Qt4 and NVIDIA drivers on Linux

[SpartanJ]

From some time ago im having problems with Qt4 applications, they run very very slow compared to Qt3 apps.
For example when i scroll in some application (Arora Browser, KSysmonitor, etc) my CPU usage raise up to 100 % on one core, and the rendering is slow. The performance improve a little in the new drivers 173.14.05 (before that, i had installed 173.08), but still very slow. I think that is a font rendering problem, i tried disabling the font smoothing and the performance speed up a little, but still slow...
I want to say that the problems are equal on my 9600GT and my 6600GT. Tried activating GlyphCache but the problem persist.
I really want to use KDE4 but is practically impossible with this problem.

Sorry for my bad English and thanks for all!
I'll appreciate any help

[Linuxhippy]

I experience currently the same problem, and I guess its because the XRender extension is not accelerated well by nvidia's binary drivers.
The nvidia developers said they know about it and will work on fixing these issues sooner or later.

lg Clemens

PS: Fixing it won't let my GF488Go revive, and I am even not sure wether my GF6600 will still by supported by non-legacy drivers when they finally accalerate it well :-/
I hope nouveu will progress, any maybe Nvidia will release the specs as AMD did. I guess I don't have to say that this *will* influence future purchases.

[Plagman]

Qt4 method of rendering anti-aliased text differs slightly, and wasn't optimally accelerated by the display driver until 173.14.05. To get optimal text rendering performance on KDE4, please use:

nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1

You can add that to your .xinitrc or any similar script, preferably before starting your desktop environment. Note that you need InitialPixmapPlacement 2 for the GlyphCache to take full effect. Also, this feature is only supported on Geforce 8 and 9 series.

[SpartanJ]

Thank's for your reply Plagman, i still getting a very high CPU usage on some app's compared with Qt3, but the performance improved in some Qt4 Demos.
For example, i compared scrolling same page (tested with last.fm and reddit.com) with Konqueror and Arora or Konqueror KDE4 and the first one simply doesn't use more than 2 % of CPU usage, and the others use 100 % of one core (and scroll slowly). The difference is huge, and... what will happend with the people that use 5, 6 and 7 series of GeForce?
Anyway, thank's a lot for your help.

[pawels133]

Originally Posted by Plagman

Qt4 method of rendering anti-aliased text differs slightly, and wasn't optimally accelerated by the display driver until 173.14.05. To get optimal text rendering performance on KDE4, please use:

nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1

You can add that to your .xinitrc or any similar script, preferably before starting your desktop environment. Note that you need InitialPixmapPlacement 2 for the GlyphCache to take full effect. Also, this feature is only supported on Geforce 8 and 9 series.

What about older cards like Geforce 6800? You don't support them anymore?

[kriko]

Is there a fix for older cards like 7600GT? KDE4 is unbearably choppy when resizing windows.

[capthookb]

SpartanJ do you have kwin compositing effects enabled;
Look if you have a variable KWIN_NVIDIA_HACK=1 that keeps cpu working at 100% in order for nvidia cards to have smoother effects (minimize, maximize etc).
I wonder why this would be needed in the first place though....

[NvFuchs]

Originally Posted by capthookb

SpartanJ do you have kwin compositing effects enabled;
Look if you have a variable KWIN_NVIDIA_HACK=1 that keeps cpu working at 100% in order for nvidia cards to have smoother effects (minimize, maximize etc).
I wonder why this would be needed in the first place though....

Because of powermizer, it is not needed on all cards
and there are better ways to accomplish this than by
keeping the gpu load at 100%,
which is obviously a bad idea for mobile devices.

Fuchs

[SpartanJ]

Originally Posted by capthookb

SpartanJ do you have kwin compositing effects enabled;
Look if you have a variable KWIN_NVIDIA_HACK=1 that keeps cpu working at 100% in order for nvidia cards to have smoother effects (minimize, maximize etc).
I wonder why this would be needed in the first place though....

Thank's for your help, but i don't use any desktop effect, i'm on KDE3 for now, and with all the desktop effects disabled. (composite is disabled)

[kriko]

nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1

This helps even on 7600GT, but still not smooth ad on kde3.

[txf]

The newest drivers really are quite a bit better than all the previous drivers under kde4 especially with glyph cache and setting the pixmap cache size to 200000 pixels. This helps out in text rendering only unfortunately.

On Intel igps I've found that on resizing a window the contents get repainted just fine. On the nvidia cards that I have tested (8600m gt and 8400 gs) there is noticeable delay between resize and repaints. On my 8600m powermizer has been disabled. Whats really sucky is that it still has to be off to get decent performance even if compositing is disabled. I guess this is related to the general 2d slowness on newer nvidia gpu's.

Originally Posted by kriko

nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1

This helps even on 7600GT, but still not smooth ad on kde3.

It shouldn't seeing as this is not supported on less than 8 series cards. read post #3

[vampire_donkey]

Originally Posted by txf

The newest drivers really are quite a bit better than all the previous drivers under kde4 especially with glyph cache and setting the pixmap cache size to 200000 pixels.

How do you set the pixmap cache size? I did some searching around expecting it to be something like

nvidia-settings -a PixmapCacheSize=200000

But this doesn't seem to work and I couldn't find any documentation on the driver attributes other than glyphcache and InitialPixmapPlacement.

I still have trouble believing my 5 or something year old mobile Go440 beats the pants of my expensive (when I bought it) 8600GT. *sigh* Please Nvidia, get those fixes out for this issue soon!