cp performance issue #7092
Description
As is observed in nushell/nushell#14778, uu_cp seems to have performance issues when dealing with large directories.
> timeit ~/.cargo/bin/coreutils cp cymbol_out/ -r cymbol_out_bak
52sec 95ms 4µs 960ns
> timeit ~/.cargo/bin/coreutils rm -rf cymbol_out_bak
10ms 929µs 36ns
> ~/.cargo/bin/coreutils -h
coreutils 0.0.28 (multi-call binary)
...In my case, the directory is of ~2.5GB containing a list of big json files. GNU coreutils cp takes <3s to complete the operation but uu_cp takes ~50s. I've also tried on zsh with similar results.
> time ~/.cargo/bin/coreutils cp cymbol_out -r cymbol_out_bak
real 50.43s
user 0.00s
sys 3.23s
> time ~/.cargo/bin/coreutils rm -r cymbol_out_bak
real 0.56s
user 0.00s
sys 0.56s
> time cp cymbol_out -r cymbol_out_bak
real 2.81s
user 0.00s
sys 2.81s
> time rm -r cymbol_out_bak
real 0.54s
user 0.00s
sys 0.54s