On 4/30/20 4:33 PM, Valentin Schneider wrote: > On 30/04/20 14:46, Benjamin GAIGNARD wrote: >>> That's not what I meant. >>> >>> I suppose that the interrupt processing in question takes place in >>> process context and so you may set the lower clamp on the utilization >>> of the task carrying that out. >> I have try to add this code when starting streaming (before the first >> interrupt) the frames from the sensor: >> const struct sched_attr sched_attr = { >> .sched_util_min = 10000, /* 100% of usage */ > Unless you play with SCHED_CAPACITY_SHIFT, the max should be 1024 - > i.e. SCHED_CAPACITY_SCALE. That's a really big boost, but that's for you to > benchmark. > >> .sched_flags = SCHED_FLAG_UTIL_CLAMP_MIN, >> }; >> >> sched_setattr(current, &sched_attr); >> >> I don't see any benefices maybe there is some configuration flags to set. >> >> How changing sched_util_min could impact cpufreq ondemand governor ? >> Does it change the value returned when the governor check the idle time ? >> > You'll have to use the schedutil governor for uclamp to have an effect. And > arguably that's what you should be using, unless something explicitly > prevents you from doing that. Even with schedutil and SCHED_CAPACITY_SCALE that it doesn't work. cpufreq/cpuinfo_cur_freq values are always on the max value even if the stats show transitions between the available frequencies. I see two possibles reasons to explain that: - sched_setattr() is called in userland process context, but the threaded irq handler is running in another process. - because this use case is almost running all in hardware the process isn't doing anything so the scheduler doesn't take care of it. > >>> Alternatively, that task may be a deadline one.