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I explain more my critics about the USL methodology...

Ramine

4/15/2016 10:29:00 PM

Hello,

I explain more my critics about the USL methodology...

If you have read my previous post, i have based my proof on
this affimation that is more ituitive, read it carefully:

"I have just thought about his methodology of using Parallel
systems as a black box using mathematical regression to quantify
and predict scalability, and i think he is wrong doing it so,
because when the serial part is for example 1/8 of the parallel part,
you can probabilistically get much more scalability with less parallel
threads and less cores than when testing with more and more cores,
because with more and more cores you will get more and more contention
on the serial part , so the Dr. Gunther methodology fails , because
it is testing the system with less cores and less threads, so it will
not get and predict the right or a better approximation of the
scalability" [1]


And if you look at the following web page from Dr. Gunther:

http://perfdynamics.blogspot.ca/2009/04/assessing-usl-scalability-with-...

He is applying the USL methodology to a mixed workload to
predict the response-time etc.

But i think he is wrong, because there is an unknown that
is the number of cores and the number of server threads on
the server side of the database system, so you can not more
exactly predict scalability because as i said in [1] above,
you can not predict in general how much contention there is
on the serial part represented by coefficient Alpha and you
can not predict how much cross-talk there is represented by
the Beta coefficient.. so i hope that my more intuitive
affirmation [1] above is clear.

So i say that Dr. Gunther methodology of USL fails and is
not the right tool, and more than that , as i said before it is not
suited for critical systems that demand and require us to know
the worst-case performance.

Thank you,
Amine Moulay Ramdane.