Re: sched/deadline: Use revised wakeup rule for dl_server

[Andreas Ziegler]

Hi Juri,

On 2026-05-11 12:46, Juri Lelli wrote:
> Hello,
>
> On 08/05/26 08:09, Andreas Ziegler wrote:
> > Linux kernel version: 6.12
> >   CONFIG_PREEMPT_RT (w/ PREEMPT_RT patch applied)
> > Architecture: aarch64
> > Platform: Raspberry Pi 4
> >
> > Hi everyone,
> >
> > Commit d66792919d4f (sched/deadline: Use revised wakeup rule for 
> > dl_server)
> > [1] introduced a marked degradation in scheduling latency for 
> > real-time
> > tasks in the presence of heavy I/O load.
>
> Can this be the same regression reported here?
>
> https://marc.info/?l=linux-rt-users&m=177844667227991

Yes, this is the same issue. I wonder where the 50 ms are coming from 
... The value is fairly consistent also in my results.

> Please notice the list of missing subsequent fixes Mike is suggesting 
> to
> test with.
>
> https://marc.info/?l=linux-rt-users&m=177847863710263&w=2

I will take a look at the mentioned patches.

> Thanks,
> Juri

Thank you for the update,
Andreas