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

Chris Mason
2025-11-12T22:00:23Z

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