[Mesa-dev] [PATCH rfc 0/3] Be able to disable EGL/GLX_EXT_buffer_age

Thomas Hellstrom thellstrom at vmware.com
Thu Jul 5 14:26:06 UTC 2018

On 07/05/2018 03:54 PM, Emil Velikov wrote:
> On 5 July 2018 at 14:31, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> Hi Qiang Yu
>> On 5 July 2018 at 03:31, Qiang Yu <yuq825 at gmail.com> wrote:
>>> For GPU like ARM mali Utgard EGL/GLX_EXT_buffer_age will make
>>> performace worse. But mesa has no way to disable it.
>>> This patch series make driver be able to disable it and add a
>>> gallium pipe cap for gallium driver usage. Due to currently
>>> only out of tree lima driver need it, and not sure if this is
>>> the right way to disable it, so I send this RFC before lima be
>>> able to upstream.
>> Pretty sure we already have a way to handle that. Look for
>> glx_disable_ext_buffer_age - it was introduced for the VMWare driver.
>> Although we should:
>> a) tweak the name - kind of split if we need to
>> b) add glx/dri2 and egl support
> Looking at the implementation - it uses a driver query, meaning that
> one could enable it at a later stage.
> No need to worry if the user has old drirc/etc as with current solution.
> Having two ways of doing the same thing is a bad idea.
> Perhaps we can remove the drirc implementation and use this instead?
> Thomas, what do you think?

The thing is that we only notice a performance regression with GL 
compositors like gnome-shell and compiz, and that's typically because of 
side effects of these compositors. They're using full buffer swaps when 
the extension is enabled rather than damage regions. For other 
applications we want it enabled.

So we need a way to turn it off for certain apps.


> Thanks
> Emil

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