linux-kernel - [PATCH 2/3] sched/uclamp: Ignore (util == 0) optimization in feec() when p_util

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Message-Id: <20230129161444.1674958-3-qyousef@layalina.io>
Date:   Sun, 29 Jan 2023 16:14:43 +0000
From:   Qais Yousef <qyousef@...alina.io>
To:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     linux-kernel@...r.kernel.org, Lukasz Luba <lukasz.luba@....com>,
        Wei Wang <wvw@...gle.com>, Xuewen Yan <xuewen.yan94@...il.com>,
        Hank <han.lin@...iatek.com>,
        Jonathan JMChen <Jonathan.JMChen@...iatek.com>,
        Qais Yousef <qyousef@...alina.io>
Subject: [PATCH 2/3] sched/uclamp: Ignore (util == 0) optimization in feec() when p_util_max = 0

find_energy_efficient_cpu() bails out early if effective util of the
task is 0. When uclamp is being used, this could lead to wrong decisions
when uclamp_max is set to 0. Cater for that.

Fixes: d81304bc6193 ("sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition")
Signed-off-by: Qais Yousef (Google) <qyousef@...alina.io>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ca2c389d3180..3521aad67aa0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7382,7 +7382,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 	target = prev_cpu;
 
 	sync_entity_load_avg(&p->se);
-	if (!uclamp_task_util(p, p_util_min, p_util_max))
+	if (!uclamp_task_util(p, p_util_min, p_util_max) && p_util_max != 0)
 		goto unlock;
 
 	eenv_task_busy_time(&eenv, p, prev_cpu);
-- 
2.25.1