1TAPRIO(8) Linux TAPRIO(8)
2
6 TAPRIO - Time Aware Priority Shaper
7
9 tc qdisc ... dev dev parent classid [ handle major: ] taprio num_tc tcs
10 map P0 P1 P2 ... queues count1@offset1 count2@offset2 ...
11 base-time base-time clockid clockid
12 sched-entry <command 1> <gate mask 1> <interval 1>
13 sched-entry <command 2> <gate mask 2> <interval 2>
14 sched-entry <command 3> <gate mask 3> <interval 3>
15 sched-entry <command N> <gate mask N> <interval N>
16
19 The TAPRIO qdisc implements a simplified version of the scheduling
20 state machine defined by IEEE 802.1Q-2018 Section 8.6.9, which allows
21 configuration of a sequence of gate states, where each gate state al‐
22 lows outgoing traffic for a subset (potentially empty) of traffic
23 classes.
24 How traffic is mapped to different hardware queues is similar to
26 mqprio(8) and so the map and queues parameters have the same meaning.
27 The other parameters specify the schedule, and at what point in time it
29 should start (it can behave as the schedule started in the past).
30
33 num_tc Number of traffic classes to use. Up to 16 classes supported.
34 map
37 The priority to traffic class map. Maps priorities 0..15 to a
38 specified traffic class. See mqprio(8) for more details.
39 queues
42 Provide count and offset of queue range for each traffic class.
43 In the format, count@offset. Queue ranges for each traffic
44 classes cannot overlap and must be a contiguous range of queues.
45 base-time
48 Specifies the instant in nanoseconds, using the reference of
49 clockid, defining the time when the schedule starts. If 'base-
50 time' is a time in the past, the schedule will start at
51 base-time + (N * cycle-time)
53 where N is the smallest integer so the resulting time is greater
55 than "now", and "cycle-time" is the sum of all the intervals of
56 the entries in the schedule;
57 clockid
60 Specifies the clock to be used by qdisc's internal timer for
61 measuring time and scheduling events. This argument must be
62 omitted when using the full-offload feature (flags 0x2), since
63 in that case, the clockid is implicitly /dev/ptpN (where N is
64 given by ethtool -T eth0 | grep 'PTP Hardware Clock' ), and
65 therefore not necessarily synchronized with the system's
66 CLOCK_TAI.
67 sched-entry
70 There may multiple sched-entry parameters in a single schedule.
71 Each one has the
72 sched-entry <command> <gatemask> <interval>
74 format. The only supported <command> is "S", which means "Set‐
76 GateStates", following the IEEE 802.1Q-2018 definition (Table
77 8-7). <gate mask> is a bitmask where each bit is a associated
78 with a traffic class, so bit 0 (the least significant bit) being
79 "on" means that traffic class 0 is "active" for that schedule
80 entry. <interval> is a time duration, in nanoseconds, that
81 specifies for how long that state defined by <command> and <gate
82 mask> should be held before moving to the next entry.
83 flags
86 This is a bit mask which specifies different modes for taprio.
87 0x1 Enables the txtime-assist feature. In this mode, taprio
89 will set the transmit timestamp depending on the interval
90 in which the packet needs to be transmitted. It will then
91 utililize the etf(8) qdisc to sort and transmit the pack‐
92 ets at the right time. The second example can be used as
93 a reference to configure this mode.
94 0x2 Enables the full-offload feature. In this mode, taprio
96 will pass the gate control list to the NIC which will ex‐
97 ecute it cyclically in hardware. When using full-off‐
98 load, there is no need to specify the clockid argument.
99 The txtime-assist and full-offload features are mutually
101 exclusive, i.e. setting flags to 0x3 is invalid.
102 txtime-delay
105 This parameter is specific to the txtime offload mode. It speci‐
106 fies the maximum time a packet might take to reach the network
107 card from the taprio qdisc. The value should always be greater
108 than the delta specified in the etf(8) qdisc.
109
112 The following example shows how an traffic schedule with three traffic
113 classes ("num_tc 3"), which are separated different traffic classes, we
114 are going to call these TC 0, TC 1 and TC 2. We could read the "map"
115 parameter below as: traffic with priority 3 is classified as TC 0, pri‐
116 ority 2 is classified as TC 1 and the rest is classified as TC 2.
117 The schedule will start at instant 1528743495910289987 using the refer‐
119 ence CLOCK_TAI. The schedule is composed of three entries each of 300us
120 duration.
121 # tc qdisc replace dev eth0 parent root handle 100 taprio \
123 num_tc 3 \
124 map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \
125 queues 1@0 1@1 2@2 \
126 base-time 1528743495910289987 \
127 sched-entry S 01 300000 \
128 sched-entry S 02 300000 \
129 sched-entry S 04 300000 \
130 clockid CLOCK_TAI
131 Following is an example to enable the txtime offload mode in taprio.
133 See etf(8) for more information about configuring the ETF qdisc.
134 # tc qdisc replace dev eth0 parent root handle 100 taprio \
136 num_tc 3 \
137 map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \
138 queues 1@0 1@0 1@0 \
139 base-time 1528743495910289987 \
140 sched-entry S 01 300000 \
141 sched-entry S 02 300000 \
142 sched-entry S 04 400000 \
143 flags 0x1 \
144 txtime-delay 200000 \
145 clockid CLOCK_TAI
146 # tc qdisc replace dev $IFACE parent 100:1 etf skip_skb_check \
148 offload delta 200000 clockid CLOCK_TAI
149 The following is a schedule in full offload mode. The base-time is 200
151 ns and the cycle-time is implicitly calculated as the sum of all sched-
152 entry durations (i.e. 20 us + 20 us + 60 us = 100 us). Although the
153 base-time is in the past, the hardware will start executing the sched‐
154 ule at a PTP time equal to the smallest integer multiple of 100 us,
155 plus 200 ns, that is larger than the NIC's current PTP time.
156 # tc qdisc add dev eth0 parent root taprio \
158 num_tc 8 \
159 map 0 1 2 3 4 5 6 7 \
160 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 \
161 base-time 200 \
162 sched-entry S 80 20000 \
163 sched-entry S a0 20000 \
164 sched-entry S df 60000 \
165 flags 0x2
166
169 Vinicius Costa Gomes <vinicius.gomes@intel.com>
170iproute2 25 Sept 2018 TAPRIO(8)