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

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Date:	Fri, 16 Mar 2007 16:42:45 +0000
From:	Pavel Machek <pavel@....cz>
To:	Con Kolivas <kernel@...ivas.org>
Cc:	Mike Galbraith <efault@....de>, 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

Hi!

> >> > Killing the known corner case starvation scenarios 
> >is wonderful, but
> >> > let's not just pretend that interactive tasks don't 
> >have any special
> >> > requirements.
> >>
> >> Now you're really making a stretch of things. Where 
> >on earth did I say that
> >> interactive tasks don't have special requirements? 
> >It's a fundamental feature
> >> of this scheduler that I go to great pains to get 
> >them as low latency as
> >> possible and their fair share of cpu despite having a 
> >completely fair cpu
> >> distribution.
> >
> >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...
> 
> 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?
> nice 5 is 75% the cpu of nice 0. nice 10 is 50%, nice 15 
> is 25%, nice

Hmm, I'd certainly expect nice to be stronger. nice 5 should be 50% or
less of nice 0... You'll not even notice nice 2 if that is 90%...

And I guess it nicely solves problem in this thread, too...
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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