unexplained micro-bench results

Hi

I’m trying to evaluate JavaSpaces performances running some micro-bench.

Question 1:
I’ve read messages about people complaining the JavaSpace could not hold
all of their entries even though the entries were small because the
overhead introduced by JavaSpace/Jini/RMI is important. What is the
amount of this overhead exactly? If the Entry I write to a space has
only an empty non arg constructor and a unique attribute which is an
array of d doubles, what is the size of the object written to the space?

Question 2:
I’ve run an experiment where I write x entries to a local javaspace,
next I read the x entries, and after that I take the x entries. I
measure the time taken by each of the 3 steps and compute the cost (in
second) per data-byte (of "useful" information in the entry). I run this
experiment with different values for x and I don’t understand why the
bigger x, the smaller the cost per byte. It also looks like the first
write operation on a "fresh" javaspace takes longer than the other
operations (I only measure the time taken by the write, not the time
taken by the lookup). I’m not using snapshot or bulk functionalities, is
there some kind of caching mechanism which could explain the results I’m
observing?

I’ve put more details (code, figures, graphs…) at:
http://www.metz.supelec.fr/metz/personnel/galtier/PagesPerso/Recherche/JavaSpaces/MicroBench/index.html

Any hint/help appreciated…

V. Galtier

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