User Manual

Rev 2.2-1.0.1
Mellanox Technologies
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be used. mlnx_qos gets a list of a mapping between UPs to TCs. For example, mlnx_qos -
ieth0 -p 0,0,0,0,1,1,1,1
maps UPs 0-3 to TC0, and Ups 4-7 to TC1.
4.6.7 Quality of Service Properties
The different QoS properties that can be assigned to a TC are:
• Strict Priority (see “Strict Priority”)
• Minimal Bandwidth Guarantee (ETS) (see “Minimal Bandwidth Guarantee (ETS)”)
• Rate Limit (see “Rate Limit”)
4.6.7.1 Strict Priority
When setting a TC's transmission algorithm to be 'strict', then this TC has absolute (strict) prior-
ity over other TC strict priorities coming before it (as determined by the TC number: TC 7 is
highest priority, TC 0 is lowest). It also has an absolute priority over non strict TCs (ETS).
This property needs to be used with care, as it may easily cause starvation of other TCs.
A higher strict priority TC is always given the first chance to transmit. Only if the highest strict
priority TC has nothing more to transmit, will the next highest TC be considered.
Non strict priority TCs will be considered last to transmit.
This property is extremely useful for low latency low bandwidth traffic. Traffic that needs to get
immediate service when it exists, but is not of high volume to starve other transmitters in the sys
-
tem.
4.6.7.2 Minimal Bandwidth Guarantee (ETS)
After servicing the strict priority TCs, the amount of bandwidth (BW) left on the wire may be
split among other TCs according to a minimal guarantee policy.
If, for instance, TC0 is set to 80% guarantee and TC1 to 20% (the TCs sum must be 100), then
the BW left after servicing all strict priority TCs will be split according to this ratio.
Since this is a minimal guarantee, there is no maximum enforcement. This means, in the same
example, that if TC1 did not use its share of 20%, the reminder will be used by TC0.
4.6.7.3 Rate Limit
Rate limit defines a maximum bandwidth allowed for a TC. Please note that 10% deviation from
the requested values is considered acceptable.
4.6.8 Quality of Service Tools
4.6.8.1 mlnx_qos
mlnx_qos is a centralized tool used to configure QoS features of the local host. It communicates
directly with the driver thus does not require setting up a DCBX daemon on the system.
The mlnx_qos tool enables the administrator of the system to:
• Inspect the current QoS mappings and configuration
The tool will also display maps configured by TC and vconfig set_egress_map tools, in
order to give a centralized view of all QoS mappings.
• Set UP to TC mapping