Code memory size different from dev to prod

[tj0]

Thank you @LostKobrakai @josevalim .

Code path pruning
I had skipped a rather important word when reading about code path pruning.

@LostKobrakai

There is no automatic prunning of modules or functions. The feature added in 1.15 is around code paths, which brings mix projects closer to how releases are built by excluding everything but explicit dependencies mostly to otp applications. Previously all of OTP would be available for loading on demand

Code memory usage
Turns out running mix release.init creates rel/env.sh.eex which has the RELEASE_MODE option right at the top . I migrated from distillery, so it wasn’t obvious what I was looking for. Anyone starting off with a fresh project would easily find this option.

rel/env.sh.eex

# # Set the release to load code on demand (interactive) instead of preloading (embedded).
# export RELEASE_MODE=interactive

Also, this may not affect startup time in OTP 26.

@josevalim

interactive mode was slower to boot but that’s not necessarily the case from Erlang/OTP 26.

Final results
Using interactive mode after going thru all the routes has reduced the memory:

Production is running at 23MB right now, but I expect it will grow to at least 30MB. Embedded mode which preloads everything had code memory usage at 48MB. Super-helpful when running on lower memory nodes. A MB saved is a MB earned.