linux-kernel - Re: [PATCH linux-next v2] sched/psi: Avoid update triggers and rtpoll

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Date:   Mon, 9 Oct 2023 12:49:44 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     yang.yang29@....com.cn
Cc:     surenb@...gle.com, peterz@...radead.org, hannes@...xchg.org,
        mingo@...hat.com, linux-kernel@...r.kernel.org,
        juri.lelli@...hat.com
Subject: Re: [PATCH linux-next v2] sched/psi: Avoid update triggers and
 rtpoll_total when it is unnecessary


* yang.yang29@....com.cn <yang.yang29@....com.cn> wrote:

> From: Yang Yang <yang.yang29@....com.cn>
> 
> When psimon wakes up and there are no state changes for rtpoll_states,
> it's unnecessary to update triggers and rtpoll_total because the pressures
> being monitored by user have not changed. This will help to slightly reduce
> unnecessary computations of psi.
> 
> There are also some minor related optimizations, please see below.
> 
> The parameter update_total in update_triggers() is useless now. Since if
> changed_states & group->rtpoll_states is true, new_stall in update_triggers()
> will be true, then update_total should also be true. We have no need for
> update_total to help judgment whether to update rtpoll_total, so delete
> update_total.
> 
> Update_triggers() always return now + group->rtpoll_min_period, and the
> return value is only used by psi_rtpoll_work(), so change update_triggers()
> to a void function, let group->rtpoll_next_update = now +
> group->rtpoll_min_period directly.

Yeah, so please split this up into 3 patches: one change per patch, even
if each patch is relatively small.

Thanks,

	Ingo