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

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Date:   Thu, 29 Jul 2021 19:21:03 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Juri Lelli <juri.lelli@...hat.com>,
        Quentin Perret <qperret@...gle.com>
Cc:     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 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;