Features/ControlGroups

Feature Name

ControlGroups

Summary

Improve the existing tools where necessary and feasible and/or to create new ones e.g. to create or modify persistent cgroups configuration (using libcgroups package).

Owner

• Nils Philippsen
• Ivana Varekova

Current status

• Targeted release:
• Last updated: 2009-01-19
• Percentage of completion: 0%

Detailed Description

Since kernel 2.6.24, Linux has so called control groups as a means to partition available resources between running processes. Libcgroups makes that functionality available to programmers and contains two tools, cgexec and cgclassify, to start processes in a control group or move existing processes from one control group to another.

Our goals are to improve the existing tools where necessary and feasible and/or to create new ones e.g. to create or modify persistent cgroups configuration. At the beginning the focus will be on command line tools, but we'll keep in mind that in the long term we'll likely want to have graphical tools. These would offer similar functionality and we should try to make sure that any non-UI code written is usable from both kinds of frontends.

Benefit to Fedora

Libcgroups handles the new kernel features which are able to restrict the sources for tasks. This project should help the user to make the best of this feature.

Scope

currently in process

How To Test

For now it is necessary to have a kernel with cgroups support (Documentation/cgroups.txt) and the libcgroups package.

Start the cgconfig service:

• Create the /etc/cgconfig.conf configuration file (the example is in the /samples section, the initscript from version 0.32.2 is able to create the mount point itself and mount the filesystem to it).
• For each mount point create the relevant directory and mount it. The filesystem type is cgroup, so an fstab line would look like this:

cgroup                   <mount-point>                cgroup  defaults        0 0

or you can mount it manually with this command:

mount -t cgroup cgroup <mount-point>

(see scripts/doc/howto.txt - this mentions that the script would mount it but this doesn't seem to work, probably a problem in the cgroup init script)

• Then you can start the service:

/sbin/service cgconfig start

Problems (in 0.32.2)

• Test example of cgconfig.conf from scripts/doc/howto.txt does not work.
• Changing /etc/cgconfig.conf while cgconfig is running leads to a bunch of error messages if you try to restart it.

User Experience

For now libcgroups package has several bug - so they have to be fixed at first

Dependencies

Depends on kernel > 2.6.24 which is already in fedora and libcgroups which is (the last version 0.32.2) in fedora - the package is there from f-9.

Contingency Plan

At first there have to be tested libcgroups to finds bugs and create more stable package - then there could be created any

Documentation

• kernel documentation is: http://www.mjmwired.net/kernel/Documentation/cgroups.txt

libcg package -

• upstream sites: http://libcg.sourceforge.net/
• libcg: design and plans: http://lwn.net/Articles/271788/

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