{"id":2840,"date":"2022-12-20T15:17:27","date_gmt":"2022-12-20T18:17:27","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/taprio-man8\/"},"modified":"2022-12-20T15:17:27","modified_gmt":"2022-12-20T18:17:27","slug":"taprio-man8","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/taprio-man8\/","title":{"rendered":"TAPRIO (man8)"},"content":{"rendered":"

TAPRIO<\/h1>\n

NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
PARAMETERS<\/a>
EXAMPLES<\/a>
AUTHORS<\/a> <\/p>\n

\n

NAME <\/a> <\/h2>\n

TAPRIO \u2212 Time Aware Priority Shaper<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

tc qdisc … dev<\/b> dev parent<\/b> classid [ handle<\/b> major: ] taprio num_tc<\/b> tcs
map<\/b> P0 P1 P2 … queues<\/b> count1@offset1 count2@offset2 …
base-time<\/b> base-time clockid<\/b> clockid
sched-entry<\/b>
sched-entry<\/b>
sched-entry<\/b>
sched-entry<\/b> <\/p>\n

DESCRIPTION <\/a> <\/h2>\n

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.<\/p>\n

How traffic is mapped to different hardware queues is similar to mqprio(8)<\/b> and so the map<\/b> and queues<\/b> parameters have the same meaning.<\/p>\n

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).<\/p>\n

PARAMETERS <\/a> <\/h2>\n\n\n\n\n
<\/td>\n\n

num_tc<\/p>\n<\/td>\n

<\/td>\n\n

Number of traffic classes to use. Up to 16 classes supported.<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

map<\/p>\n<\/td>\n

<\/td>\n\n

The priority to traffic class map. Maps priorities 0..15 to a specified traffic class. See mqprio(8)<\/b> for more details.<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

queues<\/p>\n<\/td>\n

<\/td>\n\n

Provide count and offset of queue range for each traffic class. In the format, count@offset.<\/b> Queue ranges for each traffic classes cannot overlap and must be a contiguous range of queues.<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

base-time<\/p>\n

Specifies the instant in nanoseconds, using the reference of clockid,<\/b> defining the time when the schedule starts. If \u2019base-time\u2019 is a time in the past, the schedule will start at<\/p>\n

base-time + (N bodies manpages.csv script_extrae_body.sh script.sh usr cycle-time)<\/p>\n

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;<\/p>\n

clockid<\/p>\n

Specifies the clock to be used by qdisc\u2019s 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 ethtool -T eth0 | grep \u2019PTP Hardware Clock\u2019<\/b> ), and therefore not necessarily synchronized with the system\u2019s CLOCK_TAI.<\/p>\n

sched-entry<\/p>\n

There may multiple sched-entry<\/b> parameters in a single schedule. Each one has the<\/p>\n

sched-entry <\/p>\n

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.<\/p>\n\n\n
<\/td>\n\n

flags<\/p>\n<\/td>\n

<\/td>\n\n

This is a bit mask which specifies different modes for taprio.<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

0x1<\/i><\/p>\n\n\n\n
<\/td>\n<\/td>\n<\/td>\n\n

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 etf(8)<\/b> qdisc to sort and transmit the packets at the right time. The second example can be used as a reference to configure this mode.<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

0x2<\/i><\/p>\n<\/td>\n

<\/td>\n\n

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 clockid<\/b> argument.<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

The txtime-assist and full-offload features are mutually exclusive, i.e. setting flags to 0x3 is invalid.<\/p>\n

txtime-delay<\/p>\n

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)<\/b> qdisc.<\/p>\n

EXAMPLES <\/a> <\/h2>\n

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.<\/p>\n

The schedule will start at instant 1528743495910289987 using the reference CLOCK_TAI. The schedule is composed of three entries each of 300us duration.<\/p>\n

# 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<\/p>\n

Following is an example to enable the txtime offload mode in taprio. See etf(8)<\/b> for more information about configuring the ETF qdisc.<\/p>\n

# 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<\/p>\n

# tc qdisc replace dev $IFACE parent 100:1 etf skip_skb_check
offload delta 200000 clockid CLOCK_TAI<\/p>\n

The following is a schedule in full offload mode. The base-time<\/b> is 200 ns and the cycle-time<\/b> is implicitly calculated as the sum of all sched-entry<\/b> 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\u2019s current PTP time.<\/p>\n

# 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<\/p>\n

AUTHORS <\/a> <\/h2>\n

Vinicius Costa Gomes <\/p>\n

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