Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

Peter Zijlstra
2024-09-11T09:13:42Z

On Wed, Sep 11, 2024 at 11:10:26AM +0200, Mike Galbraith wrote:
> On Wed, 2024-09-11 at 10:45 +0200, Peter Zijlstra wrote:
> > On Wed, Sep 11, 2024 at 09:35:16AM +0100, Luis Machado wrote:
> > > >
> > > > I'm assuming that removing the usage sites restores function?
> > >
> > > It does restore function if we remove the usage.
> > >
> > > From an initial look:
> > >
> > > cat /sys/kernel/debug/sched/debug | grep -i delay
> > >   .h_nr_delayed                  : -4
> > >   .h_nr_delayed                  : -6
> > >   .h_nr_delayed                  : -1
> > >   .h_nr_delayed                  : -6
> > >   .h_nr_delayed                  : -1
> > >   .h_nr_delayed                  : -1
> > >   .h_nr_delayed                  : -5
> > >   .h_nr_delayed                  : -6
> > >
> > > So probably an unexpected decrement or lack of an increment somewhere.
> >
> > Yeah, that's buggered. Ok, I'll go rebase sched/core and take this patch
> > out. I'll see if I can reproduce that.
>
> Hm, would be interesting to know how the heck he's triggering that.
>
> My x86_64 box refuses to produce any such artifacts with anything I've
> tossed at it, including full LTP with enterprise RT and !RT configs,
> both in master and my local SLE15-SP7 branch. Hohum.

Yeah, my hackbench runs also didn't show that. Perhaps something funny
with cgroups. I didn't test cgroup bandwidth for exanple.