tc-mqprio

MQPRIO(8)                            Linux                           MQPRIO(8)

NAME
       MQPRIO - Multiqueue Priority Qdisc (Offloaded Hardware QOS)

SYNOPSIS
       tc  qdisc ... dev dev ( parent classid | root) [ handle major: ] mqprio
       [ num_tc tcs ] [ map P0 P1 P2...  ] [ queues count1@offset1 count2@off-
       set2  ...  ] [ hw 1|0 ] [ mode dcb|channel] ] [ shaper dcb| [ bw_rlimit
       min_rate min_rate1 min_rate2 ...  max_rate max_rate1 max_rate2 ...  ]]

DESCRIPTION
       The MQPRIO qdisc is a simple queuing  discipline  that  allows  mapping
       traffic  flows  to hardware queue ranges using priorities and a config-
       urable priority to traffic class mapping. A traffic class in this  con-
       text  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 us-
       ing  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 trans-
       mission  rates  on each traffic class. Also further qdiscs may be added
       to the classes of MQPRIO to create more complex configurations.

ALGORITHM
       On creation with 'tc qdisc add', eight traffic classes are created map-
       ping  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  pro-
       vide hardware offloaded support for this TSA.

CLASSIFICATION
       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 sock-
              ets  belong  to an application. See kernel and cgroup documenta-
              tion for details.

QDISC PARAMETERS
       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.

       min_rate
              Minimum value of bandwidth rate limit for a traffic class.

       max_rate
              Maximum value of bandwidth rate limit for a traffic class.

AUTHORS
       John Fastabend, <john.r.fastabend@intel.com>

iproute2                         24 Sept 2013                        MQPRIO(8)