On Wed, 2025-02-26 at 10:17 +0100, Sebastian Andrzej Siewior wrote:
> On 2025-02-25 16:16:25 [+0100], Florian Bezdeka wrote:
> > > which version is this? I think is is an imported issue. Is v6.1.119-rt45
> > > also affected?
> >
> > This is a typo, right? You mean it is an important issue, no?
>
> No, the version is correct. And I meant "imported" as in we got it from
> the stable queue.
>
> > We can see that on
> >
> > - v6.1.90-rt (Debian -rt kernel)
> > - v6.1.120-rt (Debian -rt kernel)
> > - v6.1.119-rt45 (So yes, this is also affected)
> > - v6.1.120-rt47
>
> But if this is visible on v6.1.90-rt then it is not originating from
> what I assumed.
>
> > With PERIODIC you mean CONFIG_HZ_PERIODIC, right?
> correct.
>
> > We have CONFIG_NO_HZ_FULL=y set but do net set the nohz_full= cmdline
> > parameter, so that we should get CONFIG_NO_HZ_IDLE behavior at the end.
> >
> > I realized today that the warning is somehow related to our RT tuning.
> > Enabling NAPI threading makes the warning go away, even if NAPI threads
> > are tuned the same way as ksoftirqd.
> NAPI threads? You have RPS enabled by any chance?
> Would commit
> dad6b97702639 ("net: Allow to use SMP threads for backlog NAPI.")
> 80d2eefcb4c84 ("net: Use backlog-NAPI to clean up the defer_list.")
With NAPI threads I meant the kernel threads driving the NAPI poll
which can be activated by "echo 1 > /sys/class/net/$device/threaded"
RPS is build configuration wise enabled but not configured.
As Felix already reported, backporting the mentioned commits to 6.1
would require some manual work. Simply picking all the dependencies
seems too much for now. Will have a look again...
>
> help?
>
> > I will have to look into that in more depth.
> >
> > Thanks for your input Sebastian.
>
> You are welcome.
>
> Sebastian
