Re: [PATCH 0/6] Add latency_nice priority

[Dietmar Eggemann <dietmar.eggemann@arm.com>]

On 11/03/2022 17:14, Vincent Guittot wrote:
> This patchset restarts the work about adding a latency nice priority to
> describe the latency tolerance of cfs tasks.
> 
> The patches [1-4] have been done by Parth:
> https://lore.kernel.org/lkml/20200228090755.22829-1-parth@linux.ibm.com/
> 
> I have just rebased and moved the set of latency priority outside the
> priority update. I have removed the reviewed tag because the patches
> are 2 years old.
> 
> The patches [5-6] use latency nice priority to decide if a cfs task can
> preempt the current running task. Patch 5 gives some tests results with
> cyclictests and hackbench to highlight the benefit of latency nice
> priority for short interactive task or long intensive tasks.

The Android specific `latency_nice` (in Android `latency_sensitive`
[latency_nice < 0]) use case `Skip energy aware task placement` favors
an idle CPU over the EAS search path for a `latency_sensitive` task.

https://lkml.kernel.org/r/2aa4b838-c298-ec7d-08f3-caa50cc87dc2@arm.com

This is Android proprietary code similar to what we have in
find_idlest_group_cpu() in mainline.
We talked to the Android folks last week and IMHO they are not convinced
that they can switch this to the proposed `latency_nice->tweak
preemption` use case.