topic Re: Memory Utilisation is high in Operating System - HP-UX

Memory Utilisation is high

rahul90 — Mon, 29 Oct 2007 04:27:43 GMT

Hi

I am using rp3440 server with OS HP-UX 11.11.In this server the Memory utilisation is at 100%.I checked the swap uitilisation but its 28% only.I hv 4gb of physical memory.I dont know Why its not using the swap space fully.Any settings for reducing memory utilisation ?.

Re: Memory Utilisation is high

Murat SULUHAN — Mon, 29 Oct 2007 04:34:49 GMT

Hi Rajeshraj

Please run top tool to find out which process utilize your memory

You can also submit top output

Best Regards
Murat

Re: Memory Utilisation is high

Mike Shilladay — Mon, 29 Oct 2007 04:35:09 GMT

Hi,

It is probabaly the buffer cache, which by default is set to 50%. You can reduce this by changing the kernel parameter dbc_max_pct from 50 to something smaller.

Mike.

Re: Memory Utilisation is high

Dennis Handly — Mon, 29 Oct 2007 05:22:15 GMT

>In this server the Memory utilisation is at 100%. I checked the swap utilisation but it's 28% only.

This is a GOOD thing.

>I don't know why its not using the swap space fully.

Using swapspace is a bad thing. (I'm assuming that the amount of swapspace is more than your 4 Gb.)

As Mike said, it is probably the buffer cache.
What is the output of "swapinfo -tam"?

Re: Memory Utilisation is high

whiteknight — Mon, 29 Oct 2007 05:22:27 GMT

hi Raj,

mike is right. Check dbc_max_pct what is the value, if it is 50 default, do consider to reduce to 20.

Swap space would not utilize because your memory is sufficient, which is good!

WK

Re: Memory Utilisation is high

Hasan Atasoy — Mon, 29 Oct 2007 05:48:31 GMT

you can find top memory users by this command..

UNIX95=1 ps -e -o vsz,pid,ruser,args | sort -rn

mathmad.

Re: Memory Utilisation is high

rahul90 — Mon, 29 Oct 2007 05:49:34 GMT

Hi

Here I pasted the kernel parameter for the buffer cache.

kmtune | grep dbc
dbc_max_pct 8 - 8
dbc_min_pct 5 - 5

Can u help me on this ?

Re: Memory Utilisation is high

Bill Hassell — Mon, 29 Oct 2007 19:28:43 GMT

4GB RAM means dbc_min = 200 megs, dbc_max = 320 megs, a bit low for this system. You need about 600-800 megs with this class of server for good filesystem performance. Leave dbc_min_pct=5 and change dbc_max_pct to 16. This will probably increase the swap space usage a bit more -- which is the way HP-UX is designed. If you want to use more swap space, just have more users login and run more processes.

Now as Dennis mentioned previously, using swapspace is a bad thing. It means that you have used all your memory and processes are being deactivated and paged out to make room for more processes. HP-UX is a virtual memory design and you can continue adding more processes as long as you have swap space. But the performance will be awful. Almost no work will get done while all the processes are fighting for memory so they can run.

There are two solutions:

1. Do not run as many processes at the same time,

2. double the amount of memory you have installed

The second choice will greatly improve performance on your system as swap usage will now be 0%.