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Subject[CFS Bandwidth Control v4 4/7] sched: unthrottle cfs_rq(s) who ran out of quota at period refresh
At the start of a new period there are several actions we must take:
- Refresh global bandwidth pool
- Unthrottle entities who ran out of quota as refreshed bandwidth permits

Unthrottled entities have the cfs_rq->throttled flag set and are re-enqueued
into the cfs entity hierarchy.

sched_rt_period_mask() is refactored slightly into sched_bw_period_mask()
since it is now shared by both cfs and rt bandwidth period timers.

The !CONFIG_RT_GROUP_SCHED && CONFIG_SMP case has been collapsed to use
rd->span instead of cpu_online_mask since I think that was incorrect before
(don't want to hit cpu's outside of your root_domain for RT bandwidth).

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
kernel/sched.c | 16 +++++++++++
kernel/sched_fair.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++-
kernel/sched_rt.c | 19 -------------
3 files changed, 90 insertions(+), 19 deletions(-)

Index: tip/kernel/sched.c
===================================================================
--- tip.orig/kernel/sched.c
+++ tip/kernel/sched.c
@@ -1561,6 +1561,8 @@ static int tg_nop(struct task_group *tg,
}
#endif

+static inline const struct cpumask *sched_bw_period_mask(void);
+
#ifdef CONFIG_SMP
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
@@ -8503,6 +8505,18 @@ void set_curr_task(int cpu, struct task_

#endif

+#ifdef CONFIG_SMP
+static inline const struct cpumask *sched_bw_period_mask(void)
+{
+ return cpu_rq(smp_processor_id())->rd->span;
+}
+#else
+static inline const struct cpumask *sched_bw_period_mask(void)
+{
+ return cpu_online_mask;
+}
+#endif
+
#ifdef CONFIG_FAIR_GROUP_SCHED
static void free_fair_sched_group(struct task_group *tg)
{
@@ -9240,6 +9254,8 @@ static int tg_set_cfs_bandwidth(struct t

raw_spin_lock_irq(&rq->lock);
init_cfs_rq_quota(cfs_rq);
+ if (cfs_rq_throttled(cfs_rq))
+ unthrottle_cfs_rq(cfs_rq);
raw_spin_unlock_irq(&rq->lock);
}
mutex_unlock(&mutex);
Index: tip/kernel/sched_fair.c
===================================================================
--- tip.orig/kernel/sched_fair.c
+++ tip/kernel/sched_fair.c
@@ -327,6 +327,13 @@ static inline u64 sched_cfs_bandwidth_sl
return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}

+static inline
+struct cfs_rq *cfs_bandwidth_cfs_rq(struct cfs_bandwidth *cfs_b, int cpu)
+{
+ return container_of(cfs_b, struct task_group,
+ cfs_bandwidth)->cfs_rq[cpu];
+}
+
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
return &tg->cfs_bandwidth;
@@ -1513,6 +1520,33 @@ out_throttled:
update_cfs_rq_load_contribution(cfs_rq, 1);
}

+static void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
+{
+ struct rq *rq = rq_of(cfs_rq);
+ struct sched_entity *se;
+
+ se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
+
+ update_rq_clock(rq);
+ /* (Try to) avoid maintaining share statistics for idle time */
+ cfs_rq->load_stamp = cfs_rq->load_last = rq->clock_task;
+
+ cfs_rq->throttled = 0;
+ for_each_sched_entity(se) {
+ if (se->on_rq)
+ break;
+
+ cfs_rq = cfs_rq_of(se);
+ enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
+ if (cfs_rq_throttled(cfs_rq))
+ break;
+ }
+
+ /* determine whether we need to wake up potentally idle cpu */
+ if (rq->curr == rq->idle && rq->cfs.nr_running)
+ resched_task(rq->curr);
+}
+
static void account_cfs_rq_quota(struct cfs_rq *cfs_rq,
unsigned long delta_exec)
{
@@ -1535,8 +1569,46 @@ static void account_cfs_rq_quota(struct

static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
{
- return 1;
+ int i, idle = 1;
+ u64 delta;
+ const struct cpumask *span;
+
+ if (cfs_b->quota == RUNTIME_INF)
+ return 1;
+
+ /* reset group quota */
+ raw_spin_lock(&cfs_b->lock);
+ cfs_b->runtime = cfs_b->quota;
+ raw_spin_unlock(&cfs_b->lock);
+
+ span = sched_bw_period_mask();
+ for_each_cpu(i, span) {
+ struct rq *rq = cpu_rq(i);
+ struct cfs_rq *cfs_rq = cfs_bandwidth_cfs_rq(cfs_b, i);
+
+ if (cfs_rq->nr_running)
+ idle = 0;
+
+ if (!cfs_rq_throttled(cfs_rq))
+ continue;
+
+ delta = tg_request_cfs_quota(cfs_rq->tg);
+
+ if (delta) {
+ raw_spin_lock(&rq->lock);
+ cfs_rq->quota_assigned += delta;
+
+ /* avoid race with tg_set_cfs_bandwidth */
+ if (cfs_rq_throttled(cfs_rq) &&
+ cfs_rq->quota_used < cfs_rq->quota_assigned)
+ unthrottle_cfs_rq(cfs_rq);
+ raw_spin_unlock(&rq->lock);
+ }
+ }
+
+ return idle;
}
+
#endif

#ifdef CONFIG_SMP
Index: tip/kernel/sched_rt.c
===================================================================
--- tip.orig/kernel/sched_rt.c
+++ tip/kernel/sched_rt.c
@@ -252,18 +252,6 @@ static int rt_se_boosted(struct sched_rt
return p->prio != p->normal_prio;
}

-#ifdef CONFIG_SMP
-static inline const struct cpumask *sched_rt_period_mask(void)
-{
- return cpu_rq(smp_processor_id())->rd->span;
-}
-#else
-static inline const struct cpumask *sched_rt_period_mask(void)
-{
- return cpu_online_mask;
-}
-#endif
-
static inline
struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
{
@@ -321,11 +309,6 @@ static inline int rt_rq_throttled(struct
return rt_rq->rt_throttled;
}

-static inline const struct cpumask *sched_rt_period_mask(void)
-{
- return cpu_online_mask;
-}
-
static inline
struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
{
@@ -543,7 +526,7 @@ static int do_sched_rt_period_timer(stru
if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
return 1;

- span = sched_rt_period_mask();
+ span = sched_bw_period_mask();
for_each_cpu(i, span) {
int enqueue = 0;
struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);



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