Message-ID: <44F6BB8A.7090001@control.lth.se>
Date: Thu, 31 Aug 2006 12:35:54 +0200
From: Martin Ohlin <martin.ohlin@control.lth.se>
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To: Mike Galbraith <efault@gmx.de>
CC: Peter Williams <pwil3058@bigpond.net.au>, balbir@in.ibm.com,
       linux-kernel@vger.kernel.org
Subject: Re: A nice CPU resource controller
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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.

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.

/Martin
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