Subject: Re: Yet another base64 patch

From: "H. Peter Anvin" <[email-masked]>
Date: Thu, 14 Apr 2005 10:02:55 -0700

Linus Torvalds wrote:
> 
> So why is "base64" worse than the stock one?
> 
> As mentioned, the "flat" version may be faster, but it really isn't an
> option. 32000 objects is peanuts. Any respectable source tree may hit that
> in a short time, and will break in horrible ways on many Linux
> filesystems.
> 

If it does, it's not because of n_link; see previous email.

I have used ext2 filesystems with hundreds of thousands of files per 
directory back in 1996.  It was slow but didn't break anything.

The only filesystem I know of which has a 2^16 entry limit is FAT.

> So you need at least a single level of subdirectory. 
> 
> What I don't get is why the stock hex version would be better than base64.
> 
> I like the result, I just don't _understand_ it.

The base64 version has 2^12 subdirectories instead of 2^8 (I just used 2 
characters as the hash key just like the hex version.)  So it ascerbates 
the performance penalty of subdirectory hashing.

	-hpa