linux-kernel - Re: [PATCH 4/6 v5] sched: propagate load during synchronous attach/detach

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Date:   Wed, 26 Oct 2016 14:31:26 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Yuyang Du <yuyang.du@...el.com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
        Paul Turner <pjt@...gle.com>, Ben Segall <bsegall@...gle.com>,
        Wanpeng Li <kernellwp@...il.com>
Subject: Re: [PATCH 4/6 v5] sched: propagate load during synchronous attach/detach

On 26 October 2016 at 13:16, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Oct 26, 2016 at 09:05:49AM +0200, Vincent Guittot wrote:
>> >
>> > The 'detach across' and 'attach across' in detach_task_cfs_rq() and
>> > attach_entity_cfs_rq() do the same so couldn't you not create a
>> > function propagate_foo() for it? This would avoid this ifdef as
>> > well.
>> >
>> > You could further create in your '[PATCH 1/6 v5] sched: factorize attach entity':
>> >
>> > detach_entity_cfs_rq() {
>> >   update_load_avg()
>> >   detach_entity_load_avg()
>> >   update_tg_load_avg()
>> >   propagate_load_avg()
>> > }
>> >
>> > and then we would have:
>> >
>> > attach_task_cfs_rq() -> attach_entity_cfs_rq() -> propagate_foo()
>> > detach_task_cfs_rq() -> detach_entity_cfs_rq() -> propagate_foo()
>> >
>> > I guess you didn't because it would be only called one time but this
>> > symmetric approaches are easier to remember (at least for me).
>>
>> Yes i haven't created attach_entity_cfs_rq because it would be used only once.
>> Regarding the creation of a propagate_foo function, i have just
>> followed a similar skeleton as what is done in
>> enqueue/dequeue_task_fair
>>
>> I don't have strong opinion about creating this indirection for code
>> readability. Others, have you got a preference ?
>
> I think I agree with Dietmar. Duplicate code needs a helper function and
> it would be nice to keep symmetry, even if there's only a single
> call site.

OK