Help me with a performance bottleneck; lots of calls to a single function

Hi all, i'm currently hitting a bottleneck. Some context;

I'm presently writing a culling manager. It's purpose is to track hundreds (maybe thousands) of small physics objects, and take actions against them to ensure the game's framerate remains consistent. Stuff like altering their collision filter, collider shape, or just plain destroying them if needed. I'm not that far in yet though.

Right now i'm at the registration stage, all these little objects register themselves with the culling...

Help me with a performance bottleneck; lots of calls to a single function