MQPRIO(8)                                                              Linux                                                             MQPRIO(8)

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 config-
       urable 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  coordina-
       tion.

       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)