The following commit has been merged into the sched/core branch of tip:
Commit-ID: 2ab4092fc82d6001fdd9d51dbba27d04dec967e0
Gitweb: https://git.kernel.org/tip/2ab4092fc82d6001fdd9d51dbba27d04dec967e0
Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
AuthorDate: Fri, 18 Oct 2019 15:26:34 +02:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Mon, 21 Oct 2019 09:40:54 +02:00
sched/fair: Spread out tasks evenly when not overloaded
When there is only one 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@xxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Morten.Rasmussen@xxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: hdanton@xxxxxxxx
Cc: parth@xxxxxxxxxxxxx
Cc: pauld@xxxxxxxxxx
Cc: quentin.perret@xxxxxxx
Cc: riel@xxxxxxxxxxx
Cc: srikar@xxxxxxxxxxxxxxxxxx
Cc: valentin.schneider@xxxxxxx
Link: https://lkml.kernel.org/r/1571405198-27570-8-git-send-email-vincent.guittot@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 40 ++++++++++++++++++++++++++++------------
1 file changed, 28 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e6a3db0..f489f60 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8591,18 +8591,34 @@ 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 just moving the imbalance to 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_h_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 */
|