From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57597) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1afouD-0006t4-Aj for qemu-devel@nongnu.org; Tue, 15 Mar 2016 09:21:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1afou9-00010A-Fd for qemu-devel@nongnu.org; Tue, 15 Mar 2016 09:21:01 -0400 Received: from g1t6213.austin.hp.com ([15.73.96.121]:42768) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1afou9-0000y3-At for qemu-devel@nongnu.org; Tue, 15 Mar 2016 09:20:57 -0400 References: <1457082167-12254-1-git-send-email-jitendra.kolhe@hpe.com> <20160310094912.GC9715@rkaganb.sw.ru> <56E25EBF.6050109@hpe.com> <56E29BD9.8010306@hpe.com> <56E2D88D.2060702@hpe.com> From: Jitendra Kolhe Message-ID: <56E80C2D.9020304@hpe.com> Date: Tue, 15 Mar 2016 18:50:45 +0530 MIME-Version: 1.0 In-Reply-To: <56E2D88D.2060702@hpe.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v1] migration: skip sending ram pages released by virtio-balloon driver. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Li, Liang Z" , Roman Kagan , "qemu-devel@nongnu.org" , "dgilbert@redhat.com" , "simhan@hpe.com" , "mohan_parthasarathy@hpe.com" On 3/11/2016 8:09 PM, Jitendra Kolhe wrote: >> You mean the total live migration time for the unmodified qemu and the >> 'you modified for test' qemu >> are almost the same? >> > > Not sure I understand the question, but if 'you modified for test' mean= s > below modifications to save_zero_page(), then answer is no. Here is wha= t > I tried, let=92s say we have 3 versions of qemu (below timings are for > 16GB idle guest with 12GB ballooned out) > > v1. Unmodified qemu =96 absolutely not code change =96 Total Migration = time > =3D ~7600ms (I rounded this one to ~8000ms) > v2. Modified qemu 1 =96 with proposed patch set (which skips both zero > pages scan and migrating control information for ballooned out pages) - > Total Migration time =3D ~5700ms > v3. Modified qemu 2 =96 only with changes to save_zero_page() as discus= sed > in previous mail (and of course using proposed patch set only to > maintain bitmap for ballooned out pages) =96 Total migration time is > irrelevant in this case. > Total Zero page scan time =3D ~1789ms > Total (save_page_header + qemu_put_byte(f, 0)) =3D ~556ms. > Everything seems to add up here (may not be exact) =96 5700+1789+559 =3D > ~8000ms > > I see 2 factors that we have not considered in this add up a. overhead > for migrating balloon bitmap to target and b. as you mentioned below > overhead of qemu_clock_get_ns(). Missed one more factor of testing each page against balloon bitmap=20 during migration, which is consuming around ~320ms for same=20 configuration. If we remove this overhead which is introduced by=20 proposed patch set from above calculation we almost get total migration=20 time for unmodified qemu (5700-320+1789+559=3D~7700ms) Thanks, - Jitendra