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 <bad> <good> where <bad> and <good> 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