qdisc с приоритетом в несколько очередей (QOS с разгруженным оборудованием) (Multiqueue Priority Qdisc (Offloaded Hardware QOS))
Имя (Name)
MQPRIO - Multiqueue Priority Qdisc (Offloaded Hardware QOS)
Синопсис (Synopsis)
tc qdisc ... dev dev ( parent classid | root) [ handle major: ]
mqprio [ num_tc tcs ] [ map P0 P1 P2... ] [ queues
count1@offset1 count2@offset2 ... ] [ hw 1|0 ] [ mode
dcb|channel] ] [ shaper dcb| [ bw_rlimit min_rate min_rate1
min_rate2 ... max_rate max_rate1 max_rate2 ... ]]
Описание (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 map parameter and
hashed across the indicated queues in the offset and count. By
default these parameters are configured by the hardware driver to
match the hardware QOS structures.
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 shaper parameter. 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.
Алгоритм (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.
Классификация (Classification)
Multiple methods are available to set the SKB priority which
MQPRIO uses to select which traffic class to enqueue the packet.
From user space
A process with sufficient privileges can encode the
destination class directly with SO_PRIORITY, see
socket(7).
with iptables/nftables
An iptables/nftables rule can be created to match traffic
flows and set the priority. iptables(8)
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.
Параметры QDISC (QDISC parameters)
num_tc Number of traffic classes to use. Up to 16 classes
supported.
map The priority to traffic class map. Maps priorities 0..15
to a specified traffic class.
queues Provide count and offset of queue range for each traffic
class. In the format, count@offset. Queue ranges for each
traffic classes cannot overlap and must be a contiguous
range of queues.
hw Set to 1 to support hardware offload. Set to 0 to
configure user specified values in software only.
mode Set to channel for full use of the mqprio options. Use dcb
to offload only TC values and use hardware QOS defaults.
Supported with 'hw' set to 1 only.
shaper Use bw_rlimit to set bandwidth rate limits for a traffic
class. Use dcb for hardware QOS defaults. Supported with
'hw' set to 1 only.
min_rate
Minimum value of bandwidth rate limit for a traffic class.
max_rate
Maximum value of bandwidth rate limit for a traffic class.
