linux-ext4 - Re: Question about ext4 online defrag test case

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Message-ID: <37d33d831001150541o1b674580u14719e72e3ad8e78@mail.gmail.com>
Date:	Fri, 15 Jan 2010 19:11:28 +0530
From:	SandeepKsinha <sandeepksinha@...il.com>
To:	Greg Freemyer <greg.freemyer@...il.com>
Cc:	Akira Fujita <a-fujita@...jp.nec.com>,
	Theodore Tso <tytso@....edu>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: Question about ext4 online defrag test case

On Fri, Jan 15, 2010 at 2:34 AM, Greg Freemyer <greg.freemyer@...il.com> wrote:
> On Thu, Jan 14, 2010 at 5:19 AM, Akira Fujita <a-fujita@...jp.nec.com> wrote:
>> Hi Ted,
>>
>>> E2defrag should hopefully be releasable in Karmic+1.
>>> There are still a lot of bugs that are still being fixed in the defrag
>>> code,
>>> some of which could cause data loss. They work fine
>>> if the system isn't under stress, sure, but acid test is to make sure
>>> things work OK even when the system is under memory pressure and
>>> swapping heavily, or when the file is being actively modified at the point
>>> where the defrag takes place.
>>
>> I found your comment about ext4 online defrag on Ubuntu BBS by accident.
>> https://bugs.launchpad.net/ubuntu/+source/e2fsprogs/+bug/321528
>>
>> I would like to address this problem so I ran e4defrag on the system
>> which was under memory pressure. But unfortunately I could not find the bug.
>> If you have already known how to reproduce this kind of problem,
>> could you teach me how?
>>
>> Regards,
>> Akira Fujita
>
> Sandeep, I've added you and I to this thread since oshm is using the
> same ext4_move_extents ioctl as E2defrag.
>
> Also, the above highlights the need for us to test ohsm relocates with
> data updates in progress.  Also with memory pressure which I had not
> really thought about before.
>

We have been testing ext4_move_extent through OHSM relocation till now.
Also, we have been testing it on real-world data
(http://edrm.net/activities/projects/data-set).

But yes we surely need to test then on a system under memory pressure.

> We can discuss that on the ohsm list if needed.
>
> Greg
>

-- 
Regards,
Sandeep
OHSM Team
https://sourceforge.net/projects/ohsm/


“To learn is to change. Education is a process that changes the learner.”
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