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Subject: Re: [PATCH RFC] sched/deadline: Use the revised wakeup rule for
 suspending constrained dl tasks
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Xunlei Pang <xpang@redhat.com>, Juri Lelli <juri.lelli@arm.com>,
        Luca Abeni <luca.abeni@santannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@sssup.it>,
        Romulo Silva de Oliveira <romulo.deoliveira@ufsc.br>,
        linux-kernel@vger.kernel.org
References: <5c6933890ea6daa3b4edb4983b0c6f094ad3903d.1493045834.git.bristot@redhat.com>
 <20170424130043.0b9c9881@gandalf.local.home>
From: Daniel Bristot de Oliveira <bristot@redhat.com>
Message-ID: <5fd0446b-0c5c-ce82-7e18-c56140e1a83b@redhat.com>
Date: Mon, 24 Apr 2017 20:51:46 +0200
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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