linux-kernel - Re: RFC for a new Scheduling policy/class in the Linux-kernel

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Message-Id: <1247478955.8107.24.camel@Palantir>
Date:	Mon, 13 Jul 2009 11:55:55 +0200
From:	Raistlin <raistlin@...ux.it>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Henrik Austad <henrik@...tad.us>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Bill Huey <billh@...ppy.monkey.org>,
	Linux RT <linux-rt-users@...r.kernel.org>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	"James H. Anderson" <anderson@...unc.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Douglas Niehaus <niehaus@...c.ku.edu>,
	Ted Baker <baker@...fsu.edu>,
	Dhaval Giani <dhaval.giani@...il.com>
Subject: Re: RFC for a new Scheduling policy/class in the Linux-kernel

On Sat, 2009-07-11 at 20:28 +0200, Peter Zijlstra wrote: 
> > There are still some issues left to solve, for instance how to best
> > handle sporadic tasks, and whether or not deadline-miss should be allow,
> > or just 'bounded deadline tardiness'. Either way, EFF should be able to
> > handle it. Then, there are problems concerning blocking of tasks. One
> > solution would be BWI or PEP, but I have not had the time to read
> > properly through those, but from what I've gathered a combination of BWI
> > and PEP looks promising (anyone with good info about BWI and PEP - feel
> > free to share! (-: ).
> 
> Our SSSUP friends have a BWI paper here:
> 
>   http://retis.sssup.it/~tommaso/publications/OSPERT-2008.pdf
> 
And here we are! :-)

The paper Peter pointed you to mainly describes the work I did some
months ago to implement BandWidth Inheritance inside one real-time Linux
variant of us (ReTiS Lab, in Pisa, Italy)... Feel free to ask anything
related to it directly to me.

It is exactly implemented as a "proxy execution" protocol and things
were easy there, since --for now-- the framework I was talking about is
UP-only! :-(

Now we are back on work on it, especially thinking on how to extend the
protocol to SMP architectures...

> Thing is, both BWI and PEP seems to work brilliantly on Uni-Processor
> but SMP leaves things to be desired. Dhaval is currently working on a
> PEP implementation that will migrate all the blocked tasks to the
> owner's cpu, basically reducing it to the UP problem.
> 
Nice... Only one question, doesn't this impact with task affinity
related issues?

regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://blog.linux.it/raistlin / raistlin@...ga.net /
dario.faggioli@...ber.org

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