From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: [PATCH 2/2] net: add documentation for net_prio cgroups (v2) Date: Thu, 17 Nov 2011 16:47:52 -0500 Message-ID: <1321566472-28969-3-git-send-email-nhorman@tuxdriver.com> References: <1321476666-8225-1-git-send-email-nhorman@tuxdriver.com> <1321566472-28969-1-git-send-email-nhorman@tuxdriver.com> Cc: Neil Horman , John Fastabend , Robert Love , "David S. Miller" To: netdev@vger.kernel.org Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:42504 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753244Ab1KQVuW (ORCPT ); Thu, 17 Nov 2011 16:50:22 -0500 In-Reply-To: <1321566472-28969-1-git-send-email-nhorman@tuxdriver.com> Sender: netdev-owner@vger.kernel.org List-ID: Add the requisite documentation to explain to new users how net_prio cgroups work Signed-off-by:Neil Horman Signed-off-by: John Fastabend CC: Robert Love CC: "David S. Miller" --- Documentation/cgroups/net_prio.txt | 53 ++++++++++++++++++++++++++++++++++++ 1 files changed, 53 insertions(+), 0 deletions(-) create mode 100644 Documentation/cgroups/net_prio.txt diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt new file mode 100644 index 0000000..01b3226 --- /dev/null +++ b/Documentation/cgroups/net_prio.txt @@ -0,0 +1,53 @@ +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 +applications + +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 + +net_prio.prioidx +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. + +net_prio.ifpriomap +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 . Contents of this file +can be modified by echoing a string into the file using the same tuple format. +for example: + +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 +priority. + +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 +DCBX. -- 1.7.6.4