[Mesa-dev] [RFC PATCH shader-db 2/2] run: request a debug context

[Ilia Mirkin]

On Mon, Nov 9, 2015 at 2:02 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> On Mon, Nov 9, 2015 at 1:56 PM, Matt Turner <mattst88 at gmail.com> wrote:
>> On Mon, Nov 9, 2015 at 10:46 AM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>> On Mon, Nov 9, 2015 at 1:35 PM, Matt Turner <mattst88 at gmail.com> wrote:
>>>> On Sun, Nov 8, 2015 at 8:53 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>>>> st/mesa only prints messages in a debug context. Without always enabling
>>>>> the message generation, I don't see a way to hook into the glEnable() to
>>>>> turn it on/off.
>>>>> ---
>>>>>  run.c | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/run.c b/run.c
>>>>> index 73e468d..1d8d3b1 100644
>>>>> --- a/run.c
>>>>> +++ b/run.c
>>>>> @@ -417,6 +417,7 @@ main(int argc, char **argv)
>>>>>          EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT_KHR,
>>>>>          EGL_CONTEXT_MAJOR_VERSION_KHR, 3,
>>>>>          EGL_CONTEXT_MINOR_VERSION_KHR, 2,
>>>>> +        EGL_CONTEXT_FLAGS_KHR, EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR,
>>>>>          EGL_NONE
>>>>>      };
>>>>>      EGLContext core_ctx = eglCreateContext(egl_dpy, cfg, EGL_NO_CONTEXT,
>>>>
>>>> Is this a limitation of st/mesa, or am I using the KHR_debug API
>>>> incorrectly? It's my understanding that you can get KHR_debug messages
>>>> without a debug context by calling glEnable(GL_DEBUG_OUTPUT), and it
>>>> looks like this is supported by the KHR_debug spec.
>>>
>>> But I don't want to be generating the debug info in my driver for no
>>> reason. For example I have a timing-type debug message which gets the
>>> current time (to report how long a sync fence wait takes). This is a
>>> non-free operation that I want to avoid if no one's looking.
>>
>> Huh, looks like we do quite a bit of work before we throw the message
>> away. We could probably make that process a lot simpler.
>>
>>> I can see this both ways... perhaps the more expensive messages should
>>> be keyed on whether it's a debug context and the compiler message
>>> should always be reported. Or perhaps we can just create a debug
>>> context here and be done with it.
>>
>> I guess you can determine that based on
>> DEBUG_SEVERITY_{HIGH,MEDIUM,LOW,NOTIFICATION}?
>
> There's no driver notification about that (that I'm aware). Should there be?
>
> I don't really see how that can work, since I think you're supposed to
> be able to have multiple ones in a group. But I'm new to that API...
> if there's a driver hook that I missed or variable I should be looking
> at, please educate :)
>
>   -ilia

So what's the conclusion here? Request debug contexts, or I keep this
patch local for now until such a time that I can redo the gallium impl
to also pass messages through for non-debug contexts and teach nouveau
to look at context type to determine whether to do potentially
expensive debug things instead of whether there's a debug callback
set? [Aka for the foreseeable future.]

  -ilia