Re: [PATCH 1/4] sched/fair: Be less aggressive in calling cpufreq_update_util()

[Hongyan Xia <hongyan.xia2@arm.com>]

On 12/12/2023 12:35, Qais Yousef wrote:
> On 12/12/23 11:46, Dietmar Eggemann wrote:
>> On 08/12/2023 02:52, Qais Yousef wrote:
>>> Due to the way code is structured, it makes a lot of sense to trigger
>>> cpufreq_update_util() from update_load_avg(). But this is too aggressive
>>> as in most cases we are iterating through entities in a loop to
>>> update_load_avg() in the hierarchy. So we end up sending too many
>>> request in an loop as we're updating the hierarchy.
>>
>> But update_load_avg() calls cfs_rq_util_change() which only issues a
>> cpufreq_update_util() call for the root cfs_rq?
> 
> Yes I've noticed that and wondered. Maybe my analysis was flawed and I was just
> hitting the issue of iowait boost request conflicting with update_load_avg()
> request.
> 
> Let me have another look. I think we'll still end up needing to take the update
> out of util_avg to be able to combine the two calls.

I agree. Currently it does not express the intention clearly. We only 
want to update the root CFS but the code was written in a misleading way 
that suggests we want to update for every cfs_rq. A single update at the 
end looks much nicer and makes other patches easier.

Hongyan