linux-kernel - [PATCH] sched: fix the inconsistent of SCHED

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Date:   Sat, 28 Jan 2017 22:00:49 +0800
From:   Shile Zhang <shile.zhang@...ia.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
CC:     <linux-kernel@...r.kernel.org>, Shile Zhang <shile.zhang@...ia.com>
Subject: [PATCH] sched: fix the inconsistent of SCHED_RR timeslice tuning knob showing

Clark add SCHED_RR tuning knob in commit ce0dbbbb30ae ("sched/rt: Add a
tuning knob to allow changing SCHED_RR timeslice"). The tuning knob
sched_rr_timeslice_ms gets user visible value in milliseconds, but it
shows still in jiffies as it is stored.
This inconsistence is confusing when HZ is not 1000, it seems like the
value set failed, such as HZ=100:

root# echo 100 > /proc/sys/kernel/sched_rr_timeslice_ms
root# cat /proc/sys/kernel/sched_rr_timeslice_ms
10

This fix makes the sched_rr_timeslice shows in milliseconds.

Signed-off-by: Shile Zhang <shile.zhang@...ia.com>
---
 include/linux/sched/sysctl.h | 1 +
 kernel/sched/core.c          | 5 +++--
 kernel/sched/rt.c            | 1 +
 kernel/sysctl.c              | 2 +-
 4 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 4411453..49308e1 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -59,6 +59,7 @@ extern unsigned int sysctl_sched_cfs_bandwidth_slice;
 extern unsigned int sysctl_sched_autogroup_enabled;
 #endif
 
+extern int sysctl_sched_rr_timeslice;
 extern int sched_rr_timeslice;
 
 extern int sched_rr_handler(struct ctl_table *table, int write,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c56fb57..9297563 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8369,8 +8369,9 @@ int sched_rr_handler(struct ctl_table *table, int write,
 	/* make sure that internally we keep jiffies */
 	/* also, writing zero resets timeslice to default */
 	if (!ret && write) {
-		sched_rr_timeslice = sched_rr_timeslice <= 0 ?
-			RR_TIMESLICE : msecs_to_jiffies(sched_rr_timeslice);
+		sched_rr_timeslice =
+			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
+			msecs_to_jiffies(sysctl_sched_rr_timeslice);
 	}
 	mutex_unlock(&mutex);
 	return ret;
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 2516b8d..8737a0e 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -9,6 +9,7 @@
 #include <linux/irq_work.h>
 
 int sched_rr_timeslice = RR_TIMESLICE;
+int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
 
 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8dbaec0..9a90097 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -416,7 +416,7 @@ static struct ctl_table kern_table[] = {
 	},
 	{
 		.procname	= "sched_rr_timeslice_ms",
-		.data		= &sched_rr_timeslice,
+		.data		= &sysctl_sched_rr_timeslice,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= sched_rr_handler,
-- 
2.6.2