Hello filesystem hackers, Over in coreutils issue https://bugs.gnu.org/29921 we have found that unlink()ing `n` many files seems to take in general O(n²) wall time. So far me and others (in CC) have benchmarked `rm -r` and other methods of unlink()ing multiple files and we've found approximately quadratic performance across: * ext4, XFS and zfs-on-linux on spinning disks * ext4 on SSDs * the other combinations were not tested yet Please find the exact numbers https://bugs.gnu.org/29921. So far we've observed apparently linear deletion time on: * XFS on NVMe It would be great to hear any kind of insights you may have regarding this issue, implementation details that might be relevant here, or even some quick benchmarks on your systems to confirm or refute our findings. Unless instructed otherwise, I would also go ahead and file bugs for the respective filesystem types, as quadratic deletion time makes for a bad user experience and lots of sysadmin tears. Happy new year, Niklas
