High CPU system usage

[Neil Armstrong]

On a V-class 2500 with 8gb ram and 8x440 CPUs after adding a further 8x440 CPUs making 16x440s in total our CPU user usage went down but the system usage actually went up to 47% - 12 CPUs are added to informix 7.31UC5

[Stefan Farrelly]

The system cpu usage has gone up because it has to manage the extra cpus you installed. HP-UX now has to decide which processes can run on which of the new cpus, check when theyre done or need more time, etc.
The problem is that HP-UX has a single-threaded part in the kernel for criticial locking and no matter how many cpus you have every process will need to use this single-threaded part of the kernel at some point, which means you add more cpus, more procces can run, but the queue of processes to access the single-threaded part of the kernel has increased, ie. system cpu has gone up.

But despite this, overall you doubling your number of cpus should still show a considerable performance improvement.

[CHRIS_ANORUO]

Use Glance and sar to monitor and check this documents for troubleshooting the problem:
Description: Sys Adm: determining the cause of system performance problem
Doc. Ids S310000231A,B, and C.

[Darrel Louis]

Hi,

The twelve CPU's for Informix.
Are the number of VCPU in onconfig(Informix config file) 12?
If you monitor the system, which processes are causing the high CPU usage?
Are these unix processes or Informix processes?

What is the nember of Page cleaners in your ONCONFIG file and how often do they start, after every 300 seconds or when it's X precent full.
Check the CPU usage within Informix:
onstat -g ???, don't know the exact option.

Unix:
When you use sar or top or glance, what do you see
# sar -u -q 2 10
# sar -c -q 2 10
The information is too little, to give a correct answer.