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From: helen@uhccux.UUCP (Helen Rapozo)
Newsgroups: comp.os.vms
Subject: Re: Running images at priority 1
Message-ID: <684@uhccux.UUCP>
Date: Wed, 15-Jul-87 01:43:08 EDT
Article-I.D.: uhccux.684
Posted: Wed Jul 15 01:43:08 1987
Date-Received: Fri, 17-Jul-87 03:21:34 EDT
References: <8707110202.AA28088@ucbvax.Berkeley.EDU>
Organization: U. of Hawaii, Manoa (Honolulu)
Lines: 34
Summary: Doing useful work

In article <8707110202.AA28088@ucbvax.Berkeley.EDU>, 13501ADC@MSU.BITNET ("Alan D. Cabrera") writes:
> 
> I've been submitting CPU intensive batch jobs on our VAX 8650 with the
> priority set at 1.  It uses some pretty big arrays so it tends to page
> ALOT.  When I run my job people say that they notice a degredation to
> the system.  I say that my job shouldn't pose a problem because it's
> priority is lower than theirs.
> 
> Am I wrong in assumming that since my job's priority is set at 1, it
> shouldn't interfere with anybody with a higher priority?

The only reason why a job running at priority 1 is executing is because
the other process on the system that have priority 2 to 31 is not
using the CPU in the first place.  If you think about
the NULL process runs at priority 0 so if the system is not doing
anything else it will execute that process which happens to be
an infinite loop.  If this job that runs at priority 1 is doing
useful work then the system is doing more useful work.

Seriously tho, since the job pages a lot that could explain the
degredation in response time.  You could do the following things:

a) Run the job at priority 0.  What will happen is that whatever
CPU cycles that are left will be split between NULL and your
process.

b) Somehow get a bigger working size for your job, the less paging
you do the faster things will go.

c) If you are the system manager there is a parameter that
deals with the timeslice, if you decrease the timeslice the effect
to the users will be one of faster response time.

Let me know how this turns out.