linux-kernel - [RFC PATCH] sched/deadline: show leftover runtime and abs deadline in /proc/-/sched

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Date:   Tue, 25 Oct 2016 00:32:53 +0200
From:   Tommaso Cucinotta <tommaso.cucinotta@...up.it>
To:     Luca Abeni <luca.abeni@...tn.it>,
        Juri Lelli <juri.lelli@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-dl@...is.sssup.it,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Daniel Bistrot de Oliveira <danielbristot@...il.com>
Subject: [RFC PATCH] sched/deadline: show leftover runtime and abs deadline in /proc/-/sched

Hi all,

this is a tiny patch providing readings of the current (leftover)
runtime and absolute deadline in /proc/*/sched. Mostly useful for
debugging, I heard others playing with SCHED_DEADLINE had some need
for similar patches as well.

In addition to debugging, reading the leftover runtime is generally
useful for adaptive/incremental RT logics that need to check whether
there's enough runtime left for refining the computed result, or just
use what we've computed so far and block till the next instance.
Also, knowing what the absolute scheduling deadline is (along with
what clock it refers to) might be useful for synchronization purposes.
(albeit, for real production code, I wouldn't like to parse /proc anyway,
rather I'd prefer to retrieve those params via eg sched_getscheduler()?)

Please, share your thoughts, thanks.

  Tommaso