[kbolino]

For what it's worth, most modern file systems (JFS, XFS, ext4, reiserfs, btrfs, ...) have logarithmic (or better) directory lookup times. This is achieved using hashes and b-trees (or even hash tables).

[lubutu]

Fair point. Though anything using the standard POSIX dirent API would still get the performance hit (even if path resolution doesn't).