choosing display manager

monsm · Guru Joined: 26 Sep 2007 Posts: 467 Location: London, UK

Hi,
Slight newbie question i guess, but does the display manager do anything after login?

Reason I ask is that I have an old PC (1.2 GHz) and I am interested in maximizing the performance on it. I want to stick with XFCE and I used to have KDE on this machine, so currently I have KDM. I have now removed KDE itself and is using XFCE exclusively, but for now I have kept KDM to log in.

Disk space wise I am ok, so if KDM takes lots of disk space I am not worried, but I am worried about memory and impact on performance after login.

So would my runtime performance be affected if I e.g. switched to SLIM?

Mons

Sadako · Posted: Sat Oct 17, 2009 9:13 pm Post subject:

kdm being a kde application, I'd imagine it loads quite a few kde and qt applications, which will absolutely result in wasted memory if you don't make use any other apps using the same shared libs.

Run `ldd /usr/bin/kdm` (path may be different, like sbin rather than bin), this will tell you what libraries kdm loads.
Compare to the output of ldd on the xdm and/or slim binary to see the difference.
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monsm · Guru Joined: 26 Sep 2007 Posts: 467 Location: London, UK

Hi,
I take it that the display manager only handle login and logout. So that during a session it most likely would be swapped out (if memory was getting tight) and matter very little even on memory usage. Is that correct?

As to slim vs kdm (3.5) I am not convinced slim is any slimmer. Just look at this:

Anon-E-moose · Posted: Sun Oct 18, 2009 6:16 pm Post subject:

http://slim.berlios.de/

as far as runtime size, you can't go by the number of libraries that show up in an ldd command.

Edit to add:
I don't run kde but if I wanted to install kdm then this is what would be pulled in

Sadako · Posted: Sun Oct 18, 2009 6:28 pm Post subject:

Anon-E-moose · Posted: Sun Oct 18, 2009 6:35 pm Post subject:

After you get logged in, I think either one would not take up much memory.

I use gdm and it only shows as using appx 6 meg of memory

I'm pretty sure that kdm or slim or any other display manger would be about the same.
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taipan67 · Posted: Sun Oct 18, 2009 6:41 pm Post subject:

Those "ldd" outputs are extremely surprising - i wonder if kdm builds itself statically against 'qt' and/or 'kde' libs..? If it does, it'd probably be considerably heavier on memory-usage...

I don't know about kdm, but i believe 'gdm' is used after login by xscreensaver if you build it so it's capable of screen-locking and session-switching - so maybe kdm is used similarly by any kde-optimised screensavers that you may or may not have..?

Also, as far as i'm aware, SLiM is no longer being maintained - a couple of other display-managers that hadn't yet hit portage last time i looked are LXDM and Orthos. :wink:

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monsm · Guru Joined: 26 Sep 2007 Posts: 467 Location: London, UK

mv · Watchman Joined: 20 Apr 2005 Posts: 6749

monsm · Guru Joined: 26 Sep 2007 Posts: 467 Location: London, UK

FieserKiller · Posted: Wed Oct 28, 2009 1:15 am Post subject:

FYI (just in case you don't know, you mentioned you are pretty new in linux), if you are worried about memory usage on your system, you can simply don't use any display manager..
in fact, you can go further and dont need any desktop environment at all while you are still not stuck to console applications only.
On my notebook I just start pure X, then xbindkeys, compiz and emerald. thats it..
xbindkeys binds some hotkeys to apps i use frequently (urxvt, firefox, pidgin).
if you need more comfort, just add components like a menu, a taskbar, a file browser, etc..
I heard (although never tried for myself) eg all LXDE components can run stand alone and have a relatively small memory footprint.
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monsm · Guru Joined: 26 Sep 2007 Posts: 467 Location: London, UK

Hi,
I have been around Linux for quite a while already. Never paid much attention to the display manager though.

I'll keep kdm on my system. In fact I just upgraded to the latest KDM 4. The login screen looks great. And the best thing, although kdm_greet is bigger (now 4.3% on my system), kdm itself is still the same at 0.1% memory. That is acceptable given that kdm_greet disappear after login.

I have also heard good things about LXDE. Might give that a try at some point.

Mons