[OpenAFS] 1.4.8, Rx Performance Improvements, and a Small Business Innovative Research grant

[Chas Williams (CONTRACTOR)]

In message <20081007.100150.249414631.haba@habanero.pdc.kth.se>,Harald Barth wr
ites:
>As xplot was not available as portage I tried xplot->gnuplot.
>Don't do that. The xplot graphics shows much better what is
>going on than the converted gnuplot. I used xplot 0.90.7.1
>from http://www.xplot.org/.

i added some sample plots from some early results. 

write.xplot shows a 1m write from a client to the server.  it consists of
two calls (and i think the retransmit message from rxtrace2xplot is bogus
here since it doesnt understand the backward direction of the exchange).

compare this with read.xplot from the same directory.  this is a ready
of a 1m file with a cache chunksize of 14.  (i think i am missing some
arrow heads).  note that there is an rx call for chunksize.  this makes
the plot somewhat difficult to read but you can see that this doesnt
perform well (perhaps i should put arrows pointing down for one direction
and point up for the other direction).  with 11 rx datagrams per read
(2^14/RX_DATAGRAM_SIZE) you can see that rx never really gets out of
slow start.  you get 3 packets, 4 and then the last 4.  next call, you
restart at 3 packets again.  the rx window never gets close to filling.
also, every 11 packets, you need to wait for a another complete roundtrip
to the server.

so while rx could be improved, afs' usage thereof could be improved a
bit.