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Gullible Jones 04-06-2011 06:01 PM

KDE4... Why the sluggish performance? [SOLVED for now]
Everywhere I look, people rave about how fast KDE4 is. I've even seen reports that it works great on an Eee700 netbook. So I try it on my Eee1005HAB...

And it's slower than molasses.

Windows resized in jerks. Menus lag. Window redraws take 2-3 seconds. I can tell windows to only show frames while being resized, and still see the redraws. It makes Windows Vista look like a speed demon.

I've tried a number of tweaks. Setting Qt to the "Low resolution and low CPU" setting... Skipping ARGB visuals... Disabling IPV6... Switching to the raster graphics engine... Disabling the Composite extension... Even switching in Openbox as a window manager (which messes up the Plasma desktop). None of it works at all. Everything's still incredibly slow, on hardware that really should not have a problem with it. And this is without compositing. With compositing, it's like a slide show.

What am I doing wrong here? There must be something I'm missing...

jlinkels 04-06-2011 10:34 PM

It looks like the wrong graphic driver. What VGA card do you have in that eeePC. Ironically, on my wife's eeeePC KDE runs very smooth. Start a console, issue top command and check whether the CPU usage of xorg rockets to 100% when you move something. If so, you probably are using th wrong graphic driver.


cascade9 04-07-2011 03:08 AM


Originally Posted by Gullible Jones (Post 4316407)
Everywhere I look, people rave about how fast KDE4 is. I've even seen reports that it works great on an Eee700 netbook. So I try it on my Eee1005HAB...

I used KDE4.X, and while I like it a lot I'd never go on about how fast it is. IMO KDE4.X is not fast at all. Sure, with decent hardware its not slow, but for speed a *box, Lxde or Xfce are what you should be looking at. IMO KDE4.X needs a decent video card, and a fairly nice CPU.

However some people out there might not notice what I do, so maybe there are folks around who think that KDE4.X is fast. If thats what they think, then I'm not going to convince them they are wrong....

I would guess that jlinkels is right, its video card related. Window redrawing shouldnt take 2-3 seconds.

BTW, the video chip is GMA950 from, what I can see. IIRC there has been some issues with the GMA950 with linux generally. GMA is a long, long way from a decent video card though. No support for hardware transform and lighting, or shaders. I've tried running KDE4.X on (proper) GPUs, not intel video chips and and it can still be sluggish with older video hardware. Still, it shouldnt be that slow.

salasi 04-07-2011 05:47 AM


Originally Posted by Gullible Jones (Post 4316407)
Everywhere I look, people rave about how fast KDE4 is.

The only people I've seen saying that KDE 4 is fast (not just not slow, but actually fast) have been Windows Vista users, and they may have, errr, unusual expectations in this area.

having said that
  • KDE 4.x is heavy on memory, and how bad that is depends on how much memory you have and whether you are doing memory intensive stuff on top of kde itself. does the disk drive light blink constantly and have you had a look at the system monitor (ksysguard) to see if anything shows up?
  • On the same theme, you'll probably see memory leaks with earlier versions and extended uptimes. Does it slow down over time and does it get better (somewhat) after a reboot?
  • In general, early versions of kde 4. are a bit crap. If you are using, say, 4.2.x or earlier, then try something later. (You really need to be in the 4.3.x series, or later, for usability.)
  • And even more particular, the redesign of the video system at 4.6 is probably advantageous. and a bit more efficient, but I do find that I have to use Xrender rather than OpenGL for compositing, but ymmv.
  • ...and even if you have everything humming along nicely in KDE4, it is unlikely that you will outpace kde3. Or XFCE. Or enlightenment. Or any of the lighter alternatives.

jlinkels 04-07-2011 09:12 AM

This doesn't really contribute to the discussion (sorry about that) but I do have to vent my frustration.

BTW salasi is completely right on what he is saying that at best KDE4 is not slow, as opposed to fast.

This week I upgraded one of my older laptops to Debian Squeeze including KDE4.4.5. The laptop has an ATI Radeon R300 card. Driver is installed correctly, compositing works, etc. The only thing which is really sluggish is the resizing of windows, about 3-4 fps. Other graphical effects like wobbly windows, magic lamp effect when closing windows and cube rotation are smooth.

However, sometimes when I rotate the cube, it is slow, frame rate goes down considerably, and motion becomes jerky. For this purpose I opened a konsole and showed top. Xorg was running about 25% processor capacity during cube rotation. Then a message popped up: It seems that animation runs slow. Therefor compositing has been disabled. So I enabled it again, and presto! cube rotation was smooth again, while processor load of Xorg increased to 29%. :confused:

Once more I was wondering why KDE4 is still loaded with bugs after 4 years of development. If KDE4 is complicated, in fact too complicated to get it right, they should not have completely disposed KDE3. After all, KDE4 seems to imitate Vista as much as possible. Not just in appearance but as well in speed, bugginess, user frustration and being on the wrong track. It had not been necessary to follow Microsoft. Next step is KDE7?


Gullible Jones 04-07-2011 12:28 PM

Yeah, the graphics hardware is Intel GMA945. IOW, garbage.

But GTK applications don't care that the GPU is rubbish, and redraw quite speedily. Same with pure Qt apps... And, for that matter, with KDE apps running outside the desktop environment. Try running Dolphin under an Openbox session, for instance.

So why does running stuff in the KDE desktop magically make it sluggish?

Gullible Jones 04-18-2011 04:33 PM

Okay, what I've found so far:

- Disabling sound notifications makes menus no longer sluggish, for some reason. Supposedly this is a bug in Phonon's Xine backend? Weird.

- Making windows show only as frames when moving/resizing hides most of the sluggish redraws. Unfortunately, it also creates occasional graphical artifacts where frames overlap window borders. Disabling the Composite extension helps, but doesn't remove the artifacts entirely - if anyone can tell me how to get rid of those, that'd be nice... TIA.

Gullible Jones 05-05-2011 11:06 PM

Okay, it turns out I'd been doing things wrong when trying to disable ARGB visuals. The correct environment variable to export is


This makes things ludicrously faster, so I'm going to mark this as solved.

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