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Subject: Re: [Regression] 2.6.24-git9: RT sched mishandles artswrapper
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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Dmitry Adamushko <dmitry.adamushko@gmail.com>, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>,
       Steven Rostedt <rostedt@goodmis.org>
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Date: Wed, 06 Feb 2008 23:34:27 +0100
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On Wed, 2008-02-06 at 23:18 +0100, Rafael J. Wysocki wrote:
> On Wednesday, 6 of February 2008, Peter Zijlstra wrote:
> > 
> > On Wed, 2008-02-06 at 22:50 +0100, Rafael J. Wysocki wrote:
> > > On Wednesday, 6 of February 2008, Peter Zijlstra wrote:
> > 
> > > > Well, that whole queue.
> > > 
> > > It doesn't compile for me.
> > 
> > I did solve some compile issues since posting, Ingo should have the
> > compiling version in sched-devel soonish (don't know if he pushed it
> > already).
> 
> Can you point me to the cleaned up version, please?

http://programming.kicks-ass.net/kernel-patches/sched-rt-group/

on top of sched-devel.

> > > > Your test program just failed to obtain realtime scheduling
> > > 
> > > Well, it shouldn't.  The expected result is to obtain realtime scheduling
> > > or we will break existing setups.
> > 
> > Thats a case of wrong expectations in my book. You enabled group
> > scheduling and hence behaviour changes.
> 
> So, I'd have to unset FAIR_GROUP_SCHED to obtain the previous behavior?

With the mainline stuff, with the new stuff just ensure
CONFIG_RT_GROUP_SCHED=n.

> > There is just nothing much one can do about it, if you don't assign bandwidth
> > to a group, it won't be able to run anything. Better to refuse to run, than to sit
> > idle, right? 
> 
> As a general rule, probably yes.
> 
> > But I appreciate the situation, therefore I made the whole rt-group
> > scheduling a separate .config option (which defaults to n)
> 
> Which is introduced by the new patches, isn't it?

Yes.