Cost of a virtual function in a tight loop

Question

I am in a situation where I have game objects that have a virtual function Update(). There are a lot of game objects (currently a little over 7000) and the loop calls update

Answer 1

A virtual function call is not going to add much more than a single indirection and a hard-to-predict jump. That means that usually you're down one pipeline flush or about 20 cycles per virtual function. 7000 of them is about 140000 cycles, which should be negligible compared to your average update function. If it isn't, say that most of your update functions are just empty, you can consider putting the update-able objects in a separate list for this purpose.

Removing the virtual function is just going to lead to one of you replacing it with an identical but self-implemented system. This is the exact kind of place where a virtual function makes sense.

Per reference, 140000 cycles is about 50 microseconds. That's assuming a P4 with a huge pipeline and always a full pipeline flush (which you don't usually get).