'TIME+' column shows a 2% spread 
> >between the slowest and the fastest loop after just 1 minute of runtime 
> >(and the spread gets narrower with time).
> 
> Is there a way in CFS to tune the amount of time over which the load 
> balancer is fair?  (Of course there would be some overhead involved.)

it should be fair pretty fast (see the 10 seconds run of massive_intr) - 
so it's not 1 minute (if you were worried about that).

	Ingo
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