On Tue, Jan 15, 2019 at 10:15:05AM +0000, Patrick Bellasi wrote: > @@ -342,11 +350,24 @@ static void sugov_iowait_boost(struct sugov_cpu > *sg_cpu, u64 time, > return; > sg_cpu->iowait_boost_pending = true; > > + /* > + * Boost FAIR tasks only up to the CPU clamped utilization. > + * > + * Since DL tasks have a much more advanced bandwidth control, it's > + * safe to assume that IO boost does not apply to those tasks.
I'm not buying that argument. IO-boost isn't related to b/w management. IO-boot is more about compensating for hidden dependencies, and those don't get less hidden for using a different scheduling class. Now, arguably DL should not be doing IO in the first place, but that's a whole different discussion. > + * Instead, since RT tasks are not utilization clamped, we don't want > + * to apply clamping on IO boost while there is blocked RT > + * utilization. > + */ > + max_boost = sg_cpu->iowait_boost_max; > + if (!cpu_util_rt(cpu_rq(sg_cpu->cpu))) > + max_boost = uclamp_util(cpu_rq(sg_cpu->cpu), max_boost); > + > /* Double the boost at each request */ > if (sg_cpu->iowait_boost) { > sg_cpu->iowait_boost <<= 1; > - if (sg_cpu->iowait_boost > sg_cpu->iowait_boost_max) > - sg_cpu->iowait_boost = sg_cpu->iowait_boost_max; > + if (sg_cpu->iowait_boost > max_boost) > + sg_cpu->iowait_boost = max_boost; > return; > } Hurmph... so I'm not sold on this bit.