linux-ext4 - Re: [PATCH 01/11 RESEND] libe2p: Add new function get_fragment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 28 Jun 2011 09:53:20 -0400
From:	Greg Freemyer <greg.freemyer@...il.com>
To:	Kazuya Mio <k-mio@...jp.nec.com>
Cc:	Andreas Dilger <aedilger@...il.com>,
	Eric Sandeen <sandeen@...hat.com>, "Ted Ts'o" <tytso@....edu>,
	ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 01/11 RESEND] libe2p: Add new function get_fragment_score()

On Tue, Jun 28, 2011 at 6:21 AM, Kazuya Mio <k-mio@...jp.nec.com> wrote:
> 2011/06/26 11:16, Greg Freemyer wrote:
>>
>> I'm talking about sparse files.
>>
>> Where you might have:
>>
>> block_group1 - hole - block_group2 - hole - block_group3.
>>
>> Block_group2 has a head and a tail extent.  In my mind, from a
>> performance perspective, they are symmetric.  Meaning that having a
>> small extent at the beginning is no better and no worse than having a
>> small extent at the end.
>
> Thanks for your kind description. Your point is right. I'll think a little
> more
> about the fragmentation score.
>
> Regards,
> Kazuya Mio

Kazuya,

While you're thinking about the issue:

As I hope I've said before, for sparse file I think e4defrag should
score and defrag one block_group at a time.  Thus if a VM backing
storage file has 100 block_groups (as I'm using the term), then it
should score each of the 100 separately and if needed defrag them one
at a time.

I can see no benefit from treating a large sparse file as monolithic
for the decision process.

fyi: Is there an agreed on term for what I'm calling a block_group.  I
believe e4defrag uses the term "extent group" in the comments, but
sparse files exist in non-extent based filesystems, so it's not a very
portable name.

Greg
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html