Re: Is it supposed to be faster to call a C function than a Lua function when in Lua?

[Eric Wing <ewmailing@...>]

> If you look at the c code of the Lua interpreter, this is not really
> surprising. There is not really a language bridge at that point. The Lua
> interpreter is in C as well. All it does is a call of a C function pointer.
>

So just as an additional data point, I've been looking at
JavaScriptCore and v8 which are also implemented in C/C++.
(JavaScriptCore's JIT is disabled since I am testing it on iOS, while
I'm doing v8 on Android which cannot disable JIT).

In both cases, calling to C from Javascript was more expensive than
calling C from Lua. In JSCore, the Javascript empty function call was
faster than calling the C empty function, but both were slower than
Lua calling a Lua function.

In v8, the empty Javascript function call was much faster, about 10x
faster than the C call and about 5x faster than Lua. But I think I'm
more surprised that v8's JIT didn't completely optimize out the loop
and empty function and make the time 0.



Thanks,
Eric
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Beginning iPhone Games Development
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