From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54592) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aLMhl-0005B1-Ip for qemu-devel@nongnu.org; Mon, 18 Jan 2016 22:11:38 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aLMhi-0002WE-Ch for qemu-devel@nongnu.org; Mon, 18 Jan 2016 22:11:37 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:46931) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aLMhh-0002W0-Js for qemu-devel@nongnu.org; Mon, 18 Jan 2016 22:11:34 -0500 References: <1452851297-11198-1-git-send-email-liang.z.li@intel.com> <5698C735.3020409@huawei.com> <569CA9CC.80603@huawei.com> From: Hailiang Zhang Message-ID: <569DA952.3090501@huawei.com> Date: Tue, 19 Jan 2016 11:11:14 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] migration: not send zero page header in ram bulk stage List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Li, Liang Z" , "qemu-devel@nongnu.org" Cc: "amit.shah@redhat.com" , "pbonzini@redhat.com" , peter.huangpeng@huawei.com, "dgilbert@redhat.com" , "quintela@redhat.com" On 2016/1/19 9:26, Li, Liang Z wrote: >> On 2016/1/15 18:24, Li, Liang Z wrote: >>>> It seems that this patch is incorrect, if the no-zero pages are >>>> zeroed again during !ram_bulk_stage, we didn't send the new zeroed >>>> page, there will be an error. >>>> >>> >>> If not in ram_bulk_stage, still send the header, could you explain why it's >> wrong? >>> >>> Liang >>> >> >> I have made a mistake, and yes, this patch can speed up the live migration >> time, especially when there are many zero pages, it will be more obvious. >> I like this idea. Did you test it with postcopy ? Does it break postcopy ? >> > > Not yet, I saw Dave's comment's, it will beak post copy, it's not hard to fix this. > A more important thing is Paolo's comments, I don't know in which case this patch will break LM. Do you have any idea about this? > Hope that QEMU don't write data to the block 'pc.ram'. > Paolo is right, for VM in destination, QEMU may write VM's memory before VM starts. So your assumption that "VM's RAM pages are initialized to zero" is incorrect. This patch will break LM. > Liang > >> Thanks, >> zhanghailiang >> > > . >