linux/Documentation/cgroups/net_prio.txt
<<
>>
Prefs
   1Network priority cgroup
   2-------------------------
   3
   4The Network priority cgroup provides an interface to allow an administrator to
   5dynamically set the priority of network traffic generated by various
   6applications
   7
   8Nominally, an application would set the priority of its traffic via the
   9SO_PRIORITY socket option.  This however, is not always possible because:
  10
  111) The application may not have been coded to set this value
  122) The priority of application traffic is often a site-specific administrative
  13   decision rather than an application defined one.
  14
  15This cgroup allows an administrator to assign a process to a group which defines
  16the priority of egress traffic on a given interface. Network priority groups can
  17be created by first mounting the cgroup filesystem.
  18
  19# mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio
  20
  21With the above step, the initial group acting as the parent accounting group
  22becomes visible at '/sys/fs/cgroup/net_prio'.  This group includes all tasks in
  23the system. '/sys/fs/cgroup/net_prio/tasks' lists the tasks in this cgroup.
  24
  25Each net_prio cgroup contains two files that are subsystem specific
  26
  27net_prio.prioidx
  28This file is read-only, and is simply informative.  It contains a unique integer
  29value that the kernel uses as an internal representation of this cgroup.
  30
  31net_prio.ifpriomap
  32This file contains a map of the priorities assigned to traffic originating from
  33processes in this group and egressing the system on various interfaces. It
  34contains a list of tuples in the form <ifname priority>.  Contents of this file
  35can be modified by echoing a string into the file using the same tuple format.
  36for example:
  37
  38echo "eth0 5" > /sys/fs/cgroups/net_prio/iscsi/net_prio.ifpriomap
  39
  40This command would force any traffic originating from processes belonging to the
  41iscsi net_prio cgroup and egressing on interface eth0 to have the priority of
  42said traffic set to the value 5. The parent accounting group also has a
  43writeable 'net_prio.ifpriomap' file that can be used to set a system default
  44priority.
  45
  46Priorities are set immediately prior to queueing a frame to the device
  47queueing discipline (qdisc) so priorities will be assigned prior to the hardware
  48queue selection being made.
  49
  50One usage for the net_prio cgroup is with mqprio qdisc allowing application
  51traffic to be steered to hardware/driver based traffic classes. These mappings
  52can then be managed by administrators or other networking protocols such as
  53DCBX.
  54
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.