linux-kernel - Re: SCHED

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Message-ID: <20090508091052.GA10429@januz.myftp.org>
Date:	Fri, 8 May 2009 11:10:52 +0200
From:	Henrik Austad <henrik@...tad.us>
To:	GeunSik Lim <leemgs1@...il.com>
Cc:	finarfin@...amos.org, linux-kernel@...r.kernel.org
Subject: Re: SCHED_EDF infos

On Fri, May 08, 2009 at 11:35:58AM +0900, GeunSik Lim wrote:
> Hi Henlik,

Hi Lim,


First off, to all of you, sorry for my last, very poorly formatted email. I 
have now tranceded into the realms of mutt.

> [..]
> I think so.
> How can we approach  EDF implementation like Pfair as a generic solution
> for Multicore in Linux?

I am working on an implementation now, and I hope to be able to release a 
prototype by the end of next week. I think we can continue the discussion 
then based on that.

> > I'm working on SCHED_PFAIR :-) Which is a multicore, ratebased deadline 
> > driven global scheduling policy where I use the PD^2 rules to solve 
> > tie-breaks. In theory, it can reach 100% utilization on all cores 
> > without missing deadlines (but in practice you will only get close to 
> > 100% as it is not perfect).

> > [..]
> > I'd suggest getting the scheduler running first, then look at those
> > problems later. If you spend all your time trying to learn the 
> > scheduler and design in every little feature you need, you'll never 
> > finish in time.

> In fact, I also  don't have perfect know how to solve PI in Multicore.
> [...]
> > deadline inversion will be a problem, in fact, whatever you chooose to 
> > be the 'key' for picking tasks (priority, niceness, deadlines, wind 
> > direction, <whatever>), you can pretty much take that and add a 
> > -inversion after it. :)

No, PI is going to be deadly no matter what you do.

Henrik
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