KWin causing abnormally high CPU usage

[GJones]

Trying Mageia KDE again on my netbook, I noticed once again that performance was awful. Looking at htop, I found that KWin was pegged at 10% CPU usage when using OpenGL effects, and 6% when using XRender.

However, the bad performance persisted when composite effects were disabled. Looking at htop again, I noticed that some programs were using untoward amounts of CPU power; e.g. htop itself was using a steady 50%. Also, window movement was jerky, and window repaints were visibly slow.

On a hunch that KWin might still be the problem, I installed Openbox and switched KDE's default window manager to it. Lo and behold, it worked; repaints are now mostly invisble, window movement is smooth, and htop's CPU usage is 3-5%.

I'm quite happy using KDE with Openbox for now, but I'm interested in knowing what might cause this problem with KWin. Any ideas?

(The netbook in question is an Eee PC 1005HAB: Intel Atom N270 processor, Intel 945GM graphics chipset, 10.5 inch screen.)

[wintpe]

you did not mension which magia version you referd to, im assuming mga2.

however i am running mga1 flawlessly on a samsung NC10, which as pretty much the same hardware as the eeePC you have.

ive not tested mga2 on it yet, but I have tested mga2 on an atom 270 miniITX board that has pretty much the same standard 270 chipset.

that works very reasonable, performance wise.

I use KDE only.

Ive installed 2 gig of ram in both.

when i first installed mga2 on the miniITX board i had 1 gig of ram and the performance was not great, the extra gig realy helped aliviate what was a slow system.

perhaps , the same applies I dont know.

regards peter

[GJones]

Yeah, it was Mageia 2.

I don't think the issue is due to lack of RAM. Less than half of available RAM was in use by programs when I checked htop, and no swap was being used at all. My suspsicion is still that it's a KWin bug.

Hmm. Perhaps using the raster Qt graphics system would help? That's been unnecessary (counterproductive in fact) in recent KDE versions, but who knows... I'll get back to you on it.

Edit: Using the raster engine helps the situation but doesn't fix it; KWin is still pegged at 2-3% CPU. I also tried switching to a lighter window decoration; that did nothing at all.