topic Re: Swap 86% utilized. in Operating System - HP-UX

Swap 86% utilized.

jaivinder — Tue, 10 Feb 2009 01:43:08 GMT

Hi Gurus,

I have a RP7420 box running HPUX 11i V1, From last one month the swap utilization is more than 86%. Can anybody help me how to reslove this issue.

root@tsttib06[/root]# model
9000/800/rp7420
root@tsttib06[/root]# uname -a
HP-UX tsttib06 B.11.11 U 9000/800 1350824619 unlimited-user license

root@tsttib06[/root]# swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 16384 130 16254 1% 0 - 1 /dev/vg00/lvswap
reserve - 16254 -16254
memory 25550 19746 5804 77%
total 41934 36130 5804 86% - 0 -

Thanks in advance,
Jaivinder

Re: Swap 86% utilized.

Jeeshan — Tue, 10 Feb 2009 03:40:11 GMT

add more swap spaces.

Re: Swap 86% utilized.

Avinash20 — Tue, 10 Feb 2009 04:25:24 GMT

You could observe in the above output that you have device swap of 16384 MB

Here around 16254 MB of swap is already been reserved by the process.

You need to increase the swap space for the same, else your process might not find enough swap to reserve and hence will get terminated

You also will see message in dmesg "Deffered Swap reservation..."

Hence increasing the swap is advisable.

Re: Swap 86% utilized.

Bill Hassell — Tue, 10 Feb 2009 04:26:04 GMT

Actually, using swap space is a bad thing, especially if the page out rate is 2 or 3 digits. Use the command:

vmstat 2 2

Look at the "po" column. Anything over 25-50 indicates that your RAM (memory) is not large enough. Anything over 100 indicates severe memory shortage. There are two 3 choices:

1. accept the slow speed of all the processes

2. Stop running so many processes, and/or reduce memory usage for programs that can be controlled.

3. Add a LOT more memory. You need to double your RAM for optimum performance.

Re: Swap 86% utilized.

Avinash20 — Tue, 10 Feb 2009 04:47:38 GMT

Ah !! Yes,, I never observed,. Swap is Being 1% used, This means that swapping is taking place.

Please check for po secion in vmstat output as suggested above

If the po (page-outs) are very high, please check the free memory available from the top command in Memory section

If the free memory is low, you need to find the process which are utilizing more physical memory. Script like kmeminfo/glance help us to find the same

Also see that the kernel parameters dbc_max_pct is tuned correctly from the default 50 which is very high in case if you are not using this as a backup server.

Re: Swap 86% utilized.

Frank de Vries — Tue, 10 Feb 2009 06:44:08 GMT

There are different opions on this.
That swap is being used in practical terms is not so bad.
We have oracle servers here that run for a decade with high totals like your 86% with
no impact to the end user at all.

You will see that it will go down as well after a while.

It is wise however, to monitor this.

If you really want to be pro-active,
check if the sizes of your SGA can be sized down.

Rule of thumb , do not use more then 40% of total memory for your SGA. Ideally not more then 33%.

Re: Swap 86% utilized.

Steven E. Protter — Tue, 10 Feb 2009 08:36:03 GMT

Shalom,

Your system is under memory pressure.

dev 16384 130 16254 1% 0 - 1 /dev/vg00/lvswap
reserve - 16254 -16254

This is like a market. Either you increase the supply of memory or you decrease the demand. Demand is high.

Increasing the supply by adding swap will not improve system performance.

If you have oracle databases, see about decreasing demand in the SGA configuration. Or see about adding physical memory.

Performance measurement:
http://www.hpux.ws/?p=6

Memory leak detector:
http://www.hpux.ws/?p=8

A program/app with a memory leak could cause this problem.

SEP