We installed a vanilla Suse 8.1 on Dell Xeon 2.4Ghz Dual box
with 1GB Ram. The running kernel is a Linux 2.4.19-64GB-SMP #1 SMP.
Now I tested the system with rather computational intensive numerical
simmulations. If I run a single job, it takes about 1h 20min to finish.
However, when I launching two identical jobs, these jobs need now 2h!
Alternativly, I can launch the same job but runing the calculation in
two threads, using pthread. Then, the job is finished in about 1hour,
indicating a performance of ca 195% CPU time.
However, I was wandering, if anybody has any suggestions, what might
be the performace decrease from 1 running job to two jobs by about 35%.
Does that have to do with the 64GB kernel, since I do not notice this
decrease on an Athlon MP Dual box, but using an Linux 2.4.18-4GB-SMP kernel?
Any suggestings appreciated.