From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:58280) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UCWww-00065U-Gt for qemu-devel@nongnu.org; Mon, 04 Mar 2013 10:05:12 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UCWwn-0001Fk-GS for qemu-devel@nongnu.org; Mon, 04 Mar 2013 10:05:10 -0500 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:42365) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UCWwm-0001Bq-Sw for qemu-devel@nongnu.org; Mon, 04 Mar 2013 10:05:01 -0500 Received: from /spool/local by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 5 Mar 2013 00:58:27 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id A8E61357802D for ; Tue, 5 Mar 2013 02:04:50 +1100 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r24F4lRN35127446 for ; Tue, 5 Mar 2013 02:04:47 +1100 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r24F4nqD023750 for ; Tue, 5 Mar 2013 02:04:49 +1100 Message-ID: <5134B7F0.5020008@linux.vnet.ibm.com> Date: Mon, 04 Mar 2013 23:04:16 +0800 From: Wenchao Xia MIME-Version: 1.0 References: <1362038985-19008-1-git-send-email-xiawenc@linux.vnet.ibm.com> <20130228105035.GE2429@dhcp-200-207.str.redhat.com> <513013F0.2030007@linux.vnet.ibm.com> In-Reply-To: <513013F0.2030007@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 0/4] savevm: save vmsate with fixed size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: stefanha@gmail.com, aliguori@us.ibm.com, pbonzini@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com >> You probably get some improvements of the file size when the migration >> takes a while, depending on how much of the memory actually has to be >> saved. You might however end up with a lot more small writes instead of >> some big ones before, which might hurt performance. >> >> Do you have any data about the resulting performance and file size? >> > ah, an important issue I haven't test, thanks for tipping it, let > me add code for migration to file, and have a test. It also > can be optimized a bit in qemu_fseek(), but IMHO the optimization > for small writes would better goto block layer either in qemu > or underling components in system. > Hi,Juan talking about performance, in migration there are two buffer used, one in qemu_file as static array, and one in migration as dynamic allocated buffer, should they be merged to avoid extra memcpy?