Question about statistics of shader per line profile in xcode

Hi, I am using xcode frame capture to profile my app's shader. And I got some question about the shader per line profile statistics. Please see the two screen shot first, it is my compute shader.

Begin:

End:

The first image is the head of the shader. The profile show's that the shader entry function takes 72.44% of the time.

And at the end of the shader, the profile shows that the right brace '}' takes 60.45%.

Here is my question:

  1. How to properly understand the profile data? What's the real performance data of this shader?
  2. Why the shader entry function does not take 100% of the time?

Can someone help me to answer the question?

Thanks! Boson

Question about statistics of shader per line profile in xcode
 
 
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