[PATCH] sched/fair: fix statistics for find_idlest_group()

[PATCH] sched/fair: fix statistics for find_idlest_group()

[Vincent Guittot]

sgs->group_weight is not set while gathering statistics in
update_sg_wakeup_stats(). This means that a group can be classified as
fully busy with 0 running tasks if utilization is high enough.

This path is mainly used for fork and exec.

Fixes: 57abff067a08 ("sched/fair: Rework find_idlest_group()")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a7e11b1bb64c..643ed6d8b8ff 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8354,6 +8354,8 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 
 	sgs->group_capacity = group->sgc->capacity;
 
+	sgs->group_weight = group->group_weight;
+
 	sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
 
 	/*
-- 
2.17.1

Re: [PATCH] sched/fair: fix statistics for find_idlest_group()

[Peter Zijlstra]

On Tue, Feb 18, 2020 at 03:45:34PM +0100, Vincent Guittot wrote:
> sgs->group_weight is not set while gathering statistics in
> update_sg_wakeup_stats(). This means that a group can be classified as
> fully busy with 0 running tasks if utilization is high enough.
> 
> This path is mainly used for fork and exec.
> 
> Fixes: 57abff067a08 ("sched/fair: Rework find_idlest_group()")
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

Thanks!

[tip: sched/urgent] sched/fair: Fix statistics for find_idlest_group()

[tip-bot2 for Vincent Guittot]

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     289de35984815576793f579ec27248609e75976e
Gitweb:        https://git.kernel.org/tip/289de35984815576793f579ec27248609e75976e
Author:        Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate:    Tue, 18 Feb 2020 15:45:34 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 27 Feb 2020 10:08:27 +01:00

sched/fair: Fix statistics for find_idlest_group()

sgs->group_weight is not set while gathering statistics in
update_sg_wakeup_stats(). This means that a group can be classified as
fully busy with 0 running tasks if utilization is high enough.

This path is mainly used for fork and exec.

Fixes: 57abff067a08 ("sched/fair: Rework find_idlest_group()")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/r/20200218144534.4564-1-vincent.guittot@linaro.org
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3c8a379..c1217bf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8337,6 +8337,8 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 
 	sgs->group_capacity = group->sgc->capacity;
 
+	sgs->group_weight = group->group_weight;
+
 	sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
 
 	/*