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

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Message-Id: <1477473437-10346-2-git-send-email-tommaso.cucinotta@sssup.it>
Date:   Wed, 26 Oct 2016 11:17:17 +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>,
        Ingo Molnar <mingo@...nel.org>
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 of a SCHED_DEADLINE task through /proc/*/sched
(entries dl.runtime and dl.deadline), while debugging/testing.

Signed-off-by: Tommaso Cucinotta <tommaso.cucinotta@...up.it>
Reviewed-by: Juri Lelli <juri.lelli@....com>
Reviewed-by: Luca Abeni <luca.abeni@...tn.it>
Acked-by: Daniel Bistrot de Oliveira <danielbristot@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
---
 Documentation/scheduler/sched-deadline.txt | 6 ++++++
 kernel/sched/debug.c                       | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
index 8e37b0b..cbc1b46 100644
--- a/Documentation/scheduler/sched-deadline.txt
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -408,6 +408,11 @@ CONTENTS
   * the new scheduling related syscalls that manipulate it, i.e.,
     sched_setattr() and sched_getattr() are implemented.
 
+ For debugging purposes, the leftover runtime and absolute deadline of a
+ SCHED_DEADLINE task can be retrieved through /proc/<pid>/sched (entries
+ dl.runtime and dl.deadline, both values in ns). A programmatic way to
+ retrieve these values from production code is under discussion.
+
 
 4.3 Default behavior
 ---------------------
@@ -476,6 +481,7 @@ CONTENTS
 
  Still missing:
 
+  - programmatic way to retrieve current runtime and absolute deadline
   - refinements to deadline inheritance, especially regarding the possibility
     of retaining bandwidth isolation among non-interacting tasks. This is
     being studied from both theoretical and practical points of view, and
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index fa178b6..109adc0 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -953,6 +953,10 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
 #endif
 	P(policy);
 	P(prio);
+	if (p->policy == SCHED_DEADLINE) {
+		P(dl.runtime);
+		P(dl.deadline);
+	}
 #undef PN_SCHEDSTAT
 #undef PN
 #undef __PN
-- 
2.7.4