linux-kernel - Re: [PATCH v2] sched/deadline: fix runtime accounting in documentation

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Date:   Tue, 14 Nov 2017 11:41:50 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Claudio Scordino <claudio@...dence.eu.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Jonathan Corbet <corbet@....net>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>
Subject: Re: [PATCH v2] sched/deadline: fix runtime accounting in documentation

Hi Claudio,

On 14 November 2017 at 04:19, Claudio Scordino <claudio@...dence.eu.com> wrote:
> Signed-off-by: Claudio Scordino <claudio@...dence.eu.com>
> Signed-off-by: Luca Abeni <luca.abeni@...tannapisa.it>
> Acked-by: Daniel Bristot de Oliveira <bristot@...hat.com>
> CC: Jonathan Corbet <corbet@....net>
> CC: "Peter Zijlstra (Intel)" <peterz@...radead.org>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: linux-doc@...r.kernel.org
> Cc: Tommaso Cucinotta <tommaso.cucinotta@...up.it>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---

Please add a short description for your change, even if it is trivial.


>  Documentation/scheduler/sched-deadline.txt | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
> index e89e36e..8ce78f8 100644
> --- a/Documentation/scheduler/sched-deadline.txt
> +++ b/Documentation/scheduler/sched-deadline.txt
> @@ -204,10 +204,17 @@ CONTENTS
>   It does so by decrementing the runtime of the executing task Ti at a pace equal
>   to
>
> -           dq = -max{ Ui, (1 - Uinact) } dt
> +           dq = -max{ Ui / Umax, (1 - Uinact - Uextra) } dt
>
> - where Uinact is the inactive utilization, computed as (this_bq - running_bw),
> - and Ui is the bandwidth of task Ti.
> + where:
> +
> +  - Ui is the bandwidth of task Ti;
> +  - Umax is the maximum reclaimable utilization (subjected to RT throttling
> +    limits);
> +  - Uinact is the (per runqueue) inactive utilization, computed as
> +    (this_bq - running_bw);
> +  - Uextra is the (per runqueue) extra reclaimable utilization
> +    (subjected to RT throttling limits).

I think there would be value in defining 'dq' and 'dt'.  That way
people know exactly what they are and it leaves no room for
interpretation.

Thanks,
Mathieu

>
>
>   Let's now see a trivial example of two deadline tasks with runtime equal
> --
> 2.7.4
>