man/man8/tc-mqprio.8

   1 .TH MQPRIO 8 "24 Sept 2013" "iproute2" "Linux"
   2 .SH NAME
   3 MQPRIO \- Multiqueue Priority Qdisc (Offloaded Hardware QOS)
   4 .SH SYNOPSIS
   5 .B tc qdisc ... dev
   6 dev
   7 .B  ( parent
   8 classid
   9 .B | root) [ handle
  10 major:
  11 .B ] mqprio [ num_tc
  12 tcs
  13 .B ] [ map
  14 P0 P1 P2...
  15 .B ] [ queues
  16 count1@offset1 count2@offset2 ...
  17 .B ] [ hw
  18 1|0
  19 .B ] [ mode
  20 dcb|channel]
  21 .B ] [ shaper
  22 dcb|
  23 .B [ bw_rlimit
  24 .B min_rate
  25 min_rate1 min_rate2 ...
  26 .B max_rate
  27 max_rate1 max_rate2 ...
  28 .B ]]
  29
  30
  31 .SH DESCRIPTION
  32 The MQPRIO qdisc is a simple queuing discipline that allows mapping
  33 traffic flows to hardware queue ranges using priorities and a configurable
  34 priority to traffic class mapping. A traffic class in this context is
  35 a set of contiguous qdisc classes which map 1:1 to a set of hardware
  36 exposed queues.
  37
  38 By default the qdisc allocates a pfifo qdisc (packet limited first in, first
  39 out queue) per TX queue exposed by the lower layer device. Other queuing
  40 disciplines may be added subsequently. Packets are enqueued using the
  41 .B map
  42 parameter and hashed across the indicated queues in the
  43 .B offset
  44 and
  45 .B count.
  46 By default these parameters are configured by the hardware
  47 driver to match the hardware QOS structures.
  48
  49 .B Channel
  50 mode supports full offload of the mqprio options, the traffic classes, the queue
  51 configurations and QOS attributes to the hardware. Enabled hardware can provide
  52 hardware QOS with the ability to steer traffic flows to designated traffic
  53 classes provided by this qdisc. Hardware based QOS is configured using the
  54 .B shaper
  55 parameter.
  56 .B bw_rlimit
  57 with minimum and maximum bandwidth rates can be used for setting
  58 transmission rates on each traffic class. Also further qdiscs may be added
  59 to the classes of MQPRIO to create more complex configurations.
  60
  61 .SH ALGORITHM
  62 On creation with 'tc qdisc add', eight traffic classes are created mapping
  63 priorities 0..7 to traffic classes 0..7 and priorities greater than 7 to
  64 traffic class 0. This requires base driver support and the creation will
  65 fail on devices that do not support hardware QOS schemes.
  66
  67 These defaults can be overridden using the qdisc parameters. Providing
  68 the 'hw 0' flag allows software to run without hardware coordination.
  69
  70 If hardware coordination is being used and arguments are provided that
  71 the hardware can not support then an error is returned. For many users
  72 hardware defaults should work reasonably well.
  73
  74 As one specific example numerous Ethernet cards support the 802.1Q
  75 link strict priority transmission selection algorithm (TSA). MQPRIO
  76 enabled hardware in conjunction with the classification methods below
  77 can provide hardware offloaded support for this TSA.
  78
  79 .SH CLASSIFICATION
  80 Multiple methods are available to set the SKB priority which MQPRIO
  81 uses to select which traffic class to enqueue the packet.
  82 .TP
  83 From user space
  84 A process with sufficient privileges can encode the destination class
  85 directly with SO_PRIORITY, see
  86 .BR socket(7).
  87 .TP
  88 with iptables/nftables
  89 An iptables/nftables rule can be created to match traffic flows and
  90 set the priority.
  91 .BR iptables(8)
  92 .TP
  93 with net_prio cgroups
  94 The net_prio cgroup can be used to set the priority of all sockets
  95 belong to an application. See kernel and cgroup documentation for details.
  96
  97 .SH QDISC PARAMETERS
  98 .TP
  99 num_tc
 100 Number of traffic classes to use. Up to 16 classes supported.
 101
 102 .TP
 103 map
 104 The priority to traffic class map. Maps priorities 0..15 to a specified
 105 traffic class.
 106
 107 .TP
 108 queues
 109 Provide count and offset of queue range for each traffic class. In the
 110 format,
 111 .B count@offset.
 112 Queue ranges for each traffic classes cannot overlap and must be a
 113 contiguous range of queues.
 114
 115 .TP
 116 hw
 117 Set to
 118 .B 1
 119 to support hardware offload. Set to
 120 .B 0
 121 to configure user specified values in software only.
 122
 123 .TP
 124 mode
 125 Set to
 126 .B channel
 127 for full use of the mqprio options. Use
 128 .B dcb
 129 to offload only TC values and use hardware QOS defaults. Supported with 'hw'
 130 set to 1 only.
 131
 132 .TP
 133 shaper
 134 Use
 135 .B bw_rlimit
 136 to set bandwidth rate limits for a traffic class. Use
 137 .B dcb
 138 for hardware QOS defaults. Supported with 'hw' set to 1 only.
 139
 140 .TP
 141 min_rate
 142 Minimum value of bandwidth rate limit for a traffic class.
 143
 144 .TP
 145 max_rate
 146 Maximum value of bandwidth rate limit for a traffic class.
 147
 148
 149 .SH AUTHORS
 150 John Fastabend, <john.r.fastabend@intel.com>