tc-taprio(8) — Linux manual page


TAPRIO(8)                         Linux                        TAPRIO(8)

NAME         top

       TAPRIO - Time Aware Priority Shaper

SYNOPSIS         top

       tc qdisc ... dev dev parent classid [ handle major: ] taprio
       num_tc tcs
               map P0 P1 P2 ...  queues count1@offset1 count2@offset2
               base-time base-time clockid clockid
               sched-entry <command 1> <gate mask 1> <interval 1>
               sched-entry <command 2> <gate mask 2> <interval 2>
               sched-entry <command 3> <gate mask 3> <interval 3>
               sched-entry <command N> <gate mask N> <interval N>

DESCRIPTION         top

       The TAPRIO qdisc implements a simplified version of the
       scheduling state machine defined by IEEE 802.1Q-2018 Section
       8.6.9, which allows configuration of a sequence of gate states,
       where each gate state allows outgoing traffic for a subset
       (potentially empty) of traffic classes.

       How traffic is mapped to different hardware queues is similar to
       mqprio(8) and so the map and queues parameters have the same

       The other parameters specify the schedule, and at what point in
       time it should start (it can behave as the schedule started in
       the past).

PARAMETERS         top

       num_tc  Number of traffic classes to use. Up to 16 classes

              The priority to traffic class map. Maps priorities 0..15
              to a specified traffic class. See mqprio(8) for more

              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.

              Specifies the instant in nanoseconds, using the reference
              of clockid, defining the time when the schedule starts. If
              'base-time' is a time in the past, the schedule will start

              base-time + (N * cycle-time)

              where N is the smallest integer so the resulting time is
              greater than "now", and "cycle-time" is the sum of all the
              intervals of the entries in the schedule;

              Specifies the clock to be used by qdisc's internal timer
              for measuring time and scheduling events.

              There may multiple sched-entry parameters in a single
              schedule. Each one has the

              sched-entry <command> <gatemask> <interval>

              format. The only supported <command> is "S", which means
              "SetGateStates", following the IEEE 802.1Q-2018 definition
              (Table 8-7). <gate mask> is a bitmask where each bit is a
              associated with a traffic class, so bit 0 (the least
              significant bit) being "on" means that traffic class 0 is
              "active" for that schedule entry.  <interval> is a time
              duration, in nanoseconds, that specifies for how long that
              state defined by <command> and <gate mask> should be held
              before moving to the next entry.

              Specifies different modes for taprio. Currently, only
              txtime-assist is supported which can be enabled by setting
              it to 0x1. In this mode, taprio will set the transmit
              timestamp depending on the interval in which the packet
              needs to be transmitted. It will then utililize the etf(8)
              qdisc to sort and transmit the packets at the right time.
              The second example can be used as a reference to configure
              this mode.

              This parameter is specific to the txtime offload mode. It
              specifies the maximum time a packet might take to reach
              the network card from the taprio qdisc. The value should
              always be greater than the delta specified in the etf(8)

EXAMPLES         top

       The following example shows how an traffic schedule with three
       traffic classes ("num_tc 3"), which are separated different
       traffic classes, we are going to call these TC 0, TC 1 and TC 2.
       We could read the "map" parameter below as: traffic with priority
       3 is classified as TC 0, priority 2 is classified as TC 1 and the
       rest is classified as TC 2.

       The schedule will start at instant 1528743495910289987 using the
       reference CLOCK_TAI. The schedule is composed of three entries
       each of 300us duration.

       # tc qdisc replace dev eth0 parent root handle 100 taprio \
                     num_tc 3 \
                     map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \
                     queues 1@0 1@1 2@2 \
                     base-time 1528743495910289987 \
                     sched-entry S 01 300000 \
                     sched-entry S 02 300000 \
                     sched-entry S 04 300000 \
                     clockid CLOCK_TAI

       Following is an example to enable the txtime offload mode in
       taprio. See etf(8) for more information about configuring the ETF

       # tc qdisc replace dev eth0 parent root handle 100 taprio \
                     num_tc 3 \
                     map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \
                     queues 1@0 1@0 1@0 \
                     base-time 1528743495910289987 \
                     sched-entry S 01 300000 \
                     sched-entry S 02 300000 \
                     sched-entry S 04 400000 \
                     flags 0x1 \
                     txtime-delay 200000 \
                     clockid CLOCK_TAI

       # tc qdisc replace dev $IFACE parent 100:1 etf skip_skb_check \
                     offload delta 200000 clockid CLOCK_TAI

AUTHORS         top

       Vinicius Costa Gomes <>

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
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iproute2                      25 Sept 2018                     TAPRIO(8)