How to determine what value to use for maxswapchunks ?

[Jerry_109]

What is the formula to determine kernel value for "maxswapchunks" ?


# uname -a ; model ; swapinfo -tam ; kmtune | grep maxsw
HP-UX airlock B.11.11 U 9000/800/rp3410


Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 0 4096 0% 0 - 1 /dev/vg00/swap
dev 4096 0 4096 0% 0 - 0 /dev/vg00/swap1
reserve - 727 -727
memory 4689 3429 1260 73%
total 12881 4156 8725 32% - 0 -


maxswapchunks 4096 - 4096



####################################

root@airlock[/root]
# kmtune | grep chunk
maxswapchunks 4096 - 4096
swchunk 2048 - 2048

[Sundar_7 · Accepted solution]

Simple. You should have left the maxswapchunks at the default of 16384. Then you would not need to worry about increasing the maxswapchunks as long as your swap devices size is less than 32 GB.

System wil only recognize ( maxswapchunks * swchunk ) of the swap devices configured.

So with your current setting, your system could only use approximately 8 GB of swap space.

Set it to the default value, it doesnt hurt.

[Jollyjet]

Hi,

Check out these threads which will help you.


http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=971888

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1041791

[Ashish Parashar]

Hello Jerry

Formula is

maxswapchunk * swchunks * DEV_BSIZE =swapspace.

if you HP-UX 11.23 then

maxswapchunks has default maximum value.


Regards

Ashish

[Rasheed Tamton]

Maxswapchunks:
Maximum number of swap chunks where SWCHUNK is the swap chunk size (1 KB blocks - related to parameter swchunk)

used with HP-UX 11, 11i, 11iv1.6
not used >= HP-UX 11iv2

Default: 2048
recommended:
<= Oracle 8i = 4096
>= Oracle 9i = 16384
=============
Swap Chunk Size (1K Blocks):
(related to kernel parameter maxswapchunks)
default: 2048
recommended: 4096 (up to 65536 for large RAM)