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Solarflare Server Adapter User Guide
Solarflare Adapters on Linux
Issue 20 © Solarflare Communications 2017 72
Configuring Task Offloading
Solarflare adapters support transmit (Tx) and receive (Rx) checksum offload, as well
as TCP segmentation offload. To ensure maximum performance from the adapter,
all task offloads should be enabled, which is the default setting on the adapter. For
more information, see Performance Tuning on Linux on page 103 .
To change offload settings for Tx and Rx, use the ethtool command:
ethtool ‐‐ offload <ethX> [rx on|off] [tx on|off]
Configuring Receive/Transmit Ring Buffer Size
By default receive and transmit ring buffers on the Solarflare adapter support 1024
descriptors. The user can identify and reconfigure ring buffer sizes using the ethtool
command.
To identify the current ring size:
ethtool ‐ g ethX
To set the new transmit or receive ring size to value N
ethtool ‐ G ethX [rx N| tx N]
The ring buffer size must be a value between 128 and 4096. On the SFN7000 and
SFN8000 series adapters the maximum TX buffer size is restricted to 2048. Buffer
size can also be set directly in the
modprobe.conf
file or add the options line to a
file under the
/etc/modprobe.d
directory e.g.
options sfc rx_ring=4096
Using the modprobe method sets the value for all Solarflare interfaces. Then reload
the driver for the option to become effective:
modprobe ‐ r sfc

modprobe sfc
Configuring Jumbo Frames
Solarflare adapters support frame sizes from 1500 bytes to 9216 bytes. For example,
to set a new frame size (MTU) of 9000 bytes, enter the following command:
ifconfig <ethX> mtu 9000
To make the changes permanent, edit the network configuration file for <
ethX
>; for
example,
/etc/sysconfig/network ‐ scripts/ifcfg ‐ eth1
and append the
following configuration directive, which specifies the size of the frame in bytes:
MTU=9000