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Date: Fri, 9 Sep 2016 08:40:26 +0100
From: Juri Lelli <juri.lelli@arm.com>
To: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Cc: Luca Abeni <luca.abeni@unitn.it>, Juri Lelli <juri.lelli@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, linux-dl@retis.sssup.it
Subject: Re: [PATCH] sched/deadline: document behavior of sched_yield()
Message-ID: <20160909074026.GC10409@e106622-lin>
References: <1473365399-29430-1-git-send-email-tommaso.cucinotta@sssup.it>
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Hi Tommaso,

On 08/09/16 22:09, Tommaso Cucinotta wrote:
> This is a documentation only patch, explaining the
> behavior of sched_yield() when a SCHED_DEADLINE
> task calls it (give up remaining runtime and
> suspend till next period).

I like the patch, but changelog lacks a SoB.

Thanks,

- Juri

> ---
>  Documentation/scheduler/sched-deadline.txt | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
> index 53a2fe1..cb43421 100644
> --- a/Documentation/scheduler/sched-deadline.txt
> +++ b/Documentation/scheduler/sched-deadline.txt
> @@ -16,6 +16,7 @@ CONTENTS
>     4.1 System-wide settings
>     4.2 Task interface
>     4.3 Default behavior
> +   4.4 Behavior of sched_yield()
>   5. Tasks CPU affinity
>     5.1 SCHED_DEADLINE and cpusets HOWTO
>   6. Future plans
> @@ -426,6 +427,18 @@ CONTENTS
>   Finally, notice that in order not to jeopardize the admission control a
>   -deadline task cannot fork.
>  
> +4.4 Behavior of sched_yield()
> +-----------------------------
> +
> + When a SCHED_DEADLINE task calls sched_yield(), it gives up its
> + remaining runtime and is suspended till the next reservation period,
> + when its runtime will be replenished.  This allows the task to
> + wake-up exactly at the beginning of the next period. Also, this may
> + be useful in the future with bandwidth reclaiming mechanisms, where
> + sched_yield() will make the leftoever runtime available for
> + reclamation by other SCHED_DEADLINE tasks.
> +
> +
>  5. Tasks CPU affinity
>  =====================
>  
> -- 
> 2.7.4
>