Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [RFC][PATCH 09/22] sched: add period support for -deadline tasks | From | Peter Zijlstra <> | Date | Thu, 11 Nov 2010 20:43:55 +0100 |
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On Thu, 2010-11-11 at 20:31 +0100, Raistlin wrote: > On Thu, 2010-11-11 at 20:17 +0100, Peter Zijlstra wrote: > > On Fri, 2010-10-29 at 08:34 +0200, Raistlin wrote: > > > Make it possible to specify a period (different or equal than > > > deadline) for -deadline tasks. > > > > > I would expect it to be: > > > > runtime <= deadline <= period > > > Well, apart from that really unhappy comment/changelog, it should be > like that in the code, and if it's not, it is what I meant and I'll > change to that as soon as I can! :-) > > 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.
> The more correct --in the sense that it at least yield a sufficient (not > necessary!) condition-- thing to do would be > sum_i(runtime_i/min{deadline_i,period_i})<=threshold. > > So, what you think we should do? Can I go for this latter option?
I remember we visited this subject last time, but I seem to have forgotten most details.
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?
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