[Mesa-dev] [PATCH] mesa: detect inefficient buffer use and report through debug output

[Ilia Mirkin]

On Wed, Dec 9, 2015 at 5:23 PM, Brian Paul <brianp at vmware.com> wrote:
> On 12/09/2015 11:43 AM, Ilia Mirkin wrote:
>>
>> On Mon, Dec 7, 2015 at 8:42 PM, Brian Paul <brianp at vmware.com> wrote:
>>>
>>> When a buffer is created with GL_STATIC_DRAW, its contents should not
>>> be changed frequently.  But that's exactly what one application I'm
>>> debugging does.  This patch adds code to try to detect inefficient
>>> buffer use in a couple places.  The GL_ARB_debug_output mechanism is
>>> used to report the issue.
>>>
>>> NVIDIA's driver detects these sort of things too.
>>>
>>> Other types of inefficient buffer use could also be detected in the
>>> future.
>>> ---
>>>   src/mesa/main/bufferobj.c | 55
>>> +++++++++++++++++++++++++++++++++++++++++++++++
>>>   src/mesa/main/mtypes.h    |  4 ++++
>>>   2 files changed, 59 insertions(+)
>>>
>>> diff --git a/src/mesa/main/bufferobj.c b/src/mesa/main/bufferobj.c
>>> index f985982..6bc1b5e 100644
>>> --- a/src/mesa/main/bufferobj.c
>>> +++ b/src/mesa/main/bufferobj.c
>>> @@ -51,6 +51,34 @@
>>>
>>>
>>>   /**
>>> + * We count the number of buffer modification calls to check for
>>> + * inefficient buffer use.  This is the number of such calls before we
>>> + * issue a warning.
>>> + */
>>> +#define BUFFER_WARNING_CALL_COUNT 4
>>> +
>>> +
>>> +/**
>>> + * Helper to warn of possible performance issues, such as frequently
>>> + * updating a buffer created with GL_STATIC_DRAW.
>>> + */
>>> +static void
>>> +buffer_usage_warning(struct gl_context *ctx, const char *fmt, ...)
>>> +{
>>> +   va_list args;
>>> +   GLuint msg_id = 0;
>>
>>
>> This needs to be wrapped in a macro, with a 'static' id (at each macro
>> invocation), otherwise a fresh id will get generated each time this is
>> called, which is presumably not desirable. Same as what I did with
>> pipe_debug_message/_pipe_debug_message.
>
>
> Is the macro required, or can I just pass a pointer to a static GLuint from
> each call site?  I took a quick stab at the macro but I'm having trouble
> with the varargs stuff.

The macro is not required... but you can copy the one I used for
pipe_debug_message. Passing in a different static variable from each
callsite would work too -- that's precisely what the macro would be
doing in the first place.

  -ilia