linux-kernel - [PATCH 5.5 053/257] sched/fair: Fix condition of avg

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Date:   Thu, 16 Apr 2020 15:21:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tao Zhou <ouwen210@...mail.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Mel Gorman <mgorman@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.5 053/257] sched/fair: Fix condition of avg_load calculation

From: Tao Zhou <ouwen210@...mail.com>

[ Upstream commit 6c8116c914b65be5e4d6f66d69c8142eb0648c22 ]

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:
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 0ff2f43ac9cd7..1f5ea23c752be 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8323,7 +8323,8 @@ 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;
 }
-- 
2.20.1