[systemd-devel] Parallel startup with sockets and without killing the machine?

[Gustavo Sverzut Barbieri]

On Mon, May 9, 2011 at 11:52 PM, Scott James Remnant <scott at netsplit.com>wrote:

> On Mon, May 9, 2011 at 12:16 PM, Gustavo Sverzut Barbieri <
> barbieri at profusion.mobi> wrote:
>
>>
>>> Well, right now let's make clear that Firefox/Chromium or other X clients
>>> won't be started by systemd as they are user session applications, and
>>> systemd itself will just deal with system context (ie: up to GDM/KDM...).
>>>
>>
>> Really?
>
> A major feature of systemd I understood was that it would also manage user
> sessions as a seamless part of boot along with the system session. Is that
> not the case?
>

Not yet. It is planned but we're trying to get the system-wide part done
first. The system part is what is in Fedora 15 and all other distros using
it.

The desktop part will need some investigation. Lennart does have some ideas,
but even he said he will need to analyze what exists now, some "why?" and
then do a ConsoleKit-free desktop, see if that's enough and get the actual
patches out to interested peers (Gnome in his case, I'll do stuff for
Enlightenment, etc).

In his conversion he will rework the concept of session. The session will
not be a shell login or X11 login, instead it will be the whole lifetime of
user in the platform, if you login from tty1/getty then x11 you have the
same session, then logout from tty1 your session will still alive until the
last logs out. This is likely to require some PAM help and will require
changes to DBus and maybe others.

I'm not following all the user-session discussion, but AFAIU this management
will be done by the same code, but not same process (it's not PID1). PAM (or
another entity that has a role in the login/logout) will talk to systemd
(PID1) and ask for a new service to be started to handle this user-session.
This will still be the same code, but of course on the user context and not
handle things like actual reboot/halt of the machine, mounting system
filesystems. But again, I'm not following it closely and I might be wrong
here.



>
>
>> But using your case, just like I said above, you really want that. You'd
>> chromium and X11 to be loaded at the same time, because the kernel will
>> handle the load and may load chromium executable while X11 is doing EDID
>> read, then may let the dynamic linker work while X11 asks for input device,
>> etc.
>>
>> Or the kernel might load Chromium completely before giving X any time at
> all; between picking the right thing and the wrong thing, without
> information, the kernel seems to more usually pick the latter.
>

If that happens then not a big problem as on X connection Chromium would
block or would sleep while it's ready, leaving time for X11 to run.

Yes, this would not respect your "priority request", but I don't think the
kernel would starve X11 load in benefit for Chromium load for no good.
Either X11 was sleeping on some probe or something like that.


-- 
Gustavo Sverzut Barbieri
http://profusion.mobi embedded systems
--------------------------------------
MSN: barbieri at gmail.com
Skype: gsbarbieri
Mobile: +55 (19) 9225-2202
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