suddenly low gaming performance

till yesterday i used to play battlefield 4 on ultra settings with resolution scale to 130 on 1080p it was butter smooth 60 fps constant but now cpu is suddenly spiking and going 100 it never happened before while in game 2 processes popsup one is windows audio service it takes a little cpu and other is system interrupts it also takes cpu i have already reinsalled windows with iso and performed in place upgrade and keep all my files but it is same

Use Task Manager to disable auto-start apps you don't need, and to see what's running before you start the game—sort by the CPU column so you easily see if something is using CPU.

ETA
You might find help in Brink's tutorial:
Dedicate Resources to Game in Windows 10 Game Bar