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Date: Thu, 20 Jun 2002 00:54:52 +0100
From: "Stephen C. Tweedie" <sct@redhat.com>
To: Andrew Morton <akpm@zip.com.au>
Cc: Christopher Li <chrisl@gnuchina.org>,
       "Stephen C. Tweedie" <sct@redhat.com>,
       Alexander Viro <viro@math.psu.edu>, DervishD <raul@pleyades.net>,
       Linux-kernel <linux-kernel@vger.kernel.org>,
       ext2-devel@lists.sourceforge.net
Subject: Re: [Ext2-devel] Re: Shrinking ext3 directories
Message-ID: <20020620005452.M5119@redhat.com>
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In-Reply-To: <20020619234340.A24016@redhat.com>; from sct@redhat.com on Wed, Jun 19, 2002 at 11:43:40PM +0100
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Hi,

On Wed, Jun 19, 2002 at 11:43:40PM +0100, Stephen C. Tweedie wrote:

> Well, it has some interesting properties, such as the hash function
> being a constant:
> 
> +	return 80; /* FIXME: for test only */
> 
> which I assume was an artifact of some testing Christopher was doing.
> :)
> 
> I'm checking out a proper hash function at the moment.

Done, checked into ext3 cvs (features-branch again.)

Deleting and recreating 100,000 files with this kernel:

[root@spock test0]# time xargs rm -f < /root/flist.100000 

real    0m14.305s
user    0m0.750s
sys     0m5.430s
[root@spock test0]# time xargs touch < /root/flist.100000 

real    0m16.244s
user    0m0.530s
sys     0m6.660s

that's an average of 160usec per create, 140usec per delete elapsed
time, and 66/54usec respectively system time.  

I assume the elapsed time is greater only because we're starting to
wrap the journal due to the large amount of metadata being touched
(we're touching a lot of inodes doing the above, which I could avoid
by making hard links instead of new files.)  Certainly, limiting the
test to 10,000 files lets it run at 100% cpu.

--Stephen
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