linux-kernel - Re: [PATCH 0/4] sched: The newidle balance regression

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <6825c50d-7fa7-45d8-9b81-c6e7e25738e2@meta.com>
Date: Wed, 12 Nov 2025 16:59:45 -0500
From: Chris Mason <clm@...a.com>
To: Peter Zijlstra <peterz@...radead.org>,
        Joseph Salisbury <joseph.salisbury@...cle.com>,
        Adam Li <adamli@...amperecomputing.com>,
        Hazem Mohamed Abuelfotoh <abuehaze@...zon.com>,
        Josh Don <joshdon@...gle.com>
Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] sched: The newidle balance regression

On 11/7/25 11:06 AM, Peter Zijlstra wrote:
> Hi!
> 
> So most of you ran into Chris' commit 155213a2aed4 ("sched/fair: Bump
> sd->max_newidle_lb_cost when newidle balance fails") [*]
> 
> And I posted a patch with a few alternative options. And while I've heard back
> from a number of you, indicating that NI_TARGET (the effective revert) works
> for you. Not many tested TARGET+RANDOM (thanks Adam!).
> 
> In my limited schbench testing that combination isn't horrible, and per Adam
> that combination also doesn't suck for him. Chris, could you please see what
> this does for your machines with your actual workload?
> 
> Anyway, here are a few patches that basically do the revert and introduce the
> proportional newidle balance -- the NI_TARGET+NI_RANDOM equivalent.
> 
> Also at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/newidle
> 
> Please all, give it a whirl. Hopefully I didn't wreck it, its Friday after all :-)
> 
> [*] https://lkml.kernel.org/r/006c9df2-b691-47f1-82e6-e233c3f91faf@oracle.com 

This is working well for my original benchmark.  Focusing on newidle
balance schedstat counters (10 second interval):

Linus:
lb_balance_newly_idle              22854

Mason-revert:
lb_balance_newly_idle            2334059

Peter:
lb_balance_newly_idle              75271

The rest of the schbench numbers look good too.

Thanks everyone,
Chris