I am looking into how to reduce the size of mirageos images. Currently I am playing around with the ukvm target. Using 4.06.1+lto, the size of hello.ukvm is 6M (stripped). (–gc-sections gets me to 5.5M.) I have read somewhere that I can use ocamlclean to reduce the image size. Is this still the ca…

ocamlclean is only for bytecode binaries, so for native code (which is the main backend for MirageOS unikernels these days), the LTO patch is the way to go. It would be good to do some investigations into why the hello world is so big; for example, a fix merged today to the ppx libraries stopped co…

Cool. ppx_tools_versioned 5.2.1 gets hello.ukvm to 1.8 M :slight_smile: Out of curiosity: this paper Unikernels: Library Operating Systems for the Cloud in 2013 reports that the size of mirageOS images was much smaller, Web Server 0.673 MB (and 0.172 MB after ocamlclean). I wonder why we cannot hav…

@Keiko : you can use upx --best and/or strip to reduce the binary size even further. The hello-world for native apps should be between 500k and 850k (depending on the target).

@samoht : 1.8 M is strip-ed and linked with --gc-sections. The target is ukvm. upx --best hello.ukvm fails with UnknownExecutableFormatException :’-(

upx will only work on a unix target. In any case, it only reduces the on-disk executable size, not the memory requirement.

Triggered by the discussion here I looked into modules linked into our binaries and I see a lot of modules that I suspect belong to PPX processors but should not be in the binary. @hannes discovered such a problem in a pull request avoid compiler-libs runtime dependency in ppx_cstruct . Examples for …

Is there a way to (semi-)automatically infer which library brings them in?

ocamlfind query -r package shows all dependencies of package. These should include compile-time dependencies. I looked at the binary directly and also inspected the linking step. I don’t know of a good way to find the packages that brings in certain dependencies. Opam 2 during installation of a pack…

You can use opam list --recursive --required-by some-package to list all recursive dependencies for some-package. Unfortunately I’ve found this includes the union of dependencies for all versions of some-package. To avoid this you should specify a specific version of some-package: opam list --recurs…

Reducing mirageos image size using ocamlclean?

Ecosystem

lindig August 27, 2018, 4:21pm 7

I asked about rising binary sizes before: Large binaries - break down the size by library? Is there a chance that the PPX mechanism is responsible for this (at least in part)?

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Reducing mirageos image size using ocamlclean?

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