linux-kernel - Re: [PATCH RFC] sched/deadline: Use the revised wakeup rule for suspending constrained dl tasks

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Date:   Mon, 24 Apr 2017 20:51:46 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Xunlei Pang <xpang@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Romulo Silva de Oliveira <romulo.deoliveira@...c.br>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] sched/deadline: Use the revised wakeup rule for
 suspending constrained dl tasks

On 04/24/2017 07:00 PM, Steven Rostedt wrote:
>> +static void
>> +update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
>> +{
>> +	u64 density = div64_u64(dl_se->dl_runtime << 20, dl_se->dl_deadline);
> Hmm, dl_runtime and dl_deadline don't get updated that often. Can't we
> simply keep a static dl_se->dl_density, and update it when dl_runtime
> or dl_deadline get updated? That would get rid of the divide in the
> middle of a wake up call.

Yeah, I agree! Juri also pointed in the same direction, I will add it in
the possible next version ;-).

Thanks for the feedback!

-- Daniel