Another daemon for managing control groups [LWN.net]

Another daemon for managing control groups

Posted Dec 10, 2013 17:59 UTC (Tue) by jubal (subscriber, #67202)
In reply to: Another daemon for managing control groups by rgmoore
Parent article: Another daemon for managing control groups

You might want to read the whole of my comment (yes, it contains two rather long quotes) and judge for yourself.

The italicised note was just a commentary, not a point in itself. The quotes were the point.

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Another daemon for managing control groups

Posted Dec 10, 2013 20:58 UTC (Tue) by rgmoore (✭ supporter ✭, #75) [Link] (3 responses)

I did read your comment, including the long quotes. I think Lennart is making a cogent point about why it makes sense to roll cgroup control into systemd. He might have been more polite about it, but his technical point seems sound. You have not yet addressed that technical point.

Another daemon for managing control groups

Posted Dec 11, 2013 13:27 UTC (Wed) by jubal (subscriber, #67202) [Link] (2 responses)

I don't see any technical point in telling other customers of the cgroups subsystem (and Google is probably the largest one at all, and will be in the foreseeable future) that their only options are to start using systemd or match its behaviour to the iota, just because it's more convenient for the authors of the systemd environment.

Another daemon for managing control groups

Posted Dec 11, 2013 15:23 UTC (Wed) by raven667 (guest, #5198) [Link] (1 responses)

What do you mean "match its behavior"? Do you mean having a system with a single writer or do you mean it's DBUS API? If you aren't using systemd as PID 1 and you don't need your userspace cgroup management client portable for other peoples who do run systemd then what systemd does or doesn't do is of no consequence to you, right? If anything you need to work with the kernel developers to make sure you understand their concerns and they understand your use cases. As has been pointed out many times the idea of a single userspace cgroups manager was an idea the kernel team had to remove cgroupfs as an attack surface for untrusted customer containers, they only wanted cgroupfs to provide the mechanism for changing settings and not also complicating the internals by encoding the security policy in the kernel.

Another daemon for managing control groups

Posted Dec 11, 2013 16:10 UTC (Wed) by jubal (subscriber, #67202) [Link]

That's grand and I don't think we're really in disagreement.

You may note I was referring to an old e-mail exchange (June, I believe), where Tim Hockin proposed to use a low-level library to provide basic cgroup management functions, a library that would be then used by both systemd and any non-systemd cgroup manager.

This approach was, as you may see, rejected by Mr. Poettering et co. as not viable and possibly non-constructive.