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

[Matt Turner]

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}?