tc-mqprio(8) — Linux manual page


MQPRIO(8)                           Linux                          MQPRIO(8)

NAME         top

       MQPRIO - Multiqueue Priority Qdisc (Offloaded Hardware QOS)

SYNOPSIS         top

       tc qdisc ... dev dev ( parent classid | root) [ handle major: ]
       mqprio [ num_tc tcs ] [ map P0 P1 P2...  ] [ queues count1@offset1
       count2@offset2 ...  ] [ hw 1|0 ] [ mode dcb|channel] ] [ shaper dcb|
       [ bw_rlimit min_rate min_rate1 min_rate2 ...  max_rate max_rate1
       max_rate2 ...  ]]

DESCRIPTION         top

       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 map parameter and hashed across the indicated
       queues in the offset and count.  By default these parameters are
       configured by the hardware driver to match the hardware QOS

       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 shaper parameter.
       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

ALGORITHM         top

       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

       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 socket(7).

       with iptables/nftables
              An iptables/nftables rule can be created to match traffic
              flows and set the priority.  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.


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

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

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

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

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

       shaper Use bw_rlimit to set bandwidth rate limits for a traffic
              class. Use 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.

AUTHORS         top

       John Fastabend, <>

COLOPHON         top

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iproute2                        24 Sept 2013                       MQPRIO(8)

Pages that refer to this page: tc(8)