Multiprocessor system VS one processor system

[Simon]

While FreeBSD 4.9 can only run one process per CPU, in a multi-user
environment, you will have multiple processes running on multiple CPUs
at the same time. You can't do this with 1 CPU, even if that one CPU
is faster. Of course, an outdated dual CPU server is not a lot faster than
a 2x+ faster newer single CPU server.

FreeBSD 5.x is going to change this all, read:

http://www.lemis.com/grog/SMPng/Singapore/paper.pdf

-Simon

On Fri, 12 Mar 2004 13:28:18 +0300, Artem Koutchine wrote:

>Hi!
>
>I need to understand something very clear.
>
>As I understand FreeBSD (as of 4.9) runs one process
>per one CPU. This means, that if i have dual systems
>with 500Mhz CPUs one process can never run faster
>than on a single 500Mhz CPU. However, if i substitute
>those two CPUs with one 1000Mhz, that one process will run
>twice as fast than on dual 500Mhz, however, to box will
>become a bit less responsive, because in a dual box
>when one CPU is loaded, another one may have some
>spare time to respond. However, in case of very loaded
>box both CPUs a extremely loaded and the box will
>be as responsive as single 1000Mhz CPU  box 100% loaded.
>So, according to what i just said there is not real reason to
>setup a dual CPU box under FREEBSD unless you want to
>have 5000Mhz box, but there is no CPU with such speed, so
>you put two 2500Mhz CPU in it and if you are running a lot
>of processes with short run periods you will get overal
>perfomance somewhere near 5000Mhz. However, when i 
>subsituted two 500Mhz CPUs with 1500Mhz one (even with
>less 2nd level cache) on a heavy loaded web server i notice
>that sites started to load faster. So, it seems as 
>one 3X Mhz  CPU is faster that two X MHz CPUs, at least
>for web server with sql base and many perl scripts.
>
>So, there are two questions:
>1) Am I right or am wrong?
>2) Does FreeBSD 5.X  run one process only on one CPU
>or it can run on thread of a process on one CPU and another 
>thread on another CPU?
>
>Regards,
>Artem
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