Messages in this thread | | | Date | Fri, 27 Jul 2018 09:09:04 +0100 | From | Quentin Perret <> | Subject | Re: [PATCH v2 08/12] sched/core: uclamp: extend cpu's cgroup controller |
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On Thursday 26 Jul 2018 at 17:39:19 (-0700), Joel Fernandes wrote: > On Tue, Jul 24, 2018 at 06:29:02AM -0700, Tejun Heo wrote: > > Hello, Patrick. > > > > On Mon, Jul 23, 2018 at 06:22:15PM +0100, Patrick Bellasi wrote: > > > However, the "best effort" bandwidth control we have for CFS and RT > > > can be further improved if, instead of just looking at time spent on > > > CPUs, we provide some more hints to the scheduler to know at which > > > min/max "MIPS" we want to consume the (best effort) time we have been > > > allocated on a CPU. > > > > > > Such a simple extension is still quite useful to satisfy many use-case > > > we have, mainly on mobile systems, like the ones I've described in the > > > "Newcomer's Short Abstract (Updated)" > > > section of the cover letter: > > > https://lore.kernel.org/lkml/20180716082906.6061-1-patrick.bellasi@arm.com/T/#u > > > > So, that's all completely fine but then let's please not give it a > > name which doesn't quite match what it does. We can just call it > > e.g. cpufreq range control. > > But then what name can one give it if it does more than one thing, like > task-placement and CPU frequency control? > > It doesn't make sense to name it cpufreq IMHO. Its a clamp on the utilization > of the task which can be used for many purposes.
Indeed, the scheduler could use clamped utilization values in several places. The capacity-awareness bits (mostly useful for big.LITTLE platforms) could already use that today I guess.
And on the longer term, depending on where the EAS patches [1] end up, utilization clamping might actually become very useful to bias task placement decisions. EAS basically decides where to place tasks based on their utilization, so util_clamp would make a lot of sense there IMO.
Thanks, Quentin
[1] https://lkml.org/lkml/2018/7/24/420
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