From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([140.186.70.92]:56956)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <guijianfeng@cn.fujitsu.com>) id 1QoVOk-0000ha-Eh
	for qemu-devel@nongnu.org; Wed, 03 Aug 2011 02:57:47 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <guijianfeng@cn.fujitsu.com>) id 1QoVOj-00066M-Ib
	for qemu-devel@nongnu.org; Wed, 03 Aug 2011 02:57:46 -0400
Received: from [222.73.24.84] (port=64429 helo=song.cn.fujitsu.com)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <guijianfeng@cn.fujitsu.com>) id 1QoVOi-00064X-Qa
	for qemu-devel@nongnu.org; Wed, 03 Aug 2011 02:57:45 -0400
Message-ID: <4E38DA6C.7070406@cn.fujitsu.com>
Date: Wed, 03 Aug 2011 13:19:40 +0800
From: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=ISO-8859-1
Subject: [Qemu-devel] Question about posixaio thread number.
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/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: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org

Hi Anthony,

I started a guest with cache=none and aio=threads

When i did some io tests in Guest say dd like
dd if=/dev/zero oflag=direct of=/mnt/sdb1/date.img bs=4k count=262114

qemu will start one or several threads to perform IO requests.

It seems qemu makes use of its own posixaio. I'm wondering how qemu
decides how many threads should be created to perform io operation?

Thanks,
Gui