# phpman > man > TAPRIO(8) [TAPRIO(8)](https://www.chedong.com/phpMan.php/man/TAPRIO/8/markdown) Linux [TAPRIO(8)](https://www.chedong.com/phpMan.php/man/TAPRIO/8/markdown) ## 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** **sched-entry** **sched-entry** **sched-entry** ## 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)](https://www.chedong.com/phpMan.php/man/mqprio/8/markdown)** 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)](https://www.chedong.com/phpMan.php/man/mqprio/8/markdown)** 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 con‐ tiguous 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 "cy‐ cle-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 sched‐ uling events. This argument must be omitted when using the full-offload feature (flags 0x2), since in that case, the clockid is implicitly /dev/ptpN (where N is given by **ethtool** **-T** **eth0** **|** **grep** **'PTP** **Hardware** **Clock'** ), and therefore not necessarily synchro‐ nized with the system's CLOCK_TAI. sched-entry There may multiple **sched-entry** parameters in a single schedule. Each one has the sched-entry format. The only supported is "S", which means "SetGateStates", following the IEEE 802.1Q-2018 definition (Table 8-7). 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. is a time duration, in nanoseconds, that specifies for how long that state defined by and should be held before moving to the next entry. flags This is a bit mask which specifies different modes for taprio. _0x1_ Enables the txtime-assist feature. In this mode, taprio will set the transmit timestamp depending on the interval in which the packet needs to be transmit‐ ted. It will then utililize the [**etf(8)](https://www.chedong.com/phpMan.php/man/etf/8/markdown)** qdisc to sort and transmit the packets at the right time. The second example can be used as a reference to configure this mode. _0x2_ Enables the full-offload feature. In this mode, taprio will pass the gate con‐ trol list to the NIC which will execute it cyclically in hardware. When using full-offload, there is no need to specify the **clockid** argument. The txtime-assist and full-offload features are mutually exclusive, i.e. set‐ ting flags to 0x3 is invalid. 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)](https://www.chedong.com/phpMan.php/man/etf/8/markdown)** 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)](https://www.chedong.com/phpMan.php/man/etf/8/markdown)** for more in‐ formation 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 The following is a schedule in full offload mode. The **base-time** is 200 ns and the **cycle-time** is implicitly calculated as the sum of all **sched-entry** durations (i.e. 20 us + 20 us + 60 us = 100 us). Although the base-time is in the past, the hardware will start executing the schedule at a PTP time equal to the smallest integer multiple of 100 us, plus 200 ns, that is larger than the NIC's current PTP time. # tc qdisc add dev eth0 parent root taprio \ num_tc 8 \ map 0 1 2 3 4 5 6 7 \ queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 \ base-time 200 \ sched-entry S 80 20000 \ sched-entry S a0 20000 \ sched-entry S df 60000 \ flags 0x2 ## AUTHORS Vinicius Costa Gomes <> iproute2 25 Sept 2018 [TAPRIO(8)](https://www.chedong.com/phpMan.php/man/TAPRIO/8/markdown)