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)?
-- Steve
> Patch against tip/master, currently 3.7-rc3.
>
> Signed-off-by: Clark Williams <willi...@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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