From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=43271 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1OYJ9i-0007oH-J6
	for qemu-devel@nongnu.org; Mon, 12 Jul 2010 09:34:47 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <gg.mariotti@gmail.com>) id 1OYJ9h-0008Iu-Ih
	for qemu-devel@nongnu.org; Mon, 12 Jul 2010 09:34:46 -0400
Received: from mail-wy0-f173.google.com ([74.125.82.173]:40638)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <gg.mariotti@gmail.com>) id 1OYJ9h-0008Il-Cp
	for qemu-devel@nongnu.org; Mon, 12 Jul 2010 09:34:45 -0400
Received: by wyb35 with SMTP id 35so3533743wyb.4
	for <qemu-devel@nongnu.org>; Mon, 12 Jul 2010 06:34:44 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <4C3ABF96.9070405@msgid.tls.msk.ru>
References: <AANLkTin1uF6WbVvxJ84oO1NKnCU-6VHrmWU1XFYTlqtp@mail.gmail.com>
	<4C3ABF96.9070405@msgid.tls.msk.ru>
Date: Mon, 12 Jul 2010 15:34:44 +0200
Message-ID: <AANLkTim7A9teJtk5c1jh2g6mDv07HAi72d5S6WveL8Gp@mail.gmail.com>
From: Giangiacomo Mariotti <gg.mariotti@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Subject: [Qemu-devel] Re: BTRFS: Unbelievably slow with kvm/qemu
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-kernel@vger.kernel.org, qemu-devel <qemu-devel@nongnu.org>

On Mon, Jul 12, 2010 at 9:09 AM, Michael Tokarev <mjt@tls.msk.ru> wrote:
>
> This looks quite similar to a problem with ext4 and O_SYNC which I
> reported earlier but no one cared to answer (or read?) - there:
> http://permalink.gmane.org/gmane.linux.file-systems/42758
> (sent to qemu-devel and linux-fsdevel lists - Cc'd too). =C2=A0You can
> try a few other options, esp. cache=3Dnone and re-writing some guest
> files to verify.
>
> /mjt
>
Either way, changing to cache=3Dnone I suspect wouldn't tell me much,
because if it's as slow as before, it's still unusable and if instead
it's even slower, well it'd be even more unusable, so I wouldn't be
able to tell the difference. What I can say for certain is that with
the exact same virtual hd file, same options, same system, but on an
ext3 fs there's no problem at all, on a Btrfs is not just slower, it
takes ages.

--=20
Giangiacomo