Messages in this thread | | | Date | Tue, 28 Jan 2014 10:31:01 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/deadline: Add sched_dl documentation |
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On Fri, Jan 24, 2014 at 10:08:35AM +0000, Tommaso Cucinotta wrote: > > We should also again talk about what it would take to allow > > unprivileged access to SCHED_DEADLINE. The things I can remember are the > > obvious cap on utilization and a minimum period -- the latter so that we > > don't DoS the system with a metric ton of tiny tasks. > > > > But I seem to remember there were a few other issues. > > Exactly. I can remember also a huge period might be harmful, because with it > even a tiny utilization may lead to a big runtime that starves the whole non > RT tasks for a significant time.
Another way to solve that is with explicit slack time scheduling, where slack here means the time/utilization not allocated to dl tasks (a quick google shows various different usages of slack, including laxity).
So suppose we have 50% utilization but with a huge period, we could schedule the other 50% at a fixed but smaller period and have that run the rt/fair/etc tasks.
So effectively we'll always fill up the utilization to 100% and use the 'slack' time as a server for the other classes.
> Just in case, I had this paper > > http://retis.sssup.it/~tommaso/papers/rtas08.php > > discussing the issues I had found, and how they were tackled in the AQuoSA > supervisor. See Section 3.1.
/me *click*
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