linux-kernel - Re: [patch] CFS scheduler, -v8

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Date:	Mon, 7 May 2007 19:52:57 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	William Lee Irwin III <wli@...omorphy.com>
Cc:	Damien Wyart <damien.wyart@...e.fr>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	"Tong N. Li" <tong.n.li@...el.com>
Subject: Re: [patch] CFS scheduler, -v8

On Thu, May 03, 2007 at 08:53:47AM -0700, William Lee Irwin III wrote:
> On Thu, May 03, 2007 at 08:23:18PM +0530, Srivatsa Vaddagiri wrote:
> > And what about group scheduling extensions? Do you have plans to work on
> > it? I was begining to work on a prototype to do group scheduling based
> > on CFS, basically on the lines of what you and Linus had outlined
> > earlier:
> > 	http://lkml.org/lkml/2007/4/18/271
> > 	http://lkml.org/lkml/2007/4/18/244
> 
> Tong Li's Trio scheduler does a bit of this, though it doesn't seem to
> have the mindshare cfs seems to have acquired.
> 
> The hyperlink seems to have broken, though:
> 	http://www.cs.duke.edu/~tongli/linux/linux-2.6.19.2-trio.patch

The big question I have is, how well does DWRR fits into the "currently hot" 
scheduling frameworks like CFS? For ex: if the goal is to do
fair (group) scheduling of SCHED_NORMAL tasks, can CFS and DWRR co-exist?
Both seem to be radically different algorithms and my initial impressions 
of them co-existing is "No", but would be glad to be corrected if I am
wrong. If they can't co-exist, then we need a different way of doing
group scheduling on top of CFS, as that is gaining more popularity on
account of better handling of interactivity.

Tong,
	I understand a center hallmark of DWRR is SMP fairness.
Have you considered how bad/good the other alternative to achieve SMP fairness 
which is in vogue today : pressure/weight based balancing (ex: smpnice and 
CKRM CPU scheduler - ckrm.sourceforge.net/downloads/ckrm-ols03-slides.pdf)?

-- 
Regards,
vatsa
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