phpman > man > mqprio(8)

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@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  subse‐
       quently.  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 con‐
       figurations 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 max‐
       imum  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 clas‐
       sification 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 appli‐
              cation. 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 con‐
              tiguous 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 AT intel.com>



iproute2                                    24 Sept 2013                                   MQPRIO(8)