linux-kernel - Re: [PATCH v6 2/2] sched: update the rq->avg_idle when a task is moved to an idle CPU

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Message-ID: <6667e71b-a9ef-4c01-9453-171c07b2753f@arm.com>
Date: Wed, 7 Jan 2026 16:48:38 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Shijie Huang <shijie@...eremail.onmicrosoft.com>,
 Huang Shijie <shijie@...amperecomputing.com>, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org
Cc: patches@...erecomputing.com, cl@...ux.com,
 Shubhang@...amperecomputing.com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, linux-kernel@...r.kernel.org, vschneid@...hat.com,
 vineethr@...ux.ibm.com, kprateek.nayak@....com
Subject: Re: [PATCH v6 2/2] sched: update the rq->avg_idle when a task is
 moved to an idle CPU

On 17.12.25 17:15, Dietmar Eggemann wrote:
> On 15.12.25 10:35, Shijie Huang wrote:
>>
>> On 12/12/2025 22:22, Dietmar Eggemann wrote:

[...]

> I think Vincent is right by saying the update_rq_avg_idle() should be
> put into put_prev_task_idle() instead.
> 
> Still waiting for the DCPerf Mediawiki test results to see if this
> change fixes my 'rq->avg_idle being too big' issue.

Turns out the patch didn't fix this issue. Still seeing a huge number of
sched_balance_newidle() calls in which the system is (1) overloaded and
(2) this_rq->avg_idle >= sd->max_newidle_lb_cost so that there is no
early bailout and no task is pulled at the end. Must be something else ...