linux-kernel - [PATCH 2/2] sched/rt: Document RT_RUNTIME

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Message-Id: <dc42945fc19eacd41acebc2be2425a4d9af2b82b.1479204252.git.bristot@redhat.com>
Date:   Tue, 15 Nov 2016 11:39:11 +0100
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Clark Williams <williams@...hat.com>,
        "Luis Claudio R . Goncalves" <lgoncalv@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] sched/rt: Document RT_RUNTIME_SHARE sched feature

Add a comment explaining the RT_RUNTIME_SHARE sched feature.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Clark Williams <williams@...hat.com>
Cc: Luis Claudio R. Goncalves <lgoncalv@...hat.com>
Cc: linux-kernel@...r.kernel.org

diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 5fffebfe..531c4bb 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -65,7 +65,17 @@ SCHED_FEAT(RT_PUSH_IPI, true)
 #endif
 
 SCHED_FEAT(FORCE_SD_OVERLAP, false)
+
+/*
+ * Enables the sharing of rt_runtime between CPUs, allowing a CPU to
+ * run a real-time task up to 100% of the time while leaving more
+ * space for non-real-time tasks to run on the CPU that lend rt_runtime.
+ *
+ * WARNING: This may allow the starvation of non-real-time tasks pinned
+ * to the CPU in which a spinning rt-task runs forever.
+ */
 SCHED_FEAT(RT_RUNTIME_SHARE, false)
+
 SCHED_FEAT(LB_MIN, false)
 SCHED_FEAT(ATTACH_AGE_LOAD, true)
 
-- 
2.7.4