topic Re: multiprocessing in Operating System - HP-UX

multiprocessing

Asad Malik — Wed, 12 Jul 2000 14:01:33 GMT

Hi
Machine Hp9000, N class 4000, running HP-UX 11.0 has four CPUs. while monitoring performance we have noticed cpu0 is being overloaded(utilization 100% sometimes) while other three processor's utilization stays below 10% all the time. Any suggestions please.

Thanks

Re: multiprocessing

Kofi ARTHIABAH — Wed, 12 Jul 2000 14:04:24 GMT

Does the software you are running lend itself to multiprocessing? ie what are you running?

Re: multiprocessing

Andy Monks — Wed, 12 Jul 2000 14:10:25 GMT

Sounds like your application does a lot of network things. Try loading the patch PHNE_21433. This fixes problems where networking code only runs on processor 0.

Re: multiprocessing

Brian M. Fisher — Wed, 12 Jul 2000 14:19:13 GMT

Unless the running program is multi-threaded the most the process can do is use a total of 100% of a single cpu, it is unable to use 100% of all cpus. Can more processes be started?

Brian
<*(((>< er

Re: multiprocessing

Andy Monks — Wed, 12 Jul 2000 14:26:28 GMT

Although Brian is right, unless it's a multithreaded app you can't use more than 100%, a patch will fix the problem of cpu 0 using 100% and the rest are basically idle (assuming your running more than 1 process in total!) which I'm sure you are.

Re: multiprocessing

Tim Malnati — Wed, 12 Jul 2000 15:00:08 GMT

Mosts applications are multiuser but not multitheaded. Typically a process that is a heavy cpu user will NOT always appear on the same cpu though. Your thought that something may be wrong is something I would question also. Maybe it's the network patch thing that Andy has mentioned or maybe it's something in the way an N class machine distributes processor load. In any event, if the patch does not correct the situation, I would certainly follow this situation up with a call to the Response Center. Maybe it's normal in this class box, but I doubt it.

Re: multiprocessing

Berlene Herren — Wed, 12 Jul 2000 15:06:56 GMT

Have you checked into using APA?

http://docs.hp.com/hpux/pdf/J4240-90005.pdf

Berlene

Re: multiprocessing

CHRIS_ANORUO — Wed, 12 Jul 2000 15:38:25 GMT

Tune CPU performance by using processor affinity, or improve priorities of processes with nice or rtprio.

Re: multiprocessing

Asad Malik — Wed, 12 Jul 2000 15:45:07 GMT

we installed patch PHKL_21532, as recommended by HP but the problem remains.

Re: multiprocessing

Jason Luginbuhl — Wed, 12 Jul 2000 16:13:48 GMT

It sure sounds like you could use a document that explains the multiprocessor environment and/or processor affinity. It looks like your application is coded in a way that makes it run on this one processor. For more information I encourage you to look over the following document which is available on the HP ITRC's Technical Knowledge Base:

UNX1030249 Control on which processor process runs in multi-processor system

Re: multiprocessing

Bill Hassell — Wed, 12 Jul 2000 18:25:35 GMT

If there is just one process consuming 100% CPU (typical for a long numerical problems), then it would be expected that only one processor will be used. Use top to see if a single process is consuming most of the CPU cycles. Starting additional copies of the same program will cause the other CPUs to start using CPU power. Threading is a technique where parts of a single program can be executed at the same time on different processors (if available), but the program must be rewritten to allow for threading (very non-trival task).

Re: multiprocessing

Andy Monks — Thu, 13 Jul 2000 06:36:55 GMT

Asad,

Load PHNE_21433 like I said earlier. If you read the patch text it's a perfect match for your problem!

Re: multiprocessing

Andy Monks — Thu, 13 Jul 2000 06:38:06 GMT

Asad,

And to prove it's networking compile up and run this program. You'll see that you have perfect load balancing.

You MUST compile it with :-

cc +O1 cpuhog.c -o cpuhog

Optimization any higher will take out the loop (it doesn't do much really)

Re: multiprocessing

Asad Malik — Thu, 13 Jul 2000 11:06:28 GMT

As a work-around for now, we found and are using a utility mpctl to move processes
off of CPU 0 and get them floating among CPUs again. It is working as load is being distributed on all 4 cpus.
Andy
we will read about the patch you have suggested and may be that is the answer.

Re: multiprocessing

Asad Malik — Thu, 13 Jul 2000 11:08:14 GMT

Re: multiprocessing

Andy Monks — Thu, 13 Jul 2000 19:14:06 GMT

Asad,

If it is the problem I think it is, then using processor affinity, you will probably either see in glance, that the processes are still moving (but coming back to the processor you tied them too), or your getting messages in dmesg saying things about threads being moved.

Try my test program if you get a chance too.

Re: multiprocessing

Asad Malik — Mon, 17 Jul 2000 11:24:44 GMT

Andy
we have applied patch PHNE_21433 and all 4 cpu's are being utilized and the load is balanced. Thanks.

Re: multiprocessing

Andy Monks — Mon, 17 Jul 2000 11:25:59 GMT

Hi Asad,

Thanks for letting me know.