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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 ]

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.

       Enabled  hardware  can  provide  hardware  QOS  with the ability to steer traffic flows to
       designated traffic classes provided by this qdisc.  Configuring  the  hardware  based  QOS
       mechanism  is  outside  the scope of this qdisc. Tools such as lldpad and ethtool exist to
       provide this functionality. 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 upto 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 use hardware QOS defaults. Set to 0 to override hardware defaults  with
              user specified values.

AUTHORS

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