From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:53483) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TNgVh-0002bq-NC for qemu-devel@nongnu.org; Mon, 15 Oct 2012 04:58:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TNgVb-0000YF-P1 for qemu-devel@nongnu.org; Mon, 15 Oct 2012 04:58:53 -0400 Received: from mail-bk0-f45.google.com ([209.85.214.45]:62067) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TNgVb-0000Y2-GQ for qemu-devel@nongnu.org; Mon, 15 Oct 2012 04:58:47 -0400 Received: by mail-bk0-f45.google.com with SMTP id jf3so1952609bkc.4 for ; Mon, 15 Oct 2012 01:58:46 -0700 (PDT) Date: Mon, 15 Oct 2012 10:58:42 +0200 From: Stefan Hajnoczi Message-ID: <20121015085842.GA29120@stefanha-thinkpad.redhat.com> References: <20121012173423.27389.27726.malonedeb@chaenomeles.canonical.com> <20121012173423.27389.27726.malonedeb@chaenomeles.canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121012173423.27389.27726.malonedeb@chaenomeles.canonical.com> Subject: Re: [Qemu-devel] [Bug 1066055] [NEW] Network performance regression with vde_switch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bug 1066055 <1066055@bugs.launchpad.net> Cc: qemu-devel@nongnu.org On Fri, Oct 12, 2012 at 05:34:23PM -0000, Edivaldo de Araujo Pereira wrote: > I've noticed a significant network performance regression when using > vde_switch, starting about one week ago (10/05/2012); before that date, > I used to get about 1.5 Gbits host to guest, but now I can only get > about 320 Mbits; I didn't find any modification in net/vde.*, just in > hw/virtio*. > > My command line: > qemu-system-i386 -cdrom /bpd/bpd.iso -m 512 -boot d -enable-kvm \ > -localtime -ctrl-grab -usbdevice tablet \ > -device virtio-net-pci,mac=52:54:00:18:01:01,netdev=vde0,tx=bh,ioeventfd=on,x-txburst=32 \ > -netdev vde,id=vde0 -vga std -tb-size 2M -cpu host -clock unix > > My host runs a kernel 3.6.1 and my guest runs a kernel 3.5.4; the same > problem happens with other host and guest versions, too. > > I know there are better ways of running a guest, but using vde I get a > cleaner environment in the host (just one tun/tap interface to > manage...), which is quite good when running some accademic experiments. > > Interestingly, at the same time I've noticed a performance enhancement > of about 25~30 % when using a tun/tap interface, bridged or not. Hi Edivaldo, It would be great if you can help find the commit that caused this regression. The basic process is: 1. Identify a QEMU release or git tree that gives you 1.5 Gbit/s. 2. Double-check that qemu.git/master suffers reduced performance. 3. git bisect start where and are the git commits that show differing performance (for example, bad=HEAD good=v1.1.0) Then git will step through the commit history and ask you to test at each step. (This is a binary search so even finding regressions that happened many commits ago requires few steps.) You can read more about git-bisect(1) here: http://git-scm.com/book/en/Git-Tools-Debugging-with-Git#Binary-Search http://www.kernel.org/pub/software/scm/git/docs/git-bisect.html The end result is the commit introduced the regression. Please post what you find! Stefan