From: Vincent Guittot <vincent.guittot@linaro.org>
To: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org
Cc: quentin.perret@arm.com, dietmar.eggemann@arm.com,
Morten.Rasmussen@arm.com, pauld@redhat.com,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH 5/5] sched/fair: evenly spread tasks when not overloaded
Date: Fri, 19 Jul 2019 09:58:25 +0200 [thread overview]
Message-ID: <1563523105-24673-6-git-send-email-vincent.guittot@linaro.org> (raw)
In-Reply-To: <1563523105-24673-1-git-send-email-vincent.guittot@linaro.org>
When there is only 1 cpu per group, using the idle cpus to evenly spread
tasks doesn't make sense and nr_running is a better metrics.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/fair.c | 42 +++++++++++++++++++++++++++++-------------
1 file changed, 29 insertions(+), 13 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c221713..a60ddef 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8353,7 +8353,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
env->src_grp_type = migrate_task;
imbalance = max_t(long, 0, (local->idle_cpus - busiest->idle_cpus) >> 1);
- if (sds->prefer_sibling)
+ if (sds->prefer_sibling || busiest->group_weight == 1)
/*
* When prefer sibling, evenly spread running tasks on
* groups.
@@ -8531,18 +8531,34 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
busiest->sum_nr_running > local->sum_nr_running + 1)
goto force_balance;
- if (busiest->group_type != group_overloaded &&
- (env->idle == CPU_NOT_IDLE ||
- local->idle_cpus <= (busiest->idle_cpus + 1)))
- /*
- * If the busiest group is not overloaded
- * and there is no imbalance between this and busiest group
- * wrt idle CPUs, it is balanced. The imbalance
- * becomes significant if the diff is greater than 1 otherwise
- * we might end up to just move the imbalance on another
- * group.
- */
- goto out_balanced;
+ if (busiest->group_type != group_overloaded) {
+ if (env->idle == CPU_NOT_IDLE)
+ /*
+ * If the busiest group is not overloaded (and as a
+ * result the local one too) but this cpu is already
+ * busy, let another idle cpu try to pull task.
+ */
+ goto out_balanced;
+
+ if (busiest->group_weight > 1 &&
+ local->idle_cpus <= (busiest->idle_cpus + 1))
+ /*
+ * If the busiest group is not overloaded
+ * and there is no imbalance between this and busiest
+ * group wrt idle CPUs, it is balanced. The imbalance
+ * becomes significant if the diff is greater than 1
+ * otherwise we might end up to just move the imbalance
+ * on another group. Of course this applies only if
+ * there is more than 1 CPU per group.
+ */
+ goto out_balanced;
+
+ if (busiest->sum_nr_running == 1)
+ /*
+ * busiest doesn't have any tasks waiting to run
+ */
+ goto out_balanced;
+ }
force_balance:
/* Looks like there is an imbalance. Compute it */
--
2.7.4
prev parent reply other threads:[~2019-07-19 7:59 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 7:58 [PATCH 0/5] sched/fair: rework the CFS load balance Vincent Guittot
2019-07-19 7:58 ` [PATCH 1/5] sched/fair: clean up asym packing Vincent Guittot
2019-07-19 7:58 ` [PATCH 2/5] sched/fair: rename sum_nr_running to sum_h_nr_running Vincent Guittot
2019-07-19 12:51 ` Peter Zijlstra
2019-07-19 13:44 ` Vincent Guittot
2019-07-26 2:17 ` Srikar Dronamraju
2019-07-26 8:41 ` Vincent Guittot
2019-07-19 7:58 ` [PATCH 3/5] sched/fair: rework load_balance Vincent Guittot
2019-07-19 12:52 ` Peter Zijlstra
2019-07-19 13:46 ` Vincent Guittot
2019-07-19 12:54 ` Peter Zijlstra
2019-07-19 14:02 ` Vincent Guittot
2019-07-20 11:31 ` Peter Zijlstra
2019-07-19 13:06 ` Peter Zijlstra
2019-07-19 13:57 ` Vincent Guittot
2019-07-19 13:12 ` Peter Zijlstra
2019-07-19 14:13 ` Vincent Guittot
2019-07-19 13:22 ` Peter Zijlstra
2019-07-19 13:55 ` Vincent Guittot
2019-07-25 17:17 ` Valentin Schneider
2019-07-26 9:01 ` Vincent Guittot
2019-07-26 10:41 ` Valentin Schneider
2019-07-26 12:30 ` Vincent Guittot
2019-07-26 14:01 ` Valentin Schneider
2019-07-26 14:47 ` Vincent Guittot
2019-07-29 14:28 ` Valentin Schneider
2019-07-26 13:58 ` Srikar Dronamraju
2019-07-26 14:09 ` Valentin Schneider
2019-07-26 14:42 ` Vincent Guittot
2019-07-31 13:43 ` Srikar Dronamraju
2019-07-31 15:37 ` Vincent Guittot
2019-07-19 7:58 ` [PATCH 4/5] sched/fair: use load instead of runnable load Vincent Guittot
2019-07-19 7:58 ` Vincent Guittot [this message]
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