Re: IO scheduler based IO Controller V2

From: Peter Zijlstra
Date: Sat May 09 2009 - 05:24:37 EST


On Fri, 2009-05-08 at 17:56 -0400, Vivek Goyal wrote:
> So, we shall have to come up with something better, I think Dhaval was
> implementing upper limit for cpu controller. May be PeterZ and Dhaval can
> give us some pointers how did they manage to implement both proportional
> and max bw control with the help of a single tree while maintaining the
> notion of prio with-in cgroup.

We don't do max bandwidth control in the SCHED_OTHER bits as I oppose to
making it non work conserving.

SCHED_FIFO/RR do constant bandwidth things and are always scheduled in
favour of SCHED_OTHER.

That is, we provide a minimum bandwidth for real-time tasks, but since
having a maximum higher than the minimum is useless since one cannot
rely on it (non deterministic) we put max = min.

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