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Add documentation for the latest options, flags and txtime-delay, to the taprio manpage. This also adds an example to run tc in txtime offload mode. Signed-off-by: Vedang Patel <vedang.patel@intel.com> Signed-off-by: David Ahern <dsahern@gmail.com>
183 lines
5.0 KiB
Groff
183 lines
5.0 KiB
Groff
.TH TAPRIO 8 "25 Sept 2018" "iproute2" "Linux"
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.SH NAME
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TAPRIO \- Time Aware Priority Shaper
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.SH SYNOPSIS
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.B tc qdisc ... dev
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dev
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.B parent
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classid
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.B [ handle
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major:
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.B ] taprio num_tc
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tcs
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.ti +8
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.B map
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P0 P1 P2 ...
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.B queues
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count1@offset1 count2@offset2 ...
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.ti +8
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.B base-time
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base-time
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.B clockid
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clockid
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.ti +8
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.B sched-entry
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<command 1> <gate mask 1> <interval 1>
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.ti +8
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.B sched-entry
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<command 2> <gate mask 2> <interval 2>
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.ti +8
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.B sched-entry
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<command 3> <gate mask 3> <interval 3>
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.ti +8
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.B sched-entry
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<command N> <gate mask N> <interval N>
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.SH DESCRIPTION
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The TAPRIO qdisc implements a simplified version of the scheduling
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state machine defined by IEEE 802.1Q-2018 Section 8.6.9, which allows
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configuration of a sequence of gate states, where each gate state
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allows outgoing traffic for a subset (potentially empty) of traffic
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classes.
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How traffic is mapped to different hardware queues is similar to
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.BR mqprio(8)
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and so the
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.B map
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and
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.B queues
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parameters have the same meaning.
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The other parameters specify the schedule, and at what point in time
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it should start (it can behave as the schedule started in the past).
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.SH PARAMETERS
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.TP
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num_tc
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.BR
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Number of traffic classes to use. Up to 16 classes supported.
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.TP
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map
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.br
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The priority to traffic class map. Maps priorities 0..15 to a specified
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traffic class. See
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.BR mqprio(8)
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for more details.
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.TP
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queues
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.br
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Provide count and offset of queue range for each traffic class. In the
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format,
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.B count@offset.
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Queue ranges for each traffic classes cannot overlap and must be a
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contiguous range of queues.
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.TP
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base-time
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.br
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Specifies the instant in nanoseconds, using the reference of
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.B clockid,
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defining the time when the schedule starts. If 'base-time' is a time
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in the past, the schedule will start at
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base-time + (N * cycle-time)
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where N is the smallest integer so the resulting time is greater than
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"now", and "cycle-time" is the sum of all the intervals of the entries
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in the schedule;
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.TP
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clockid
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.br
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Specifies the clock to be used by qdisc's internal timer for measuring
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time and scheduling events.
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.TP
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sched-entry
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.br
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There may multiple
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.B sched-entry
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parameters in a single schedule. Each one has the
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sched-entry <command> <gatemask> <interval>
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format. The only supported <command> is "S", which
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means "SetGateStates", following the IEEE 802.1Q-2018 definition
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(Table 8-7). <gate mask> is a bitmask where each bit is a associated
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with a traffic class, so bit 0 (the least significant bit) being "on"
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means that traffic class 0 is "active" for that schedule entry.
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<interval> is a time duration, in nanoseconds, that specifies for how
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long that state defined by <command> and <gate mask> should be held
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before moving to the next entry.
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.TP
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flags
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.br
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Specifies different modes for taprio. Currently, only txtime-assist is
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supported which can be enabled by setting it to 0x1. In this mode, taprio will
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set the transmit timestamp depending on the interval in which the packet needs
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to be transmitted. It will then utililize the
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.BR etf(8)
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qdisc to sort and transmit the packets at the right time. The second example
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can be used as a reference to configure this mode.
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.TP
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txtime-delay
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.br
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This parameter is specific to the txtime offload mode. It specifies the maximum
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time a packet might take to reach the network card from the taprio qdisc. The
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value should always be greater than the delta specified in the
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.BR etf(8)
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qdisc.
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.SH EXAMPLES
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The following example shows how an traffic schedule with three traffic
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classes ("num_tc 3"), which are separated different traffic classes,
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we are going to call these TC 0, TC 1 and TC 2. We could read the
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"map" parameter below as: traffic with priority 3 is classified as TC
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0, priority 2 is classified as TC 1 and the rest is classified as TC
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2.
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The schedule will start at instant 1528743495910289987 using the
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reference CLOCK_TAI. The schedule is composed of three entries each of
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300us duration.
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.EX
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# tc qdisc replace dev eth0 parent root handle 100 taprio \\
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num_tc 3 \\
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map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \\
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queues 1@0 1@1 2@2 \\
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base-time 1528743495910289987 \\
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sched-entry S 01 300000 \\
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sched-entry S 02 300000 \\
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sched-entry S 04 300000 \\
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clockid CLOCK_TAI
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.EE
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Following is an example to enable the txtime offload mode in taprio. See
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.BR etf(8)
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for more information about configuring the ETF qdisc.
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.EX
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# tc qdisc replace dev eth0 parent root handle 100 taprio \\
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num_tc 3 \\
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map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \\
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queues 1@0 1@0 1@0 \\
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base-time 1528743495910289987 \\
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sched-entry S 01 300000 \\
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sched-entry S 02 300000 \\
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sched-entry S 04 400000 \\
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flags 0x1 \\
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txtime-delay 200000 \\
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clockid CLOCK_TAI
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# tc qdisc replace dev $IFACE parent 100:1 etf skip_skb_check \\
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offload delta 200000 clockid CLOCK_TAI
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.EE
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.SH AUTHORS
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Vinicius Costa Gomes <vinicius.gomes@intel.com>
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