linux-kernel - Re: [RFC][PATCH 02/22] sched: add extended scheduling interface

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Date:	Thu, 11 Nov 2010 14:54:08 +0100
From:	Raistlin <raistlin@...ux.it>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Friesen <cfriesen@...tel.com>, oleg@...hat.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Johan Eker <johan.eker@...csson.com>,
	"p.faure" <p.faure@...tech.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Claudio Scordino <claudio@...dence.eu.com>,
	michael trimarchi <trimarchi@...is.sssup.it>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Tommaso Cucinotta <cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Nicola Manica <nicola.manica@...i.unitn.it>,
	Luca Abeni <luca.abeni@...tn.it>,
	Dhaval Giani <dhaval@...is.sssup.it>,
	Harald Gustafsson <hgu1972@...il.com>,
	paulmck <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 02/22] sched: add extended scheduling interface

On Thu, 2010-11-11 at 14:32 +0100, Peter Zijlstra wrote:
> > BTW, as Dhaval was suggesting, are (after those changes) fine with this
> > new sched_param? Do we need some further mechanism to grant its
> > extendability?
> > Padding?
> > Versioning?
> > void *data field?
> > Whatever?
> > 
> > :-O
> > 
> > I'd like very much to have some discussion here, if you think it is
> > needed, in hope of avoiding future ABI issues as much as possible! :-P
> 
> Right, so you mentioned doing s/_ex/2/ on all this stuff, which brings
> it more in line with that other syscalls have done.
> 
Sure, this is necessary and easy to achieve. :-)

> The last three parameters look to be output only as I've not yet found
> code that reads it, and __getparam_dl() doesn't even appear to set
> used_runtime.
> 
Yeah, just kind of statistical reporting of the task's behaviour. That's
why I was in agreement with Dhaval about using schedstats for those
(bumping the version, obviously). What do you think?

> One thing you can do is add some padding, versioning and void*
> extentions are doable for the setparam() path, but getparam() is going
> to be mighty interesting.
> 
Mmm... So, tell me if I got it well: I remove the last three parameters
(e.g., moving them toward schedstats) and add (besides _var and _max)
some padding? It that correct?

what about the len <== sizeof(struct sched_param2) in
sched_{set,get}{param,scheduler}2()... Does this still make sense, or
are we removing it?

Thanks,
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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