From: Fengguang Wu <fengguang.wu@gmail.com>
Subject: Re: How git affects kernel.org performance
Date: Wed, 10 Jan 2007 09:57:39 +0800
Message-ID: <20070110015739.GA26978__11276.4408383102$1168394293$gmane$org@mail.ustc.edu.cn>
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Cc: Theodore Tso <tytso@mit.edu>,
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To: Linus Torvalds <torvalds@osdl.org>
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On Tue, Jan 09, 2007 at 08:23:32AM -0800, Linus Torvalds wrote:
>
>
> On Tue, 9 Jan 2007, Fengguang Wu wrote:
> > >
> > > The fastest and probably most important thing to add is some readahead
> > > smarts to directories --- both to the htree and non-htree cases.  If
> >
> > Here's is a quick hack to practice the directory readahead idea.
> > Comments are welcome, it's a freshman's work :)
>
> Well, I'd probably have done it differently, but more important is whether
> this actually makes a difference performance-wise. Have you benchmarked it
> at all?

Yes, a trivial test shows a marginal improvement, on a minimal debian system:

# find / | wc -l
13641

# time find / > /dev/null

real    0m10.000s
user    0m0.210s
sys     0m4.370s

# time find / > /dev/null

real    0m9.890s
user    0m0.160s
sys     0m3.270s

> Doing an
>
> 	echo 3 > /proc/sys/vm/drop_caches
>
> is your friend for testing things like this, to force cold-cache
> behaviour..

Thanks, I'll work out numbers on large/concurrent dir accesses soon.

Regards,
Wu