From: Greg Freemyer <greg.freemyer@gmail.com>
Subject: Re: [PATCH 1/3] e4defrag: output blocks per extent by -c option
Date: Wed, 30 Sep 2009 14:28:12 -0400
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Cc: linux-ext4@vger.kernel.org, Theodore Tso <tytso@mit.edu>
To: Kazuya Mio <k-mio@sx.jp.nec.com>
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2009/9/30 Kazuya Mio <k-mio@sx.jp.nec.com>:
> e4defrag with -c option outputs "ratio" that means the levels of
> fragmentation. However, it's difficult for users to understand, so we=
 will
> use blocks per extent instead of ratio.
>
> Before:
> # e4defrag -c /mnt/mp1/file
> <File> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 now/best =A0 =A0 =A0 =A0 =A0ratio
> /mnt/mp1/file =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 14/1 =A0 =A0 =A0 =A0 =A0 =A0 0.01%
>
> =A0Total/best extents =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 14/1
> =A0Fragmentation ratio =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A00.01%
> =A0Fragmentation score =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A00.10
> =A0[0-30 no problem: 31-55 a little bit fragmented: 55- needs defrag]
> =A0This file(/mnt/mp1/file) does not need defragmentation.
> =A0Done.
>
> After:
> # e4defrag -c /mnt/mp1/file
> <File> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 now/best =A0 =A0 =A0 =A0blk/ext
> /mnt/mp1/file =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 14/1 =A0 =A0 =A0 =A0 =A0 =A0 =A07142
>
> =A0Total/best extents =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 14/1
> =A0Average blocks per extent =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A07142
> =A0Fragmentation score =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A00
> =A0[0-30 no problem: 31-55 a little bit fragmented: 55- needs defrag]
> =A0This file(/mnt/mp1/file) does not need defragmentation.
> =A0Done.

RFC

If we are going go that far (which I like), how about adding the avg
extent size in bytes.  (ie. 7142 * blocksize I assume).

Also a note about the max blocks / extent might be good.

ie. Add a more or less hard coded line
Ext4 max blocks per extent     32,768  (128MiB)

Otherwise your typical user won't know what perfect is.

Greg
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