Another daemon for managing control groups [LWN.net]

Another daemon for managing control groups

Posted Dec 10, 2013 3:53 UTC (Tue) by pizza (subscriber, #46)
In reply to: Another daemon for managing control groups by Cyberax
Parent article: Another daemon for managing control groups

Wow, way to throw out some strawmen arguments, peppered liberally with more uncalled-for Lennart-bashing. How was that in any way related to what I'd asked? How is *any* of this cgroup API nonsense Lennart's doing?

It's not like he wrote the original cgroup API, pointed out the problems with it, or wrote the new API. systemd was a user of the old API then adapted to kernel-imposed requirements with the new API, not the other way around.

I find it disappointing that you are trying to split hairs here, given how generously you tend to berate others for doing the same.

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Another daemon for managing control groups

Posted Dec 10, 2013 4:07 UTC (Tue) by Cyberax (✭ supporter ✭, #52523) [Link] (6 responses)

> How is *any* of this cgroup API nonsense Lennart's doing?

Stop pretending. Systemd drives cgroup development (Tejun Heo works at RedHat, remember) and Lennart gleefully supported "single-writer" model.

> It's not like he wrote the original cgroup API, pointed out the problems with it, or wrote the new API. systemd was a user of the old API then adapted to kernel-imposed requirements with the new API, not the other way around.

Wrong. Tejun Heo basically redesigned cgroups to better fit SystemD model. Everything else (nesting, delegation) is brushed aside as "impossible" or "insecure" without explanations (really, try to find them - there are none).

And it shows, Lennart basically goes out and says: "if we allow delegation and nesting then we'd have to actually treat cgroups interface as a kernel ABI, and if we don't then we can pretend that systemd is the sole user of cgroups and do whatever we want with it in future".

Now, I really like SystemD and I'd like to see it in Debian. But I totally disdain the behavior of cgroups developers.

Another daemon for managing control groups

Posted Dec 10, 2013 5:47 UTC (Tue) by raven667 (guest, #5198) [Link] (1 responses)

Well you've laid out a clear worldview of you you see things, I don't think there is anything that can be added or taken away. I have to add though that I don't see the corruption and negativity that you see so I don't know if that means I'm blind or if you just need to relax. All the best.

Another daemon for managing control groups

Posted Dec 10, 2013 5:53 UTC (Tue) by Cyberax (✭ supporter ✭, #52523) [Link]

It's not a corruption in the sense of taking bribes or anything. It's just tunnel vision - cgroups and systemd developers simply do only what they need, and nothing more. All the requests to be more reasonable are simply ignored.

I'd very much prefer if systemd and cgroups were developed by two different competing companies. Absent that, I hope that someone with a large enough cluebat makes cgroup developers see the error of their way.

Another daemon for managing control groups

Posted Dec 10, 2013 13:50 UTC (Tue) by corbet (editor, #1) [Link] (3 responses)

Having watched this whole process, I have to disagree a bit. Tejun set in to the task of reworking cgroups to make them more maintainable and usable; the systemd folks found themselves having to react to that change. Systemd was using the multiple hierarchy feature, keeping its own special cgroup hierarchy off to the side. Remember the PaxControlGroups document? See this note from last June (and this one) where systemd's response to the cgroup changes was worked out.

Now, in the process of redesigning things, Tejun has certainly talked to the users of cgroups, including the systemd developers. Doing otherwise would not have been smart. But I do not think it's fair to say that systemd has driven these changes.

Another daemon for managing control groups

Posted Dec 10, 2013 16:12 UTC (Tue) by Cyberax (✭ supporter ✭, #52523) [Link] (2 responses)

I was referring to these messages as well. They read exactly as if Tejun Heo privately talked to SystemD developers and then systemd and cgroup folks presented the future changes as a fait-accompli with no public discussions.

Another daemon for managing control groups

Posted Dec 10, 2013 17:23 UTC (Tue) by rahulsundaram (subscriber, #21946) [Link] (1 responses)

In other words, your assertion is a guess and you don't really know but the language you use makes it sound almost like a conspiracy. It is misleading at best.

Another daemon for managing control groups

Posted Dec 10, 2013 18:06 UTC (Tue) by Cyberax (✭ supporter ✭, #52523) [Link]

Well, from my vantage point it definitely looks like cgroups developers are doing only what systemd developers want. It might be accidental, but I really don't care.