From mboxrd@z Thu Jan 1 00:00:00 1970 From: Orit Wasserman Subject: Re: [PATCH 00/21][RFC] postcopy live migration Date: Sun, 01 Jan 2012 11:43:34 +0200 Message-ID: <4F002AC6.7080007@redhat.com> References: <4EFCEC38.3080308@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, satoshi.itoh@aist.go.jp, t.hirofuchi@aist.go.jp, Juan Quintela , Michael Roth , qemu-devel@nongnu.org, Isaku Yamahata To: Anthony Liguori Return-path: In-Reply-To: <4EFCEC38.3080308@codemonkey.ws> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org On 12/30/2011 12:39 AM, Anthony Liguori wrote: > On 12/28/2011 07:25 PM, Isaku Yamahata wrote: >> Intro >> ===== >> This patch series implements postcopy live migration.[1] >> As discussed at KVM forum 2011, dedicated character device is used for >> distributed shared memory between migration source and destination. >> Now we can discuss/benchmark/compare with precopy. I believe there are >> much rooms for improvement. >> >> [1] http://wiki.qemu.org/Features/PostCopyLiveMigration >> >> >> Usage >> ===== >> You need load umem character device on the host before starting migration. >> Postcopy can be used for tcg and kvm accelarator. The implementation depend >> on only linux umem character device. But the driver dependent code is split >> into a file. >> I tested only host page size == guest page size case, but the implementation >> allows host page size != guest page size case. >> >> The following options are added with this patch series. >> - incoming part >> command line options >> -postcopy [-postcopy-flags] >> where flags is for changing behavior for benchmark/debugging >> Currently the following flags are available >> 0: default >> 1: enable touching page request >> >> example: >> qemu -postcopy -incoming tcp:0:4444 -monitor stdio -machine accel=kvm >> >> - outging part >> options for migrate command >> migrate [-p [-n]] URI >> -p: indicate postcopy migration >> -n: disable background transferring pages: This is for benchmark/debugging >> >> example: >> migrate -p -n tcp::4444 >> >> >> TODO >> ==== >> - benchmark/evaluation. Especially how async page fault affects the result. > > I'll review this series next week (Mike/Juan, please also review when you can). > > But we really need to think hard about whether this is the right thing to take into the tree. I worry a lot about the fact that we don't test pre-copy migration nearly enough and adding a second form just introduces more things to test. > > It's also not clear to me why post-copy is better. If you were going to sit down and explain to someone building a management tool when they should use pre-copy and when they should use post-copy, what would you tell them? Start with pre-copy , if it doesn't converge switch to post-copy Orit > > Regards, > > Anthony Liguori > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:36225) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RhHxt-0000oo-G1 for qemu-devel@nongnu.org; Sun, 01 Jan 2012 04:44:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RhHxr-0005vN-LC for qemu-devel@nongnu.org; Sun, 01 Jan 2012 04:44:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44853) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RhHxr-0005tU-CO for qemu-devel@nongnu.org; Sun, 01 Jan 2012 04:44:27 -0500 Message-ID: <4F002AC6.7080007@redhat.com> Date: Sun, 01 Jan 2012 11:43:34 +0200 From: Orit Wasserman MIME-Version: 1.0 References: <4EFCEC38.3080308@codemonkey.ws> In-Reply-To: <4EFCEC38.3080308@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 00/21][RFC] postcopy live migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: kvm@vger.kernel.org, satoshi.itoh@aist.go.jp, t.hirofuchi@aist.go.jp, Juan Quintela , Michael Roth , qemu-devel@nongnu.org, Isaku Yamahata On 12/30/2011 12:39 AM, Anthony Liguori wrote: > On 12/28/2011 07:25 PM, Isaku Yamahata wrote: >> Intro >> ===== >> This patch series implements postcopy live migration.[1] >> As discussed at KVM forum 2011, dedicated character device is used for >> distributed shared memory between migration source and destination. >> Now we can discuss/benchmark/compare with precopy. I believe there are >> much rooms for improvement. >> >> [1] http://wiki.qemu.org/Features/PostCopyLiveMigration >> >> >> Usage >> ===== >> You need load umem character device on the host before starting migration. >> Postcopy can be used for tcg and kvm accelarator. The implementation depend >> on only linux umem character device. But the driver dependent code is split >> into a file. >> I tested only host page size == guest page size case, but the implementation >> allows host page size != guest page size case. >> >> The following options are added with this patch series. >> - incoming part >> command line options >> -postcopy [-postcopy-flags] >> where flags is for changing behavior for benchmark/debugging >> Currently the following flags are available >> 0: default >> 1: enable touching page request >> >> example: >> qemu -postcopy -incoming tcp:0:4444 -monitor stdio -machine accel=kvm >> >> - outging part >> options for migrate command >> migrate [-p [-n]] URI >> -p: indicate postcopy migration >> -n: disable background transferring pages: This is for benchmark/debugging >> >> example: >> migrate -p -n tcp::4444 >> >> >> TODO >> ==== >> - benchmark/evaluation. Especially how async page fault affects the result. > > I'll review this series next week (Mike/Juan, please also review when you can). > > But we really need to think hard about whether this is the right thing to take into the tree. I worry a lot about the fact that we don't test pre-copy migration nearly enough and adding a second form just introduces more things to test. > > It's also not clear to me why post-copy is better. If you were going to sit down and explain to someone building a management tool when they should use pre-copy and when they should use post-copy, what would you tell them? Start with pre-copy , if it doesn't converge switch to post-copy Orit > > Regards, > > Anthony Liguori >