[lxc-devel] cgroup management daemon

[Tim Hockin]

On Tue, Nov 26, 2013 at 8:37 AM, Serge E. Hallyn <serge at hallyn.com> wrote:
> Quoting Tim Hockin (thockin at google.com):
>> At the start of this discussion, some months ago, we offered to
>> co-devel this with Lennart et al.  They did not seem keen on the idea.
>>
>> If they have an established DBUS protocol spec,
>
> see http://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/
> and http://man7.org/linux/man-pages/man5/systemd.cgroup.5.html
>
>>  we should consider
>> adopting it instead of a new one, but we CAN'T just play follow the
>> leader and do whatever they do, change whenever they feel like
>> changing.
>
> Right.  And if we suspect that the APIs will always be at least
> subtly different, then keeping them obviously visually different
> seems to have some benefit.  (i.e.
>         systemctl set-property httpd.service CPUShares=500 MemoryLimit=500M
> vs
>         dbus-send cgmanager set-value http.server "cpushares:500 memorylimit:500M swaplimit:1G"
> ) rather than have admins try to remember "now why did that not work
> here, oh yeah, MemoryLimit over here should be Memorylimit" or whatever.
>
> Then again if lmctfy is the layer which admins will use, then it
> doesn't matter as much.
>
>> It would be best if we could get a common DBUS api specc'ed and all
>> agree to it.  Serge, do you feel up to that?
>
> Not sure what you mean - I'll certainly send the API to these lists as

What I meant was whether it is worth opening a discussion with the
systemd folks on a common lowest-level DBUS interface.  But it looks
like their work is already a bit higher level, so it's probably moot.

> the code is developed, and will accept all feedback that I get.  My only
> requirements are that the requirements I've listed in the document
> be feasible, and be feasible back to, say, 3.2 kernels.  So that is
> why we must send an scm-cred for the pid to move into a cgroup.  (With
> 3.12 we may have alterntives, accepting a vpid as a simple dbus message
> and setns()ing into the requestor's pidns to echo the pid into the
> cgroup.tasks file.)
>
> -serge