|Network priority cgroup
|The Network priority cgroup provides an interface to allow an administrator to
|dynamically set the priority of network traffic generated by various
|Nominally, an application would set the priority of its traffic via the
|SO_PRIORITY socket option. This however, is not always possible because:
|1) The application may not have been coded to set this value
|2) The priority of application traffic is often a site-specific administrative
| decision rather than an application defined one.
|This cgroup allows an administrator to assign a process to a group which defines
|the priority of egress traffic on a given interface. Network priority groups can
|be created by first mounting the cgroup filesystem.
|# mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio
|With the above step, the initial group acting as the parent accounting group
|becomes visible at '/sys/fs/cgroup/net_prio'. This group includes all tasks in
|the system. '/sys/fs/cgroup/net_prio/tasks' lists the tasks in this cgroup.
|Each net_prio cgroup contains two files that are subsystem specific
|This file is read-only, and is simply informative. It contains a unique integer
|value that the kernel uses as an internal representation of this cgroup.
|This file contains a map of the priorities assigned to traffic originating from
|processes in this group and egressing the system on various interfaces. It
|contains a list of tuples in the form <ifname priority>. Contents of this file
|can be modified by echoing a string into the file using the same tuple format.
|echo "eth0 5" > /sys/fs/cgroups/net_prio/iscsi/net_prio.ifpriomap
|This command would force any traffic originating from processes belonging to the
|iscsi net_prio cgroup and egressing on interface eth0 to have the priority of
|said traffic set to the value 5. The parent accounting group also has a
|writeable 'net_prio.ifpriomap' file that can be used to set a system default
|Priorities are set immediately prior to queueing a frame to the device
|queueing discipline (qdisc) so priorities will be assigned prior to the hardware
|queue selection being made.
|One usage for the net_prio cgroup is with mqprio qdisc allowing application
|traffic to be steered to hardware/driver based traffic classes. These mappings
|can then be managed by administrators or other networking protocols such as
|A new net_prio cgroup inherits the parent's configuration.