Warning

Before making any changes to your system, please read everything carefully and try to understand what you are doing. If you're modifying any files on your system, keep copies of the unmodified version and be sure you can revert to those old version - even if your Xserver is not starting any longer.

Warning

Some of the changes mentioned below are said to increase the temperature of your GPU. In any case, monitor your graphic card to make sure it isn't getting too hot!

Primer

Several popular graphics cards out there - especiall NVIDIA ones - exhibit performance problems with KDE4. These performance hits mostly concern Plasma - the KDE4 desktop - and KWin - the KDE window-manager. Generally speaking this isn't due to KDE4 being unoptimized but a problem with the cards' graphics drivers. This page encompasses certain problems that might arise and how to get rid of them.

General hints

Graphics driver

For both of the big graphics chip manufacturers there's 2 seperate graphics drivers each:

For NVIDIA cards there's the free nv and the proprietary nvidia driver. While KDE4 should work fine with the former, it doesn't offer 3D acceleration, so the latter may be your only choice. All NVIDIA subsections herein only refer to the proprietary driver (there's also a 3rd free driver called nouveau that's currently being written. Unfortunately I don't know how usable it is so far). Due to licensing restrictions most distributions don't install the proprietary driver by default. Please refer to your distribution for information on how to install it.

Note

TODO: section about radeonhd and fglrx driver - I don't own an ATI card Lemma

It's usually advisable to stay up-to-date as improvements are being made in the drivers. Thus a first step in improving your KDE4 experience should be checking your current driver and updating if it's outdated. Please refer to your distribution's documentation on how to do that.

While it might increase performance even more I do NOT recommend to install beta quality drivers because your system's stability will usually decreases a lot.

nvidia-settings

Attributes set using the nvidia-settings utility aren't permanently saved. Thus you have to set them every time you restart your Xserver. This can be done conveniently by adding the lines to set the features to your ~/.xinitrc.

systemsettings

KDE4's systemsettings allows you to tweak some kwin settings as well. You can find the settings in Desktop -> Desktop Effects -> Advanced Options. Depending on your card either OpenGL or XRender might work better. For OpenGL changing the OpenGL mode might change performance as well. Please bear in mind that changing some of the tweaks mentioned below might force you to change your settings.

Example:

Setting InitialPixmapPlacement to 2 might improve plasma's performance but might make kwin hang sometimes.
Setting OpenGL mode to Shared Memory might make kwin more responsive again.

If for some reason your Xserver hangs after hitting the Apply button on the dialog and your settings get reverted because you can't confirm your changes in time, try again. Usually it will be faster on one of the subsequent tries. If it doesn't you can still change your settings in ~/.kde4/share/config/kwinrc.

Problems

This section summarizes several symptoms you might encounter and tries to explain possible causes.

Resizing certain windows is choppy

Explanation: This might be due to your card advertising ARGB Visuals (basically translucency) without having proper support for them. Applications/windows concerned are the plasma desktop, the krunner dialog (Alt+F2), plasma's Add new widget dialog or a konsole window.

Test

If you want to make sure this issue is a problem for you, run

$ XLIB_SKIP_ARGB_VISUALS=1 konsole

on the command-line and try to resize the new konsole window (setting the environment variable XLIB_SKIP_ARGB_VISUALS turns off ARGB visuals). If it resizes without problems, then this is certainly one of the problems you're facing.

General

You can set the BackingStore options in your xorg.conf:

Section "Device"
    ...
    Option "BackingStore" "true"
    ...
EndSection "Device"

This works for some (eg. konsole) but unfortunately not all windows.

As a last resort you can try setting XLIB_SKIP_ARGB_VISUALS=1 in your ~/.xinitrc but this isn't pretty.

NVIDIA

You can set the IntialPixmapPlacement with the nvidia-settings utility:
```
$ nvidia-settings -a InitialPixmapPlacement=2
```
This works for some (but unfortunately not all) NVIDIA cards.

ATI

TODO

Plasma performance is bad

Explanation: Unfortunately the reasons for plasma being choppy seem to be numerous so it's hard to tell where your choppiness comes from.

Test: Usually plasma performance problems can be seen best on the Folder View plasmoid. Moving it or scrolling inside the folder might be pretty slow.

General

Please make sure this is not (only) related to the ARGB Visuals mentioned in the above section.

NVIDIA

You can set the IntialPixmapPlacement and the GlyphCache option with the nvidia-settings utility:
```
$ nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1
```
This works for some (but unfortunately not all) NVIDIA cards. Some cards reportedly work better using InitialPixmapPlacement=1 (or maybe even 3)

Options that are said to work well on 8xxx cards but are untested (by me)
- Option "RenderAccel" "True"
  - enabled by default
- Option "TripleBuffer" "True"
  - Enables triple buffering. "Decreases the time an application stalls while waiting for vblank events, but increases latency slightly" (NVIDIA Readme)
- Option "DamageEvents" "True"
  - Recommended by NVIDIA if running composite+glx, increases performance, enabled by default
- Option "UseCompositeWrapper" "True"
  - Enables the X server's composite wrapper instead of the builtin one.
- Option "AllowIndirectPixmaps" "True"
  - Could improve hardware rendering on G80+ cards with more than 256 MB of video memory.
- Option "BackingStore" "True"
  - Cache overlayed areas in case they get redisplayed later
- Option "PixmapCacheSize" "200000"
  - allocate said number of pixels for pixmap caches

ATI

TODO

Links/References

[1] -- Thread about graphics issues on the NVIDIA forums.