linux-kernel - Re: [PATCH 2/4] sched/fair: Small cleanup to sched_balance

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Message-ID: <CAKfTPtAvNxLfayOqpXzKth9gbdv73OXt2MtRf6gbHfnoZwLVTw@mail.gmail.com>
Date: Fri, 14 Nov 2025 14:11:16 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Shrikanth Hegde <sshegde@...ux.ibm.com>, mingo@...hat.com, juri.lelli@...hat.com, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org, 
	Chris Mason <clm@...a.com>, Joseph Salisbury <joseph.salisbury@...cle.com>, 
	Adam Li <adamli@...amperecomputing.com>, 
	Hazem Mohamed Abuelfotoh <abuehaze@...zon.com>, Josh Don <joshdon@...gle.com>
Subject: Re: [PATCH 2/4] sched/fair: Small cleanup to sched_balance_newidle()

On Fri, 14 Nov 2025 at 12:05, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Nov 14, 2025 at 11:22:48AM +0100, Vincent Guittot wrote:
>
> > sched_balance_update_blocked_averages() can be costly so we want to
> > include it in the sd->max_idle_balance_cost so we skip newidle lb and
> > update blocked load if avg_idle is shorter than doin the update and
> > the newidle lb of the 1st level
>
> Ah, fair enough.
>
> > when sd is null we should still skip
> > sched_balance_update_blocked_averages() is its cost is higher than
> > avg_idle but it seems that we don't.
>
> When !sd there is no balancing to be had.
>
> Anyway, I'll keep the patch as is -- introducing an early exit for !sd
> and I'll post a few more cleanups after this.

okay