From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=45573 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PSDWQ-0000NL-CY for qemu-devel@nongnu.org; Mon, 13 Dec 2010 13:53:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PSDWP-00084t-82 for qemu-devel@nongnu.org; Mon, 13 Dec 2010 13:53:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49674) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PSDWO-00084n-TO for qemu-devel@nongnu.org; Mon, 13 Dec 2010 13:53:17 -0500 Date: Mon, 13 Dec 2010 20:52:51 +0200 From: "Michael S. Tsirkin" Message-ID: <20101213185251.GA9554@redhat.com> References: <20101212210959.GA25136@redhat.com> <20101213103836.GG25590@redhat.com> <20101213133538.GA2731@redhat.com> <20101213133615.GB2731@redhat.com> <20101213161219.GA6715@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] Re: [PATCH v5 0/4] virtio: Use ioeventfd for virtqueue notify List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org On Mon, Dec 13, 2010 at 05:57:28PM +0000, Stefan Hajnoczi wrote: > On Mon, Dec 13, 2010 at 4:28 PM, Stefan Hajnoczi w= rote: > > On Mon, Dec 13, 2010 at 4:12 PM, Michael S. Tsirkin = wrote: > >> On Mon, Dec 13, 2010 at 03:27:06PM +0000, Stefan Hajnoczi wrote: > >>> On Mon, Dec 13, 2010 at 1:36 PM, Michael S. Tsirkin wrote: > >>> > On Mon, Dec 13, 2010 at 03:35:38PM +0200, Michael S. Tsirkin wrot= e: > >>> >> On Mon, Dec 13, 2010 at 01:11:27PM +0000, Stefan Hajnoczi wrote: > >>> >> > Fresh results: > >>> >> > > >>> >> > 192.168.0.1 - host (runs netperf) > >>> >> > 192.168.0.2 - guest (runs netserver) > >>> >> > > >>> >> > host$ src/netperf -H 192.168.0.2 -- -m 200 > >>> >> > > >>> >> > ioeventfd=3Don > >>> >> > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.1= 68.0.2 > >>> >> > (192.168.0.2) port 0 AF_INET > >>> >> > Recv =A0 Send =A0 =A0Send > >>> >> > Socket Socket =A0Message =A0Elapsed > >>> >> > Size =A0 Size =A0 =A0Size =A0 =A0 Time =A0 =A0 Throughput > >>> >> > bytes =A0bytes =A0 bytes =A0 =A0secs. =A0 =A010^6bits/sec > >>> >> > =A087380 =A016384 =A0 =A0200 =A0 =A010.00 =A0 =A01759.25 > >>> >> > > >>> >> > ioeventfd=3Doff > >>> >> > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.1= 68.0.2 > >>> >> > (192.168.0.2) port 0 AF_INET > >>> >> > Recv =A0 Send =A0 =A0Send > >>> >> > Socket Socket =A0Message =A0Elapsed > >>> >> > Size =A0 Size =A0 =A0Size =A0 =A0 Time =A0 =A0 Throughput > >>> >> > bytes =A0bytes =A0 bytes =A0 =A0secs. =A0 =A010^6bits/sec > >>> >> > > >>> >> > =A087380 =A016384 =A0 =A0200 =A0 =A010.00 =A0 =A01757.15 > >>> >> > > >>> >> > The results vary approx +/- 3% between runs. > >>> >> > > >>> >> > Invocation: > >>> >> > $ x86_64-softmmu/qemu-system-x86_64 -m 4096 -enable-kvm -netde= v > >>> >> > type=3Dtap,id=3Dnet0,ifname=3Dtap0,script=3Dno,downscript=3Dno= -device > >>> >> > virtio-net-pci,netdev=3Dnet0,ioeventfd=3Don|off -vnc :0 -drive > >>> >> > if=3Dvirtio,cache=3Dnone,file=3D$HOME/rhel6-autobench-raw.img > >>> >> > > >>> >> > I am running qemu.git with v5 patches, based off > >>> >> > 36888c6335422f07bbc50bf3443a39f24b90c7c6. > >>> >> > > >>> >> > Host: > >>> >> > 1 Quad-Core AMD Opteron(tm) Processor 2350 @ 2 GHz > >>> >> > 8 GB RAM > >>> >> > RHEL 6 host > >>> >> > > >>> >> > Next I will try the patches on latest qemu-kvm.git > >>> >> > > >>> >> > Stefan > >>> >> > >>> >> One interesting thing is that I put virtio-net earlier on > >>> >> command line. > >>> > > >>> > Sorry I mean I put it after disk, you put it before. > >>> > >>> I can't find a measurable difference when swapping -drive and -netd= ev. > >> > >> One other concern I have is that we are apparently using > >> ioeventfd for all VQs. E.g. for virtio-net we probably should not > >> use it for the control VQ - it's a waste of resources. > > > > One option is a per-device (block, net, etc) bitmap that masks out > > virtqueues. =A0Is that something you'd like to see? > > > > I'm tempted to mask out the RX vq too and see how that affects the > > qemu-kvm.git specific issue. >=20 > As expected, the rx virtqueue is involved in the degradation. I > enabled ioeventfd only for the TX virtqueue and got the same good > results as userspace virtio-net. >=20 > When I enable only the rx virtqueue, performs decreases as we've seen a= bove. >=20 > Stefan Interesting. In particular this implies something's wrong with the queue: we should not normally be getting notifications from rx queue at all. Is it running low on buffers? Does it help to increase the vq size? Any other explanation? --=20 MST