linux-kernel - Re: [PATCH 2/2] sched: Don't report SCHED_FLAG_SUGOV in sched

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Message-ID: <YQLlHKFgRwLVW6rE@google.com>
Date:   Thu, 29 Jul 2021 18:28:11 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Juri Lelli <juri.lelli@...hat.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched: Don't report SCHED_FLAG_SUGOV in
 sched_getattr()

On Thursday 29 Jul 2021 at 19:21:03 (+0200), Dietmar Eggemann wrote:
> On 28/07/2021 14:36, Juri Lelli wrote:
> > On 28/07/21 10:39, Quentin Perret wrote:
> >> On Wednesday 28 Jul 2021 at 11:12:03 (+0200), Juri Lelli wrote:
> 
> [...]
> 
> >>> Maybe we can do this in the previous patch so that it's kept confined to
> >>> deadline bits?
> >>
> >> That works too, it just felt like this could happen again if we start
> >> using non-standard flags outside of deadline for any reason at some
> >> point in the future. But no strong opinion really.
> > 
> > Yeah, I also see this point. :)
> > 
> > So no prob with me to keep it in core.c as you do here.
> > 
> > Best,
> > Juri
> > 
> 
> I would vote for not exporting SCHED_FLAG_SUGOV from __getparam_dl() in
> patch 1/2 to underpin the idea that this flag is a hack.
> 
> @ -2759,7 +2759,7 @@ void __getparam_dl(struct task_struct *p, struct
> sched_attr *attr)
>         attr->sched_deadline = dl_se->dl_deadline;
>         attr->sched_period = dl_se->dl_period;
>         attr->sched_flags &= ~SCHED_DL_FLAGS;
> -       attr->sched_flags |= dl_se->flags;
> +       attr->sched_flags |= dl_se->flags & ~SCHED_FLAG_SUGOV;

Alright, that's 2 votes against 1, you win!
I'll post a v2 shortly.

Cheers,
Quentin