调用DLL function性能开销？

Question

I'm in a situation when I will often call two DLL functions from other DLL, and I need those functions to be separate, as I call them in different places as well. But since I'm often calling them together, does it make sense to create another DLL function that will call those two, to call it in places where I need to call them both?

Answer 1

Possibly, yes, due to inlining . Calling a DLL function is relatively cheap on modern processors (especially when it is often called and the cache is warm). However, if the function last for a very short time, it can still add a significant overhead. Adding a DLL function calling the two others in the same module can prevent a function call. In some case, the inlining help the compiler to optimize the code further . For example, the constant propagation is often an optimization that matters a lot in such a case. That being said, if the two functions are not related each other, the benefit should be small.

Note that this is a micro-optimization and its benefit should be relatively small in most cases. If the frequency of DLL calls is very high, then it should be much better to redesign your code (eg. typically by working on data chunks, using an optimizing JIT).