Messages in this thread | | | Date | Tue, 28 Jan 2014 18:22:34 +0000 | From | Tommaso Cucinotta <> | Subject | Re: [PATCH] sched/deadline: Add sched_dl documentation |
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On 28/01/14 09:31, Peter Zijlstra wrote: >> 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.
Yesss :-)! Indeed, AFAICR in the AQuoSA API there was the QOS_F_DEFAULT flag
http://aquosa.sourceforge.net/aquosa-docs/aquosa-qosres/html/qos__types_8h_source.html
(that could only be set by a privileged process) just there to allow for creating a server serving "default" tasks (namely, every non-aquosa task). This way, you could create for example at system boot time a default reservation with a precise (runtime, period) for Linux, so that non-aquosa tasks could have a chance to run in that reservation, even in presence of a RT reservation with a significantly long runtime.
T.
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