Systemd & cgroups & NWO

[Lennart Poettering]

On Mon, 17.03.14 17:09, Tim St Clair (tstclair at redhat.com) wrote:

> What is the status of fedora & systemd cgroup integration outlined here: http://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/
> 
> Current build is 211-1.  
> 
> The reason for asking is in the document: short-term, medium-term, & long-term are not fully defined.

Well, the nebulous choice of words is intended, since we don't want to
make specific promises on time-frames...

The APIs described (tersely) at the end of the wiki page describe the
status quo with systemd 211.

The "single-writer" cgroup tree stuff Tejun has been working on for the
kernel is now working on his machine, but it's not pushed upstream and
will take a while before it will hit Fedora.

At this point in time you hence still may create cgroups directly
yourself (but only if you follow the pax cgroup document), however, we
strongly encourage you to instead use scopes/slices to create them, as
discussed on the wiki page. This way the cgroups transition will be
abstracted away from yu. You have control of a number of knobs that
systemd will expose for you, such as CPUShares=, BlockIOWeight= and so
on, but this is not complete, and primarily so because it's not clear
that those other properties will continue to exist the way they are in
the kernel. To read statistics data or to write knobs that systemd
doesn't cover you need to go directly to the cgroupfs. For that, simply
read /proc/self/cgroup to find out your own cgroup, and then operate on
that. However, as during the single-writer cgroup transition the kernel
interface how we set things up will change, be prepared that things
might break...

Lennart

-- 
Lennart Poettering, Red Hat