Commit ce0dbbbb authored by Clark Williams's avatar Clark Williams Committed by Ingo Molnar
Browse files

sched/rt: Add a tuning knob to allow changing SCHED_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: default avatarClark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20130207094704.13751796@riff.lan


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent cf4aebc2

include/linux/sched/sysctl.h

+14 −1
Original line number Diff line number Diff line
@@ -73,6 +73,13 @@ static inline unsigned int get_sysctl_timer_migration(void) 
	return 1;

}

#endif



/*

 *  control realtime throttling:

 *

 *  /proc/sys/kernel/sched_rt_period_us

 *  /proc/sys/kernel/sched_rt_runtime_us

 */

extern unsigned int sysctl_sched_rt_period;

extern int sysctl_sched_rt_runtime;
@@ -90,7 +97,13 @@ extern unsigned int sysctl_sched_autogroup_enabled; 
 */

#define RR_TIMESLICE		(100 * HZ / 1000)



int sched_rt_handler(struct ctl_table *table, int write,

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);



extern int sched_rt_handler(struct ctl_table *table, int write,

		void __user *buffer, size_t *lenp,

		loff_t *ppos);

kernel/sched/core.c

+19 −0
Original line number Diff line number Diff line
@@ -7509,6 +7509,25 @@ 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)

kernel/sched/rt.c

+4 −2
Original line number Diff line number Diff line
@@ -7,6 +7,8 @@ 


#include <linux/slab.h>



int sched_rr_timeslice = RR_TIMESLICE;



static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);



struct rt_bandwidth def_rt_bandwidth;
@@ -2016,7 +2018,7 @@ 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
@@ -2047,7 +2049,7 @@ 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;

}

kernel/sysctl.c

+7 −0
Original line number Diff line number Diff line
@@ -404,6 +404,13 @@ 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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