How do you define significant? It is noticeable as compared to C. It is nothing compared to Python.

> Are there any benchmarks on this?

You will see an additional ~20ns per call (assuming the gc compiler; tinygo, for example, can call C functions as fast as C can). In other words, you're not ever going to notice unless you're making millions of calls in a hot loop. The bigger problem in a highly concurrent environment is that blocking C functions can start to mess with the scheduler if they are slow to return. You, again, would never notice in a program of this nature, though. The feature is there to be use. It being a "bad idea" is nonsense.

Some added pain in compilation is, fairly, a tradeoff to consider. But that's just because C compilers, for the most part, aren't very good. It is not like those problems go away if you use C instead.