From: Alexander Thieme (athieme@PHYSnet.uni-hamburg.de)
Date: Mon Jul 01 2002 - 12:49:02 EDT
Dear Managers,
I am using my alpha boxes for physical research. Lately I discovered an
annoying fact:
If 2 (or more) applications with intensive CPU usage are run
simultaneously, it is clear, that the execution time of a single
application must be doubled. The real suprise is, that also the CPU time
of each process is significantly increased.
In some cases the CPU time was increased by 50%, so the resulting
computing performace dropped below an acceptable limit.
I am aware, that multitasking causes overhead, but I guess, its not the
real root of the problem. At least my theory is (I dont know if it is
accurate at all), that the performance drop is caused by cache misses of
the CPU. If the OS switches frequently between processes, the cache data
also becomes useless rather frequently.
So my question is: is there a way to alter the process scheduling, ie. :
to increase the time a single process is active until the OS switches to
the next one?
My system ist Tru64 5.1A and I have alpha 6.8AL CPUs.
Any hint would be greatly appreciated!
A.Thieme
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int i=1,j;int r(){j>2?i%--j?r(j):0:printf("%i,",i);}int main(){for(;;)r(j=++i);}
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