Enabling and disabling TCP segmentation offload

6.18 LPAR mode z/VM guest

Offloading the TCP segmentation operation from the Linux® network stack to the adapter can lead to enhanced performance.

About this task

TCP segmentation offload is supported for OSA connections on layer 3. On layer 2 it is available as of z14 for OSA Express6S and newer adapters. Use the ethtool -k (see example in Configuring hardware offload operations) to check whether your system supports it.

Procedure

Outbound (TX) checksumming and scatter gather are prerequisites for TCP segmentation offload (TSO). You must turn on scatter gather and outbound checksumming before configuring TSO.

All three options can be turned on or off with a single ethtool command of the form:

# ethtool -K <interface_name> tx <value> sg <value> tso <value>

where <value> is either on or off.

Examples

To enable TSO for a network device eth0 issue:
```
# ethtool -K eth0 tx on sg on tso on
```
To disable TSO for a network device eth0 issue:
```
# ethtool -K eth0 tx off sg off tso off
```