topic Re: Difference between user mode and system mode in Operating System - HP-UX

Difference between user mode and system mode

kenny chia — Mon, 09 Feb 2004 00:18:38 GMT

Hi
the sar command reports user mode, system mode, wait IO and idle percentages.
What is the difference between user and system mode?
Does user + system + wait IO + idle = 100% ?
Will a slow disk system increase wait IO?

Re: Difference between user mode and system mode

Steven E. Protter — Mon, 09 Feb 2004 00:27:03 GMT

A system will slow if its waiting for I/O.

Attaching a little script that gives you some more performance output in a format you can read more easily.

SEP

Re: Difference between user mode and system mode

Sridhar Bhaskarla — Mon, 09 Feb 2004 00:32:26 GMT

Hi,

Yes. user mode is the utilization spent while running user instructions like arthmetic operations. System mode is the utilization spent while running the system calls for ex., open(), close() etc., %wio in sar output is not really the CPU utilization. It's to be accounted as idle except that the processes are waiting on responses from the IO subsystem. Yes. A slow disk subsystem can make this figure high. However, use 'sar -d 2 20' to get a good picture on the disk utilization. A high avserv indicates a slower system.

Glance can give you a very good picture. But you have to purchase it.

-Sri