linux-kernel - Re: [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets refcounting

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Message-ID: <20190314132730.GI5996@hirez.programming.kicks-ass.net>
Date:   Thu, 14 Mar 2019 14:27:30 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets
 refcounting

On Thu, Mar 14, 2019 at 11:03:30AM +0000, Patrick Bellasi wrote:

> void uclamp_rq_dec_id(struct rq *rq, int clamp_id, int bucket_id) {
>     if (__builtin_expect(!!(rq->uclamp[clamp_id].bucket[bucket_id].tasks), 1))
>         return;
>     rq->uclamp[clamp_id].bucket[bucket_id].tasks--;
> }
> ---8<---
> 
> generates something like:
> 
> ---8<---
> uclamp_rq_dec_id:
>         sxtw    x1, w1
>         add     x3, x1, x1, lsl 1
>         lsl     x3, x3, 2
>         sub     x3, x3, x1
>         lsl     x3, x3, 2
>         add     x2, x3, x2, sxtw 3
>         add     x0, x0, x2
>         ldr     w1, [x0, 8]
>         cbz     w1, .L4
>         ret
> .L4:
>         mov     w1, -1
>         str     w1, [x0, 8]
>         ret
> ---8<---
> 
> 
> which looks "sane" and quite expected, isn't it?

Yep, thanks! Sometimes I worry about silly things.