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
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 <willi...@redhat.com>
---
include/linux/sched.h | 7 ++++++-
kernel/sched/core.c | 30 ++++++++++++++++++++++++++++++
kernel/sched/rt.c | 4 ++--
kernel/sysctl.c | 7 +++++++
4 files changed, 45 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 03be150..1e2f38a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2071,11 +2071,16 @@ static inline unsigned int
get_sysctl_timer_migration(void) #endif /* CONFIG_SCHED_DEBUG */
extern unsigned int sysctl_sched_rt_period;
extern int sysctl_sched_rt_runtime;
-
+extern int sysctl_sched_rr_timeslice_ms;
+extern int sched_rr_timeslice;
int sched_rt_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
+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 c2e077c..318f617 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -288,6 +288,17 @@ __read_mostly int scheduler_running;
int sysctl_sched_rt_runtime = 950000;
+/*
+ * SCHED_RR timeslice in jiffies
+ *
+ */
+int sched_rr_timeslice = RR_TIMESLICE;
+int sysctl_sched_rr_timeslice_ms;
+
+static inline void init_rr_timeslice()
+{
+ sysctl_sched_rr_timeslice_ms = msecs_to_jiffies(RR_TIMESLICE);
+}
/*
* __task_rq_lock - lock the rq @p resides on.
@@ -6863,6 +6874,8 @@ void __init sched_init(void)
init_rt_bandwidth(&def_rt_bandwidth,
global_rt_period(), global_rt_runtime());
+ init_rr_timeslice();
+
#ifdef CONFIG_RT_GROUP_SCHED
init_rt_bandwidth(&root_task_group.rt_bandwidth,
global_rt_period(), global_rt_runtime());
@@ -7543,6 +7556,23 @@ int sched_rt_handler(struct ctl_table *table,
int write, return ret;
}
+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 we maintain jiffies internally */
+ if (!ret && write)
+ sched_rr_timeslice = (sysctl_sched_rr_timeslice_ms <=
0) ?
+ RR_TIMESLICE :
msecs_to_jiffies(sysctl_sched_rr_timeslice_ms);
+ mutex_unlock(&mutex);
+ return ret;
+}
+
#ifdef CONFIG_CGROUP_SCHED
/* return corresponding task_group object of a cgroup */
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 418feb0..71aa6d0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -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
*/
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 b769d25..9fa0885 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -403,6 +403,13 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = sched_rt_handler,
},
+ {
+ .procname = "sched_rr_timeslice_ms",
+ .data = &sysctl_sched_rr_timeslice_ms,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = sched_rr_handler,
+ },
#ifdef CONFIG_SCHED_AUTOGROUP
{
.procname = "sched_autogroup_enabled",
--
1.7.11.7
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