[arch-general] When will Arch switch to Systemd

[C Anthony Risinger]

On Thu, Jan 20, 2011 at 3:10 PM,  <fons at kokkinizita.net> wrote:
> On Thu, Jan 20, 2011 at 02:54:24PM -0600, C Anthony Risinger wrote:
>> On Thu, Jan 20, 2011 at 2:34 PM,  <fons at kokkinizita.net> wrote:
>> >
>> > So here's my question: will a system using systemd still allow
>> > this, *without* requiring source modifications to each and every
>> > application (to join a specific cgroup), and *whitout* every
>> > application requiring real-time or memory locks to be 'registered'
>> > somewhere ?
>>
>> i don't believe it would have any ill effect, but would need some testing.
>>
>> i'm not 100% how it all ties into systemd, but a process being in a
>> cgroup does not need permission/acceptance/patch from the process;
>> it's just in it.  cgroups are also hierarchical, so you can have
>> groups of groups.  there are several cgroup types (cpu/mem/etc) and
>> each process can be in exactly one of each.
>
> All correct. But a system using systemd (and hence cgroups) will
> put an application either into some default cgroup (which will
> very probably not have the required privileges, and hence needs
> code in the application to move to another cgroup), or it will
> require some 'registry' of applications that require a specific
> cgroup to run in. Both are a real PITA compared to what whe have
> today.

afaik it's not possible for a process to switch groups once it's
started, by any means but dying and being restarted, but things may
have changed on this front.  i wouldn't think systemd does any
limiting unless it's specified in the service files (again i'm not
100%)

soooo.... what i think you'd do is create a high level target pointing
to all the apps you need grouped together.  if systemd config supports
it, you would define the things you need in that.  if it doesn't, you
simply `echo` the values you want directly into the appropriate group
in /sys/fs/cgroup.  i don't see where you'd need to `register`
applications or anything convoluted like that; it seems to me like
you'd only need to create a single file.

C Anthony