topic Re: swap in Operating System - HP-UX

swap

kholikt — Mon, 24 Dec 2001 02:31:23 GMT

This is the output of my swapinfo.
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 512 191 321 37% 0 - 1 /dev/vg00/lvol2
reserve - 245 -245
memory 172 42 130 24%
total 684 478 206 70% - 0 -

Sometimes the device swap is heavily used especially when the backup started. I am thinking of adding an secondary swap.

Here is my kernel parameter.

maxswapchunks 256
swchunk 2048

Is this okay for me to one additional 512MB of secondary swap without any reboot

Re: swap

Steven Sim Kok Leong — Mon, 24 Dec 2001 02:59:01 GMT

Hi,

Yes you can.

Use either SAM or the swapon command eg.

# swapon /dev/dsk/c0t1d0

For more options, man swapon.

If your maxswapchucks kernel parameter has a value that is too small, SAM will complain.

Hope this helps. Regards.

Steven Sim Kok Leong
Brainbench MVP for Unix Admin
http://www.brainbench.com

Re: swap

Bill Hassell — Mon, 24 Dec 2001 03:57:21 GMT

Adding more swap will allow you to run more processes at the same time, but at a terrible performance penalty. Swap is good for the occasional overflow ort for lots of programs that are interactive and have long wait times between activities.

But if swapping is going for continuous jobs (such as backup) then throughput will be reduced as much as 100:1, and pauses in the data stream will waste space on tape as well as time.

The only fix is to increase RAM substantially.

Re: swap

Wodisch — Mon, 24 Dec 2001 10:16:49 GMT

Hello Kholikt,

you could first try to reduce the amount of RAM "wasted".
Look for processes you do not need (NFS perhaps), the amount of UN*X buffer cache (the default of up to 50% of your RAM is too high for your system, I guess).
That way you could free up precious RAM and then (perhaps, read: if you free up enough) your system won't swap any longer...

Just my $0.02,
Wodisch

Re: swap

John Bolene — Mon, 24 Dec 2001 14:11:07 GMT

As it looks like you have 256Meg of memory, the 512Meg of current swap is plenty.

Check to see if you have swapmem_on set to 1 in your kernel parms. This will enable pseudo swap.

Otherwise, you will need more memory to perform the tasks that you want to do.