Why need to pay more time when access the array at first time?

General Usage
8

Here is the results, changed to @time a = Vector{ComplexF64}(undef, 2^25) to measure allocation time.

For WSL, the results is

  0.031786 seconds (2 allocations: 512.000 MiB, 99.88% gc time)
  0.336840 seconds
  0.048195 seconds
  0.046878 seconds

  0.031919 seconds (2 allocations: 512.000 MiB, 99.84% gc time)
  0.335299 seconds
  0.048593 seconds
  0.048650 seconds

  0.032231 seconds (2 allocations: 512.000 MiB, 99.80% gc time)
  0.336596 seconds
  0.049577 seconds
  0.048941 seconds

  0.034741 seconds (2 allocations: 512.000 MiB, 99.87% gc time)
  0.334516 seconds
  0.049514 seconds
  0.049246 seconds

  0.031316 seconds (2 allocations: 512.000 MiB, 99.88% gc time)
  0.335624 seconds
  0.049551 seconds
  0.048465 seconds

  0.034916 seconds (2 allocations: 512.000 MiB, 99.85% gc time)
  0.334452 seconds
  0.048894 seconds
  0.048763 seconds

And for REPL in windows, the results is

  0.041377 seconds (2 allocations: 512.000 MiB, 99.94% gc time)
  0.074445 seconds
  0.046818 seconds
  0.046252 seconds

  0.040182 seconds (2 allocations: 512.000 MiB, 99.86% gc time)
  0.074390 seconds
  0.048710 seconds
  0.047181 seconds

  0.039944 seconds (2 allocations: 512.000 MiB, 99.94% gc time)
  0.075219 seconds
  0.047892 seconds
  0.046741 seconds

  0.039637 seconds (2 allocations: 512.000 MiB, 99.94% gc time)
  0.074268 seconds
  0.046461 seconds
  0.046737 seconds

  0.039268 seconds (2 allocations: 512.000 MiB, 99.93% gc time)
  0.074602 seconds
  0.047076 seconds
  0.048861 seconds

  0.039869 seconds (2 allocations: 512.000 MiB, 99.94% gc time)
  0.074913 seconds
  0.048400 seconds
  0.048094 seconds

It seems that WSL cost much more times at first time. Is this because WSL is a virtual machine?