Messages in this thread | | | Subject | Re: [RFC][PATCH 09/22] sched: add period support for -deadline tasks | From | Peter Zijlstra <> | Date | Fri, 12 Nov 2010 14:45:33 +0100 |
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On Fri, 2010-11-12 at 14:33 +0100, Raistlin wrote: > On Thu, 2010-11-11 at 20:43 +0100, Peter Zijlstra wrote: > > > Since you spotted it... The biggest issue here is admission control > > > test. Right now this is done against task's bandwidth, i.e., > > > sum_i(runtime_i/period_i)<=threshold, but it is unfortunately wrong... > > > Or at least very, very loose, to the point of being almost useless! :-( > > > > Right, I have some recollection on that. > > > :-) > > > So sufficient (but not necessary) means its still a pessimistic approach > > but better than the one currently employed, or does it mean its > > optimistic and allows for unschedulable sets to be allowed in? > > > Tommaso already gave the best possible explanation of this! :-P > > So, trying to recap: > - using runtime/min(deadline,period) _does_ guarantee schedulability, > but also rejects schedulable situations in UP/partitioning. Quite > sure it _does_not_ guarantee schedulability in SMP/global, but > *should* enable bounded tardiness; > - using runtime/period _does_not_ guarantee schedulability nor in > UP/partitioning neither in SMP/global, but *should* enable bounded > tardiness for _both_.
> Thus, all this being said, what do you want me to do? :-D
runtime/min(deadline,period) sounds fine, as its more useful than runtime/period.
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