Re: [REGRESSION] sched/fair: Add lag based placement

[Joseph Salisbury]

On 11/13/24 13:22, Joseph Salisbury wrote:
> On 11/13/24 13:19, Phil Auld wrote:
> > Hi,
> >
> > On Wed, Nov 13, 2024 at 01:03:00PM -0500 Joseph Salisbury wrote:
> > > Hello,
> > >
> > > During performance testing, we found a regression of ~9% performance 
> > > with
> > > the TPCC benchmark.   This performance regression was introduced in
> > > v6.6-rc1.  After a bisect, the following commit was identified as 
> > > the cause
> > > of the regression:
> > >
> > > 86bfbb7ce4f6 ("sched/fair: Add lag based placement")
> > >
> > > I was hoping to get some feedback from the scheduler folks. Do you 
> > > think
> > > gathering any additional data will help diagnose this issue? Are 
> > > there any
> > > tunable options that can changed to see how performance is affected?
> > You can try turning off the PLACE_LAG sched feature:
> >
> >      echo NO_PLACE_LAG > /sys/kernel/debug/sched/features
> >
> > It's not what I'd call a tunable but it would allow you to test w/o 
> > it and
> > see what it does.  It should allow you to switch back and forth 
> > easily for
> > testing.
> >
> >
> > Cheers,
> > Phil
> Thanks so much for the suggestion, Phil!  I will give that a try and 
> report the results.
> > > Thanks,
> > >
> > > Joe
I just noticed this thread, which is probably related:
https://lore.kernel.org/lkml/ZxuujhhrJcoYOdMJ@xxxxxxxxxxxxxxxxxxxx/T/