topic Load distribution on Multi processor system in Operating System - HP-UX

Load distribution on Multi processor system

suresh_7 — Mon, 19 Nov 2001 19:13:14 GMT

Hi all,
I am working with a multi processor system (HP R class with two processor). I am working on a performance monitoring work on that box. May I know, how th OS distributes the load between the processors.

Thanks

Suresh

Re: Load distribution on Multi processor system

harry d brown jr — Mon, 19 Nov 2001 19:15:57 GMT

With a scheduler. There are many things that can happen to a process to cause it to be "paged" out and other reasons why processes are started up.

live free or die
harry

Re: Load distribution on Multi processor system

paul courry — Mon, 19 Nov 2001 23:32:04 GMT

Lund Performance solutions has some excellent works on the subject.

www.lund.com

Re: Load distribution on Multi processor system

Steven Sim Kok Leong — Tue, 20 Nov 2001 00:49:42 GMT

Hi,

Load distribution over processors is performed by smpsched.

smpsched is the Symmetric Multiprocessor Scheduler. It schedules your process threads for execution.

Priorities can be manipulated with the nice and renice commands and the setpri and setpriority system calls, as before. The scheduler allows a given thread to run for at most one time slice before forcing it to yield to the next dispatchable thread of the same or higher priority.

Hope this helps. Regards.

Steven Sim Kok Leong
Brainbench MVP for Unix Admin
http://www.brainbench.com

Re: Load distribution on Multi processor system

Bill Hassell — Tue, 20 Nov 2001 00:55:07 GMT

HP-UX operates in the SMP (Symmetric Multi-Processor) mode. It is very important to note that if you run one normal program, it will run on only 1 processor. There is no way to split the sequential tasks of normal programs and work on sections independently in different processors.

Now if a program is threaded, then threads will be allocated to any available processors. Threading requires that the program has been designed and written for this capability.

A common multi-threaded program is Netscape or Internet Explorer. These programs actually schedule multiple tasks as separate mini-programs (threads), and these will indeed use ogther processors independently. The program code keep everything straight.

NOte: most HP-UX servers that are used as database servers are seldom compute-bound so processor usage is not much of a performance factor.