Re: xennet performance collapses with multiple vCPU

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

On Wed, 25 Mar 2020, Jaromír DoleÄ~Mek wrote:
> Le mar. 24 mars 2020 Ã  15:13, Stephen Borrill <netbsd%precedence.co.uk@localhost> a
> écrit :
>
> > All using NetBSD 9.99.51 (XEN3_DOMU) #0: Sun Mar 22 17:35:29 UTC 2020
> >
> > Note that increasing the vCPUs from 1 to 4 (2 gives same result as 4)
> > drops the throughput to about 10%. No offloads configured in domU:
> I found out the problem appeared between 2020-01-08 00:00 (that was still
> good) and 2020-01-14 00:00 (that is already bad).
>
> There were some CPU scheduling changes by Andrew Doran around that time, so
> it's likely the culprit.
>
> I'm working on bisecting this further. It's complicated, between 01-08 and
> 01-14 there were some bugs which prevent the Xen DomU MP kernel from
> booting.

Well, that's reassuring for me as none of my machines run -current. I 
thought that running a -current kernel for the benchmarking I wanted to do 
would be a good idea because of your recent changes. I should have also 
checked with the original netbsd-9 kernel on the machine.

--
Stephen