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

Jesse Gross jesse at nicira.com
Thu Nov 3 01:36:46 UTC 2011

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.

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