User Manual

Driver FeaturesRev 2.0-3.0.0
Mellanox Technologies
60
1. The application sets the ToS of the socket using setsockopt (IP_TOS, value).
2. ToS is translated into the sk_prio using a fixed translation:
3. The Socket Priority is mapped to the UP:
• If the underlying device is a VLAN device, egress_map is used controlled by the vconfig
command. This is per VLAN mapping.
• If the underlying device is not a VLAN device, the tc command is used. In this case, even
though
tc manual states that the mapping is from the sk_prio to the TC number, the
mlx4_en driver interprets this as a sk_prio to UP mapping.
Mapping the sk_prio to the UP is done by using tc_wrap.py -i <dev name> -u
0,1,2,3,4,5,6,7
4. The the UP is mapped to the TC as configured by the mlnx_qos tool or by the lldpad daemon
if DCBX is used.
4.5.4 RoCE Quality of Service Mapping
Applications use RDMA-CM API to create and use QPs.
The following is the RoCE QoS mapping flow:
1. The application sets the ToS of the QP using the rdma_set_option option
(
RDMA_OPTION_ID_TOS, value).
2. ToS is translated into the Socket Priority (sk_prio) using a fixed translation:
3. The Socket Priority is mapped to the User Priority (UP) using the tc command.
In case of a VLAN device, the parent real device is used for the purpose of this mapping.
TOS 0 <=> sk_prio 0
TOS 8 <=> sk_prio 2
TOS 24 <=> sk_prio 4
TOS 16 <=> sk_prio 6
Socket applications can use setsockopt (SK_PRIO, value) to directly set the sk_prio
of the socket. In this case the ToS to
sk_prio fixed mapping is not needed. This allows
the application and the administrator to utilize more than the 4 values possible via ToS.
In case of VLAN interface, the UP obtained according to the above mapping is also used
in the VLAN tag of the traffic
TOS 0 <=> sk_prio 0
TOS 8 <=> sk_prio 2
TOS 24 <=> sk_prio 4
TOS 16 <=> sk_prio 6