Multiprocessor system VS one processor system

[Lawrence Farr]

I think you need to take into account everything else 
that changed as well, memory speed, disk controllers
etc.

Lawrence Farr
EPC Direct Limited  

> -----Original Message-----
> From: owner-freebsd-hardware at freebsd.org 
> [mailto:owner-freebsd-hardware at freebsd.org] On Behalf Of 
> Artem Koutchine
> Sent: 12 March 2004 10:28
> To: freebsd-hardware at freebsd.org
> Subject: Multiprocessor system VS one processor system
> 
> 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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