On Thu, 24 Jan 2013 17:59:55 +0100 Ingo Molnar <mi...@kernel.org> wrote:
>
> * Clark Williams <willi...@redhat.com> wrote:
>
> > This version stores the user-input value in a separate
> > location from the jiffies values used by the scheduler, to
> > prevent a race condition.
> >
> > Subject: [PATCH v2] sched: add a tuning knob to allow changing
> > RR timeslice
>
> looks useful.
>
> > @@ -2010,7 +2010,7 @@ static void task_tick_rt(struct rq *rq, struct
> > task_struct *p, int queued) if (--p->rt.time_slice)
> > return;
> >
> > - p->rt.time_slice = RR_TIMESLICE;
> > + p->rt.time_slice = sched_rr_timeslice;
> >
> > /*
> > * Requeue to the end of queue if we (and all of our
> > ancestors) are the @@ -2041,7 +2041,7 @@ static unsigned int
> > get_rr_interval_rt(struct rq *rq, struct task_struct *task)
> > * Time slice is 0 for SCHED_FIFO tasks
>
> Patch wont apply due to patch corruption, alas.
>
>
Easily fixed. Modified for 3.8-rc4:
commit 0e2d40c5c84d06670f85cc212591f27f69f59c62
Author: Clark Williams <willi...@redhat.com>
Date: Thu Jan 24 13:51:01 2013 -0600
[kernel] sched: add a tuning knob to allow changing RR timeslice
Add a /proc/sys/kernel scheduler knob named sched_rr_timeslice_ms
that 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).
Signed-off-by: Clark Williams <willi...@redhat.com>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6fc8f45..d803690 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2082,6 +2082,11 @@ 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/core.c b/kernel/sched/core.c
index 257002c..5675074 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7507,6 +7507,24 @@ 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 ?
+ RR_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 418feb0..6c54e83 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -11,6 +11,8 @@ static int do_sched_rt_period_timer(struct rt_bandwidth
*rt_b, int overrun);
struct rt_bandwidth def_rt_bandwidth;
+int sched_rr_timeslice = RR_TIMESLICE;
+
static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
{
struct rt_bandwidth *rt_b =
@@ -2010,7 +2012,7 @@ static void task_tick_rt(struct rq *rq, struct
task_struct *p, int queued)
if (--p->rt.time_slice)
return;
- p->rt.time_slice = RR_TIMESLICE;
+ p->rt.time_slice = sched_rr_timeslice;
/*
* Requeue to the end of queue if we (and all of our ancestors) are the
@@ -2041,7 +2043,7 @@ 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 RR_TIMESLICE;
+ return sched_rr_timeslice;
else
return 0;
}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c88878d..1eabf86 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -403,6 +403,14 @@ 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",
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