High Send-Q values in netstat after upgrading to 12.1-RELEASE: system is unusable

[Jose G. Juanino]

On Tuesday, November 05 at 22:44:10 CET, Jose G. Juanino wrote:
> Hi all,
> 
> today I have upgraded to 12.1-RELEASE from 12.0-RELEASE-p10 via
> freebsd-update. The host is a VMware guest with vmx net interface. The
> system runs with 12.0-RELEASE perfectly, with no issue, reliably for months.
> 
> I have boot environments enabled (thanks god) and therefore I am able to
> switch between both 12.0 and 12.1 versions.
> 
> Just after boot the new 12.1 release, I noticed that my apache did not
> serve pages with the previous speed, but rather the opposite: any web
> operation from clients hangs.
> 
> After a single inspection in the FreeBSD 12.1 server, I see that Send-Q
> in netstat is the root cause of the issue. While in 12.0 Send-Q is
> almost always zero or close to zero in every socket, in 12.1 I get the
> following (snipped output):
>
> [ .... ]
>

Hi again, after doing a further research, I have noticed that in 12.0
version dev.vmx.0.txq0.hstats.tso_packets is always increasing
(especially when doing large transfers), but in 12.1 is statically equal
to zero, never increases.

As workaround, I have disabled TCP segment offloading by setting the
net.inet.tcp.tso=0 sysctl in 12.1 version and the host again performs
almost as well as before in 12.0.

I hope this helps others suffering the same issue.

Regards


-- 
Jose G. Juanino