Improve REPL latency

[andreasnoack]

Currently, the new system image doesn't include the precompile information in generate_precompile.jl. Once JuliaLang/julia#30367 is included in a Julia release, it should be possible to fix this issue and therefore match the latency of the official binaries.

[Jutho]

Thanks for this package. Is there a manual fix for this issue if you have built Julia from source?

[PallHaraldsson]

@Jutho

Is there a manual fix for this issue if you have built Julia from source?

I suppose. JuliaPro had MKL at some point. I'm not sure how it was integrated, but you would have to compile Julia without GPL, and probably do more to fix the latency. As the README says, this can be fixed with Julia 1.1 (now out). I'm not sure how 1.1 fits into this, but at least a Julia (was it 0.6 version?) distro with MKL was possible (and still is available; just not recommended).

[Jutho]

Would it be just a matter of rerunning the generate_precompile.jl script? I have not tried and am not very familiar with everything related to the sysimg of julia.

[KristofferC]

Yes, it is just a matter of running that script during the creation of the sysimage.

[Jutho]

My apologies but just to make sure that I understand correctly, in some more detail:

• Install Julia (only from source, or also with binary, e.g. 1.1 ?)
• Start Julia, run import Pkg; Pkg.add("MKL")
• Find "generate_precompile.jl" and do include("generate_precompile.jl") in running Julia session?

I will give it a try asap.

[KristofferC]

No, that is not correct. The include("generate_precompile.jl") needs to happen during the generation of the sysimg so somewhere in the call to PackageCompiler.

[andreasnoack]

We can't do this for binary distributions yet since generate_precompile.jl isn't included, see JuliaLang/julia#30367. I guess we should really just merge that PR.

[Jutho]

so somewhere in the call to PackageCompiler.

I am still confused after reading JuliaLang/julia#30367: Is it at this point clear what exactly needs to happen, and is it just a matter of e.g. bundling the "generate_precompile.jl" script with the binary? Can't it just be downloaded from github when the package is build? Anyway, if so, is it possible to provide a clear set of instructions what exactly needs to be done ("change this line to that, add that line") by non-expert people (i.e. me) that want to try this out with a julia distro built from source?

Or is it still unclear exactly what to do?

[andreasnoack]

We could just download it but I'd prefer not to. Even if it was available, I'd have to figure out the correct invocation of PackageCompiler since the function I'm currently using doesn't allow me to add a file when generating the system image. It shouldn't be hard, though.

[KristofferC]

Can use PackageCompiler.build_sysimg(PackageCompiler.default_sysimg_path(), "generate_precompile.jl")

[tpapp]

The README says that REPL latency would be fixed with Julia 1.1, is it still an issue?

[andreasnoack]

Unfortunately, it is.

[aminya]

Is this issue abandoned?

[Jutho]

I've had no problems with the final suggestion, i.e. install MKL.jl and PackageCompiler.jl, and after building MKL, just run

import PackageCompiler
PackageCompiler.build_sysimg(PackageCompiler.default_sysimg_path(), "generate_precompile.jl")

You only need to make sure to have the file "generate_precompile.jl" (and execute this command in the directory where the file is located). If you build Julia from source, its in julia/contrib/, otherwise you can still download it from Github (preferably the version that matches the version of Julia you have installed, which you can obtain by browsing the source code for the release version).