linux-kernel - Re: Can we backport EEVDF performance fixes to 6.6?

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Message-ID: <7f37262c1b6ffc0cc6689fef451f170a5e005f08.camel@alliedtelesis.co.nz>
Date: Thu, 17 Jul 2025 04:27:29 +0000
From: Thomas Winter <Thomas.Winter@...iedtelesis.co.nz>
To: "peterz@...radead.org" <peterz@...radead.org>, "mingo@...hat.com"
	<mingo@...hat.com>, "juri.lelli@...hat.com" <juri.lelli@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>
Subject: Re: Can we backport EEVDF performance fixes to 6.6?

On Thu, 2025-07-17 at 16:18 +1200, Thomas Winter wrote:
> Hi All,
> 
> After upgrading a product from 5.15 to 6.6, we found that performance
> took a hit on some workloads. Narrowed this down to the switch to
> EEVDF.
> 
> I backported commit 6d71a9c61604 "sched/fair: Fix EEVDF entity
> placement bug causing scheduling lag" which appears to mostly resolve
> the issue.
> 
> I also applied related commits 4423af84b297 "sched/fair: optimize the
> PLACE_LAG when se->vlag is zero" and c70fc32f4443 "sched/fair: Adhere
> to place_entity() constraints" to avoid the warnings referenced
> there.
> 
> Can these patches be safely backported to 6.6? We would prefer to use
> an official 6.6 release with the fixes.
> Otherwise we have to wait for the next LTS to get these changes which
> were put in 6.13.
> 
> Regards,
> Thomas Winter

Sorry for resending, but my email decided not to send to Ingo or Peter.