[filmor]

Does gen_server have a measurable overhead compared to this? The main event loop of gen_server looks remarkably similar to what you are doing but handles calls, casts, hibernation, debugging, provides stacktraces and doesn't "force" exit trapping. In the "happy-path", I don't see any additional overhead to what you are doing.

I would also like to see "handle_call" and "handle_cast" (maybe even "handle_info" with a blanket noreply-implementation) optional, but until then I can deal with the additional two lines to exit on cast or call if I don't require those.

[derefr]

I don't think this approach would result in lower overhead, since `metal` here is still a separate module.

Maybe if it were instead a macro/parse-transform, injecting all the common "framework" code into the module implementing the server callbacks, you could then at least get the optimizations that result from all the calls into and out of the "framework" being local rather than remote calls. Private functions could be inlined/fused, etc.

Further, if HiPE was made to work again on Erlang 25, such a "statically-compiled" server module could also "stay native", with no context-switches to interpreted code, in a way that HiPE can't presently manage for gen_servers due to the code in `gen_server` and `proc_lib` themselves not executing natively.