Re: AMD EPYC virtual network performances

[Jürgen Groß <jgross@xxxxxxxx>]

On 13.08.24 03:10, Elliott Mitchell wrote:
> On Tue, Jul 09, 2024 at 11:37:07AM +0200, Jürgen Groß wrote:
> > In both directories you can see the number of spurious events by looking
> > into the spurious_events file.
> >
> > In the end the question is why so many spurious events are happening. Finding
> > the reason might be hard, though.
> Hopefully my comments on this drew your attention, yet lack of response
> suggests otherwise.  I'm wondering whether this is an APIC misprogramming
> issue, similar to the x2APIC issue which was causing trouble with recent
> AMD processors.
>
> Trying to go after the Linux software RAID1, my current attempt is
> "iommu=debug iommu=no-intremap".  I'm seeing *lots* of messages from
> spurious events in `xl dmesg`.  So many I have a difficult time believing
> they are related to hardware I/O.
Seeing them in `xl dmesg` means those spurious events are seen by the
hypervisor, not by the Linux kernel.

So IMHO this is not a kernel issue.

> In which case could the performance problem observed by Andrei Semenov
> be due to misprogramming of [x2]APIC triggering spurious events?
I don't see a connection here, as spurious interrupts (as seen by the
hypervisor in your case) and spurious events (as seen by Andrei) are
completely different (hardware vs. software level).


Juergen