Data Leak in DataLoader ?

[camilodlt]

The MLUtils.DataLoader does not free up memory even if the object is garbage collected ? :

➜  tmp julia --project -t 16
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org/
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.6 (2025-07-09)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using MLUtils

julia> function random_data(n=1000)
           return [rand(Float32, 1000,1000, 10) for i in 1:n]
       end
random_data (generic function with 2 methods)

julia> function test(i)
           data = random_data(i*10)
           dl = DataLoader(data; batchsize = 100)
           nothing
       end
test (generic function with 1 method)

julia> for i in 1:100
           @info "RAM left : $(Sys.free_memory()/(2^20))"
           test(i*10)
           GC.gc(true)
           GC.gc()
       end
[ Info: RAM left : 108832.73046875
[ Info: RAM left : 105014.9375
[ Info: RAM left : 100209.421875
[ Info: RAM left : 96386.6953125
[ Info: RAM left : 92556.125
[ Info: RAM left : 88755.32421875
[ Info: RAM left : 84891.40625
[ Info: RAM left : 82037.58984375
[ Info: RAM left : 77238.71875
[ Info: RAM left : 74415.28515625
[ Info: RAM left : 69477.1484375
[ Info: RAM left : 65713.12109375
[ Info: RAM left : 62047.74609375
[ Info: RAM left : 58244.33203125
[ Info: RAM left : 53576.16015625
[ Info: RAM left : 50848.9375

Running the GC after the loop can free all the ram.
Running the loop without the dataloader frees at every iteration