bug#35531: problem with ls in coreutils

[Paul Eggert]

It's probably something inside the kernel (e.g., filesystem code).

What does the shell command 'strace -o /tmp/tr -s 128 -T ls -U -1
dirname | wc' say? You can see which system calls are taking the most
time by then running 'sort -t"<" -k2n /tmp/tr'. On my platform (Fedora
29 x86-64 ext4, an older desktop with only disk drives), the hoggiest
syscalls are getdents64, which are as much as 24 ms per call when the
data are not cached, and more like 0.7 ms per call when the data are
cached (each such call retrieves about 1000 directory entries). What do
you see?