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Subject[tip:sched/balancing] sched: Scale down cpu_power due to RT tasks
Commit-ID:  e9e9250bc78e7f6342517214c0178a529807964b
Gitweb: http://git.kernel.org/tip/e9e9250bc78e7f6342517214c0178a529807964b
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 1 Sep 2009 10:34:37 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 4 Sep 2009 10:09:55 +0200

sched: Scale down cpu_power due to RT tasks

Keep an average on the amount of time spend on RT tasks and use
that fraction to scale down the cpu_power for regular tasks.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083826.287778431@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
include/linux/sched.h | 1 +
kernel/sched.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++--
kernel/sched_rt.c | 6 +---
kernel/sysctl.c | 8 ++++++
4 files changed, 72 insertions(+), 7 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9c81c92..c67ddf3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1831,6 +1831,7 @@ extern unsigned int sysctl_sched_child_runs_first;
extern unsigned int sysctl_sched_features;
extern unsigned int sysctl_sched_migration_cost;
extern unsigned int sysctl_sched_nr_migrate;
+extern unsigned int sysctl_sched_time_avg;
extern unsigned int sysctl_timer_migration;

int sched_nr_latency_handler(struct ctl_table *table, int write,
diff --git a/kernel/sched.c b/kernel/sched.c
index 036600f..ab532b5 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -627,6 +627,9 @@ struct rq {

struct task_struct *migration_thread;
struct list_head migration_queue;
+
+ u64 rt_avg;
+ u64 age_stamp;
#endif

/* calc_load related fields */
@@ -863,6 +866,14 @@ unsigned int sysctl_sched_shares_ratelimit = 250000;
unsigned int sysctl_sched_shares_thresh = 4;

/*
+ * period over which we average the RT time consumption, measured
+ * in ms.
+ *
+ * default: 1s
+ */
+const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
+
+/*
* period over which we measure -rt task cpu usage in us.
* default: 1s
*/
@@ -1280,12 +1291,37 @@ void wake_up_idle_cpu(int cpu)
}
#endif /* CONFIG_NO_HZ */

+static u64 sched_avg_period(void)
+{
+ return (u64)sysctl_sched_time_avg * NSEC_PER_MSEC / 2;
+}
+
+static void sched_avg_update(struct rq *rq)
+{
+ s64 period = sched_avg_period();
+
+ while ((s64)(rq->clock - rq->age_stamp) > period) {
+ rq->age_stamp += period;
+ rq->rt_avg /= 2;
+ }
+}
+
+static void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
+{
+ rq->rt_avg += rt_delta;
+ sched_avg_update(rq);
+}
+
#else /* !CONFIG_SMP */
static void resched_task(struct task_struct *p)
{
assert_spin_locked(&task_rq(p)->lock);
set_tsk_need_resched(p);
}
+
+static void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
+{
+}
#endif /* CONFIG_SMP */

#if BITS_PER_LONG == 32
@@ -3699,7 +3735,7 @@ static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
}
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */

-unsigned long __weak arch_smt_gain(struct sched_domain *sd, int cpu)
+unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
{
unsigned long weight = cpumask_weight(sched_domain_span(sd));
unsigned long smt_gain = sd->smt_gain;
@@ -3709,6 +3745,24 @@ unsigned long __weak arch_smt_gain(struct sched_domain *sd, int cpu)
return smt_gain;
}

+unsigned long scale_rt_power(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ u64 total, available;
+
+ sched_avg_update(rq);
+
+ total = sched_avg_period() + (rq->clock - rq->age_stamp);
+ available = total - rq->rt_avg;
+
+ if (unlikely((s64)total < SCHED_LOAD_SCALE))
+ total = SCHED_LOAD_SCALE;
+
+ total >>= SCHED_LOAD_SHIFT;
+
+ return div_u64(available, total);
+}
+
static void update_cpu_power(struct sched_domain *sd, int cpu)
{
unsigned long weight = cpumask_weight(sched_domain_span(sd));
@@ -3719,11 +3773,15 @@ static void update_cpu_power(struct sched_domain *sd, int cpu)
/* here we could scale based on cpufreq */

if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
- power *= arch_smt_gain(sd, cpu);
+ power *= arch_scale_smt_power(sd, cpu);
power >>= SCHED_LOAD_SHIFT;
}

- /* here we could scale based on RT time */
+ power *= scale_rt_power(cpu);
+ power >>= SCHED_LOAD_SHIFT;
+
+ if (!power)
+ power = 1;

if (power != old) {
sdg->__cpu_power = power;
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 3d4020a..2eb4bd6 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -615,6 +615,8 @@ static void update_curr_rt(struct rq *rq)
curr->se.exec_start = rq->clock;
cpuacct_charge(curr, delta_exec);

+ sched_rt_avg_update(rq, delta_exec);
+
if (!rt_bandwidth_enabled())
return;

@@ -887,8 +889,6 @@ static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)

if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
enqueue_pushable_task(rq, p);
-
- inc_cpu_load(rq, p->se.load.weight);
}

static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
@@ -899,8 +899,6 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
dequeue_rt_entity(rt_se);

dequeue_pushable_task(rq, p);
-
- dec_cpu_load(rq, p->se.load.weight);
}

/*
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 58be760..6c9836e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -332,6 +332,14 @@ static struct ctl_table kern_table[] = {
},
{
.ctl_name = CTL_UNNUMBERED,
+ .procname = "sched_time_avg",
+ .data = &sysctl_sched_time_avg,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+ {
+ .ctl_name = CTL_UNNUMBERED,
.procname = "timer_migration",
.data = &sysctl_timer_migration,
.maxlen = sizeof(unsigned int),

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