[Mesa-dev] Time to merge threaded GL dispatch? (aka glthread)

Marek Olšák maraeo at gmail.com
Fri Feb 10 11:00:13 UTC 2017

The glmark2 issue is not important, because glthread will never
support glmark2. (because glmark2 is a SwapBuffers benchmark like


On Fri, Feb 10, 2017 at 11:32 AM, Eero Tamminen
<eero.t.tamminen at intel.com> wrote:
> Hi,
> On 09.02.2017 20:27, Ernst Sjöstrand wrote:
>> 2017-02-09 18:06 GMT+01:00 Eero Tamminen <eero.t.tamminen at intel.com
>>     My personal feeling is that minimal merging criteria should be:
>>     * no known segfaults
>> I bet that glmark2 just does something that's not allowed. Mesa can't
>> prevent all application bugs? Seems like it has a very buggy history
>> with lots of segfaults in other situations also.
> You don't know which one is at fault without investigating it.
> glmark2 is open source, so it's easy to debug, and based on my experience
> has active maintenance:
>         https://github.com/glmark2/glmark2/issues/25
> If bug turns out to be in glmark2 instead of glthread code, file a bug:
>         https://github.com/glmark2/glmark2/issues/
> If developers agree that it's bug on glmark2 side (or at least don't point
> out an issue at Mesa side), segfault is OK.
> (It would be best to test latest glmark2 git version, but IMHO waf usage
> makes it a bit pain to build.)
> glxgears uses old GL stuff:
> https://cgit.freedesktop.org/mesa/demos/tree/src/xdemos/glxgears.c
> If glthread doesn't work with that (e.g. glBegin() / glEnd()), it should
> either disable threading, or abort with warning.  Silently corrupting things
> is not OK even for optional code paths.
> I forgot one more thing from the minimum requirements:
> * Once the segfaults and piglit failures have been investigated & fixed, or
> explained not to be glthread issues, glthread still shouldn't slow Mesa down
> when it's _disabled_
> (Marginal slowdown at startup might be OK. At run-time slowdowns, when
> glmark is not enabled, are not going to fly as most programs will be run
> without enabling glthread.)
>         - Eero
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