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.TH MQPRIO 8 "24 Sept 2013" "iproute2" "Linux"
MQPRIO \- Multiqueue Priority Qdisc (Offloaded Hardware QOS)
.B tc qdisc ... dev
.B  ( parent
.B | root) [ handle
.B ] mqprio [ num_tc
.B ] [ map
P0 P1 P2...
.B ] [ queues
count1@offset1 count2@offset2 ...
.B ] [ hw
.B ] [ mode
.B ] [ shaper
.B [ bw_rlimit
.B min_rate
min_rate1 min_rate2 ...
.B max_rate
max_rate1 max_rate2 ...
.B ]]

The MQPRIO qdisc is a simple queuing discipline that allows mapping
traffic flows to hardware queue ranges using priorities and a configurable
priority to traffic class mapping. A traffic class in this context is
a set of contiguous qdisc classes which map 1:1 to a set of hardware
exposed queues.

By default the qdisc allocates a pfifo qdisc (packet limited first in, first
out queue) per TX queue exposed by the lower layer device. Other queuing
disciplines may be added subsequently. Packets are enqueued using the
.B map
parameter and hashed across the indicated queues in the
.B offset
.B count.
By default these parameters are configured by the hardware
driver to match the hardware QOS structures.

.B Channel
mode supports full offload of the mqprio options, the traffic classes, the queue
configurations and QOS attributes to the hardware. Enabled hardware can provide
hardware QOS with the ability to steer traffic flows to designated traffic
classes provided by this qdisc. Hardware based QOS is configured using the
.B shaper
.B bw_rlimit
with minimum and maximum bandwidth rates can be used for setting
transmission rates on each traffic class. Also further qdiscs may be added
to the classes of MQPRIO to create more complex configurations.

On creation with 'tc qdisc add', eight traffic classes are created mapping
priorities 0..7 to traffic classes 0..7 and priorities greater than 7 to
traffic class 0. This requires base driver support and the creation will
fail on devices that do not support hardware QOS schemes.

These defaults can be overridden using the qdisc parameters. Providing
the 'hw 0' flag allows software to run without hardware coordination.

If hardware coordination is being used and arguments are provided that
the hardware can not support then an error is returned. For many users
hardware defaults should work reasonably well.

As one specific example numerous Ethernet cards support the 802.1Q
link strict priority transmission selection algorithm (TSA). MQPRIO
enabled hardware in conjunction with the classification methods below
can provide hardware offloaded support for this TSA.

Multiple methods are available to set the SKB priority which MQPRIO
uses to select which traffic class to enqueue the packet.
From user space
A process with sufficient privileges can encode the destination class
directly with SO_PRIORITY, see
.BR socket(7).
with iptables/nftables
An iptables/nftables rule can be created to match traffic flows and
set the priority.
.BR iptables(8)
with net_prio cgroups
The net_prio cgroup can be used to set the priority of all sockets
belong to an application. See kernel and cgroup documentation for details.

Number of traffic classes to use. Up to 16 classes supported.

The priority to traffic class map. Maps priorities 0..15 to a specified
traffic class.

Provide count and offset of queue range for each traffic class. In the
.B count@offset.
Queue ranges for each traffic classes cannot overlap and must be a
contiguous range of queues.

Set to
.B 1
to support hardware offload. Set to
.B 0
to configure user specified values in software only.

Set to
.B channel
for full use of the mqprio options. Use
.B dcb
to offload only TC values and use hardware QOS defaults. Supported with 'hw'
set to 1 only.

.B bw_rlimit
to set bandwidth rate limits for a traffic class. Use
.B dcb
for hardware QOS defaults. Supported with 'hw' set to 1 only.

Minimum value of bandwidth rate limit for a traffic class.

Maximum value of bandwidth rate limit for a traffic class.

John Fastabend, <>