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I've asked ChatGPT to summarize (granted my prompt might not be ideal), but some points to note, here just first in details others in the link at the bottom:

     Calling C from Go (or vice versa) often requires switching from Go's lightweight goroutine model to a full OS thread model because:
       - Go's scheduler manages goroutines on M:N threads, but C doesn't cooperate with Go's scheduler.
       - If C code blocks (e.g., on I/O or mutex), Go must assume the worst and parks the thread, spawning another to keep Go alive.
     * Cost: This means entering/exiting cgo is significantly more expensive than a normal Go call. There’s a syscall-like overhead.
... This was only the first issue, but then it follows with "Go runtime can't see inside C to know is it allocating, blocking, spinning, etc.", then "Stack switching", "Thread Affinity and TLS", "Debug/Profiling support overhead", "Memory Ownership and GC barriers"

All here - https://chatgpt.com/share/688172c3-9fa4-800a-9b8f-e1252b57d0...



Just to roll with your way: https://chatgpt.com/share/688177c9-ebc0-8011-88cc-9514d8e167...

Please do not take the numbers below at face value. I still expect an actual reply to my initial comment.

Per-call overhead:

  C (baseline)    - ~30 ns
  Rust (unsafe)   - ~30 ns
  C# (P/Invoke)   - ~30-50 ns
  LuaJIT          - ~30-50 ns
  Go (cgo)        - ~40-60 ns
  Java (22, FFM)  - ~40-70 ns
  Java (JNI)      - ~300-1000 ns
  Perl (XS)       - ~500-1000 ns
  Python (ctypes) - ~10,000-30,000 ns
  Common Lisp (SBCL) - ~500-1500 ns
Seems like Go is still fast enough as opposed to other programming languages with GC, so I am not sure it is fair to Go.


Java now has FFM, that is far better and simpler than JNI, FWIW. and chatgpt says

Language/API | Call Overhead (no-op C) | Notes

Go (cgo) | ~40–60 ns | Stack switch + thread pinning

Java FFM | ~50 ns (downcall) | Similar to JNI, can be ~30 ns with isTrivial()

Java FFM (leaf) | ~30–40 ns | Optimized (isTrivial=true)

JNI | ~50–60 ns | Slightly slower than FFM

Rust (unsafe) | ~5–20 ns | Near-zero overhead

C# (P/Invoke) | ~20–50 ns | Depends on marshaling

Python (cffi) | 1000–10000 ns | Orders of magnitude slower |


Thanks, I added it to the list. Keep in mind that the numbers may be off (both yours and mine), so I would not take them at face value. It is interesting how in yours JNI is still pretty good. Also Rust is "~5–20 ns" in yours, so I assume "0" is the baseline.


This is chatgpt. Not my own benchmark. So it is probably hallucinating


i can't see how these numbers can be anywhere near correct (nor the ones above). in JavaScript on an old Core i5 the overhead of a simple ffi call is on the order of 5 nanoseconds. on a recent x64/arm64 cpu it's more like 2 nanoseconds.

you can verify this easily with Deno ffi which is pretty much optimal for JS runtimes. also, from everything i have seen and read, luajit should be even lower overhead than this.

you really shouldn't be asking chatgpt questions like this imo. these are facts, that need to be proven, not just vibes.


I agree. was just following the parents pattern, to make it work for me :)


> Rust (unsafe)

As if there is an alternative :)

More seriously, it’s “unsafe” from the perspective of the library calling into C, but usually “safe” for any layer above.


Hey, since I am in a thread where we are sharing what ChatGPT spits out, I just copy pasted it from there, too. :)

For what it is worth, I asked about LuaJIT after I have shared the link, and the numbers are now different for some languages, albeit not by much. Go (cgo) became ~50-100 ns. That said, I still believe it is unfair to single out Go when it does way better than some other GC languages.


oh wow I got downvoted a lot - I guess I'm bad at prompting :)


You are being downvoted because pasting AI output with no attempt at fact-checking is not bringing any real value to the discussion.


That is not it. Everyone who copy pastes output from an LLM gets downvoted (and likely flagged). Even though I simply went with your method, I got down-voted too, when down-voting the parent comment (yours) would have sufficed. Oh well.


Noted! Well maybe it makes sense! Thanks for the info!!!


I even got down-voted for telling you the truth. Lmao.

"ants_everywhere" is right.


Don't take it too personally.

The anti-LLM activists that patrol HN will often downvote comments just for stating facts that disagree with their hatred of LLMs.




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