KDE4 Kwin Desktop Effects Howto

If you wonder, just as I just did, what the different options in the Advanced section of System Settings: Desktop: Desktop Effects: Advanced Options in KDE4 means, here is the answer:

  • OpenGL is the fastest solution as it uses your graphics card's 3d acceleration for rendering.
    • Texture from Pixmap is the fastest option, as it stores the texture directly in the graphics card's memory, which is usually faster than the system ram.
    • Shared Memory stores the textures in X's shared memory, which resides in the system RAM and is usually much slower than the graphics card's memory.
    • Fallback tries Texture from Pixmap first and Shared Memory if that does not work.
  • XRender is less fast as it only uses 2d acceleration but much more compatible and works with older graphics cards as well.

The other options:

  • Direct rendering passes the commands directly to the graphics card and bypasses the X server. This is much faster as it the commands have to be copied less, but can be more instable and less compatible.
  • VSync stands for vertical synchrosation and ensures that the pictures are drawn in sync to the vertical display updates. This can be more soothing to the eyes, but is a little slower and just drawing the frames any time the graphics card is ready to do so.


  1. From my experience, you must take this advice with a grain of salt. "Shared Memory" is always slower when you have a secondary video card, but it is always FASTER when you are working with an integrated video card. Why? Because the integrated video chipset has no memory, and graphics keep themselves in, you've guessed, shared memory always. The graphic driver gives the system the illusion that it isn't using shared memory, but real video memory, and this illusion involves conversions that incur in additional performance penalties.

    Of course, if you have an integrated video chipset WITH MEMORY, "Shared Memory" will be slower. Try it. On a GeForce 6150 integrated chipset, "Shared Memory" is a lot FASTER than "Texture from Pixmap", specially when I mix it with "Direct Rendering" enabled. NVidia drivers love "Direct Rendering".

  2. Thanks a lot for that insightful explanation, Alejandro!


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