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Date: Wed, 1 Jun 2016 20:39:20 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Cc: Vincent Guittot <vincent.guittot@...aro.org>,
Ben Segall <bsegall@...gle.com>,
Morten Rasmussen <morten.rasmussen@....com>,
Yuyang Du <yuyang.du@...el.com>
Subject: [RFC PATCH 1/3] sched/fair: Aggregate task utilization only on root cfs_rq
cpu utilization (cpu_util()) is defined as the cpu (original) capacity
capped cfs_rq->avg->util_avg signal of the root cfs_rq.
With the current pelt version, the utilization of a task [en|de]queued
on/from a cfs_rq, representing a task group other than the root task group
on a cpu, is not immediately propagated down to the root cfs_rq.
This makes decisions based on cpu_util() for scheduling or cpu frequency
settings less accurate in case tasks are running in task groups.
This patch aggregates the task utilization only on the root cfs_rq,
essentially avoiding maintaining utilization for a se/cfs_rq representing
task groups other than the root task group (!entity_is_task(se) and
&rq_of(cfs_rq)->cfs != cfs_rq).
The additional if/else condition to set @update_util in
__update_load_avg() is replaced in 'sched/fair: Change @running of
__update_load_avg() to @update_util' by providing the information whether
utilization has to be maintained via an argument to this function.
The additional requirements for the alignment of the last_update_time of a
se and the root cfs_rq are handled by the patch 'sched/fair: Sync se with
root cfs_rq'.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
kernel/sched/fair.c | 48 ++++++++++++++++++++++++++++++++++++------------
1 file changed, 36 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 218f8e83db73..212becd3708f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2705,6 +2705,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
u32 contrib;
unsigned int delta_w, scaled_delta_w, decayed = 0;
unsigned long scale_freq, scale_cpu;
+ int update_util = 0;
delta = now - sa->last_update_time;
/*
@@ -2725,6 +2726,12 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
return 0;
sa->last_update_time = now;
+ if (cfs_rq) {
+ if (&rq_of(cfs_rq)->cfs == cfs_rq)
+ update_util = 1;
+ } else if (entity_is_task(container_of(sa, struct sched_entity, avg)))
+ update_util = 1;
+
scale_freq = arch_scale_freq_capacity(NULL, cpu);
scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
@@ -2750,7 +2757,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
weight * scaled_delta_w;
}
}
- if (running)
+ if (update_util && running)
sa->util_sum += scaled_delta_w * scale_cpu;
delta -= delta_w;
@@ -2774,7 +2781,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
if (cfs_rq)
cfs_rq->runnable_load_sum += weight * contrib;
}
- if (running)
+ if (update_util && running)
sa->util_sum += contrib * scale_cpu;
}
@@ -2785,7 +2792,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
if (cfs_rq)
cfs_rq->runnable_load_sum += weight * scaled_delta;
}
- if (running)
+ if (update_util && running)
sa->util_sum += scaled_delta * scale_cpu;
sa->period_contrib += delta;
@@ -2796,7 +2803,8 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
cfs_rq->runnable_load_avg =
div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
}
- sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
+ if (update_util)
+ sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
}
return decayed;
@@ -2918,7 +2926,8 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
removed_load = 1;
}
- if (atomic_long_read(&cfs_rq->removed_util_avg)) {
+ if ((&rq_of(cfs_rq)->cfs == cfs_rq) &&
+ atomic_long_read(&cfs_rq->removed_util_avg)) {
long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
sa->util_avg = max_t(long, sa->util_avg - r, 0);
sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
@@ -2982,8 +2991,12 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
se->avg.last_update_time = cfs_rq->avg.last_update_time;
cfs_rq->avg.load_avg += se->avg.load_avg;
cfs_rq->avg.load_sum += se->avg.load_sum;
- cfs_rq->avg.util_avg += se->avg.util_avg;
- cfs_rq->avg.util_sum += se->avg.util_sum;
+
+ if (!entity_is_task(se))
+ return;
+
+ rq_of(cfs_rq)->cfs.avg.util_avg += se->avg.util_avg;
+ rq_of(cfs_rq)->cfs.avg.util_sum += se->avg.util_sum;
cfs_rq_util_change(cfs_rq);
}
@@ -2996,8 +3009,14 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
- cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
- cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
+
+ if (!entity_is_task(se))
+ return;
+
+ rq_of(cfs_rq)->cfs.avg.util_avg =
+ max_t(long, rq_of(cfs_rq)->cfs.avg.util_avg - se->avg.util_avg, 0);
+ rq_of(cfs_rq)->cfs.avg.util_sum =
+ max_t(s32, rq_of(cfs_rq)->cfs.avg.util_sum - se->avg.util_sum, 0);
cfs_rq_util_change(cfs_rq);
}
@@ -3082,7 +3101,11 @@ void remove_entity_load_avg(struct sched_entity *se)
__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
- atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
+
+ if (!entity_is_task(se))
+ return;
+
+ atomic_long_add(se->avg.util_avg, &rq_of(cfs_rq)->cfs.removed_util_avg);
}
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
@@ -8460,7 +8483,9 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
#endif
#ifdef CONFIG_SMP
atomic_long_set(&cfs_rq->removed_load_avg, 0);
- atomic_long_set(&cfs_rq->removed_util_avg, 0);
+
+ if (&rq_of(cfs_rq)->cfs == cfs_rq)
+ atomic_long_set(&cfs_rq->removed_util_avg, 0);
#endif
}
@@ -8525,7 +8550,6 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
init_cfs_rq(cfs_rq);
init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
init_entity_runnable_average(se);
- post_init_entity_util_avg(se);
}
return 1;
--
1.9.1
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