From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 75B728DA8 for ; Wed, 28 Oct 2015 13:29:10 +0100 (CET) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP; 28 Oct 2015 05:29:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,209,1444719600"; d="scan'208";a="821399290" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.66.49]) by fmsmga001.fm.intel.com with ESMTP; 28 Oct 2015 05:29:08 -0700 Date: Wed, 28 Oct 2015 20:30:39 +0800 From: Yuanhan Liu To: Amnon Ilan Message-ID: <20151028123039.GA29042@yliu-dev.sh.intel.com> References: <20151014000508-mutt-send-email-mst@redhat.com> <20151016073738.GK3115@yliu-dev.sh.intel.com> <985011766.3510996.1446025964838.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <985011766.3510996.1446025964838.JavaMail.zimbra@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: dev@dpdk.org, =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , "Michael S. Tsirkin" Subject: Re: [dpdk-dev] dpdk/vhost-user and VM migration X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Oct 2015 12:29:10 -0000 On Wed, Oct 28, 2015 at 05:52:44AM -0400, Amnon Ilan wrote: > > > ----- Original Message ----- > > From: "Yuanhan Liu" > > To: "Michael S. Tsirkin" > > Cc: dev@dpdk.org > > Sent: Friday, October 16, 2015 10:37:38 AM > > Subject: Re: [dpdk-dev] dpdk/vhost-user and VM migration > > > > On Wed, Oct 14, 2015 at 12:16:29AM +0300, Michael S. Tsirkin wrote: > > > Hello! > > > I am currently looking at how using dpdk on host, accessing VM memory > > > using the vhost-user interface, interacts with VM migration. > > > > > > The issue is that any changes made to VM memory need to be tracked so > > > that updates can be sent from migration source to destination. > > > > > > At the moment, there's a proposal of an interface extension to > > > vhost-user which adds ability to do this tracking through shared memory. > > > dpdk would then be responsible for tracking these updates using atomic > > > operations to set bits (per page written) in a memory bitmap. > > > > > > This only needs to happen during migration, at other times there could > > > be a jump to skip this logging. > > > > > > Is this a reasonable approach? > > > > Hi Michael, > > > > As I stated in another email, adding dpdk/vhost-user vm migration > > support is my second TODO. However, I barely know anything about > > vm migration so far, that I can't tell now. > > > > I will re-visit this question when I finished my first item and > > after some more investigation. > > Yuanhan, > > Live-migration for vhost-user is now available upstream. Hi Ammon, Yes, I'm aware of that. > Do you need some guidance on how to implement it in DPDK? Appreciate a lot for offering the help! However, I haven't started it yet, and I should be able to start it in two or three weeks if everything goes well here. I may ask your help then if I am in trouble. --yliu > > > Would performance degradation during > > > migration associated with atomics affect the performance to a level > > > where it's no longer useful? Pls note these logs aren't latency > > > sensitive, so can be done on a separate core, and can be batched. > > > > > > > > > One alternative I'm considering is extending linux kernel so it can do > > > this tracking automatically, by marking pages read-only, detecting a > > > pagefault and logging the write, then making the pages writeable. This > > > would mean higher worst-case overhead (pagefaults are expensive) but > > > lower average one (not extra code after the first fault). Not sure how > > > feasible this is yet, this would be harder to implement and it will only > > > be apply to newer host kernels. > > > > > > Any feedback would be appreciated. > > > > > > -- > > > MST > >