linux-kernel - Re: report a bug about sched

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Date:	Fri, 24 Jul 2009 18:01:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jamie Lokier <jamie@...reable.org>
Cc:	sen wang <wangsen.linux@...il.com>, mingo@...e.hu,
	akpm@...ux-foundation.org, kernel@...ivas.org, npiggin@...e.de,
	arjan@...radead.org, linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: report a bug about sched_rt

On Fri, 2009-07-24 at 16:40 +0100, Jamie Lokier wrote:
> Peter Zijlstra wrote:
> > If you're using the bandwidth throttle to control your RT tasks so as
> > not to starve your SCHED_OTHER tasks, then I will call your system ill
> > designed.
> 
> What mechanism should be used to avoid starving SCHED_OTHER tasks, in
> the event there are unforeseen bugs or unpredictable calculation times
> in an RT task?

For bugs the throttle works, like I said a well functioning system is
not supposed to hit the throttle, obviously a bug precludes the well
functioning qualification :-)

Unpredictable calculation times can be dealt with on the application
design level, for example using techniques such as outlined here:

  http://feanor.sssup.it/~faggioli/papers/OSPERT-2009-dlexception.pdf

These really are things you should know about before writing an RT
application ;-)
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