topic Re: CPU utilization in Operating System - HP-UX

CPU utilization

ust3 — Thu, 11 Oct 2007 00:18:22 GMT

I have some process is running in the system , some of them use over 90% CPU time , I want the system not to be burden by this high CPU utilization process , can advise is it possible to limit the max. of CPU utilization of any process to 50% , so that other user can share the system resource ?

thx

Re: CPU utilization

Steven E. Protter — Thu, 11 Oct 2007 00:35:32 GMT

Shalom,

Your kernel has a scheduler that hands out tiem slices. A single process gets 90% of CPU because no other processes demand it. In a normal situation where there are a number of processes demanding CPU, no one process will get a high figure.

Limiting a single process to a certain percentage will merely slow down how quickly the system gets work done when its running single threaded.

So its not advisable to do as you suggest.

SEP

Re: CPU utilization

Dennis Handly — Thu, 11 Oct 2007 00:41:29 GMT

>SEP: In a normal situation where there are a number of processes demanding CPU, no one process will get a high figure.

If some processes are niced, they may be starved.

ust3 may want to nice that process that is getting 90% and that way the others are sure to get CPU time if they need it.

Re: CPU utilization

whiteknight — Thu, 11 Oct 2007 01:31:16 GMT

ust3,

You can consider using PRM (Performance Resource Manager) which can help you to maintain CPU threshold.

http://h20392.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=B3835DATRY

WK

http://forums1.itrc.hp.com/service/forums/helptips.do?#33

Re: CPU utilization

Bill Hassell — Thu, 11 Oct 2007 07:01:45 GMT

It's important to understand that a process that uses 100% of the CPU (no I/O or other system calls) is the least important process in the system. That's because the scheduler sees the usage and immediately reduces the program's priority until the program only gets "leftover" CPU cycles.The following is the shortest CPU hog script you can create:

while :
do
:
done

If you run this little script, one CPU will jump to 100% CPU usage. Run 10 copies on an 8-CPU system and all your CPUs will be busy BUT you can still login and run vi and database programs will run, etc. This shows that CPU usage is not an important metric by itself for performance tuning.

Now if this little script is changed to perform system calls such as date or a simple filesystem query such as echo *, then the script will have a much bigger impact on performance.

SO while you can purchase PRM and limit CPU usage, I don't think you'll see an improvement in overall performance until you look at disk and network activities. Only the Glance product will give the details that you need.