linux-kernel - Re: IRQ affinities (was: boot cgroup questions)

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Message-Id: <1210335270.13978.252.camel@twins>
Date:	Fri, 09 May 2008 14:14:30 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Paul Jackson <pj@....com>
Cc:	maxk@...lcomm.com, menage@...gle.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: IRQ affinities (was: boot cgroup questions)

On Fri, 2008-05-09 at 07:03 -0500, Paul Jackson wrote:
> Peter wrote:
> > I see two use-cases:
> > 
> >  - Isolation
> >  - NUMA node devices
> 
> Ok ... so let me propose an entirely different solution.
> 
> No doubt it has some terrible flaw, but I'll just have to
> await your replies to see what that is.
> 
> How about we have:
> 
>  1) Yet another text config file in /etc, this one containing
>     lines having two fields:
> 	* a list of IRQs, and
> 	* a cpumask.
>     This file would specify which CPUs should handle which IRQs.
> 
>  2) A utility that can be run, after changing the above file, 
>     to poke the proper cpumask to each IRQ, as specified in
>     the file.
> 
> (Obligatory "simple" marketing claim: the above requires no
> kernel changes.)
> 
> What am I missing?

Two points:

 - we can't currently set irq affinities for non-existent (aka new) IRQs
 - its a shame to duplicate the masks - most of this information would
also be used in the cpuset structure used to place the tasks.




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