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113 lines
3.4 KiB
Groff
113 lines
3.4 KiB
Groff
.TH MQPRIO 8 "24 Sept 2013" "iproute2" "Linux"
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.SH NAME
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MQPRIO \- Multiqueue Priority Qdisc (Offloaded Hardware QOS)
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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 | root) [ handle
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major:
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.B ] mqprio [ numtc
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tcs
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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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.B ] [ hw
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1|0
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.B ]
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.SH DESCRIPTION
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The MQPRIO qdisc is a simple queuing discipline that allows mapping
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traffic flows to hardware queue ranges using priorities and a configurable
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priority to traffic class mapping. A traffic class in this context is
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a set of contiguous qdisc classes which map 1:1 to a set of hardware
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exposed queues.
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By default the qdisc allocates a pfifo qdisc (packet limited first in, first
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out queue) per TX queue exposed by the lower layer device. Other queuing
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disciplines may be added subsequently. Packets are enqueued using the
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.B map
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parameter and hashed across the indicated queues in the
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.B offset
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and
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.B count.
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By default these parameters are configured by the hardware
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driver to match the hardware QOS structures.
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Enabled hardware can provide hardware QOS with the ability to steer
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traffic flows to designated traffic classes provided by this qdisc.
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Configuring the hardware based QOS mechanism is outside the scope of
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this qdisc. Tools such as
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.B lldpad
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and
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.B ethtool
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exist to provide this functionality. Also further qdiscs may be added
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to the classes of MQPRIO to create more complex configurations.
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.SH ALGORITHM
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On creation with 'tc qdisc add', eight traffic classes are created mapping
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priorities 0..7 to traffic classes 0..7 and priorities greater than 7 to
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traffic class 0. This requires base driver support and the creation will
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fail on devices that do not support hardware QOS schemes.
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These defaults can be overridden using the qdisc parameters. Providing
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the 'hw 0' flag allows software to run without hardware coordination.
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If hardware coordination is being used and arguments are provided that
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the hardware can not support then an error is returned. For many users
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hardware defaults should work reasonably well.
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As one specific example numerous Ethernet cards support the 802.1Q
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link strict priority transmission selection algorithm (TSA). MQPRIO
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enabled hardware in conjunction with the classification methods below
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can provide hardware offloaded support for this TSA.
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.SH CLASSIFICATION
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Multiple methods are available to set the SKB priority which MQPRIO
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uses to select which traffic class to enqueue the packet.
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.TP
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From user space
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A process with sufficient privileges can encode the destination class
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directly with SO_PRIORITY, see
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.BR socket(7).
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.TP
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with iptables/nftables
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An iptables/nftables rule can be created to match traffic flows and
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set the priority.
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.BR iptables(8)
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.TP
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with net_prio cgroups
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The net_prio cgroup can be used to set the priority of all sockets
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belong to an application. See kernel and cgroup documentation for details.
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.SH QDISC PARAMETERS
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.TP
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num_tc
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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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The priority to traffic class map. Maps priorities 0..15 to a specified
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traffic class.
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.TP
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queues
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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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hw
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Set to
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.B 1
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to use hardware QOS defaults. Set to
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.B 0
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to override hardware defaults with user specified values.
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.SH AUTHORS
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John Fastabend, <john.r.fastabend@intel.com>
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