[ovs-discuss] 答复: upgrade ovs kernel module from 2.9 to 2.10, the performance decrease

djliu liudj_yanjiu at 163.com
Wed Sep 25 02:22:18 UTC 2019


Hi, 
 
> On Mon, Sep 23, 2019 at 4:25 PM Ben Pfaff <blp at ovn.org> wrote:
> >
> > On Mon, Sep 16, 2019 at 07:51:08PM +0800, djliu wrote:
> > > When I upgrade ovs kernel module from 2.9.0 to 2.10.0, then use
> > > iperf3 send packets from a vpc vm to a vlan vm, the bandwidth
> > > decrease from 3Gbits/sec download to 1Gbits/sec. I
> > >
> > > reset the commit to the first commit of erspan, then the bandwidth
> > > will normal. Also, when the ovs module is 2.9.0, I can capture
> > > packet in
> > > geneve_sys_6081 port use tcpdump . When upgrade to 2.10.0,
> 
> The erspan feature in kernel module shouldn't impact performance if you're
> not using it. Do you mind doing a bi-sect to find out which commit degrades
> the performance?

I found the commit(e1ededf45f072c41295f1b441a6f106159ff191b) degrade the performance, when 
use the commit, the iperf3 result is about 1Gibts/sec, when use commit(c5b38fa1919035f25deb66e1d31fab2cb043dba7) which before it, 
the iperf3 result is 3.9Gbits/s.  In addition, my linux kernel version is 3.10.0-693.el7.x86_64, I found in the version, ovs kernel module can't
use the upstream geneve tunnel, will it affect?

> > >
> > > the tcpdump can't capture any packet in the port. Does anyone know
> why.
> 
> Can you run
> 'make check-kmod' or 'make check-kernel'
> to see whether the geneve testcase passes on your system?

I find the ovs kernel module not use the upstream geneve tunnel result in the problem. when use the upstream tunnel, the geneve packet will direct submit to dev_queue_xmit, at the time, the skb's associated netdev is type of geneve, then the packet can be captured in geneve_sys_6081. when not use the upstream tunnel, the packet was direct submit to the tcp/ip stack, it won't go through geneve netdev, so we can't capture the packet in the geneve_sys_6081 device.

> Regards,
> William
> >
> > This is a bit surprising.  Greg, do you have any thoughts about
> > potential reasons why the new kernel module would be significantly
> > slower?
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