High RenderForwardOpaque.Render in Profiler with a VR game

I am making a VR game in GearVR with S6, but I'm in trouble with a progress named RenderForwardOpaque.Render. It made a high GPU time of a sudden.
Look at this image:

It takes 2~3ms more often, but it takes 17~25ms in this situation. In fact, I had done nothing in the game, I just looked at somewhere empty all the time.

 

I want to know what does it is, and the reason why it takes a lot of GPU time.
I hope somebody to help me.

 

Have you resolved?

I have the same problem.