[Bug 42035] no way to turn off vsync

[Michal Suchanek]

2011/10/27 Michal Suchanek <hramrach at centrum.cz>:
> 2011/10/27 Michel Dänzer <michel at daenzer.net>:
>> On Mit, 2011-10-26 at 21:36 +0200, Michal Suchanek wrote:
>>>
>>> Ideally I would like no tearing and no vblank sync
>>
>> Well, the only way to avoid tearing without sync to vblank is the method
>> controlled by Option "SwapbuffersWait"...
>>
>>
>>> but both tearing prevention in the radeon driver and sync to vblank
>>> can lead to applications getting stuck in the  X server.
>>
>> Please provide details about a specific scenario where this happens with
>> vblank_mode=0.
>
> Remove all configuration pertaining to vsync/vline wait.
>
> Run recent radeon driver on 3.0.0-10 Ubuntu kernel.
>
> Run glxgears. They won't render even a single frame unless the screen
> is rotated.

Hmm, it does not depend on kernel version.

When two X servers are running the second one gets the stuck applications.

>
>>
>>
>>> In the more recent snapshot the tearing prevention is not working
>>> which is probably a bug in itself.
>>
>> Define 'not working'.
>
> fullscreen glxgears fps are not capped to the screen refresh rate.

With the current kernel and driver it seems to work more consistently.

Always synced on non-rotated screen and never synced on rotated, mapped or not.

At least fresh after booting. There seems to be some period about two
weeks long in which the behaviour may vary :-S

Thanks

Michal