[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 00:13:04 UTC 2011


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.
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