From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f177.google.com (mail-pf0-f177.google.com [209.85.192.177]) by kanga.kvack.org (Postfix) with ESMTP id D1B426B007E for ; Fri, 4 Mar 2016 05:11:12 -0500 (EST) Received: by mail-pf0-f177.google.com with SMTP id 63so32927361pfe.3 for ; Fri, 04 Mar 2016 02:11:12 -0800 (PST) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id ln6si4862935pab.182.2016.03.04.02.11.05 for ; Fri, 04 Mar 2016 02:11:05 -0800 (PST) From: "Li, Liang Z" Subject: RE: [Qemu-devel] [RFC qemu 0/4] A PV solution for live migration optimization Date: Fri, 4 Mar 2016 10:11:00 +0000 Message-ID: References: <1457001868-15949-1-git-send-email-liang.z.li@intel.com> <20160303174615.GF2115@work-vm> <20160304075538.GC9100@rkaganb.sw.ru> <20160304083550.GE9100@rkaganb.sw.ru> <20160304090820.GA2149@work-vm> <20160304114519-mutt-send-email-mst@redhat.com> In-Reply-To: <20160304114519-mutt-send-email-mst@redhat.com> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: "Michael S. Tsirkin" Cc: "Dr. David Alan Gilbert" , Roman Kagan , "ehabkost@redhat.com" , "kvm@vger.kernel.org" , "quintela@redhat.com" , "linux-kernel@vger.kernel.org" , "qemu-devel@nongnu.org" , "linux-mm@kvack.org" , "amit.shah@redhat.com" , "pbonzini@redhat.com" , "akpm@linux-foundation.org" , "virtualization@lists.linux-foundation.org" , "rth@twiddle.net" > On Fri, Mar 04, 2016 at 09:12:12AM +0000, Li, Liang Z wrote: > > > Although I wonder which is cheaper; that would be fairly expensive > > > for the guest wouldn't it? And you'd somehow have to kick the guest > > > before migration to do the ballooning - and how long would you wait f= or > it to finish? > > > > About 5 seconds for an 8G guest, balloon to 1G. Get the free pages > > bitmap take about 20ms for an 8G idle guest. > > > > Liang >=20 > Where is the time spent though? allocating within guest? > Or passing the info to host? > If the former, we can use existing inflate/deflate vqs: > Have guest put each free page on inflate vq, then on deflate vq. >=20 Maybe I am not clear enough. I mean if we inflate balloon before live migration, for a 8GB guest, it tak= es about 5 Seconds for the inflating operation to finish. For the PV solution, there is no need to inflate balloon before live migrat= ion, the only cost is to traversing the free_list to construct the free pages bitmap, and it takes about 20ms for a 8GB idle gu= est( less if there is less free pages), passing the free pages info to host will take about extra 3ms. Liang > -- > MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org