On 09/12/2011 10:41 AM, Ken Dreyer wrote:
On Mon, Sep 12, 2011 at 5:46 AM, Dale Pontius<[email protected]>  wrote:
In this case, I'm wanting something that acts more like normal AFS packets,
and I believe that's what rxdebug is doing in this case.  Some people around
here have been using ping as an indicator of network latency, and while it
can be an indicator, I don't believe it's terribly representative of what is
happening to AFS packets.  I believe the current rxdebug is more indicative,
though I can accept evidence otherwise.
A while back I looked into writing an iperf probe for Smokeping, which
would at least provide the metrics for UDP rather than ICMP, for the
reason you describe. I got pulled onto other things, but it would be
nice to have.
Maybe I'm missing what rxdebug really does, but I think it sounds just about perfect. I presume that the OpenAFS clients and servers have packet queues for moving data, and rxdebug just drops packets into those queues like any other part of afs. If the other parts of afs queue are in "distress" for whatever reason, all of the other packets in that queue will share in the distress, including my rxdebug requests. In this case, that's what I want - to be told about "distress" between the server and me, and for the first approximation I'm not too concerned about the reason, just that it exists.

The specific reason for the distress is the next layer of the onion, and the difference between (my interpretation of) the rxping and a UDP ping that doesn't go through the afs server could be part of that.

Dale Pontius

--
Dale Pontius
Senior Engineer
IBM Corporation
Phone: (802) 769-6850
Tie-Line: 446-6850
email: [email protected]

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