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

[Andreas Ziegler <br025@umbiko.net>]

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