Re: [External] : Re: [REGRESSION][v6.17-rc1]sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails

[Joseph Salisbury]

On 10/30/25 3:29 AM, Adam Li wrote:
> Hi Joseph,
>
> On 10/18/2025 1:01 AM, Joseph Salisbury wrote:
> > On 10/10/25 13:09, Peter Zijlstra wrote:
> > > On Thu, Oct 09, 2025 at 09:04:40PM -0400, Joseph Salisbury wrote:
> [...]
> > > diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> > > index 3c12d9f93331..5ded210701d0 100644
> > > --- a/kernel/sched/features.h
> > > +++ b/kernel/sched/features.h
> > > @@ -121,3 +121,8 @@ SCHED_FEAT(WA_BIAS, true)
> > >    SCHED_FEAT(UTIL_EST, true)
> > >      SCHED_FEAT(LATENCY_WARN, false)
> > > +
> > > +SCHED_FEAT(NI_TARGET, false)
> > > +SCHED_FEAT(NI_SPARE, false)
> > > +SCHED_FEAT(NI_RUNNABLE, false)
> > > +SCHED_FEAT(NI_RANDOM, false)
> [...]
> > Thanks for providing the patch!
> >
> > I performed the same testing with this patch applied to a v6.12 based kernel.  The performance regression still exists and is slightly worse.
> > The drgn stats are attached in a file named 'apache_drgn_log_NewidleRework_From_Peter.log'.
> Just wondering, did you enable NI_TARGET feature?
> It is default false in Peter's patch.
> In my test 'NI_TARGET' can fix the regression caused by commit 155213a2aed4.
>
> Thanks,
> -adam
I ran some tests with NI_TARGET enabled.  I can confirm that Peter's 
patch with NI_TARGET enabled does regain all the performance back.