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 structures.

       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 configurations.

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

       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

       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)