From: H. Peter Anvin <hpa@zytor.com>
Date: Thu, 14 Apr 2005 06:27:46 GMT
Subject: Re: Yet another base64 patch
Message-ID: <425E0D62.9000401@zytor.com>
In-Reply-To: <20050414024228.GC18655@64m.dyndns.org>

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