I don't know the technical details, but the kernel docs say "It exists because implementation in user-space, using existing tools, cannot match Windows performa

I don't know the technical details, but the kernel docs say "It exists because implementation in user-space, using existing tools, cannot match Windows performance while offering accurate semantics." https://docs.kernel.org/userspace-api/ntsync.html https://docs.kernel.org/userspace-api/ntsync.html