Question

Is there any performance gain in calling C code from Objective-C?

I’ve read somewhere that message passing is slower compared to other languages that use function calling. So if I call a C function from Objective-C code, am I avoiding the messaging overhead?

When optimizing for performance, is it recommended practice to code the most critical functions and procedures in C instead of using Objective-C objects?

EDIT:
Given the amount of answers warning about premature optimization and code readability, I want to clarify that I was not thinking on regular applications, but very specific ones such as:

• Graphics
• Encryption or compression algorithms.
• Maths

And in general, functions or procedures that do not need OO design and are intended to be called many times with parameters.

Answer 1

This is a benchmark that compares messaging to calling C functions. Here are the results of calling different implementations of the fibonacci function about 1.4 billion times.

Message Passing 23.495 seconds
IMP Calling     16.033 seconds
C Function      9.709 seconds

So yes, there is some overhead when calling an Objective C method. But, except in some situations, this is not what will impact the performance of your app. In fact, messaging is still more efficient than most other operations such as floating-point division.

In addition, the majority apps spend most time waiting for user input, downloading data, etc.