4 ms·

ah, good point. much faster than cgo. so probably that would kill you in go. i wonder if it's possible to speed up ffi in go...

• ngrilly 8y ago
  You wrote that Unity FFI is much faster than cgo. I'd be interested in knowing more about this. Why is it faster? Can you share a link to some reference material and/or benchmark?
  • dilap 8y ago
    good question! i'm not an expert. my understanding is go is slow because each function call has to copy over to a bigger stack (goroutines have tiny stacks to start, and grow on demand, but c code can't do that, natch) and because it has to tell the goroutine scheduler some stuff for hazy reasons. this github issue has a lot of interesting discussion of go ffi: https://github.com/golang/go/issues/16051 https://github.com/golang/go/issues/16051 these benchmarks https://github.com/dyu/ffi-overhead https://github.com/dyu/ffi-overhead seem to show that a c call via cgo will be about 14 (!) times slower than a c call from c# in mono, which itself is about 2 times slower than just a plain c call.
    • ngrilly 8y ago
      cgo doesn't copy the stack to a "bigger stack" when calling a C function. It just uses another stack, dedicated to cgo, and disallows passing pointers into the stack: https://github.com/golang/go/issues/11089 https://github.com/golang/go/issues/11089 So I think the slowness is caused by something else. Thanks for sharing the benchmark.
      • dilap 8y ago
        ah, that makes more sense. thanks.