I've got the Mali Debugger hooked up and am trying to profile my app, the issue is that MGD doesn't appear to recognise the end of the frame, which means that a capture also fails (or runs indefinitely). This is from a Unity GLES app. You can see from the screenshot that a single frame contains all the GLES calls once the application has started. Is this a configuration issue of any kind?
Thanks in advance.
MGD considers a frame as the sequence of function calls executed between two frame-end markers. When you capture a frame of a VR application, the capture end is delayed after the frame-end marker until all the on-going render passes are finished. The additional function call traced after the frame end are added to the next (incomplete) frame.
All the draw calls traced in a frame according to the previous definition are considered for the draw call count. I do not know what Unity's frame debugger consider for draw calls count, but a different definition of frame could explain the difference in numbers.
In VR applications the time warp compositor thread is periodically drawing the two buffer eyes (Developer Center — Documentation and SDKs | Oculus ) regardless if a new buffer eye content is available. If for whatever reason the new scene is not rendered yet, the compositor will still strive to draw the eye buffers according to the refresh rate and you will see frames where just two draw calls are present in the outline view.
If for draw timing you mean the time spent in the GPU doing the work for draw calls, MGD cannot give this information because Mali is a deferred render. MGD only reports how long is spent in the driver for each function call, and for draw calls on Mali these will return almost instantly since they only queue work up for the GPU to do later. If you interested in seeing the times calls were made you can to that in Trace View by adding the ‘Time Started’ Column to the view.
Identifying draw calls
If you want to see what each draw call is doing, consider using the MGD geometry view that allows you to see a wire frame representation of the mesh that a draw call is using without having to capture the attachments (although this currently only works for draws using GL_TRIANGLES and GL_TRIANGLE_STRIP).
Hope that helps,
Thanks for the detailed response Jonathan,
Sorry about the late reply. I've recently found a bug in the Oculus SDK that has been the cause of my performance issues, so using MGD is not a high priority for me anymore. That said, I'd like to respond and ask one more question for future reference:
The Unity Frame Debugger counts all draw calls made that composite the scene. Since they submit all of the draw commands, they must know which one make up the frame and probably don't rely on a GPU sync point. They wouldn't count a TimeWarp as a draw call.
That's disappointing about the draw timing. What is the best way to check the load on the GPU? I know you guys have a shader compiler that will tell you instruction counts, is this currently the best way to detect how heavy of a load your application will put on the GPU?
jodon wrote:That's disappointing about the draw timing. What is the best way to check the load on the GPU? I know you guys have a shader compiler that will tell you instruction counts, is this currently the best way to detect how heavy of a load your application will put on the GPU?
You can use the shader compiler (its also built into MGD in the shaders tab), this will tell you how expensive (roughly) each draw call is compared to another, altough it can't take into acount things like cache misses.
We also have a system wide profiling tool called Streamline which includes support for GPU profiling.You can use this to see which parts of the GPU and CPU are loaded at what times, and if you use it with the MGD interceptor installed (but without mgddaemon running) you will get draw calls, render passes, and frames (from MGDs point of view) annotated directly into Streamline.There will however, still be some disconnect between your application making calls and the GPU working becasue of the deferred nature I mentioned earlier.
There are some caveats to getting Streamline setup though as it depends on the device/BSP you are using. I'm afraid Streamline is not my area of expertise but if you have any questions about it I'm sure I can find someone to help you.