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

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Date:   Wed, 26 Oct 2016 11:17:16 +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>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Daniel Bistrot de Oliveira <danielbristot@...il.com>
Subject: [PATCH] sched/deadline: show leftover runtime and abs deadline in /proc/-/sched

This patch allows for reading the current (leftover) runtime and
absolute deadline in /proc/*/sched, for debugging purposes.

This revised patch:
1) has a fixed format, Signed-off-by, etc., as suggested by Juri
2) now includes related docs in Documentation/
3) now I'm sending these e-mails with the correct From:

[PATCH] sched/deadline: show leftover runtime and abs deadline in

Thanks,

  T.
--
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()?)