Hello. I am getting random gpu load drops with clocks drops in GTA V ( updated to 1.36 ).

Here is screen: ( open in new tab to see )



I added black arrows during drop to show. Both Clocks drops and gpu load drops for a fraction of second and turns back.

My pc: 6700K stock ( good temps )
16gb DDR4
Asus Strix gtx 1080 ( stock, good temps ) C
Corsair 750 RM
Asus Z170-P

I am on newest drivers . Windows 10 Anniversary.
Windows power plan : balanced
Nvidia power plan: Optimal

Question. Why it dropping clocks during gpu load drops, is this normal using optimal power?
Or something is wrong?