tc-taprio

TAPRIO(8)                            Linux                           TAPRIO(8)

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 al-
       lows 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  "Set-
              GateStates",  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-as-
              sist 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 speci-
              fies 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, pri-
       ority 2 is classified as TC 1 and the rest is classified as TC 2.

       The schedule will start at instant 1528743495910289987 using the refer-
       ence 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)