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

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Message-ID: <20251107160645.929564468@infradead.org>
Date: Fri, 07 Nov 2025 17:06:45 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: 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>
Cc: mingo@...hat.com,
 peterz@...radead.org,
 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: [PATCH 0/4] sched: The newidle balance regression

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