Re: [PATCH] sched/fair: Dequeue sched_delayed tasks when waking to a busy CPU

[Phil Auld]

On Thu, Nov 21, 2024 at 06:56:28AM -0500 Phil Auld wrote:
> On Wed, Nov 20, 2024 at 07:37:39PM +0100 Mike Galbraith wrote:
> > On Tue, 2024-11-19 at 12:51 +0100, Mike Galbraith wrote:
> > > On Tue, 2024-11-19 at 06:30 -0500, Phil Auld wrote:
> > > >
> > > > This, below, by itself, did not do help and caused a small slowdown on some
> > > > other tests.  Did this need to be on top of the wakeup change?
> > >
> > > No, that made a mess.
> > 
> > Rashly speculating that turning mobile kthread component loose is what
> > helped your write regression...
> > 
> > You could try adding (p->flags & PF_KTHREAD) to the wakeup patch to
> > only turn hard working kthreads loose to try to dodge service latency.
> > Seems unlikely wakeup frequency * instances would combine to shred fio
> > the way turning tbench loose did.
> >
> 
> Thanks, I'll try that. 
>

Also, fwiw, I think there is another report here

https://lore.kernel.org/lkml/392209D9-5AC6-4FDE-8D84-FB8A82AD9AEF@xxxxxxxxxx/

which seems to be the same thing but mis-bisected. I've asked them to try
with NO_DELAY_DEQUEUE just to be sure.  But it looks like a duck.


Cheers,
Phil

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