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diff --git a/man/man8/tc-taprio.8 b/man/man8/tc-taprio.8 new file mode 100644 index 0000000..bf489b0 --- /dev/null +++ b/man/man8/tc-taprio.8 @@ -0,0 +1,256 @@ +.TH TAPRIO 8 "25 Sept 2018" "iproute2" "Linux" +.SH NAME +TAPRIO \- Time Aware Priority Shaper +.SH SYNOPSIS +.B tc qdisc ... dev +dev +.B parent +classid +.B [ handle +major: +.B ] taprio num_tc +tcs +.ti +8 +.B map +P0 P1 P2 ... +.B queues +count1@offset1 count2@offset2 ... +.ti +8 +.B base-time +base-time +.B clockid +clockid +.ti +8 +.B sched-entry +<command 1> <gate mask 1> <interval 1> +.ti +8 +.B sched-entry +<command 2> <gate mask 2> <interval 2> +.ti +8 +.B sched-entry +<command 3> <gate mask 3> <interval 3> +.ti +8 +.B sched-entry +<command N> <gate mask N> <interval N> +.ti +8 +[ +.B max-sdu +<queueMaxSDU[TC 0]> <queueMaxSDU[TC 1]> <queueMaxSDU[TC N]> ] +.ti +8 +[ +.B fp +<adminStatus[TC 0]> <adminStatus[TC 1]> <adminStatus[TC N]> ] + +.SH 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 +.BR mqprio(8) +and so the +.B map +and +.B 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). + +.SH PARAMETERS +.TP +num_tc +.BR +Number of traffic classes to use. Up to 16 classes supported. + +.TP +map +.br +The priority to traffic class map. Maps priorities 0..15 to a specified +traffic class. See +.BR mqprio(8) +for more details. + +.TP +queues +.br +Provide count and offset of queue range for each traffic class. In the +format, +.B count@offset. +Queue ranges for each traffic classes cannot overlap and must be a +contiguous range of queues. + +.TP +base-time +.br +Specifies the instant in nanoseconds, using the reference of +.B 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; + +.TP +clockid +.br +Specifies the clock to be used by qdisc's internal timer for measuring +time and scheduling 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 +.B ethtool -T eth0 | grep 'PTP Hardware Clock' +), and therefore not necessarily synchronized with the system's CLOCK_TAI. + +.TP +sched-entry +.br +There may multiple +.B 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. + +.TP +flags +.br +This is a bit mask which specifies different modes for taprio. +.RS +.TP +.I 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 +transmitted. It will then utililize the +.BR 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. +.TP +.I 0x2 +Enables the full-offload feature. In this mode, taprio will pass the gate +control list to the NIC which will execute it cyclically in hardware. +When using full-offload, there is no need to specify the +.B clockid +argument. + +The txtime-assist and full-offload features are mutually exclusive, i.e. +setting flags to 0x3 is invalid. +.RE + +.TP +txtime-delay +.br +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 +.BR etf(8) +qdisc. + +.TP +max-sdu +.br +Specifies an array containing at most 16 elements, one per traffic class, which +corresponds to the queueMaxSDU table from IEEE 802.1Q-2018. Each array element +represents the maximum L2 payload size that can egress that traffic class. +Elements that are not filled in default to 0. The value 0 means that the +traffic class can send packets up to the port's maximum MTU in size. + +.TP +fp +.br +Selects whether traffic classes are express or preemptible. See +.BR tc-mqprio(8) +for details. + +.SH 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. + +.EX +# tc qdisc replace dev eth0 parent root handle 100 stab overhead 24 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 +.EE + +Following is an example to enable the txtime offload mode in taprio. See +.BR etf(8) +for more information about configuring the ETF qdisc. + +.EX +# tc qdisc replace dev eth0 parent root handle 100 stab overhead 24 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 +.EE + +The following is a schedule in full offload mode. The +.B base-time +is 200 ns and the +.B cycle-time +is implicitly calculated as the sum of all +.B 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. In addition, the MTU for traffic class 5 is limited to +200 octets, so that the interference this creates upon traffic class 7 during +the time window when their gates are both open is bounded. The interference is +determined by the transmit time of the max SDU, plus the L2 header length, plus +the L1 overhead (determined from the size table specified using +.BR tc-stab(8)). + +.EX +# tc qdisc add dev eth0 parent root stab overhead 24 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 \\ + max-sdu 0 0 0 0 0 200 0 0 \\ + base-time 200 \\ + sched-entry S 80 20000 \\ + sched-entry S a0 20000 \\ + sched-entry S 5f 60000 \\ + flags 0x2 +.EE + +.SH SEE ALSO +.BR tc-stab(8) + +.SH AUTHORS +Vinicius Costa Gomes <vinicius.gomes@intel.com> |