Experiments 10-20 years back in a different project, suggested there wasn’t any real performance gain with NTFS volumes when setting the RootDirectory handle. If I recall correctly, I think NTFS at the time would be reconstructing the volume-relative path and do the regular opening on it. Things may have changed since then, though. I would’ve be quite curious to know how current windows performs
Anyway, it conceptually makes perfect sense to use the RootDirectory option when possible. I think we did so in the aforementioned project despite the lack of performance gains. Cheers, Knut. > On 4. Feb 2026, at 22:18, Dan Shelton via Cygwin <[email protected]> wrote: > > Hello, > > Why does Cygwin always use absolute paths instead of > OBJECT_ATTRIBUTES.RootDirectory in NtOpenFile(), > NtSetInformationFile() for rename and hardlinks > > This slows down Cygwin path lookups a lot, and with lots of path > elements each lookup with a relative RootDirectory might be a lot > faster, e.g. for openat(), linkat(), renameat(). > > Dan > -- > Dan Shelton - Cluster Specialist Win/Lin/Bsd > > -- > Problem reports: https://cygwin.com/problems.html > FAQ: https://cygwin.com/faq/ > Documentation: https://cygwin.com/docs.html > Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple > -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
