linux-kernel - Re: [PATCH 00/28] PM: QoS: Get rid of unuseful code and rework CPU latency QoS interface

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Date:   Wed, 12 Feb 2020 10:17:08 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH 00/28] PM: QoS: Get rid of unuseful code and rework CPU
 latency QoS interface

On Wed, Feb 12, 2020 at 9:38 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> On Wed, 12 Feb 2020 at 00:39, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> >
> > Hi All,
> >
> > This series of patches is based on the observation that after commit
> > c3082a674f46 ("PM: QoS: Get rid of unused flags") the only global PM QoS class
> > in use is PM_QOS_CPU_DMA_LATENCY, but there is still a significant amount of
> > code dedicated to the handling of global PM QoS classes in general.  That code
> > takes up space and adds overhead in vain, so it is better to get rid of it.
> >
> > Moreover, with that unuseful code removed, the interface for adding QoS
> > requests for CPU latency becomes inelegant and confusing, so it is better to
> > clean it up.
> >
> > Patches [01/28-12/28] do the first part described above, which also includes
> > some assorted cleanups of the core PM QoS code that doesn't go away.
> >
> > Patches [13/28-25/28] rework the CPU latency QoS interface (in the classic
> > "define stubs, migrate users, change the API proper" manner), patches
> > [26-27/28] update the general comments and documentation to match the code
> > after the previous changes and the last one makes the CPU latency QoS depend
> > on CPU_IDLE (because cpuidle is the only user of its target value today).
> >
> > The majority of the patches in this series don't change the functionality of
> > the code at all (at least not intentionally).
> >
> > Please refer to the changelogs of individual patches for details.
> >
> > Thanks!
>
> A big thanks for cleaning this up! The PM_QOS_CPU_DMA_LATENCY and
> friends, has been annoying me for a long time. This certainly makes
> the code far better and more understandable!
>
> I have looked through the series and couldn't find any obvious
> mistakes, so feel free to add:
>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Thanks for the review, much appreciated!

> Note, the review tag also means, that's fine for you to pick the mmc
> patch via your tree.

Thank you!