HP Integrity Virtual Machines 4.3: Release Notes (5900-2265, May 2012)

7.2.8 Vswitch Use Disables TSO and CKO Capabilities on the IP Address on the
Backing LAN Interface
When a LAN interface has IP addresses configured and used by a vswitch, Integrity VM disables
the TSO and CKO capabilities on the interface’s IP addresses. Consequently, poorer than expected
performance is experienced from these IP addresses. However, the TSO and CKO capabilities
remain unchanged (enabled by default) in the VM Host’s and guest’s data-link layer, that is, the
traffic from guest AVIO LAN interfaces to the network is not being degraded by this feature.
Degradation is seen only on traffic destined to or sent from the VM Host.
Also, after a vswitch is halted, the TSO and CKO capabilities remain disabled on the IP addresses
of the backing LAN interface. Integrity VM does not restore these properties back to their original
states. To restore the TSO and CKO on the IP addresses, unconfigure the IP addresses and then
reconfigure them.
7.2.9 Vswitch Use Disables TSO and CKO Capabilities on IP Addresses and Online
VM Migration
Because Integrity VM disables the TSO and CKO capabilities on the LAN interface's IP address
(resulting in poorer than expected VM Host data-transfer performance) HP recommends that you
dedicate a LAN interface solely for Online VM Migration data transfer to improve data transfer
time. That is, to receive the best performance on host-to-remote data transfers on a LAN interface,
do not configure a vswitch over it.
7.2.10 Software LRO to be on by default on Host and Guest Interfaces
The newer 10 Gig cards have a new feature that allows the driver to combine TCP segments and
pass the combined packet to the upper layers. This new feature is known as Packet reassembly
(PR) or Large Receive Offload (LRO). The newer 10 Gig interfaces default to s/w LRO enabled as
of the HP–UX 11i v3 September 2011 update, resulting in much better inbound performance for
the VM Host. The HP–UX 11i v3 March 2011 versions of these drivers might also be capable of
software LRO and can be enabled with the nwmgr command:
nwmgr -s -A drv_pr=on -c lanPPA
The guest also supports LRO in the igssn driver, and it is on by default. Enabling or disabling s/w
LRO for the 10 Gigabit drivers in the VM Host does not affect the performance of the guest. See
the driver release notes for other considerations regarding the use of s/w LRO.
7.2 Changes and Issues in the V4.3 Release 31