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To: Andreas Dilger <adilger@turbolabs.com>
Cc: Andrew Morton <akpm@zip.com.au>, "Albert D. Cahalan" <acahalan@cs.uml.edu>,
        Mike Fedyk <mfedyk@matchmail.com>, lkml <linux-kernel@vger.kernel.org>,
        ext2-devel@lists.sourceforge.net
Subject: Re: [Ext2-devel] disk throughput
In-Reply-To: <20011104193232.A16679@mikef-linux.matchmail.com> <200111050554.fA55swt273156@saturn.cs.uml.edu> <3BE647F4.AD576FF2@zip.com.au> <20011105131636.C3957@lynx.no>
From: m@mo.optusnet.com.au
Date: 06 Nov 2001 07:28:02 +1100
In-Reply-To: Andreas Dilger's message of "Mon, 5 Nov 2001 13:16:37 -0700"
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Andreas Dilger <adilger@turbolabs.com> writes:
> On Nov 05, 2001  00:04 -0800, Andrew Morton wrote:
[..]
> > With the ialloc.c change, plus the other changes I mentioned
> > the time to create all these directories and files and then run
> > /bin/sync fell from 1:53 to 0:28.  Fourfold.
> 
> In the end, though, while the old heuristic has a good theory, it _may_
> be that in practise, you are _always_ seeking to get data from different
> groups, rather than _theoretically_ seeking because of fragmented files.
> I don't know what the answer is - probably depends on finding "valid"
> benchmarks (cough).

Another heuristic to try make be to only use a different blockgroup
for when the mkdir()s are seperate in time. i.e. rather than
doing 
	if ( 0 && .. 
use something like
	if ((last_time + 100) < jiffes && ... 
		last_time = jiffies;
which would in theory use the old behaviour for sparodic mkdirs
and the new behaviour for things like 'untar' et al.

M.
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