Subject: [PATCH] sched: add a tuning knob to allow changing RR timeslice
User wanted a facility simliar to the ability on Solaris to adjust
the SCHED_RR timeslice value. Add a /proc/sys/kernel scheduler knob
named sched_rr_timeslice_ms which allows global changing of the SCHED_RR
timeslice value. User visable value is in milliseconds but is stored as
jiffies. Setting to 0 (zero) resets to the default (currently 100ms).
Patch against tip/master, currently 3.7-rc3.
Signed-off-by: Clark Williams <[email protected]>
---
include/linux/sched.h | 6 +++++-
kernel/sched.c | 19 +++++++++++++++++++
kernel/sched_rt.c | 4 ++--
kernel/sysctl.c | 8 ++++++++
4 files changed, 34 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 12317b6..214bf27 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2097,11 +2097,15 @@ static inline unsigned int get_sysctl_timer_migration(void)
#endif
extern unsigned int sysctl_sched_rt_period;
extern int sysctl_sched_rt_runtime;
-
int sched_rt_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
+extern int sched_rr_timeslice;
+extern int sched_rr_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);
+
#ifdef CONFIG_SCHED_AUTOGROUP
extern unsigned int sysctl_sched_autogroup_enabled;
diff --git a/kernel/sched.c b/kernel/sched.c
index cdf9484..c63c3a4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -120,6 +120,7 @@
* Timeslices get refilled after they expire.
*/
#define DEF_TIMESLICE (100 * HZ / 1000)
+int sched_rr_timeslice = DEF_TIMESLICE;
/*
* single value that denotes runtime == period, ie unlimited time.
@@ -9614,6 +9615,24 @@ static int sched_rt_global_constraints(void)
}
#endif /* CONFIG_RT_GROUP_SCHED */
+int sched_rr_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+ static DEFINE_MUTEX(mutex);
+
+ mutex_lock(&mutex);
+ ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ /* make sure that internally we keep jiffies */
+ /* also, writing zero resets timeslice to default */
+ if (!ret && write)
+ sched_rr_timeslice = sched_rr_timeslice <= 0 ?
+ DEF_TIMESLICE : msecs_to_jiffies(sched_rr_timeslice);
+ mutex_unlock(&mutex);
+ return ret;
+}
+
int sched_rt_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index c108b9c..799dd09 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1791,7 +1791,7 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
if (--p->rt.time_slice)
return;
- p->rt.time_slice = DEF_TIMESLICE;
+ p->rt.time_slice = sched_rr_timeslice;
/*
* Requeue to the end of queue if we are not the only element
@@ -1819,7 +1819,7 @@ static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
* Time slice is 0 for SCHED_FIFO tasks
*/
if (task->policy == SCHED_RR)
- return DEF_TIMESLICE;
+ return sched_rr_timeslice;
else
return 0;
}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ea7ec7f..10b1129 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -362,6 +362,14 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = sched_rt_handler,
},
+ {
+ .procname = "sched_rr_timeslice_ms",
+ .data = &sched_rr_timeslice,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = sched_rr_handler,
+ },
+
#ifdef CONFIG_SCHED_AUTOGROUP
{
.procname = "sched_autogroup_enabled",
--
1.7.11.7