Jim,

Within MPE there is an animal called the Dispatcher.  The dispatcher is
code responsible for launching, rescheduling and blocking processes.  (The
"marching orders" for the dispatcher are the queue settings, btw.)

The dispatcher uses a queue known as the Dispatcher Ready Queue (DRQ) to
manage what processes are launched and when.  There is currently only one
DRQ regardless of how many processors your system has.  When a CPU becomes
available a process is plucked off the DRQ (based on priority) and assigned
to the available CPU ("launched").

Rather than a "round robin" assignment, for some reason the dispatcher
attempts to assign processes to the "outer" processor first.  That is, if
you have eight processors the dispatcher with try to assign a process to
processor 8 then 7 then 6, etc.  One diagnostic technique in determining
the level of CPU pressure is to see how evenly balanced the utilization of
each processor is.  If the eight processors are utilized 100, 95, 90, 80,
60, 50, 45, 40 overall utilization would average 70 percent but there would
clearly be a significant amount of CPU available.

If the utilization is 100, 100, 100, 100, 100, 100 , 100, 100 AND it is
primarily high priority (A, B, C queue) processing you likely have a CPU
shortage.

That all being said, the best diagnostic metric for determining CPU
pressure is to look at how many processes are sitting on the DRQ waiting
for dispatching.  The longer the queue, the surer a CPU shortage.
Generally, if the DRQ (also called the CPU Queue Length in SOS) exceeds 10
consistently, you have a CPU shortage.

A final note, in determining a CPU shortage be sure to take into account
the different natures of interactive and batch requirements.  Generally,
batch processing isn't as critical in terms of immediacy of throughput than
is the interactive processing.  Generally, if a system is 80 percent busy
on C queue interactive processing, that is far more indicative of a CPU
shortage than if the system is 80 percent busy, 40 percent of which is
interactive and 40 percent of which is batch.

YMMV.

Bill Lancaster


At 06:53 AM 1/19/00 -0500, Jim Marshall wrote:
>We are considering upgrading a 979/100 to a 979/200 due to heavy CPU usage
>per SOS from Lund.  Do the apps automatically take advantage of the second
>CPU, or is this software specific (3rd party).  We run mostly home-grown
>COBOL apps.
>
>Jim Marshall
>D.P. Operations
>Steel Warehouse Company
>(219) 236-5104
>[log in to unmask]
>
>