linux-kernel - Re: INGO Why you remove set_user

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Date:	Mon, 14 Sep 2009 17:45:23 +0200
From:	Mike Galbraith <efault@....de>
To:	Chris Friesen <cfriesen@...tel.com>
Cc:	pavel@...linux.ru, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: INGO Why you remove  set_user_nice() from kernel/kthread.c

On Mon, 2009-09-14 at 09:12 -0600, Chris Friesen wrote:
> On 09/14/2009 08:05 AM, Mike Galbraith wrote:
> > If you're asking Ingo a question, maybe a CC is in order.
> > 
> > On Mon, 2009-09-14 at 17:42 +0400, Pavel Vasilyev wrote:
> >>
> >> Next patсh -  
> >> http://www.kernel.org/diff/diffview.cgi?file=%2Fpub%2Flinux%2Fkernel%2F%2Fv2.6%2Fsnapshots%2Fpatch-2.6.31-git2.bz2;z=548
> >>
> >> This patch defines the core processes that are working with nice leve equal to 
> >> zero , as in the BFS. :)
> >>
> >> Why?
> > 
> > I did that, not Ingo, and did so because with kthreads that use
> > diddly-spit CPU (every one I see), it's just a waste of math.  What
> > kthreads are you seeing using so much CPU that their weight is a factor?
> > They _should_ be able to preempt and get their work done just fine
> > without a boost.
> 
> Under heavy network load ksoftirqd can use significant amounts of cpu.

OK, that may justify a weight adjustment, since it is a proxy for many.
Question is, does it really need it?

I certainly have no objection to a heavier weight for any kthread,
though I think it's a waste of cycles for the general case.

	-Mike

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