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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 14:18:53 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 14:18:53 +0000 |
commit | a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67 (patch) | |
tree | 8feaf1a1932871b139b3b30be4c09c66489918be /man/man8/tc-ets.8 | |
parent | Initial commit. (diff) | |
download | iproute2-a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67.tar.xz iproute2-a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67.zip |
Adding upstream version 6.1.0.upstream/6.1.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man/man8/tc-ets.8')
-rw-r--r-- | man/man8/tc-ets.8 | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/man/man8/tc-ets.8 b/man/man8/tc-ets.8 new file mode 100644 index 0000000..d3e6816 --- /dev/null +++ b/man/man8/tc-ets.8 @@ -0,0 +1,192 @@ +.TH TC 8 "December 2019" "iproute2" "Linux" +.SH NAME +ETS \- Enhanced Transmission Selection scheduler +.SH SYNOPSIS +.B tc qdisc ... ets [ bands +number +.B ] [ strict +number +.B ] [ quanta +bytes bytes bytes... +.B ] [ priomap +band band band... +.B ] + +.B tc class ... ets [ quantum +bytes +.B ] + +.SH DESCRIPTION + +The Enhanced Transmission Selection scheduler is a classful queuing +discipline that merges functionality of PRIO and DRR qdiscs in one +scheduler. ETS makes it easy to configure a set of strict and +bandwidth-sharing bands to implement the transmission selection described +in 802.1Qaz. + +On creation with 'tc qdisc add', a fixed number of bands is created. Each +band is a class, although it is not possible to directly add and remove +bands with 'tc class' commands. The number of bands to be created must +instead be specified on the command line as the qdisc is added. + +The minor number of classid to use when referring to a band is the band +number increased by one. Thus band 0 will have classid of major:1, band 1 +that of major:2, etc. + +ETS bands are of two types: some number may be in strict mode, the +remaining ones are in bandwidth-sharing mode. + +.SH ALGORITHM +When dequeuing, strict bands are tried first, if there are any. Band 0 is +tried first. If it did not deliver a packet, band 1 is tried next, and so +on until one of the bands delivers a packet, or the strict bands are +exhausted. + +If no packet has been dequeued from any of the strict bands, if there are +any bandwidth-sharing bands, the dequeuing proceeds according to the DRR +algorithm. Each bandwidth-sharing band is assigned a deficit counter, +initialized to quantum assigned by a +.B quanta +element. ETS maintains an (internal) ''active'' list of bandwidth-sharing +bands whose qdiscs are non-empty. This list is used for dequeuing. A packet +is dequeued from the band at the head of the list if the packet size is +smaller or equal to the deficit counter. If the counter is too small, it is +increased by +.B quantum +and the scheduler moves on to the next band in the active list. + +Only qdiscs that own their queue should be added below the +bandwidth-sharing bands. Attaching to them non-work-conserving qdiscs like +TBF does not make sense \-\- other qdiscs in the active list will be +skipped until the dequeue operation succeeds. This limitation does not +exist with the strict bands. + +.SH CLASSIFICATION +The ETS qdisc allows three ways to decide which band to enqueue a packet +to: + +- Packet priority can be directly set to a class handle, in which case that + is the queue where the packet will be put. For example, band number 2 of + a qdisc with handle of 11: will have classid 11:3. To mark a packet for + queuing to this band, the packet priority should be set to 0x110003. + +- A tc filter attached to the qdisc can put the packet to a band by using + the \fBflowid\fR keyword. + +- As a last resort, the ETS qdisc consults its priomap (see below), which + maps packets to bands based on packet priority. + +.SH PARAMETERS +.TP +strict +The number of bands that should be created in strict mode. If not given, +this value is 0. + +.TP +quanta +Each bandwidth-sharing band needs to know its quantum, which is the amount +of bytes a band is allowed to dequeue before the scheduler moves to the +next bandwidth-sharing band. The +.B quanta +argument lists quanta for the individual bandwidth-sharing bands. +The minimum value of each quantum is 1. If +.B quanta +is not given, the default is no bandwidth-sharing bands, but note that when +specifying a large number of +.B bands, +the extra ones are in bandwidth-sharing mode by default. + +.TP +bands +Number of bands given explicitly. This value has to be at least large +enough to cover the strict bands specified through the +.B strict +keyword and bandwidth-sharing bands specified in +.B quanta. +If a larger value is given, any extra bands are in bandwidth-sharing mode, +and their quanta are deduced from the interface MTU. If no value is given, +as many bands are created as necessary to cover all bands implied by the +.B strict +and +.B quanta +keywords. + +.TP +priomap +The priomap maps the priority of a packet to a band. The argument is a list +of numbers. The first number indicates which band the packets with priority +0 should be put to, the second is for priority 1, and so on. + +There can be up to 16 numbers in the list. If there are fewer, the default +band that traffic with one of the unmentioned priorities goes to is the +last one. + +.SH EXAMPLE & USAGE + +.P +Add a qdisc with 8 bandwidth-sharing bands, using the interface MTU as +their quanta. Since all quanta are the same, this will lead to equal +distribution of bandwidth between the bands, each will get about 12.5% of +the link. The low 8 priorities go to individual bands in a reverse 1:1 +fashion (such that the highest priority goes to the first band). + +.P +# tc qdisc add dev eth0 root handle 1: ets bands 8 priomap 7 6 5 4 3 2 1 0 +.br +# tc qdisc show dev eth0 +.br +qdisc ets 1: root refcnt 2 bands 8 quanta 1514 1514 1514 1514 1514 1514 1514 1514 priomap 7 6 5 4 3 2 1 0 7 7 7 7 7 7 7 7 + +.P +Tweak the first band of the above qdisc to give it a quantum of 2650, which +will give it about 20% of the link (and about 11.5% to the remaining +bands): + +.P +# tc class change dev eth0 classid 1:1 ets quantum 2650 +.br +# tc qdisc show dev eth0 +.br +qdisc ets 1: root refcnt 2 bands 8 quanta 2650 1514 1514 1514 1514 1514 1514 1514 priomap 7 6 5 4 3 2 1 0 7 7 7 7 7 7 7 7 + +.P +Create a purely strict Qdisc with reverse 1:1 mapping between priorities +and bands: + +.P +# tc qdisc add dev eth0 root handle 1: ets strict 8 priomap 7 6 5 4 3 2 1 0 +.br +# tc qdisc sh dev eth0 +.br +qdisc ets 1: root refcnt 2 bands 8 strict 8 priomap 7 6 5 4 3 2 1 0 7 7 7 7 7 7 7 7 + +.P +Add a Qdisc with 6 bands, 3 strict and 3 ETS with 35%-30%-25% weights: +.P +# tc qdisc add dev eth0 root handle 1: ets strict 3 quanta 3500 3000 2500 priomap 0 1 1 1 2 3 4 5 +.br +# tc qdisc sh dev eth0 +.br +qdisc ets 1: root refcnt 2 bands 6 strict 3 quanta 3500 3000 2500 priomap 0 1 1 1 2 3 4 5 5 5 5 5 5 5 5 5 + +.P +Create a Qdisc such that traffic with priorities 2, 3 and 4 are strictly +prioritized over other traffic, and the rest goes into bandwidth-sharing +classes with equal weights: +.P +# tc qdisc add dev eth0 root handle 1: ets bands 8 strict 3 priomap 3 4 0 1 2 5 6 7 +.br +# tc qdisc sh dev eth0 +.br +qdisc ets 1: root refcnt 2 bands 8 strict 3 quanta 1514 1514 1514 1514 1514 priomap 3 4 0 1 2 5 6 7 7 7 7 7 7 7 7 7 + +.SH SEE ALSO +.BR tc (8), +.BR tc-prio (8), +.BR tc-drr (8) + +.SH AUTHOR +Parts of both this manual page and the code itself are taken from PRIO and +DRR qdiscs. +.br +ETS qdisc itself was written by Petr Machata. |