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NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | EXAMPLES | SEE ALSO | AUTHORS | COLOPHON |
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TAPRIO(8) Linux TAPRIO(8)
TAPRIO - Time Aware Priority Shaper
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>
[ max-sdu <queueMaxSDU[TC 0]> <queueMaxSDU[TC 1]>
<queueMaxSDU[TC N]> ]
[ fp <adminStatus[TC 0]> <adminStatus[TC 1]>
<adminStatus[TC 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.
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).
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. 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
synchronized with the system's CLOCK_TAI.
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
"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.
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
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.
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
clockid argument.
The txtime-assist and full-offload features are
mutually exclusive, i.e. setting 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)
qdisc.
max-sdu
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.
fp
Selects whether traffic classes are express or
preemptible. See tc-mqprio(8) for details.
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 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
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 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
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. 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
tc-stab(8)).
# 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
tc-stab(8)
Vinicius Costa Gomes <[email protected]>
This page is part of the iproute2 (utilities for controlling
TCP/IP networking and traffic) project. Information about the
project can be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
[email protected], [email protected]. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-11.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to [email protected]
iproute2 25 Sept 2018 TAPRIO(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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