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Date: Tue, 20 Feb 2024 16:15:46 +0000
From: Qais Yousef <qyousef@layalina.io>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	linux-kernel@vger.kernel.org,
	Pierre Gondois <Pierre.Gondois@arm.com>
Subject: Re: [PATCH v5 2/2] sched/fair: Check a task has a fitting cpu when
 updating misfit
Message-ID: <20240220161546.7r3leteuqygf6jxc@airbuntu>
References: <20240205021123.2225933-1-qyousef@layalina.io>
 <20240205021123.2225933-3-qyousef@layalina.io>
 <CAKfTPtAsij+_=n9JCxHw==j3-wC9rYZHEJyVmyBJsx_-Udhzgw@mail.gmail.com>
 <20240220155913.n7uxb3e56kuhcxs2@airbuntu>
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In-Reply-To: <20240220155913.n7uxb3e56kuhcxs2@airbuntu>

On 02/20/24 15:59, Qais Yousef wrote:

> I realized that I wanted to also add a new patch to not double balance_interval
> for misfit failures. I think you indicated that seems the right thing to do?

I think this should do it?

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 70ffbb1aa15c..b12b7de495d0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11552,8 +11552,13 @@ static int load_balance(int this_cpu, struct rq *this_rq,
         * repeatedly reach this code, which would lead to balance_interval
         * skyrocketing in a short amount of time. Skip the balance_interval
         * increase logic to avoid that.
+        *
+        * Similarly misfit migration which is not necessarily an indication of
+        * the system being busy and requires lb to backoff to let it settle
+        * down.
         */
-       if (env.idle == CPU_NEWLY_IDLE)
+       if (env.idle == CPU_NEWLY_IDLE ||
+           env.migration_type == migrate_misfit)
                goto out;

        /* tune up the balancing interval */