# PackageCompiler hangs while compiling nonincremental system image on Julia v1.11

**URL:** <https://discourse.julialang.org/t/packagecompiler-hangs-while-compiling-nonincremental-system-image-on-julia-v1-11/128099>\
**Category:** General Usage\
**Created:** [April 15, 2025, 2:31pm UTC](https://discourse.julialang.org/t/packagecompiler-hangs-while-compiling-nonincremental-system-image-on-julia-v1-11/128099 "2025-04-15T14:31:09Z")\
**Posts on this page:** 1\
**Showing post:** 38

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**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [April 17, 2025, 8:39am UTC](https://discourse.julialang.org/t/packagecompiler-hangs-while-compiling-nonincremental-system-image-on-julia-v1-11/128099/38 "2025-04-17T08:39:14Z")

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> [@About Julia's development policy regarding Windows](https://discourse.julialang.org/t/about-julias-development-policy-regarding-windows/128011/58):
>
> Take the case of _PackageCompiler_. Since Julia 1.11 one cannot use more than one thread. This reduces the compilation speed a lot (for me by about 40%).

Is this really true? I can imagine 1.11 being slower in itself, but I don’t think anything in the PackageCompiler process should use threads (except a part of the very last step in outputting the sysimage and I am not sure that even uses the number of julia threads). If you turn off threading, does 1.10 also become 40% slower?

Could you explain what part of PackageCompiler you think gets faster with your threads environment variable?

I just tested myself and didn’t notice a difference (on 1.10):

```julia
# Without threads
julia> using PackageCompiler

julia> ENV["JULIA_NUM_THREADS"]
"1"

julia> Threads.nthreads()
1

julia> @time create_app("examples/MyApp", "MyAppCompiled"; force=true)
...
150.910366 seconds (1.92 M allocations: 151.919 MiB, 0.01% gc time, 0.28% compilation time)

# With threads
julia> using PackageCompiler

julia> ENV["JULIA_NUM_THREADS"]
"10"

julia> Threads.nthreads()
10

julia> @time create_app("examples/MyApp", "MyAppCompiled"; force=true)
...
148.749071 seconds (3.82 M allocations: 291.721 MiB, 0.03% gc time, 0.28% compilation time)

```

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