From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amit Shah Subject: Re: [RFC qemu 0/4] A PV solution for live migration optimization Date: Tue, 8 Mar 2016 16:44:43 +0530 Message-ID: <20160308111443.GN15443__738.061898346309$1457435718$gmane$org@grmbl.mre> References: <1457083967-13681-1-git-send-email-jitendra.kolhe@hpe.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1457083967-13681-1-git-send-email-jitendra.kolhe@hpe.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jitendra Kolhe Cc: ehabkost@redhat.com, kvm@vger.kernel.org, qemu-devel@nongnu.org, liang.z.li@intel.com, dgilbert@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com, mohan_parthasarathy@hpe.com, simhan@hpe.com, pbonzini@redhat.com, akpm@linux-foundation.org, virtualization@lists.linux-foundation.org, rth@twiddle.net List-Id: virtualization@lists.linuxfoundation.org On (Fri) 04 Mar 2016 [15:02:47], Jitendra Kolhe wrote: > > > > > > * Liang Li (liang.z.li@intel.com) wrote: > > > > The current QEMU live migration implementation mark the all the > > > > guest's RAM pages as dirtied in the ram bulk stage, all these pages > > > > will be processed and that takes quit a lot of CPU cycles. > > > > > > > > From guest's point of view, it doesn't care about the content in free > > > > pages. We can make use of this fact and skip processing the free pages > > > > in the ram bulk stage, it can save a lot CPU cycles and reduce the > > > > network traffic significantly while speed up the live migration > > > > process obviously. > > > > > > > > This patch set is the QEMU side implementation. > > > > > > > > The virtio-balloon is extended so that QEMU can get the free pages > > > > information from the guest through virtio. > > > > > > > > After getting the free pages information (a bitmap), QEMU can use it > > > > to filter out the guest's free pages in the ram bulk stage. This make > > > > the live migration process much more efficient. > > > > > > Hi, > > > An interesting solution; I know a few different people have been looking at > > > how to speed up ballooned VM migration. > > > > > > > Ooh, different solutions for the same purpose, and both based on the balloon. > > We were also tying to address similar problem, without actually needing to modify > the guest driver. Please find patch details under mail with subject. > migration: skip sending ram pages released by virtio-balloon driver The scope of this patch series seems to be wider: don't send free pages to a dest at all, vs. don't send pages that are ballooned out. Amit