Shadow Framebuffer of X Window

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There is a mode, called shadow framebuffer, where the graphics are used to display the images. All rendering is done in memory in a so-called shadow framebuffer.

Karl also had an experience that is he enabled the shadow frame buffer and XGetImage dramatically speeds up 50~100 time of non-shadow frame buffer.

I had a trial and the results are as the following statement:
on IBM A30 desktop machine, Pentium-4 500MHz cpu and 256M Bytes ram.

  1. Enable vesa framebuffer to run Xwindow and get an 1024*768*16-bits full screen frame by XShmGetImage, it takes about 160~170 milliseconds per frame.
  2. At the same condition of 1., but map /dev/fb0 frame buffer to memory and get the full screen frame from the mapped memory, it takes about 160 ~ 170 milliseconds per frame.
  3. At the same condition of 1., but use i810 driver which is auto detected by Xorg after I installed Ubuntu on IBM A30, it takes about 77 milliseconds per frame.

Reference:

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2 thoughts on “Shadow Framebuffer of X Window

    beachbody Focus T25 Review said:
    九月 16, 2013 at 12:40 上午

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