this post was submitted on 25 Apr 2025
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It isn't normally, but it, like e.g. Ext4, allows case insensitivity mostly for the sake of Wine.
But Wine could handle the case insensitivity though? NTFS is case sensitive.
It does, but having case insensitivity in the file system can get you better performance.
How would that happen?
If you're running Wine on a case-sensitive file system, and you it tries to open a file, it would first try to open a file whose case matches exactly. But if it doesn't find one, it would then need to list all the files in the directory, normalize their case, and go through them all to see if there is a file with the given name but in a different case. That can take some time if there is a lot of files in the directory.
But if you're on a case-insensitive filesystem, the FS can keep case-normalized names of all files on disk, so you can do a case-insensitive open just as fast as you can do a case-sensitive open.
BTW, another application that can benefit from this is Samba, since SMB is case-insensitive.
That –at best– gives you the same performance.
EDIT: Ok, I misunderstood – you meant the performance of "case insensitive in kernel" vs. "case insensitive in userspace". I get your point now.
No? Either the application implements its own case-insensitive index, or you'll have strictly worse performance than an implementation in the file system. The application would have to make multiple syscalls (which have a fixed overhead).