Re: [proposal] delegating cgroup manager to non-PID1

[David Lang]

On Sun, 1 Mar 2015, Luke Kenneth Casson Leighton wrote:

> in recent discussions about PID-1 alternatives (sysvinit, openrc,
> systemd, depinit) i was alerted to the idea that PID1 is to become the
> sole exlcusive process permitted to manage cgroups.  given that, just
> as one specific example, depinit is only around 2,300 lines of c code,
> adding extra code to manage cgroups is of some concern especially in
> light of the general UNIX philosophy "do one thing and do it well".
>
> to allow the general UNIX philosophy to be honoured, may i
> respectfully propose an additional linux kernel systemcall which
> permits delegation - solely and exclusively by PID1 - of the
> management of cgroups to one (and only one) other process, and that
> furthermore that the process must be an immediate child of PID1?

There is less agreement on the idea that PID1 will have exclusive control over 
cgroups than some of the posts make it seem. There are many people who use 
cgroups for things that PID1 (and systemd) aren't dealing with. The issue is 
that the people working to revamp cgroups are saying that allowing other 
processed to affect cgroups brings up hard problems that they don't want to deal 
with right now, so they want to make cgroups exclusive to PID1 as a 'temporary' 
measure, and then look at solving the problems that are needed to let other 
processes manage parts or all of the cgroups config.

David Lang
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