Messages in this thread | | | Date | Wed, 8 Jan 2020 14:44:48 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/rt: Add a new sysctl to control uclamp_util_min |
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On Fri, Dec 20, 2019 at 04:48:38PM +0000, Qais Yousef wrote: > RT tasks by default try to run at the highest capacity/performance > level. When uclamp is selected this default behavior is retained by > enforcing the uclamp_util_min of the RT tasks to be > uclamp_none(UCLAMP_MAX), which is SCHED_CAPACITY_SCALE; the maximum > value. > > See commit 1a00d999971c ("sched/uclamp: Set default clamps for RT tasks"). > > On battery powered devices, this default behavior could consume more > power, and it is desired to be able to tune it down. While uclamp allows > tuning this by changing the uclamp_util_min of the individual tasks, but > this is cumbersome and error prone. > > To control the default behavior globally by system admins and device > integrators, introduce the new sysctl_sched_rt_uclamp_util_min to > change the default uclamp_util_min value of the RT tasks. > > Whenever the new default changes, it'd be applied on the next wakeup of > the RT task, assuming that it still uses the system default value and > not a user applied one.
This is because these RT tasks are not in a cgroup or not affected by cgroup settings? I feel the justification is a little thin here.
> If the uclamp_util_min of an RT task is 0, then the RT utilization of > the rq is used to drive the frequency selection in schedutil for RT > tasks.
Did cpu_uclamp_write() forget to check for input<0 ?
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