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SubjectRe: [PATCH] sched: add a tuning knob to allow changing RR tmeslice
On Wed, 23 Jan 2013 15:09:38 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Thu, 2012-11-08 at 14:27 -0600, Clark Williams wrote:
> > 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).
> >
>
> Hmm, has this been ignored?
>
> I guess the real question, is it still needed (or wanted)?
>

Yes, we've got a couple of customers that have been asking for it.

> -- Steve
>
> > Patch against tip/master, currently 3.7-rc3.
> >
> > Signed-off-by: Clark Williams <williams@redhat.com>
> > ---
> > 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",
>
>
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