linux-kernel - [tip: sched/core] sched/fair: Fix condition of avg

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Date:   Fri, 20 Mar 2020 12:58:02 -0000
From:   "tip-bot2 for Tao Zhou" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Tao Zhou <ouwen210@...mail.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Mel Gorman <mgorman@...e.de>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: sched/core] sched/fair: Fix condition of avg_load calculation

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

Commit-ID:     6c8116c914b65be5e4d6f66d69c8142eb0648c22
Gitweb:        https://git.kernel.org/tip/6c8116c914b65be5e4d6f66d69c8142eb0648c22
Author:        Tao Zhou <ouwen210@...mail.com>
AuthorDate:    Thu, 19 Mar 2020 11:39:20 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 20 Mar 2020 13:06:20 +01:00

sched/fair: Fix condition of avg_load calculation

In update_sg_wakeup_stats(), the comment says:

Computing avg_load makes sense only when group is fully
busy or overloaded.

But, the code below this comment does not check like this.

>>From reading the code about avg_load in other functions, I
confirm that avg_load should be calculated in fully busy or
overloaded case. The comment is correct and the checking
condition is wrong. So, change that condition.

Fixes: 57abff067a08 ("sched/fair: Rework find_idlest_group()")
Signed-off-by: Tao Zhou <ouwen210@...mail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Acked-by: Mel Gorman <mgorman@...e.de>
Link: https://lkml.kernel.org/r/Message-ID:
---
 kernel/sched/fair.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 783356f..d7fb20a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8631,7 +8631,8 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 	 * Computing avg_load makes sense only when group is fully busy or
 	 * overloaded
 	 */
-	if (sgs->group_type < group_fully_busy)
+	if (sgs->group_type == group_fully_busy ||
+		sgs->group_type == group_overloaded)
 		sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
 				sgs->group_capacity;
 }