From: Chris Mason <chris.mason@oracle.com>
To: Paul Komkoff <i@stingr.net>
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: btrfs defrag: how does it work?
Date: Thu, 20 Jan 2011 16:38:18 -0500 [thread overview]
Message-ID: <1295559487-sup-9500@think> (raw)
In-Reply-To: <AANLkTikcNy1FdRjLu=bDpE=A7krUysmV2uLwN9jh4AF2@mail.gmail.com>
Excerpts from Paul Komkoff's message of 2011-01-19 17:31:56 -0500:
> On Wed, Jan 19, 2011 at 9:25 PM, Chris Mason <chris.mason@oracle.com>=
wrote:
> > The defrag code doesn't actually defrag. =C2=A0It opens up the file=
and
> > recows all the extents and then the delayed allocation code jumps i=
n and
> > makes the biggest possible extent that it can.
> >
> > The reason why you're still seeing extents after running the defrag
> > command is because the file hasn't been written yet, so the delayed
> > allocation code hasn't kicked in.
> >
> > If you use btrfs fi defrag -f it'll trigger writeback on the file a=
nd
> > you should see the results of the defrag sooner.
>=20
> I tried, and just tried it again, with the same file. I even tried
> doing btrfs fi sync in random order. No matter what I do, it's still
> 132 extents :)
Are you using compression?
-chris
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next prev parent reply other threads:[~2011-01-20 21:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-19 19:58 btrfs defrag: how does it work? Paul Komkoff
2011-01-19 21:25 ` Chris Mason
2011-01-19 22:31 ` Paul Komkoff
2011-01-19 22:49 ` Mitch Harder
2011-01-20 21:38 ` Chris Mason [this message]
2011-01-22 13:38 ` Paul Komkoff
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