Hi, On 09/02/18 11:36, Rafael J. Wysocki wrote: > On Friday, February 9, 2018 9:02:34 AM CET Claudio Scordino wrote: > > Hi Viresh, > > > > Il 09/02/2018 04:51, Viresh Kumar ha scritto: > > > On 08-02-18, 18:01, Claudio Scordino wrote: > > >> When the SCHED_DEADLINE scheduling class increases the CPU utilization, > > >> we should not wait for the rate limit, otherwise we may miss some > > >> deadline. > > >> > > >> Tests using rt-app on Exynos5422 have shown reductions of about 10% of > > >> deadline > > >> misses for tasks with low RT periods. > > >> > > >> The patch applies on top of the one recently proposed by Peter to drop > > >> the > > >> SCHED_CPUFREQ_* flags. > > >> > > [cut] > > > > > > > > > Is it possible to (somehow) check here if the DL tasks will miss > > > deadline if we continue to run at current frequency? And only ignore > > > rate-limit if that is the case ?
Isn't it always the case? Utilization associated to DL tasks is given by what the user said it's needed to meet a task deadlines (admission control). If that task wakes up and we realize that adding its utilization contribution is going to require a frequency change, we should _theoretically_ always do it, or it will be too late. Now, user might have asked for a bit more than what strictly required (this is usually the case to compensate for discrepancies between theory and real world, e.g. hw transition limits), but I don't think there is a way to know "how much". :/ Thanks, - Juri > > > > I need to think further about it. > > That would be my approach FWIW. > > Increasing the frequency beyond what is necessary means wasting energy > in any case. > > Thanks, > Rafael >