projects / mirror_iproute2.git / blame
| Commit | Line | Data |
|---|---|---|
| 39935c93 JF |
1 | .TH MQPRIO 8 "24 Sept 2013" "iproute2" "Linux" |
| 2 | .SH NAME | |
| 3 | MQPRIO \- Multiqueue Priority Qdisc (Offloaded Hardware QOS) | |
| 4 | .SH SYNOPSIS | |
| 5 | .B tc qdisc ... dev | |
| 6 | dev | |
| 7 | .B ( parent | |
| 8 | classid | |
| 9 | .B | root) [ handle | |
| 10 | major: | |
| 11 | .B ] mqprio [ numtc | |
| 12 | tcs | |
| 13 | .B ] [ map | |
| 14 | P0 P1 P2... | |
| 15 | .B ] [ queues | |
| 16 | count1@offset1 count2@offset2 ... | |
| 17 | .B ] [ hw | |
| 18 | 1|0 | |
| 19 | .B ] | |
| 20 | ||
| 21 | .SH DESCRIPTION | |
| 22 | The MQPRIO qdisc is a simple queuing discipline that allows mapping | |
| 23 | traffic flows to hardware queue ranges using priorities and a configurable | |
| 24 | priority to traffic class mapping. A traffic class in this context is | |
| 25 | a set of contiguous qdisc classes which map 1:1 to a set of hardware | |
| 26 | exposed queues. | |
| 27 | ||
| 28 | By default the qdisc allocates a pfifo qdisc (packet limited first in, first | |
| 29 | out queue) per TX queue exposed by the lower layer device. Other queuing | |
| 30 | disciplines may be added subsequently. Packets are enqueued using the | |
| 31 | .B map | |
| 32 | parameter and hashed across the indicated queues in the | |
| 33 | .B offset | |
| 34 | and | |
| 35 | .B count. | |
| 36 | By default these parameters are configured by the hardware | |
| 37 | driver to match the hardware QOS structures. | |
| 38 | ||
| 39 | Enabled hardware can provide hardware QOS with the ability to steer | |
| 40 | traffic flows to designated traffic classes provided by this qdisc. | |
| 41 | Configuring the hardware based QOS mechanism is outside the scope of | |
| 42 | this qdisc. Tools such as | |
| 43 | .B lldpad | |
| 44 | and | |
| 45 | .B ethtool | |
| 46 | exist to provide this functionality. Also further qdiscs may be added | |
| 47 | to the classes of MQPRIO to create more complex configurations. | |
| 48 | ||
| 49 | .SH ALGORITHM | |
| 50 | On creation with 'tc qdisc add', eight traffic classes are created mapping | |
| 51 | priorities 0..7 to traffic classes 0..7 and priorities greater than 7 to | |
| 52 | traffic class 0. This requires base driver support and the creation will | |
| 53 | fail on devices that do not support hardware QOS schemes. | |
| 54 | ||
| 55 | These defaults can be overridden using the qdisc parameters. Providing | |
| 56 | the 'hw 0' flag allows software to run without hardware coordination. | |
| 57 | ||
| 58 | If hardware coordination is being used and arguments are provided that | |
| 59 | the hardware can not support then an error is returned. For many users | |
| 60 | hardware defaults should work reasonably well. | |
| 61 | ||
| 62 | As one specific example numerous Ethernet cards support the 802.1Q | |
| 63 | link strict priority transmission selection algorithm (TSA). MQPRIO | |
| 64 | enabled hardware in conjunction with the classification methods below | |
| 65 | can provide hardware offloaded support for this TSA. | |
| 66 | ||
| 67 | .SH CLASSIFICATION | |
| 68 | Multiple methods are available to set the SKB priority which MQPRIO | |
| 69 | uses to select which traffic class to enqueue the packet. | |
| 70 | .TP | |
| 71 | From user space | |
| 72 | A process with sufficient privileges can encode the destination class | |
| 73 | directly with SO_PRIORITY, see | |
| 74 | .BR socket(7). | |
| 75 | .TP | |
| 76 | with iptables/nftables | |
| 77 | An iptables/nftables rule can be created to match traffic flows and | |
| 78 | set the priority. | |
| 79 | .BR iptables(8) | |
| 80 | .TP | |
| 81 | with net_prio cgroups | |
| 82 | The net_prio cgroup can be used to set the priority of all sockets | |
| 83 | belong to an application. See kernel and cgroup documentation for details. | |
| 84 | ||
| 85 | .SH QDISC PARAMETERS | |
| 86 | .TP | |
| 87 | num_tc | |
| 88 | Number of traffic classes to use upto 16 classes supported. | |
| 89 | ||
| 90 | .TP | |
| 91 | map | |
| 92 | The priority to traffic class map. Maps priorities 0..15 to a specified | |
| 93 | traffic class. | |
| 94 | ||
| 95 | .TP | |
| 96 | queues | |
| 97 | Provide count and offset of queue range for each traffic class. In the | |
| 98 | format, | |
| 99 | .B count@offset. | |
| 100 | Queue ranges for each traffic classes cannot overlap and must be a | |
| 101 | contiguous range of queues. | |
| 102 | ||
| 103 | .TP | |
| 104 | hw | |
| 105 | Set to | |
| 106 | .B 1 | |
| 107 | to use hardware QOS defaults. Set to | |
| 108 | .B 0 | |
| 109 | to override hardware defaults with user specified values. | |
| 110 | ||
| 111 | .SH AUTHORS | |
| 112 | John Fastabend, <john.r.fastabend@intel.com> |