User Manual

Rev 2.0-3.0.0

Mellanox Technologies

4.12 Flow Steering

Flow steering is a new model which steers network flows based on flow specifications to specific

QPs. Those flows can be either unicast or multicast network flows. In order to maintain flexibil-

ity, domains and priorities are used. Flow steering uses a methodology of flow attribute, which is

a combination of L2-L4 flow specifications, a destination QP and a priority. Flow steering rules

could be inserted either by using ethtool or by using InfiniBand verbs. The verbs abstraction uses

an opposed terminology of a flow attribute (ibv_flow_attr), defined by a combination of specifi-

cations (struct ibv_flow_spec_*).

4.12.1 Enable/Disable Flow Steering

Flow Steering is disabled by default and regular L2 steering is performed instead (B0 Steering).

When using SR-IOV, flow steering is enabled if there is adequate amount of space to store the

flow steering table for the guest/master.

 To enable Flow Steering:

Step 1. Open the /etc/modprobe.d/mlnx.conf file.

Step 2. Set the parameter log_num_mgm_entry_size to -1 by writing the option mlx4_core

log_num_mgm_entry_size=-1.

Step 3. Restart the driver

 To disable Flow Steering:

Step 1. Open the /etc/modprobe.d/mlnx.conf file.

Step 2. Remove the options mlx4_core log_num_mgm_entry_size= -1.

Step 3. Restart the driver

4.12.2 Flow Domains and Priorities

Flow steering defines the concept of domain and priority. Each domain represents a user agent

that can attach a flow. The domains are prioritized. A higher priority domain will always super-

sede a lower priority domain when their flow specifications overlap. Setting a lower priority

value will result in higher priority.

In addition to the domain, there is priority within each of the domains. Each domain can have at

most 2^12 priorities in accordance to its needs.

The following are the domains at a descending order of priority:

• User Verbs allows a user application QP to be attached into a specified flow when

using

ibv_create_flow and ibv_destroy_flow verbs

• ibv_create_flow

Input parameters:

• struct ibv_qp - the attached QP.

Flow Steering is applicable to the mlx4 driver only.

struct ibv_flow *ibv_create_flow(struct ibv_qp *qp, struct ibv_flow_attr *flow)