[PATCH 11/11] sched: rt-group: interface

From: Peter Zijlstra
Date: Sun Jan 06 2008 - 11:23:28 EST

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Change the rt_ratio interface to rt_runtime_us, to match rt_period_us.
This avoids picking a granularity for the ratio.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
include/linux/sched.h | 8 +++
kernel/sched.c | 116 ++++++++++++++++++++++++++++++++++----------------
kernel/sched_rt.c | 42 +++++++-----------
kernel/sysctl.c | 4 -
4 files changed, 106 insertions(+), 64 deletions(-)

Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1518,7 +1518,7 @@ extern unsigned int sysctl_sched_feature
extern unsigned int sysctl_sched_migration_cost;
extern unsigned int sysctl_sched_nr_migrate;
extern unsigned int sysctl_sched_rt_period;
-extern unsigned int sysctl_sched_rt_ratio;
+extern unsigned int sysctl_sched_rt_runtime;
#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
extern unsigned int sysctl_sched_min_bal_int_shares;
extern unsigned int sysctl_sched_max_bal_int_shares;
@@ -2014,6 +2014,12 @@ extern void sched_destroy_group(struct t
extern void sched_move_task(struct task_struct *tsk);
extern int sched_group_set_shares(struct task_group *tg, unsigned long shares);
extern unsigned long sched_group_shares(struct task_group *tg);
+extern int sched_group_set_rt_runtime(struct task_group *tg,
+ unsigned long rt_runtime_us);
+extern unsigned long sched_group_rt_runtime(struct task_group *tg);
+extern int sched_group_set_rt_period(struct task_group *tg,
+ unsigned long rt_runtime_us);
+extern unsigned long sched_group_rt_period(struct task_group *tg);

#endif

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -176,7 +176,7 @@ struct task_group {
struct sched_rt_entity **rt_se;
struct rt_rq **rt_rq;

- unsigned int rt_ratio;
+ u64 rt_runtime;
ktime_t rt_period;

/*
@@ -646,19 +646,16 @@ const_debug unsigned int sysctl_sched_fe
const_debug unsigned int sysctl_sched_nr_migrate = 32;

/*
- * period over which we measure -rt task cpu usage in us.
+ * period over which we measure rt task cpu usage in us.
* default: 1s
*/
const_debug unsigned int sysctl_sched_rt_period = 1000000;

-#define SCHED_RT_FRAC_SHIFT 16
-#define SCHED_RT_FRAC (1UL << SCHED_RT_FRAC_SHIFT)
-
/*
- * ratio of time -rt tasks may consume.
- * default: 95%
+ * part of the period that we allow rt tasks to run in us.
+ * default: 0.95s
*/
-const_debug unsigned int sysctl_sched_rt_ratio = 62259;
+const_debug unsigned int sysctl_sched_rt_runtime = 950000;

/*
* For kernel-internal use: high-speed (but slightly incorrect) per-cpu
@@ -7209,7 +7206,8 @@ void __init sched_init(void)
&per_cpu(init_sched_entity, i), i, 1);

rq->rt.rt_rq_type = RT_RQ_EDF;
- init_task_group.rt_ratio = sysctl_sched_rt_ratio; /* XXX */
+ init_task_group.rt_runtime =
+ sysctl_sched_rt_runtime * NSEC_PER_USEC;
init_task_group.rt_period =
ns_to_ktime(sysctl_sched_rt_period * NSEC_PER_USEC);
INIT_LIST_HEAD(&rq->leaf_rt_rq_list);
@@ -7606,7 +7604,7 @@ struct task_group *sched_create_group(vo
goto err;

tg->shares = NICE_0_LOAD;
- tg->rt_ratio = 0; /* XXX */
+ tg->rt_runtime = 0; /* XXX */
tg->rt_period = ns_to_ktime(sysctl_sched_rt_period * NSEC_PER_USEC);

for_each_possible_cpu(i) {
@@ -7801,41 +7799,87 @@ unsigned long sched_group_shares(struct
}

/*
- * Ensure the total rt_ratio <= sysctl_sched_rt_ratio
+ * Ensure that the real time constraints are schedulable.
*/
-int sched_group_set_rt_ratio(struct task_group *tg, unsigned long rt_ratio)
+static DEFINE_MUTEX(rt_constraints_mutex);
+
+static unsigned long to_ratio(u64 period, u64 runtime)
+{
+ u64 r = runtime * (1ULL << 16);
+ do_div(r, period);
+ return r;
+}
+
+static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
{
struct task_group *tgi;
unsigned long total = 0;
+ unsigned long global_ratio =
+ to_ratio(sysctl_sched_rt_period, sysctl_sched_rt_runtime);

rcu_read_lock();
- list_for_each_entry_rcu(tgi, &task_groups, list)
- total += tgi->rt_ratio;
+ list_for_each_entry_rcu(tgi, &task_groups, list) {
+ if (tgi == tg)
+ continue;
+
+ total += to_ratio(ktime_to_ns(tgi->rt_period), tgi->rt_runtime);
+ }
rcu_read_unlock();

- if (total + rt_ratio - tg->rt_ratio > sysctl_sched_rt_ratio)
- return -EINVAL;
+ return total + to_ratio(period, runtime) < global_ratio;
+}

- tg->rt_ratio = rt_ratio;
- return 0;
+int sched_group_set_rt_runtime(struct task_group *tg,
+ unsigned long rt_runtime_us)
+{
+ u64 rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
+ int err = 0;
+
+ mutex_lock(&rt_constraints_mutex);
+ if (!__rt_schedulable(tg, ktime_to_ns(tg->rt_period), rt_runtime)) {
+ err = -EINVAL;
+ goto unlock;
+ }
+
+ tg->rt_runtime = rt_runtime;
+ unlock:
+ mutex_unlock(&rt_constraints_mutex);
+
+ return err;
}

-unsigned long sched_group_rt_ratio(struct task_group *tg)
+unsigned long sched_group_rt_runtime(struct task_group *tg)
{
- return tg->rt_ratio;
+ u64 rt_runtime_us = tg->rt_runtime;
+
+ do_div(rt_runtime_us, NSEC_PER_USEC);
+ return rt_runtime_us;
}

-int sched_group_set_rt_period(struct task_group *tg, unsigned long rt_period)
+int sched_group_set_rt_period(struct task_group *tg, unsigned long rt_period_us)
{
- tg->rt_period = ns_to_ktime((u64)rt_period * NSEC_PER_USEC);
- return 0;
+ u64 rt_period = (u64)rt_period_us * NSEC_PER_USEC;
+ int err = 0;
+
+ mutex_lock(&rt_constraints_mutex);
+ if (!__rt_schedulable(tg, rt_period, tg->rt_runtime)) {
+ err = -EINVAL;
+ goto unlock;
+ }
+
+ tg->rt_period = ns_to_ktime(rt_period);
+ unlock:
+ mutex_unlock(&rt_constraints_mutex);
+
+ return err;
}

unsigned long sched_group_rt_period(struct task_group *tg)
{
- u64 ns = ktime_to_ns(tg->rt_period);
- do_div(ns, NSEC_PER_USEC);
- return ns;
+ u64 rt_period_us = ktime_to_ns(tg->rt_period);
+
+ do_div(rt_period_us, NSEC_PER_USEC);
+ return rt_period_us;
}

#endif /* CONFIG_FAIR_GROUP_SCHED */
@@ -7913,17 +7957,15 @@ static u64 cpu_shares_read_uint(struct c
return (u64) tg->shares;
}

-static int cpu_rt_ratio_write_uint(struct cgroup *cgrp, struct cftype *cftype,
- u64 rt_ratio_val)
+static int cpu_rt_runtime_write_uint(struct cgroup *cgrp, struct cftype *cftype,
+ u64 rt_runtime_val)
{
- return sched_group_set_rt_ratio(cgroup_tg(cgrp), rt_ratio_val);
+ return sched_group_set_rt_runtime(cgroup_tg(cgrp), rt_runtime_val);
}

-static u64 cpu_rt_ratio_read_uint(struct cgroup *cgrp, struct cftype *cft)
+static u64 cpu_rt_runtime_read_uint(struct cgroup *cgrp, struct cftype *cft)
{
- struct task_group *tg = cgroup_tg(cgrp);
-
- return (u64) tg->rt_ratio;
+ return sched_group_rt_runtime(cgroup_tg(cgrp));
}

static int cpu_rt_period_write_uint(struct cgroup *cgrp, struct cftype *cftype,
@@ -7934,7 +7976,7 @@ static int cpu_rt_period_write_uint(stru

static u64 cpu_rt_period_read_uint(struct cgroup *cgrp, struct cftype *cft)
{
- return (u64) sched_group_rt_period(cgroup_tg(cgrp));
+ return sched_group_rt_period(cgroup_tg(cgrp));
}

static struct cftype cpu_files[] = {
@@ -7944,9 +7986,9 @@ static struct cftype cpu_files[] = {
.write_uint = cpu_shares_write_uint,
},
{
- .name = "rt_ratio",
- .read_uint = cpu_rt_ratio_read_uint,
- .write_uint = cpu_rt_ratio_write_uint,
+ .name = "rt_runtime_us",
+ .read_uint = cpu_rt_runtime_read_uint,
+ .write_uint = cpu_rt_runtime_write_uint,
},
{
.name = "rt_period_us",
Index: linux-2.6/kernel/sched_rt.c
===================================================================
--- linux-2.6.orig/kernel/sched_rt.c
+++ linux-2.6/kernel/sched_rt.c
@@ -57,12 +57,12 @@ static inline int on_rt_rq(struct sched_

#ifdef CONFIG_FAIR_GROUP_SCHED

-static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
+static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
{
if (!rt_rq->tg)
- return SCHED_RT_FRAC;
+ return 0;

- return rt_rq->tg->rt_ratio;
+ return rt_rq->tg->rt_runtime;
}

static inline ktime_t sched_rt_period(struct rt_rq *rt_rq)
@@ -100,7 +100,7 @@ static inline struct rt_rq *group_rt_rq(
static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
static void dequeue_rt_entity(struct sched_rt_entity *rt_se);

-static void sched_rt_ratio_enqueue(struct rt_rq *rt_rq)
+static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
{
struct sched_rt_entity *rt_se = rt_rq->rt_se;

@@ -113,7 +113,7 @@ static void sched_rt_ratio_enqueue(struc
}
}

-static void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
+static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
{
struct sched_rt_entity *rt_se = rt_rq->rt_se;

@@ -218,9 +218,9 @@ static struct sched_rt_entity *next_rt_d

#else

-static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
+static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
{
- return sysctl_sched_rt_ratio;
+ return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
}

static inline ktime_t sched_rt_period(struct rt_rq *rt_rq)
@@ -257,11 +257,11 @@ static inline struct rt_rq *group_rt_rq(
return NULL;
}

-static inline void sched_rt_ratio_enqueue(struct rt_rq *rt_rq)
+static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
{
}

-static inline void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
+static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
{
}

@@ -300,25 +300,21 @@ static inline int rt_se_prio(struct sche
return rt_task_of(rt_se)->prio;
}

-static int sched_rt_ratio_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
{
- unsigned int rt_ratio = sched_rt_ratio(rt_rq);
- u64 period, ratio;
+ u64 runtime = sched_rt_runtime(rt_rq);

- if (rt_ratio == SCHED_RT_FRAC)
+ if (!runtime)
goto out;

if (rt_rq->rt_throttled)
goto out;

- period = sched_rt_period_ns(rt_rq);
- ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
-
- if (rt_rq->rt_time > ratio) {
+ if (rt_rq->rt_time > runtime) {
rt_rq->rt_throttled = 1;
if (rt_rq_throttled(rt_rq)) {
WARN_ON(!hrtimer_active(&rt_rq->rt_period_timer));
- sched_rt_ratio_dequeue(rt_rq);
+ sched_rt_rq_dequeue(rt_rq);
}
}

@@ -328,14 +324,12 @@ out:

static void update_sched_rt_period(struct rt_rq *rt_rq)
{
- u64 period = sched_rt_period_ns(rt_rq);
- unsigned long rt_ratio = sched_rt_ratio(rt_rq);
- u64 ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
+ u64 runtime = sched_rt_runtime(rt_rq);

- rt_rq->rt_time -= min(rt_rq->rt_time, ratio);
+ rt_rq->rt_time -= min(rt_rq->rt_time, runtime);
if (rt_rq->rt_throttled) {
rt_rq->rt_throttled = 0;
- sched_rt_ratio_enqueue(rt_rq);
+ sched_rt_rq_enqueue(rt_rq);
}
}

@@ -412,7 +406,7 @@ static void update_curr_rt(struct rq *rq
cpuacct_charge(curr, delta_exec);

rt_rq->rt_time += delta_exec;
- if (sched_rt_ratio_exceeded(rt_rq))
+ if (sched_rt_runtime_exceeded(rt_rq))
resched_task(curr);
}

Index: linux-2.6/kernel/sysctl.c
===================================================================
--- linux-2.6.orig/kernel/sysctl.c
+++ linux-2.6/kernel/sysctl.c
@@ -319,8 +319,8 @@ static struct ctl_table kern_table[] = {
},
{
.ctl_name = CTL_UNNUMBERED,
- .procname = "sched_rt_ratio",
- .data = &sysctl_sched_rt_ratio,
+ .procname = "sched_rt_runtime_us",
+ .data = &sysctl_sched_rt_runtime,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = &proc_dointvec,

--

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Next message: Peter Zijlstra: "[PATCH 02/11] sched: load_balance_monitor rename"
Previous message: Parag Warudkar: "Re: 2.6.24-rc6-git12: Reported regressions from 2.6.23"
In reply to: Peter Zijlstra: "[PATCH 00/11] another rt group sched update"
Next in thread: Peter Zijlstra: "[PATCH 02/11] sched: load_balance_monitor rename"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]