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[Bug 763005] Re: fglrx driver + compiz's "Sync to Vblank" makes display stutter/slow


** No longer affects: fglrx-installer (Ubuntu)

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  fglrx driver + compiz's "Sync to Vblank" makes display stutter/slow

Status in Compiz Core:
  Fix Released
Status in Ubutter:
  Fix Released
Status in compiz package in Ubuntu:
  Fix Released

Bug description:
  The user's display only redraws at 20-30Hz (1/3-1/2 of the correct monitor refresh rate). Making a highly unpleasant graphics experience.

  [Development Fix]
  Simplified the way the compiz opengl plugin does vsync, using fewer functions and simpler code. This works around the slow functions in the fglrx driver which are the root cause.

  [Stable Fix]
  As above.

  [Test Case]
  Make sure "Sync To VBlank" is enabled in the OpenGL section of CompizConfig Settings Manager. In Ubuntu 11.04 it is enabled by default.

  Drag some windows around. Also open and close windows. The animations
  will not be smooth as they appear to stutter. The framerate is only
  around 20-30Hz.

  Now turn "Sync To VBlank" off and repeat the above steps again. If you
  notice the animations are much smoother than with "Sync To VBlank" on
  then you are suffering from this bug.

  [Regression Potential]
  Worst case: Video tearing occurs. However this is unlikely given the fix has been in everyday use by many users of ppa:vanvugt/compiz for many months already.

  [Original Report]
  This bug is primarily for users of the fglrx driver, but the proposed fix does improve performance with other drivers. Most NVIDIA users should look at bug 92599 instead.

  Package: fglrx
  Version: 2:8.840-0ubuntu2

  01:00.0 VGA compatible controller: ATI Technologies Inc Juniper
  [Radeon HD 5700 Series]

  I have ATI's 5770 with fglrx. Having "Sync to Vblank" on makes Unity
  and many Compiz features (Enhanced Zoom, Scale etc.) really slow.
  Turning "Sync to Vblank" off has a huge effect on desktop,
  responsiveness is much, much better. Turning "tearing" off/on from
  amdccle doesn't seem to have any effect on responsiveness.

  In Maverick "Sync to Vblank" was off by default, in Natty it's on.
  This will probably have a huge impact on many fglrx users.

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