User Manual

Features Overview and ConfigurationRev 2.3-1.0.1

Mellanox Technologies

pm_qos feature is both global and static, once a request is issued, it is enforced on all CPUs and

does not change in time.

MLNX_OFED provides an option to trigger a request when required and to remove it when no

longer required. It is disabled by default and can be set/unset through the ethtool priv-flags.

For further information on how to enable/disable this feature, please refer to Table 3, “ethtool

Supported Options,” on page 50.

3.1.9 RSS Hash Function

The device has the ability to use XOR as the RSS distribution function, instead of the default

Toplitz function.

The XOR function can be better distributed among driver's receive queues in small number of

streams, where it distributes each

TCP/UDP stream to a different queue.

MLNX_OFED provides an option to change the working RSS hash function from Toplitz to

XOR (and vice versa) through ethtool priv-flags.

For further information, please refer to Table 3, “ethtool Supported Options,” on page 50.

3.1.10 Time-Stamping

3.1.10.1 Time-Stamping Service

Time Stamping is currently supported in ConnectX®-3/ConnectX®-3 Pro adapter

cards only.

Time stamping is the process of keeping track of the creation of a packet. A time-stamping ser-

vice supports assertions of proof that a datum existed before a particular time. Incoming packets

are time-stamped before they are distributed on the PCI depending on the congestion in the PCI

buf

fers. Outgoing packets are time-stamped very close to placing them on the wire.

Enabling Time Stamping

Time-stamping is off by default and should be enabled before use.

 To enable time stamping for a socket:

• Call setsockopt() with SO_TIMESTAMPING and with the following flags:

SOF_TIMESTAMPING_TX_HARDWARE: try to obtain send time stamp in hardware

SOF_TIMESTAMPING_TX_SOFTWARE: if SOF_TIMESTAMPING_TX_HARDWARE is off or

fails, then do it in software

SOF_TIMESTAMPING_RX_HARDWARE: return the original, unmodified time stamp

as generated by the hardware

SOF_TIMESTAMPING_RX_SOFTWARE: if SOF_TIMESTAMPING_RX_HARDWARE is off or

fails, then do it in software