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Message-Id: <1157033863.5789.42.camel@Homer.simpson.net>
Date: Thu, 31 Aug 2006 14:17:43 +0000
From: Mike Galbraith <efault@....de>
To: Martin Ohlin <martin.ohlin@...trol.lth.se>
Cc: Peter Williams <pwil3058@...pond.net.au>, balbir@...ibm.com,
linux-kernel@...r.kernel.org
Subject: Re: A nice CPU resource controller
On Thu, 2006-08-31 at 12:35 +0200, Martin Ohlin wrote:
> Mike Galbraith wrote:
> > On Thu, 2006-08-31 at 06:53 +0000, Mike Galbraith wrote:
> >> On Thu, 2006-08-31 at 11:07 +1000, Peter Williams wrote:
> >>
> >>> But your implication here is valid. It is better to fiddle with the
> >>> dynamic priorities than with nice as this leaves nice for its primary
> >>> purpose of enabling the sysadmin to effect the allocation of CPU
> >>> resources based on external considerations.
> >> I don't understand. It _is_ the administrator fiddling with nice based
> >> on external considerations. It just steadies the administrator's hand.
> >
> > When extended to groups, I see your point. The admin would lose his
> > ability to apportion bandwidth _within_ the group because he's already
> > turned his only knob. That is going to be just as much of a problem for
> > other methods though, and is just a question of how much complexity you
> > want to pay to achieve fine grained control.
>
> I do not see the problem. Let's say I create a group of three tasks and
> give it 50% of the CPU bandwidth (perhaps by using the same nice value
> for all the tasks in this group). If I then want to apportion the
> bandwidth within the group as you say, then the same thing can be done
> by treating them as individual tasks.
Multiplex nice? (oh my, dig foxhole)
> Maybe I am wrong, but as I see it, if one wants to control on a group
> level, then the individual shares within the group are not that
> important. If the individual share is important, then it should be
> controlled on a per-task level. Please tell me if I am wrong.
That's probably right 99% of the time.
-Mike
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