[ovs-dev] [PATCH] ovs-test: A new tool that allows to diagnose connectivity and performance issues

Ansis Atteka aatteka at nicira.com
Thu Nov 3 17:38:18 UTC 2011


On Wed, Nov 2, 2011 at 6:36 PM, Jesse Gross <jesse at nicira.com> wrote:

> On Wed, Nov 2, 2011 at 5:13 PM, Ansis Atteka <aatteka at nicira.com> wrote:
> > On Wed, Nov 2, 2011 at 3:49 PM, Jesse Gross <jesse at nicira.com> wrote:
> >>
> >> On Mon, Oct 31, 2011 at 5:00 PM, Ansis Atteka <aatteka at nicira.com>
> wrote:
> >> > UDP performance is currently limited to much lower numbers than for
> TCP.
> >> > This could be improved in future releases. The cause for UDP
> performance
> >> > penalty is:
> >> >
> >> > python uses much smaller buffers in sendto() function, and
> >> > UDP-flow control is implemented on events which are timer triggered;
> >>
> >> I think this is not that big of a deal.  Since this test is primarily
> >> about vlans and not performance, the absolute number isn't really that
> >> important.  This is particularly true with UDP where for a given size
> >> I would expect it to either work or not.
> >>
> >> UDP also almost always has lower performance than TCP anyways because
> >> there are fewer offloads.
> >>
> >> I see that you still have a fixed set of sizes to try for UDP packets,
> >> did you look into detecting the MTU?
> >
> > Yes, the correct way to do this is to use SIOCGIFMTU on the interface
> which
> > will be used by UDP sender socket (Although this is not POSIX
> standardized).
> >
> > But, I still somehow must be able to figure out which interface will be
> > actually used
> > by the UDP sender socket. I can make an assumption here by simply using
> the
> > Test IP address which user specified when he started ovs-test client. In
> my
> > opinion
> > this should work most of the time.
>
> You mean via a routing table lookup through ip or route?  I agree that
> that is good enough for a test tool.
>

I meant to use ioctl() calls from Python:

   - SIOCGIFCONF to get mapping from IP addresses to interfaces; and then
   - SIOCGIFMTU to get MTU for a particular interface.

The only thing is that I must be careful to interpret ioctl() output in a
platform dependent way.
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