if you are going to go to that much trouble, why not write a driver
that does four fork() calls and then a wait() to wait for one of them
to terminate. When the wait returns, fork() another process, and keep
this going.
this wouldn't be but 20-30 lines of code, and you could make the number
of processors a command-line option that would make your 'thing' run
cleanly on 1, 2, 4 or N processor machines...
I could help you if you need it..
Robert Hyatt Computer and Information Sciences
[EMAIL PROTECTED] University of Alabama at Birmingham
(205) 934-2213 115A Campbell Hall, UAB Station
(205) 934-5473 FAX Birmingham, AL 35294-1170
On 14 Sep 1999 [EMAIL PROTECTED] wrote:
> Terry Bullett <[EMAIL PROTECTED]> writes:
>
> > 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,
>
> yes. this is a frustrating problem and i have it too with my quad
> box. (i run multiple monte-carlo simulations.) i suspect unix was
> never really done with SMP in mind. the shells, at least, have
> precious little by way of SMP job control.
>
> i have used three methods.
>
> 1) make 4 shell scripts, each of which do 1/4 of the work. this
> leaves some slop at the end but is easy.
>
> 2) use make. make does a better job than shells at SMP. have a
> script generate a giant Makefile which simply lists all your jobs
> as dependancies for a default dummy target. make -j 4 and go.
>
> 3) submit all the jobs to batch. set batch to keep spawning jobs for
> load less 4 (or whatever works for you). this will keep all the
> processors going hot. however job control via batch can get
> tricky.
>
> i think the second (make) is probably the best but your mileage may
> vary.
>
> you can probably make your own batch a small program to fork off 4
> jobs, and spawn more as the children die until you are done.
>
> hope this helps.
>
> --
> J o h a n K u l l s t a m
> [[EMAIL PROTECTED]]
> Don't Fear the Penguin!
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