Subj : Re: MT server side app book advice
To   : comp.programming.threads
From : David Schwartz
Date : Tue May 24 2005 03:03 pm


"Uenal Mutlu" <520001085531-0001@t-online.de> wrote in message 
news:d6vf4c$u7k$05$1@news.t-online.com...

> I have not read his book, but I've participated in some discussions with
> the author in this newsgroup, and I'm afraid his views on thread 
> programming
> are not uptodate, some may even say old- or odd-style.
> He is practically saying that multithreading on a single CPU would not
> make any sense. He's saying one would need one CPU per thread. When
> I asked him how he would serve 1000 simultanous clients, ie. whether he
> would use a server with 1000 CPU's to do the job, he unfortunately refused
> to answer. So, I believe you would much be disappointed of the book.
> I would suggest a newer and a more modern book on threads programming.
> I think the following free book and examples from Sun will give you
> more than the above one: http://docs.sun.com/app/docs/doc/805-5080 (HTML 
> version)
> http://docs-pdf.sun.com/805-5080/805-5080.pdf (PDF version)

    Holy cow! You advise against the book you have not read because the 
author wouldn't answer your question?

    As a third party observer, it is my opinion that Dr. Buthenhof has given 
you *much* more of a reply than you deserve, given your unwillingness to 
even spend the time to understand anyone else's view.

    By the way, to answer your questions:

    1) Multi-threading on a single CPU makes plenty of sense. Other threads 
can continue running if one thread gets blocked on a page fault or some 
other kind of I/O. Multi-threading may also make the design cleaner in some 
cases.

    2) You do want one thread per CPU, at least, if your goal is to be able 
to make use of all the CPUs. Obviously, with five CPUs and four threads, you 
can't use all the CPUs (unless you manage to get some kernel code that is 
multi-threaded to do it for you). But you want get all the CPUs running 
application code.

    3) You don't need more CPUs or more threads to get more work done. You 
just need more CPUs to get more work done per unit time, and you may need 
more threads to keep more CPUs busy or pend more I/Os. But an increased 
number of clients does not translate into an increased need for threads, 
unless more I/Os need to be pended or more CPUs kept busy, which is not 
normally the case. An increased number of clients does not translate into an 
increased need for CPUs unless more clients means more computation is needed 
and the CPUs are the limiting factor.

    DS

.