Hi,
I've been working with SMP from the hardware side for several years
now, but am somewhat new to the applications side. Here's my situation.
I have a CPU intensive task that takes 2-3 min on a 300MHz PIII. The
timing of each run is data dependent thus can't be predicted precisely.
I need to run as many of these processes as possible usring my repeat
interval, which is 30 minutes at the moment. These processes are
launched by a shell script, which itself is called by cron.
Trouble comes when the compute time for all the processes excedes the
repeat interval. If I try to do 35 minutes of computation every 30
minutes, the number of processes increase and the system eventually
grinds to a halt. To counter this on a uni-processor system, I had the
script touch a lockfile and then refuse to run if another process was
running.
I tried this on a dual CPU system and had to make 2 separate scripts
with 2 lockfiles. It seemed ugly, for example I had to maintain 2
separate lists of tasks, but it worked.
Now I have a quad CPU system (VARserver3500 from VA Research) and I'm
looking for a more elegant way to approach the problem. Given some
relatively large number of tasks (50-100?) how can I make sure that
there are always N=2,4,8, of them running?
Any advice on where to look for info on this type of problem is
appreciated,
Terry Bullett
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