Then again jl seems to take 10s to start doing something non-trivial each time while modules are being compiled.
TLDR: There's a package called PrecompileTools.jl [2] which allows you to list: I want to compile and cache native code for the following methods on the following types. This isn't complicated stuff.
[1] https://julialang.org/blog/2023/04/julia-1.9-highlights/#cac...
If the main objective is to reduce time to load and time to first task then PackageCompiler.jl [3] is still the ultimate way to do so.
Because Julia is a dynamic language, there are some complicated compilation issues such as invalidation and recompilation that arise. Adding new methods or packages may result in already compiled code no longer statically dispatching correctly requiring invalidation and recompilation of that code.
It slightly more complicated than what you stated. It's "I want to compile and cache native code for the following methods on the following types in this particular environment". PackageCompiler.jl can wrap the entire environment into a single native library, the system image.