Unusually long GC times in 1.10 and master

[gitboy16]

Hi,

Sorry for the bad subject name but I am struggling to understand what is going on in the below code.
I noticed that vector allocation sometimes take an unusual amount of time to run. Please note the ~100ms for Julia 1.11 below. This can also be seen in 1.10.
Note I am on windows.

Regards

import Random, Dates

Random.seed!(1234)
xp = rand(10^8)

function foofoo(xp::AbstractVector{T}, len = length(xp)) where {T}
    t = Vector{Dates.DateTime}(undef, 2)
    t[1] = Dates.now()    
    vans = Vector{T}(undef, len)
    t[2] = Dates.now()
    println("Time: $(t[2]-t[1])")
    vans
end

for _ in 1:10
    foofoo(xp);
end

JULIA 1.9.2

julia> include("Untitled.jl")
Time: 1 millisecond
Time: 1 millisecond
Time: 0 milliseconds
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 1 millisecond

julia> include("Untitled.jl")
Time: 1 millisecond
Time: 1 millisecond
Time: 1 millisecond
Time: 0 milliseconds
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds

julia> include("Untitled.jl")
Time: 1 millisecond
Time: 1 millisecond
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 1 millisecond

julia> versioninfo()
Julia Version 1.9.2
Commit e4ee485e90 (2023-07-05 09:39 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 8 × Intel(R) Xeon(R) Gold 6254 CPU @ 3.10GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, skylake-avx512)
  Threads: 1 on 8 virtual cores

JULIA 1.11.0-DEV

julia> include("Untitled.jl")
Time: 0 milliseconds
Time: 13 milliseconds
Time: 106 milliseconds
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds

julia> include("Untitled.jl")
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 131 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds

julia> include("Untitled.jl")
Time: 1 millisecond
Time: 13 milliseconds
Time: 107 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds

julia> versioninfo()
Julia Version 1.11.0-DEV.291
Commit 30a73de681 (2023-08-17 02:32 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 8 × Intel(R) Xeon(R) Gold 6254 CPU @ 3.10GHz
  WORD_SIZE: 64
  LLVM: libLLVM-15.0.7 (ORCJIT, skylake-avx512)
  Threads: 1 on 8 virtual cores

[gbaraldi]

I can't reproduce on linux ;(

[d-netto]

Was able to reproduce the slowdown on macOS, though was not as severe on my machine:

• 1.9.2:

Time: 2 milliseconds
Time: 1 millisecond
Time: 1 millisecond
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds

• master:

Time: 2 milliseconds
Time: 1 millisecond
Time: 23 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds
Time: 0 milliseconds

Julia Version 1.9.2
Commit e4ee485e90* (2023-07-05 09:39 UTC)
Platform Info:
  OS: macOS (arm64-apple-darwin22.6.0)
  CPU: 12 × Apple M2 Max
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, apple-m1)
  Threads: 1 on 8 virtual cores