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From 716aa9141156b5284679b40545e20c7164957bf3 Mon Sep 17 00:00:00 2001
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From: Andrea Claudi <aclaudi@redhat.com>
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Date: Tue, 21 Apr 2020 14:32:49 +0200
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Subject: [PATCH] man: Add initial manpage for tc-cbs(8)
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1557461
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Upstream Status: iproute2.git commit d65298892062e
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commit d65298892062e8757e94d36f23fe3ea835ff66dc
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Author: Vinicius Costa Gomes <vinicius.gomes@intel.com>
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Date: Thu Oct 26 10:17:49 2017 -0700
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man: Add initial manpage for tc-cbs(8)
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Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
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Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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---
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man/man8/tc-cbs.8 | 112 ++++++++++++++++++++++++++++++++++++++++++++++
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1 file changed, 112 insertions(+)
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create mode 100644 man/man8/tc-cbs.8
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diff --git a/man/man8/tc-cbs.8 b/man/man8/tc-cbs.8
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new file mode 100644
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index 0000000000000..97e00c84ded16
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--- /dev/null
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+++ b/man/man8/tc-cbs.8
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@@ -0,0 +1,112 @@
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+.TH CBS 8 "18 Sept 2017" "iproute2" "Linux"
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+.SH NAME
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+CBS \- Credit Based Shaper (CBS) Qdisc
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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 ] cbs idleslope
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+idleslope
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+.B sendslope
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+sendslope
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+.B hicredit
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+hicredit
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+.B locredit
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+locredit
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+.B [ offload
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+0|1
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+.B ]
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+
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+.SH DESCRIPTION
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+The CBS (Credit Based Shaper) qdisc implements the shaping algorithm
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+defined by the IEEE 802.1Q-2014 Section 8.6.8.2, which applies a well
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+defined rate limiting method to the traffic.
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+
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+This queueing discipline is intended to be used by TSN (Time Sensitive
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+Networking) applications, the CBS parameters are derived directly by
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+what is described by the Annex L of the IEEE 802.1Q-2014
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+Sepcification. The algorithm and how it affects the latency are
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+detailed there.
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+
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+CBS is meant to be installed under another qdisc that maps packet
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+flows to traffic classes, one example is
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+.BR mqprio(8).
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+
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+.SH PARAMETERS
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+.TP
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+idleslope
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+Idleslope is the rate of credits that is accumulated (in kilobits per
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+second) when there is at least one packet waiting for transmission.
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+Packets are transmitted when the current value of credits is equal or
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+greater than zero. When there is no packet to be transmitted the
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+amount of credits is set to zero. This is the main tunable of the CBS
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+algorithm.
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+.TP
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+sendslope
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+Sendslope is the rate of credits that is depleted (it should be a
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+negative number of kilobits per second) when a transmission is
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+ocurring. It can be calculated as follows, (IEEE 802.1Q-2014 Section
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+8.6.8.2 item g):
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+
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+sendslope = idleslope - port_transmit_rate
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+
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+.TP
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+hicredit
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+Hicredit defines the maximum amount of credits (in bytes) that can be
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+accumulated. Hicredit depends on the characteristics of interfering
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+traffic, 'max_interference_size' is the maximum size of any burst of
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+traffic that can delay the transmission of a frame that is available
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+for transmission for this traffic class, (IEEE 802.1Q-2014 Annex L,
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+Equation L-3):
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+
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+hicredit = max_interference_size * (idleslope / port_transmit_rate)
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+
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+.TP
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+locredit
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+Locredit is the minimum amount of credits that can be reached. It is a
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+function of the traffic flowing through this qdisc (IEEE 802.1Q-2014
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+Annex L, Equation L-2):
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+
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+locredit = max_frame_size * (sendslope / port_transmit_rate)
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+
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+.TP
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+offload
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+When
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+.B offload
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+is 1,
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+.BR cbs(8)
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+will try to configure the network interface so the CBS algorithm runs
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+in the controller. The default is 0.
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+
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+.SH EXAMPLES
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+
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+CBS is used to enforce a Quality of Service by limiting the data rate
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+of a traffic class, to separate packets into traffic classes the user
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+may choose
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+.BR mqprio(8),
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+and configure it like this:
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+
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+.EX
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+# tc qdisc add dev eth0 handle 100: parent root mqprio 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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+ hw 0
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+.EE
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+.P
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+To replace the current queuing disciple by CBS in the current queueing
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+discipline connected to traffic class number 0, issue:
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+.P
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+.EX
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+# tc qdisc replace dev eth0 parent 100:4 cbs \\
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+ locredit -1470 hicredit 30 sendslope -980000 idleslope 20000
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+.EE
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+
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+These values are obtained from the following parameters, idleslope is
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+20mbit/s, the transmission rate is 1Gbit/s and the maximum interfering
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+frame size is 1500 bytes.
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+
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+.SH AUTHORS
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+Vinicius Costa Gomes <vinicius.gomes@intel.com>
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--
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2.25.3
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