Re: [PATCH 4/4] sched/fair: Proportional newidle balance

Peter Zijlstra
2025-11-14T09:35:55Z

On Wed, Nov 12, 2025 at 09:12:57PM +0530, Shrikanth Hegde wrote:
>
>
> On 11/7/25 9:36 PM, Peter Zijlstra wrote:
> > Add a randomized algorithm that runs newidle balancing proportional to
> > its success rate.
> >
> > This improves schbench significantly:
> >
> > 6.18-rc4: 2.22 Mrps/s
> > 6.18-rc4+revert: 2.04 Mrps/s
> > 6.18-rc4+revert+random: 2.18 Mrps/S
> >
>
> Could you please share the schbench command?
>
> I see command like "schbench -t 90 -r 30 -i 30" running on 60 core regress.
> Will do more iterations to confirm it (to be sure it is not run/run variation)

This was:

schbench -L -m 4 -M auto -t 256 -n 0 -r 60 -s 0

from the original thread:

https://lkml.kernel.org/r/20250626144017.1510594-2-clm@fb.com

> > + if (sd->newidle_call >= 1024) {
> > + sd->newidle_ratio = sd->newidle_success;
> > + sd->newidle_call /= 2;
> > + sd->newidle_success /= 2;
> > + }
>
> Would it be better to >> 1 ? or compiler takes care of it?

I would be very disappointed if our compilers don't do this.