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

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Message-ID: <f6d97aba-9b28-fb59-749f-7b9adf276700@redhat.com>
Date:   Mon, 24 Apr 2017 22:43:45 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Xunlei Pang <xpang@...hat.com>, Juri Lelli <juri.lelli@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        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 05:18 PM, Daniel Bristot de Oliveira wrote:
>   remaining runtime = 4
>   laxity = 5
Oops! The laxity is 5... so...

> Knowing the laxity of a task (deadline - t), it is possible to move
> it to the other side of the equality, thus enabling to define max
> remaining runtime a task can use within the absolute deadline, without
> over-running the allowed density:
> 
>   runtime = (dl_runtime / dl_deadline) * (deadline - t)
> 
> For instance, in our previous example, the task could still run:
> 
>   runtime = ( 5 / 7 ) * 4
>   runtime = 2.85 ms

This should be:
    runtime = ( 5 / 7 ) * 5
    runtime = 3.57 ms

even better :-)

-- Daniel