Multiple CPU Performance

[Kent Stewart]

On Thursday 27 November 2003 03:10 pm, JacobRhoden wrote:
> > Gerard Samuel wrote:
> > > I was fortunate to acquire a dual Slot one motherboard.
> > > I currently only have one PIII 450 in there, and its working without
> > > any problems so far.
> > > This box is primarily for www/samba/cvs.
> > > I was wondering if my PHP apps would benefit (run faster) if I
> > > introduced a 2nd CPU.
>
> I am no expert on this sort of thing, but I thought I should add one thing,
> in case you havent thought of it... What is the load  on your cpu? It can
> be found by doing a top.. if it never reaches 1.0 while running php apps,
> then an extra cpu is not going to make much difference.  In general I have
> found that the bottleneck in older computers tends to be the hard drive,
> not the CPU.
>

I saw a comment recently that stood out. It was to the effect that SMP lets 
you run more applications at the same speed. 

On buildworlds, for example, the suggestion is to use -j4 on single cpu 
systems. I find the -j4 runs a buildworld 20-30% slower than no -j at all. 
The -j8 ran faster on SMP. The process of running multiple makes has a 
process switching overhead that costs me time. I also have IDE HDs and 
suspect that the tagged queuing built into good scsi HDs gets around some of 
the HD bottle neck.

Kent

-- 
Kent Stewart
Richland, WA

http://users.owt.com/kstewart/index.html