linux-kernel - Re: [PATCH][RSDL-mm 0/7] RSDL cpu scheduler for 2.6.21-rc3-mm2

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Date:	Tue, 13 Mar 2007 06:10:39 +0100
From:	Mike Galbraith <efault@....de>
To:	Con Kolivas <kernel@...ivas.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	ck list <ck@....kolivas.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH][RSDL-mm 0/7] RSDL cpu scheduler for 2.6.21-rc3-mm2

On Tue, 2007-03-13 at 09:51 +1100, Con Kolivas wrote:
> On 13/03/07, Mike Galbraith <efault@....de> wrote:

> > As soon as your cpu is fully utilized, fairness looses or interactivity
> > loses.  Pick one.
> 
> That's not true unless you refuse to prioritise your tasks
> accordingly. Let's take this discussion in a different direction. You
> already nice your lame processes. Why? You already have the concept
> that you are prioritising things to normal or background tasks. You
> say so yourself that lame is a background task. Stating the bleedingly
> obvious, the unix way of prioritising things is via nice. You already
> do that. So moving on from that...

Sure.  If a user wants to do anything interactive, they can indeed nice
19 the rest of their box before they start.

> Your test case you ask "how can I maximise cpu usage". Well you know
> the answer already. You run two threads. I won't dispute that.
> 
> The debate seems to be centered on whether two tasks that are niced +5
> or to a higher value is background. In my opinion, nice 5 is not
> background, but relatively less cpu. You already are savvy enough to
> be using two threads and nicing them. All I ask you to do when using
> RSDL is to change your expectations slightly and your settings from
> nice 5 to nice 10 or 15 or even 19. Why is that so offensive to you?

It's not "offensive" to me, it is a behavioral regression.  The
situation as we speak is that you can run cpu intensive tasks while
watching eye-candy.  With RSDL, you can't, you feel the non-interactive
load instantly.  Doesn't the fact that you're asking me to lower my
expectations tell you that I just might have a point?

> Please don't pick 5.none of the above. Please try to work with me on this.

I'm not trying to be pig-headed.  I'm of the opinion that fairness is
great... until you strictly enforce it wrt interactive tasks.  

	-Mike

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