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Mon, 27 Apr 2020 10:34:36 +0000 (UTC) Received: from work-vm (ovpn-114-175.ams2.redhat.com [10.36.114.175]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 170A919C4F; Mon, 27 Apr 2020 10:34:34 +0000 (UTC) Date: Mon, 27 Apr 2020 11:34:32 +0100 From: "Dr. David Alan Gilbert" To: Lukas Straub Subject: Re: colo: qemu 4.2.0 vs. qemu 5.0.0-rc2 performance regression Message-ID: <20200427103432.GH2923@work-vm> References: <20200411191655.0365532d@luklap> <20200413153432.224e46b6@luklap> MIME-Version: 1.0 In-Reply-To: <20200413153432.224e46b6@luklap> User-Agent: Mutt/1.13.4 (2020-02-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/27 01:12:26 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Zhang Chen , zhanghailiang , qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Lukas Straub (lukasstraub2@web.de) wrote: > On Sat, 11 Apr 2020 19:16:54 +0200 > Lukas Straub wrote: >=20 > > Hello Everyone, > > I did some Benchmarking with iperf3 and memtester (to dirty some guest = memory) > > of colo performance in qemu 4.2.0 and in qemu 5.0.0-rc2 > > with my bugfixes on top.( https://lists.nongnu.org/archive/html/qemu-de= vel/2020-04/msg01432.html ) > >=20 > > I have taken the average over 4 runs. > > Client-to-server tcp bandwidth rose slightly from ~83.98 Mbit/s to ~89.= 40 Mbits. > > Server-to-client tcp bandwidth fell from ~9.73 Mbit/s to ~1.79 Mbit/s. > > Client-to-server udp bandwidth stayed the same at 1.05 Mbit/s > > and jitter rose from ~5.12 ms to ~10.77 ms. > > Server-to-client udp bandwidth fell from ~380.5 Kbit/s to ~33.6 Kbit/s > > and jitter rose from ~41.74 ms to ~83976.15 ms (!). > >=20 > > I haven't looked closely into it, but i think > > 0393031a16735835a441b6d6e0495a1bd14adb90 "COLO: Optimize memory back-up= process" > > is the culprint as it reduces vm downtime for the checkpoints but incre= ases > > the overall checkpoint time and we can only release miscompared primary= packets > > after the checkpoint is completely finished. > >=20 > > Another thing that I noticed: With 4.2.0, the secondary qemu uses thric= e > > the amount of gest memory. With 5.0.0-rc2 it's just double the amount o= f > > guest memory. So maybe the ram cache isn't working properly? > >=20 > > Regards, > > Lukas Straub >=20 > Hmm, > I looked at my test again and saw that the results where very noisy, so q= emu 5.0.0-rc2 > being slower was just a coincidence. I did increase the test time and the= results are=20 > more meaningful now. Now qemu 5.0.0-rc2 is around the same speed and stil= l faster > in the client-to-server tcp case. >=20 > Sorry for the noise. Is it back to using 3x RAM in the secondary? Dave >=20 > Regards, > Lukas Straub -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK