man/man8/tc-taprio.8

   1 .TH TAPRIO 8 "25 Sept 2018" "iproute2" "Linux"
   2 .SH NAME
   3 TAPRIO \- Time Aware Priority Shaper
   4 .SH SYNOPSIS
   5 .B tc qdisc ... dev
   6 dev
   7 .B parent
   8 classid
   9 .B [ handle
  10 major:
  11 .B ] taprio num_tc
  12 tcs
  13 .ti +8
  14 .B map
  15 P0 P1 P2 ...
  16 .B queues
  17 count1@offset1 count2@offset2 ...
  18 .ti +8
  19 .B base-time
  20 base-time
  21 .B clockid
  22 clockid
  23 .ti +8
  24 .B sched-entry
  25 <command 1> <gate mask 1> <interval 1>
  26 .ti +8
  27 .B sched-entry
  28 <command 2> <gate mask 2> <interval 2>
  29 .ti +8
  30 .B sched-entry
  31 <command 3> <gate mask 3> <interval 3>
  32 .ti +8
  33 .B sched-entry
  34 <command N> <gate mask N> <interval N>
  35
  36 .SH DESCRIPTION
  37 The TAPRIO qdisc implements a simplified version of the scheduling
  38 state machine defined by IEEE 802.1Q-2018 Section 8.6.9, which allows
  39 configuration of a sequence of gate states, where each gate state
  40 allows outgoing traffic for a subset (potentially empty) of traffic
  41 classes.
  42
  43 How traffic is mapped to different hardware queues is similar to
  44 .BR mqprio(8)
  45 and so the
  46 .B map
  47 and
  48 .B queues
  49 parameters have the same meaning.
  50
  51 The other parameters specify the schedule, and at what point in time
  52 it should start (it can behave as the schedule started in the past).
  53
  54 .SH PARAMETERS
  55 .TP
  56 num_tc
  57 .BR
  58 Number of traffic classes to use. Up to 16 classes supported.
  59
  60 .TP
  61 map
  62 .br
  63 The priority to traffic class map. Maps priorities 0..15 to a specified
  64 traffic class. See
  65 .BR mqprio(8)
  66 for more details.
  67
  68 .TP
  69 queues
  70 .br
  71 Provide count and offset of queue range for each traffic class. In the
  72 format,
  73 .B count@offset.
  74 Queue ranges for each traffic classes cannot overlap and must be a
  75 contiguous range of queues.
  76
  77 .TP
  78 base-time
  79 .br
  80 Specifies the instant in nanoseconds, using the reference of
  81 .B clockid,
  82 defining the time when the schedule starts. If 'base-time' is a time
  83 in the past, the schedule will start at
  84
  85 base-time + (N * cycle-time)
  86
  87 where N is the smallest integer so the resulting time is greater than
  88 "now", and "cycle-time" is the sum of all the intervals of the entries
  89 in the schedule;
  90
  91 .TP
  92 clockid
  93 .br
  94 Specifies the clock to be used by qdisc's internal timer for measuring
  95 time and scheduling events.
  96
  97 .TP
  98 sched-entry
  99 .br
 100 There may multiple
 101 .B sched-entry
 102 parameters in a single schedule. Each one has the
 103
 104 sched-entry <command> <gatemask> <interval>
 105
 106 format. The only supported <command> is "S", which
 107 means "SetGateStates", following the IEEE 802.1Q-2018 definition
 108 (Table 8-7). <gate mask> is a bitmask where each bit is a associated
 109 with a traffic class, so bit 0 (the least significant bit) being "on"
 110 means that traffic class 0 is "active" for that schedule entry.
 111 <interval> is a time duration, in nanoseconds, that specifies for how
 112 long that state defined by <command> and <gate mask> should be held
 113 before moving to the next entry.
 114
 115 .TP
 116 flags
 117 .br
 118 Specifies different modes for taprio. Currently, only txtime-assist is
 119 supported which can be enabled by setting it to 0x1. In this mode, taprio will
 120 set the transmit timestamp depending on the interval in which the packet needs
 121 to be transmitted. It will then utililize the
 122 .BR etf(8)
 123 qdisc to sort and transmit the packets at the right time. The second example
 124 can be used as a reference to configure this mode.
 125
 126 .TP
 127 txtime-delay
 128 .br
 129 This parameter is specific to the txtime offload mode. It specifies the maximum
 130 time a packet might take to reach the network card from the taprio qdisc. The
 131 value should always be greater than the delta specified in the
 132 .BR etf(8)
 133 qdisc.
 134
 135 .SH EXAMPLES
 136
 137 The following example shows how an traffic schedule with three traffic
 138 classes ("num_tc 3"), which are separated different traffic classes,
 139 we are going to call these TC 0, TC 1 and TC 2. We could read the
 140 "map" parameter below as: traffic with priority 3 is classified as TC
 141 0, priority 2 is classified as TC 1 and the rest is classified as TC
 142 2.
 143
 144 The schedule will start at instant 1528743495910289987 using the
 145 reference CLOCK_TAI. The schedule is composed of three entries each of
 146 300us duration.
 147
 148 .EX
 149 # tc qdisc replace dev eth0 parent root handle 100 taprio \\
 150               num_tc 3 \\
 151               map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \\
 152               queues 1@0 1@1 2@2 \\
 153               base-time 1528743495910289987 \\
 154               sched-entry S 01 300000 \\
 155               sched-entry S 02 300000 \\
 156               sched-entry S 04 300000 \\
 157               clockid CLOCK_TAI
 158 .EE
 159
 160 Following is an example to enable the txtime offload mode in taprio. See
 161 .BR etf(8)
 162 for more information about configuring the ETF qdisc.
 163
 164 .EX
 165 # tc qdisc replace dev eth0 parent root handle 100 taprio \\
 166               num_tc 3 \\
 167               map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \\
 168               queues 1@0 1@0 1@0 \\
 169               base-time 1528743495910289987 \\
 170               sched-entry S 01 300000 \\
 171               sched-entry S 02 300000 \\
 172               sched-entry S 04 400000 \\
 173               flags 0x1 \\
 174               txtime-delay 200000 \\
 175               clockid CLOCK_TAI
 176
 177 # tc qdisc replace dev $IFACE parent 100:1 etf skip_skb_check \\
 178               offload delta 200000 clockid CLOCK_TAI
 179 .EE
 180
 181 .SH AUTHORS
 182 Vinicius Costa Gomes <vinicius.gomes@intel.com>