NAME

       TAPRIO - Time Aware Priority Shaper

SYNOPSIS

       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

       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 meaning.

       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

       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.  See
              mqprio(8) for more details.

       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.

       base-time
              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 at

              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;

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

       sched-entry
              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.

       flags
              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.

       txtime-delay
              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) qdisc.

EXAMPLES

       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 qdisc.

       # 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

       Vinicius Costa Gomes <vinicius.gomes@intel.com>

iproute2                                          25 Sept 2018                                         TAPRIO(8)