From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44781) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VkxlN-0007XD-1W for qemu-devel@nongnu.org; Mon, 25 Nov 2013 10:07:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VkxlE-0002Of-Kp for qemu-devel@nongnu.org; Mon, 25 Nov 2013 10:07:48 -0500 Received: from mx.ipv6.kamp.de ([2a02:248:0:51::16]:36893 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VkxlE-0002OX-AK for qemu-devel@nongnu.org; Mon, 25 Nov 2013 10:07:40 -0500 Message-ID: <529367C8.7080301@kamp.de> Date: Mon, 25 Nov 2013 16:07:52 +0100 From: Peter Lieven MIME-Version: 1.0 References: <1385387840-17307-1-git-send-email-pl@kamp.de> <1385387840-17307-4-git-send-email-pl@kamp.de> <529364B5.6000202@redhat.com> In-Reply-To: <529364B5.6000202@redhat.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1.8 3/6] qemu-img: add option to specify alternate iobuffer size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com On 25.11.2013 15:54, Paolo Bonzini wrote: > Il 25/11/2013 14:57, Peter Lieven ha scritto: >> since the convert process is basically a sync operation it might >> be benificial in some case to change the hardcoded I/O buffer >> size to an alternate (greater) value. > Do you really need the extra knob? You can just add to BlockLimits the > optimal transfer length, and use it unconditionally. If you say patch 5 and 3 are ok. What could be done is to remove this knob and increase the iobuf_size to cluster_size if cluster_size is greater. I do not want to increase the default iobuf size to anything greater than 2MB. I do not know why this was choosen, but maybe there was a reason for it. The storages we use here have a very strange page size of 15MB. If I sent aligned 15MB chunks the performace is about +50% compared to the original qemu-img. Peter