Subject: Re: Yet another base64 patch

From: "H. Peter Anvin" <[email-masked]>
Date: Wed, 13 Apr 2005 23:27:46 -0700

Christopher Li wrote:
> 
> But if you write a large number of random files, when htree has three
> levels index. htree will suffer on the effect that it dirty random block
> very quickly, most block get dirty only contain one or two new entries.
> Ext3 will choke on it due to the limited journal size.
> 
> While non-index directory, new entry are very compact on the blocks.
> So it end up dirty a lot less blocks, of course, lookup will suffer.
> 
> Depend on you want check out fast or write a big tree fast, you can't
> win it all.
> 

Actually, the subdirectory hack has the same effect, so you lose 
regardless.  Doesn't mean that you can't construct cases where the 
subdirectory hack doesn't win, but I maintain that those are likely to 
be artificial.

It's probably worth noting that you have to assume htree is on, since 
that's the typical default for a Linux installation, even if you use the 
subdirectory hack.

	-hpa