GLES Disjoint timer query unexpected value

Hi Pete,

There is a check in the code for that and I just double checked and there doesn't seem to be one occurring. The start timer bit of the code looks roughly like this:

GLint disjointOccurred = false;
glGetIntegerv(GL_GPU_DISJOINT, &disjointOccurred);
if (disjointOccurred) 
{
 // ...
  Debug("disjoint exception");
}

GLuint available = 0;
glGetQueryObjectuiv(queryObject, GL_QUERY_RESULT_AVAILABLE, &available);
if (available == GL_TRUE) 
{
  GLuint64 elapsed_time_ns;
  glGetQueryObjectui64vEXT(queryObject, GL_QUERY_RESULT, &elapsed_time_ns);
  if (glGetError() == GL_NO_ERROR) 
  {
    ...
  }
  ...
}

I'm not seeing any "disjoint exception" message popping up on logcat though. Any other thoughts?

Thanks for checking. I'm following up with the driver team to see if they have any ideas here.

Cheers Pete! Much appreciated!

Hi Pete, did you hear back from the driver team on this? Cheers

Hi JPJ, could you find the driver version on the A20 you're using? (e.g. open chrome://gpu in Chrome and find X in GL_VERSION: OpenGL ES 3.2 v1.rXp0-01rel0). We have some known issues with this extension in older drivers that might explain what you are observing. Thanks!

Hi José! Thanks for the reply. Here's the version I have: OpenGL ES 3.2 v1.r16p0-01rel0

Hi, our r16p0 driver had a bug that the queried elapse time is a very large number (not the nano second), however, it should not be 2^64-1. Is your test like this?
glGenQueriesEXT(1, &queryObject);

glBeginQueryEXT(GL_TIME_ELAPSED_EXT, queryObject)

draw

swap or finish or nothing

glEndQueryEXT(GL_TIME_ELAPSED_EXT)

and then the query code you pasted above

From the Unity plug in, I don't know how "query_buffer_n" and "query_buffer_next_index " are set. So I don't know if it tracks the same query object (using same index/query_buffer_next_index for begin and end), can you check this? and also please check if glGetError() reports errors

Hi Sunny,

That's a fair point. If I'm getting it right you're saying that you can't be certain that I'm querying the value of an object that has been terminated? That could be a cause but I don't know why the availability would return true. I'll do some more investigation. Cheers

For the r16p0 driver, it should return a reasonable data from glGetQueryObjectui64vEXT(GL_QUERY_RESULT), the only problem for that version driver is that the returned data is not in the unit of nanosecond, you should apply this equation:

ns = result * 1000 / AGT_FREQUENCY_MHZ

AGT_FREQUENCY_MHZ is the Arm Generic Timer that used in A20, if you don't know we can check with Samsung

Hi Sunny,

I was about to reply to you. I've done some more investigation on this. I can't find any issue with the code related with the snippet above. I've tried having a single query object as well as quite a few more - the behavior is the same.
Having said this, I've run the same app on an S10e (G970F) and I also get the same large number returned, albeit, less often. Furthermore, I've also ran the app through RenderDoc to get some GL stack data. In a nutshell, here's "where" the query is placed in terms of the GL pipeline:

// App init - presumbaly Backbuffer is bound upon the initialization of eGL
glBindFramebuffer(auxFBO, DRAW)
glInvalidateFramebuffer(...) // makes no sense to me but...
// expected glGetQueryObjectui64vEXT() here
glBeginQuery()
...
... some more calls glBindFramebuffer() for shadowmap and back to auxFBO
...
glEndQuery()
... quite a few more GL calls (state, FBO binds, etc..) including draw calls
eglSwapBuffers()

So, not quite covering the whole scope of the frame. I believe glGetQueryObjectui64vEXT() is not showing up in the stack since this was done through a RenderDoc capture and it perhaps hadn't finished yet (?).

Not sure how this can influence the timer - perhaps you can shed some light on that. Thanks for your help.

Our driver will also have a wait in glGetQueryObjectui64vEXT(GL_QUERY_RESULT_EXT) if GL_QUERY_RESULT_AVAILABLE_EXT is not called, and the result is initialized to 0.

Can you please try this?

GLuint query;
        GLuint64 time;
        GLuint dis_result = 0;
        glGenQueriesEXT(1, &query);
        glBeginQueryEXT(GL_TIME_ELAPSED_EXT, query);
        glClear(GL_COLOR_BUFFER_BIT);
        glEndQueryEXT(GL_TIME_ELAPSED_EXT);

        while (!dis_result)
        {
                glGetQueryObjectuivEXT(query, GL_QUERY_RESULT_AVAILABLE_EXT, &dis_result);
        }

        glGetQueryObjectui64vEXT(query, GL_QUERY_RESULT_EXT, &time);
		__android_log_print(ANDROID_LOG_ERROR, "Timer", "elapsed time is: %lld\n", (long long)time);
        glDeleteQueriesEXT(1, &query);

I can always get something like

elapsed time is: 4273

So if you are still getting -1, I think I have to contact Samsung if they changed the driver a little bit.

Hi Sunny,

Thanks for the quick reply. I've inserted that code snippet at the beginning of the frame (after checking the disjoint query) in the same codebase I was using, like so (for clarity):

void BeforeRenderingStarts()
{
	// on disjoint exception, clear query buffer
	GLint disjointOccurred = false;
	glGetIntegerv(GL_GPU_DISJOINT, &disjointOccurred);
	if (disjointOccurred)
	{
		query_buffer_n = 0;
		__android_log_print(ANDROID_LOG_ERROR, "Timer", "Disjoint Exception occurred");
	}
	
	{
          GLuint query;
          GLuint64 time;
          GLuint dis_result = 0;
          glGenQueries(1, &query);
          glBeginQuery(GL_TIME_ELAPSED, query);
          glClear(GL_COLOR_BUFFER_BIT);
          glEndQuery(GL_TIME_ELAPSED);

          while (!dis_result)
          {
              glGetQueryObjectuiv(query, GL_QUERY_RESULT_AVAILABLE, &dis_result);
          }

          glGetQueryObjectui64vEXT(query, GL_QUERY_RESULT, &time);
          __android_log_print(ANDROID_LOG_ERROR, "Timer", "elapsed time is: %lld\n", (long long)time);
          glDeleteQueries(1, &query);
      }
      ...

I don't seem to get any issues with that though. I get different values I'd consider plausible (e.g., 461268, 741576, etc...).

Regarding the pseudo GL stack I mention above, I forgot to mention that I don't seem to be able to trigger that anomaly (the -1 value) if I remove the shadow pass. Essentially this:

// App init - presumbaly Backbuffer is bound upon the initialization of eGL
glBindFramebuffer(auxFBO, DRAW)
glInvalidateFramebuffer(...) // makes no sense to me but...
// expected glGetQueryObjectui64vEXT() here
glBeginQuery()
...
... NO SHADOW PASS IN HERE.. 
...
glEndQuery()
... quite a few more GL calls (state, FBO binds, etc..) including draw calls
eglSwapBuffers()

I can provide an MGD dump if that helps (and you have time to look into this of course). It's nothing but a simple (but rather shadowmap-heavy) scene rendering a bunch of spheres. Thanks for your help so far!

461268 and 741576 looks reasonable (just because your platform has different frequency setting)

yes, please provide an MGD or sample code for the shadow pass