topic Memory Parameters in Operating System - HP-UX

Memory Parameters

Rodwell B. Watson — Wed, 10 May 2000 17:57:52 GMT

HP-UX 11.0 on K420
I'm trying to find out how my system is managing memory. I have used 5 utilities:
top
glance
dmesg
swapinfo
sar -w
The only correlation in the memory stats is in the physical memory parameters in glance and dmesg. Why do these utilities give conficting parameters? Specifically, what do the real, virtual, and free memory stats in top mean? Also, should I trust the paging stats in glance as apposed to the swap stats in sar -w ?

Re: Memory Parameters

Paul Hite — Wed, 10 May 2000 19:25:21 GMT

First, the numbers in top are total physical memory used, how much is active, total virtual memory used, how much is active, and free memory. I trust the free memory part. The first four numbers I would tend to ignore. I think they are too process based and are confused by shared memory and such.

sar is a very old tool. I rarely use it. It does not understand paging.

HP-UX will page if memory gets tight. It no longer swaps processes at all. If the paging algorithm is not enough, it will deactivate processes. I don't know if sar would report this as "swapped". But there is no conflict if glance tells you that you are paging but sar says you are not swapping. When swapping was possible, paging but not swapping was a normal state.

Glance is a very good tool. Believe it if it says you are paging.

You did not mention "vmstat" which is another tool that I like. You might want to check it out.

swapinfo tells you about your use of your swap area.

In all, I would go with vmstat and glance to monitor memory management.

Re: Memory Parameters

CHRIS_ANORUO — Thu, 18 May 2000 13:16:33 GMT

Pls goto the online manual of top for more clarification. Use the information from glance more.

cheers!

Re: Memory Parameters

Andy Monks — Thu, 18 May 2000 13:33:38 GMT

I tend to believe Glance and vmstat the most.

There is some good documentation on your machine in :-

/usr/share/doc/mem_mgt.txt

It's work a read, as it describes how hp-ux memory management work, which will lead to a better understanding of what the tools are telling you.