33% to 69% startup regression on nightly

[PallHaraldsson]

Does anyone know why there's a regression? And why it seems worse under load?

$ hyperfine 'julia +nightly -e ""'
Benchmark 1: julia +nightly -e ""
  Time (mean ± σ):     236.2 ms ±  18.5 ms    [User: 294.3 ms, System: 83.6 ms]
  Range (min … max):   215.0 ms … 259.0 ms    11 runs

$ hyperfine 'julia +1.11 -e ""'
Benchmark 1: julia +1.11 -e ""
  Time (mean ± σ):     181.2 ms ±  13.7 ms    [User: 264.9 ms, System: 58.4 ms]
  Range (min … max):   160.5 ms … 198.2 ms    16 runs

For mean, not min, it's only 30% slower but for max it's 31% or if comparing with Firefox running, 64%. On nightly without it... compared to 1.11 with Firefox, at 69%....

I see no extra precompiles when starting (without a REPL, so not the reason), but more with:

$ julia +nightly --trace-compile=stderr
precompile(Tuple{typeof(Base.setindex!), Base.EnvDict, Bool, String})
precompile(Tuple{typeof(Base.setindex!), Base.EnvDict, Int64, String})
precompile(Tuple{Type{Pair{A, B} where B where A}, Array{String, 1}, Expr})
precompile(Tuple{typeof(Base.print_to_string), String, String, String, String, String, String, String, String, String, String, Vararg{Any}})
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.13.0-DEV.138 (2025-02-28)
 _/ |\__'_|_|_|\__'_|  |  Commit 5f13cd2ddc0 (0 days old master)
|__/                   |

julia> precompile(Tuple{typeof(Base.getproperty), REPL.REPLBackend, Symbol})
precompile(Tuple{typeof(Base.Sort.searchsortedfirst), Array{String, 1}, String})
precompile(Tuple{typeof(Base.insert!), Array{String, 1}, Int64, String})


vs.

$ julia +1.11 --trace-compile=stderr
precompile(Tuple{typeof(Base.setindex!), Base.EnvDict, Bool, String})
precompile(Tuple{typeof(Base.setindex!), Base.EnvDict, Int64, String})
precompile(Tuple{Type{Pair{A, B} where B where A}, Array{String, 1}, Expr})