Julia 1.11 sometimes takes 5 seconds to start on Windows

[sumiya11]

As illustrated by :

PS> Measure-Command { julia  --startup-file=no -e "println(1 + 2)" }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 5
Milliseconds      : 853
Ticks             : 58533488
TotalDays         : 6.77470925925926E-05
TotalHours        : 0.00162593022222222
TotalMinutes      : 0.0975558133333333
TotalSeconds      : 5.8533488
TotalMilliseconds : 5853.3488

Other times it is fine:

PS> Measure-Command { julia  --startup-file=no -e "println(1 + 2)" }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 0
Milliseconds      : 374
Ticks             : 3749323
TotalDays         : 4.33949421296296E-06
TotalHours        : 0.000104147861111111
TotalMinutes      : 0.00624887166666667
TotalSeconds      : 0.3749323
TotalMilliseconds : 374.9323

The 5 second case sometimes happens when running the command in a fresh terminal. Subsequent calls are fine.

I have not observed this on 1.10.

julia> versioninfo()
Julia Version 1.11.1
Commit 8f5b7ca12a (2024-10-16 10:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 8 × Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, skylake)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

[giordano]

I have no clue if this is a thing on Windows, but I believe on macOS the first time you run a newly downloaded executable (e.g. a new Julia version through juliaup) you have a noticeable lag, I suspect because the operating system is performing some sort of security checks. After that, all is fine. Could it be that an antivirus or something like that is holding your process for some time? But that wouldn't explain the difference v1.10 vs v1.11. Would you be able to profile the process? But don't ask me how to do it on windows because I have no idea 🙂

[sumiya11]

Profiling the command julia --startup-file=no -e "println(1 + 2)" in VTune in user mode, I get the following.

Note: for some reason, VTune only collects counters for 1.6 seconds out of the total 5. The rest seems to be lost somewhere; not sure what to make of it.

EDIT: ah, hm, out of 5 seconds wall time, CPU time is 1.6 seconds.

[giordano]

Note that you need to export the environment variable ENABLE_JITPROFILING=1 before running VTune, to get the name of the JIT'ed functions: https://docs.julialang.org/en/v1/manual/profile/#External-Profiling