NAME

       MQPRIO - Multiqueue Priority Qdisc (Offloaded Hardware QOS)

SYNOPSIS

       tc qdisc ... dev dev ( parent classid | root) [ handle major: ] mqprio [ numtc 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

       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

       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.

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 sockets belong to an  application.  See
              kernel and cgroup documentation 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)