diff options
Diffstat (limited to '')
| -rw-r--r-- | man/man8/tc-mqprio.8 | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/man/man8/tc-mqprio.8 b/man/man8/tc-mqprio.8 new file mode 100644 index 0000000..724ef90 --- /dev/null +++ b/man/man8/tc-mqprio.8 @@ -0,0 +1,290 @@ +.TH MQPRIO 8 "24 Sept 2013" "iproute2" "Linux" +.SH NAME +MQPRIO \- Multiqueue Priority Qdisc (Offloaded Hardware QOS) +.SH SYNOPSIS +.B tc qdisc ... dev +dev ( +.B parent +classid | root) [ +.B handle +major: ] +.B mqprio +.ti +8 +[ +.B num_tc +tcs ] [ +.B map +P0 P1 P2... ] [ +.B queues +count1@offset1 count2@offset2 ... ] +.ti +8 +[ +.B hw +1|0 ] [ +.B mode +dcb|channel ] [ +.B shaper +dcb|bw_rlimit ] +.ti +8 +[ +.B min_rate +min_rate1 min_rate2 ... ] [ +.B max_rate +max_rate1 max_rate2 ... ] +.ti +8 +[ +.B fp +FP0 FP1 FP2 ... ] + +.SH DESCRIPTION +The MQPRIO qdisc is a simple queuing discipline that allows mapping +traffic flows to hardware queue ranges using priorities and a configurable +priority to traffic class mapping. A traffic class in this context is +a set of contiguous qdisc classes which map 1:1 to a set of hardware +exposed queues. + +By default the qdisc allocates a pfifo qdisc (packet limited first in, first +out queue) per TX queue exposed by the lower layer device. Other queuing +disciplines may be added subsequently. Packets are enqueued using the +.B map +parameter and hashed across the indicated queues in the +.B offset +and +.B count. +By default these parameters are configured by the hardware +driver to match the hardware QOS structures. + +.B Channel +mode supports full offload of the mqprio options, the traffic classes, the queue +configurations and QOS attributes to the hardware. Enabled hardware can provide +hardware QOS with the ability to steer traffic flows to designated traffic +classes provided by this qdisc. Hardware based QOS is configured using the +.B shaper +parameter. +.B bw_rlimit +with minimum and maximum bandwidth rates can be used for setting +transmission rates on each traffic class. Also further qdiscs may be added +to the classes of MQPRIO to create more complex configurations. + +.SH ALGORITHM +On creation with 'tc qdisc add', eight traffic classes are created mapping +priorities 0..7 to traffic classes 0..7 and priorities greater than 7 to +traffic class 0. This requires base driver support and the creation will +fail on devices that do not support hardware QOS schemes. + +These defaults can be overridden using the qdisc parameters. Providing +the 'hw 0' flag allows software to run without hardware coordination. + +If hardware coordination is being used and arguments are provided that +the hardware can not support then an error is returned. For many users +hardware defaults should work reasonably well. + +As one specific example numerous Ethernet cards support the 802.1Q +link strict priority transmission selection algorithm (TSA). MQPRIO +enabled hardware in conjunction with the classification methods below +can provide hardware offloaded support for this TSA. + +.SH CLASSIFICATION +Multiple methods are available to set the SKB priority which MQPRIO +uses to select which traffic class to enqueue the packet. +.TP +From user space +A process with sufficient privileges can encode the destination class +directly with SO_PRIORITY, see +.BR socket(7). +.TP +with iptables/nftables +An iptables/nftables rule can be created to match traffic flows and +set the priority. +.BR iptables(8) +.TP +with net_prio cgroups +The net_prio cgroup can be used to set the priority of all sockets +belong to an application. See kernel and cgroup documentation for details. + +.SH QDISC PARAMETERS +.TP +num_tc +Number of traffic classes to use. Up to 16 classes supported. +You cannot have more classes than queues + +.TP +map +The priority to traffic class map. Maps priorities 0..15 to a specified +traffic class. + +.TP +queues +Provide count and offset of queue range for each traffic class. In the +format, +.B count@offset. +Queue ranges for each traffic classes cannot overlap and must be a +contiguous range of queues. + +.TP +hw +Set to +.B 1 +to support hardware offload. Set to +.B 0 +to configure user specified values in software only. +The default value of this parameter is +.B 1 + +.TP +mode +Set to +.B channel +for full use of the mqprio options. Use +.B dcb +to offload only TC values and use hardware QOS defaults. Supported with 'hw' +set to 1 only. + +.TP +shaper +Use +.B bw_rlimit +to set bandwidth rate limits for a traffic class. Use +.B dcb +for hardware QOS defaults. Supported with 'hw' set to 1 only. + +.TP +min_rate +Minimum value of bandwidth rate limit for a traffic class. Supported only when +the +.B 'shaper' +argument is set to +.B 'bw_rlimit'. + +.TP +max_rate +Maximum value of bandwidth rate limit for a traffic class. Supported only when +the +.B 'shaper' +argument is set to +.B 'bw_rlimit'. + +.TP +fp +Selects whether traffic classes are express (deliver packets via the eMAC) or +preemptible (deliver packets via the pMAC), according to IEEE 802.1Q-2018 +clause 6.7.2 Frame preemption. Takes the form of an array (one element per +traffic class) with values being +.B 'E' +(for express) or +.B 'P' +(for preemptible). + +Multiple priorities which map to the same traffic class, as well as multiple +TXQs which map to the same traffic class, must have the same FP attributes. +To interpret the FP as an attribute per priority, the +.B 'map' +argument can be used for translation. To interpret FP as an attribute per TXQ, +the +.B 'queues' +argument can be used for translation. + +Traffic classes are express by default. The argument is supported only with +.B 'hw' +set to 1. Preemptible traffic classes are accepted only if the device has a MAC +Merge layer configurable through +.BR ethtool(8). + +.SH SEE ALSO +.BR ethtool(8) + +.SH EXAMPLE + +The following example shows how to attach priorities to 4 traffic classes ("num_tc 4"), +and then how to pair these traffic classes with 4 hardware queues with mqprio, +with hardware coordination ("hw 1", or does not specified, because 1 is the default value). +Traffic class 0 (tc0) is mapped to hardware queue 0 (q0), tc1 is mapped to q1, +tc2 is mapped to q2, and tc3 is mapped q3. + +.EX +# tc qdisc add dev eth0 root mqprio \ + num_tc 4 \ + map 0 0 0 0 1 1 1 1 2 2 2 2 3 3 3 3 \ + queues 1@0 1@1 1@2 1@3 \ + hw 1 +.EE + +The next example shows how to attach priorities to 3 traffic classes ("num_tc 3"), +and how to pair these traffic classes with 4 queues, +without hardware coordination ("hw 0"). +Traffic class 0 (tc0) is mapped to hardware queue 0 (q0), tc1 is mapped to q1, +tc2 and is mapped to q2 and q3, where the queue selection between these +two queues is somewhat randomly decided. + +.EX +# tc qdisc add dev eth0 root mqprio \ + num_tc 3 \ + map 0 0 0 0 1 1 1 1 2 2 2 2 2 2 2 2 \ + queues 1@0 1@1 2@2 \ + hw 0 +.EE + + +In both cases from above the priority values from 0 to 3 (prio0-3) are +mapped to tc0, prio4-7 are mapped to tc1, and the +prio8-11 are mapped to tc2 ("map" attribute). The last four priority values +(prio12-15) are mapped in different ways in the two examples. +They are mapped to tc3 in the first example and mapped to tc2 in the second example. +The values of these two examples are the following: + + ┌────┬────┬───────┐ ┌────┬────┬────────┐ + │Prio│ tc │ queue │ │Prio│ tc │ queue │ + ├────┼────┼───────┤ ├────┼────┼────────┤ + │ 0 │ 0 │ 0 │ │ 0 │ 0 │ 0 │ + │ 1 │ 0 │ 0 │ │ 1 │ 0 │ 0 │ + │ 2 │ 0 │ 0 │ │ 2 │ 0 │ 0 │ + │ 3 │ 0 │ 0 │ │ 3 │ 0 │ 0 │ + │ 4 │ 1 │ 1 │ │ 4 │ 1 │ 1 │ + │ 5 │ 1 │ 1 │ │ 5 │ 1 │ 1 │ + │ 6 │ 1 │ 1 │ │ 6 │ 1 │ 1 │ + │ 7 │ 1 │ 1 │ │ 7 │ 1 │ 1 │ + │ 8 │ 2 │ 2 │ │ 8 │ 2 │ 2 or 3 │ + │ 9 │ 2 │ 2 │ │ 9 │ 2 │ 2 or 3 │ + │ 10 │ 2 │ 2 │ │ 10 │ 2 │ 2 or 3 │ + │ 11 │ 2 │ 2 │ │ 11 │ 2 │ 2 or 3 │ + │ 12 │ 3 │ 3 │ │ 12 │ 2 │ 2 or 3 │ + │ 13 │ 3 │ 3 │ │ 13 │ 2 │ 2 or 3 │ + │ 14 │ 3 │ 3 │ │ 14 │ 2 │ 2 or 3 │ + │ 15 │ 3 │ 3 │ │ 15 │ 2 │ 2 or 3 │ + └────┴────┴───────┘ └────┴────┴────────┘ + example1 example2 + + +Another example of queue mapping is the following. +There are 5 traffic classes, and there are 8 hardware queues. + +.EX +# tc qdisc add dev eth0 root mqprio \ + num_tc 5 \ + map 0 0 0 1 1 1 1 2 2 3 3 4 4 4 4 4 \ + queues 1@0 2@1 1@3 1@4 3@5 +.EE + +The value mapping is the following for this example: + + ┌───────┐ + tc0────┤Queue 0│◄────1@0 + ├───────┤ + ┌─┤Queue 1│◄────2@1 + tc1──┤ ├───────┤ + └─┤Queue 2│ + ├───────┤ + tc2────┤Queue 3│◄────1@3 + ├───────┤ + tc3────┤Queue 4│◄────1@4 + ├───────┤ + ┌─┤Queue 5│◄────3@5 + │ ├───────┤ + tc4──┼─┤Queue 6│ + │ ├───────┤ + └─┤Queue 7│ + └───────┘ + + +.SH AUTHORS +John Fastabend, <john.r.fastabend@intel.com> |