linux-kernel - Re: [PATCH v2] sched/fair: Check a task has a fitting cpu when updating misfit

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Message-Id: <20231229110218.1928-1-hdanton@sina.com>
Date: Fri, 29 Dec 2023 19:02:18 +0800
From: Hillf Danton <hdanton@...a.com>
To: Qais Yousef <qyousef@...alina.io>
Cc: Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Pierre Gondois <pierre.gondois@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched/fair: Check a task has a fitting cpu when updating misfit

On 12/12/23 16:40 Qais Yousef <qais.yousef@....com>
> 
> If a misfit task is affined to a subset of the possible cpus, we need to
> verify that one of these cpus can fit it. Otherwise the load balancer
> code will continuously trigger needlessly leading the balance_interval
> to increase in return and eventually end up with a situation where real
> imbalances take a long time to address because of this impossible
> imbalance situation.
> 
> This can happen in Android world where it's common for background tasks
> to be restricted to little cores.

What sense could you make by forcing a pill down through Peter's throat
to fix the insane userspace behavior that blindly drives load balance mad
by binding background tasks to littles cores? Is eevdf failing to handle
your background tasks?