On 15 December 2015 at 13:41, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Dec 15, 2015 at 05:43:44AM +0100, Vincent Guittot wrote: >> On 14 December 2015 at 17:51, Peter Zijlstra <pet...@infradead.org> wrote: > >> > No, since the WCET can and _will_ happen, its the best you can do with >> > cpufreq. If you were to set it lower you could not be able to execute >> > correctly in your 'never' tail cases. >> >> In the context of frequency scaling, This mean that we will never >> reach low frequency > > Only if you've stuffed your machine full of deadline tasks, if you take > Luca's example of the I/B frame decoder thingy, then even the WCET for > the I frames should not be very much (albeit significantly more than B > frames).
But in this case, the impact of deadline scheduler on the remaining capacity for CFS should not be that much as well. This will not prevent a CFS task but only will only make it a bit smaller than the other > > So while the WCET is pessimistic compared to the avg case, most CPUs can > do video decoding without much effort at all, so even the WCET for the > I-frames might allow us to drop to the lowest cpufreq. > > Now, if you were to decode 10 streams at the same time, different story > of course ;-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
