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[Bug 763005] Re: Compiz's "Sync to Vblank" makes display stutter/slow with fglrx
** Description changed:
- <fill me in with explanation of severity and frequency of bug on users and justification for backporting the fix to the stable release>
+ 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.
- <fill me in with an explanation of how the bug has been addressed in the development branch, including the relevant version numbers of packages modified in order to implement the 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.
- <fill me in by pointing out a minimal patch applicable to the stable version of the package.>
+ As above.
- [Text Case]
+ [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.
- fglrx: 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.
- intel and possibly any driver: Press WinKey+S or WinKey+W rapidly to
- trigger the expo/workspace animations. These are full-screen animations.
- But are they silky-smooth?
+ 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.
- <fill me in with a discussion of likelihood and potential severity of regressions and how users could get inadvertently affected.
+ 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.
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.
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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Compiz's "Sync to Vblank" makes display stutter/slow with fglrx
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