Re: Yet another base64 patch

From: H. Peter Anvin <hpa@zytor.com>
Date: Apr 14, 2005, 17:02 UTC
Message-ID: <425EA23F.6010900@zytor.com>
In-Reply-To: <Pine.LNX.4.58.0504140114260.7211@ppc970.osdl.org>

Linus Torvalds wrote:

Show 8 quoted lines

> 
> 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.

Show 5 quoted lines

> 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