Solved Network performance tuning question

[Alexander237]

Hello,

I see the following log messages related to network (hn- synthetic Hyper-V network interface):

% tail /var/log/messages
Aug 25 09:44:58 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 09:44:58 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 09:44:58 rgt011fw kernel: hn0: exceed max page buffers,35,32
Aug 25 09:44:58 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 09:44:58 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 09:54:18 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 09:54:18 rgt011fw kernel: hn0: exceed max page buffers,36,32
Aug 25 09:54:18 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 09:54:18 rgt011fw kernel: hn0: exceed max page buffers,37,32
Aug 25 10:15:38 rgt011fw kernel: hn0: exceed max page buffers,35,32

Which /boot/loader.conf params should be used tuned to fix this?

% freebsd-version
10.2-RELEASE-p1

 

[junovitch@]

I haven't seen a large amount of Hyper-V discussion on the Forums given how relatively new it is. If you don't hear anything back consider a mail to the 'freebsd-virtualization' mailing list. You can find out more info at https://lists.FreeBSD.org/mailman/listinfo/freebsd-virtualization.

 

[C0ReDuMP]

Hello Alexander237,

Today I installed FreeBSD 10.2 on a HyperV 2012 host and I noticed the same problem you're talking about.

I noticed that hn0 uses TSO by default:

# ifconfig hn0
hn0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=31b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,TSO4,TSO6>

I tried to disable TSO with ifconfig hn0 -tso and the problem apparently disappeared.

After issuing the command ifconfig hn0 -tso you can check that TSO is disabled issuing again an ifconfig hn0, the interface now looks like:

# ifconfig hn0
hn0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=1b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING>

To disable TSO at boot time edit /etc/rc.conf and add to ifconfig_hn0 the parameter "-tso", here is an example:

ifconfig_hn0="inet 192.168.0.254 netmask 255.255.255.0 -tso"

Hope this can help you.

Kind Regards,
Davide

 

[Alexander237]

Thank you.

This definitely works. Problem is solved.