system memory and swapinfo

[TNT-IT]

Hi all,
does anybody know smthing about the following situation:
2 servers, both B2000, hpux 11.0; server "A" with 512Mb memory (from dmesg i see: Physical: 524288 Kbytes), server "B" with 2.5Gb (from dmesg: Physical: 2621440 Kbytes).
On server A swapinfo -t says:
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 1048576 0 1048576 0% 0 - 1 /dev/vg00/lvol2
reserve - 192580 -192580
memory 382588 277700 104888 73%

but on server B the same command output is:
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 1048576 0 1048576 0% 0 - 1 /dev/vg00/lvol2
reserve - 396108 -396108
total 1048576 396108 652468 38% - 0 -
And i have just a 3 lines output, without a 'memory' line.
Where is the problem? Are my 2.5Gb used??

Thanks for any suggestion.
Rgds.
Leonardo.

[Jeff Schussele · Accepted solution]

Hi Leonardo,

It's because system B does not have swapmem_on=1 in it's kernel parameters.
System A does.

HTH,
Jeff

[Borislav Perkov]

Hi Leonardo,

Third line memory on the first server is pseudo-swap memory. I think you don't have it on the second one because you don't have applicatioon running which are producing that amount of pseudo-swap.
The system pretent that it has reserved swap memory, so called pseudo swap, that is because of application need of virtual memory.
Example: if there is 5 applications and they need 20 MB of additional memory each to start working (but they will not use it completely), in case you have only 70 MB virtual memory all 5 applications can't work at once because they "need" 100MB. Those 30 MB extra will be "reserved" from nonexist pseudo swap.
Regards,
Boris

[Victor BERRIDGE]

It seems to have somthing todo with the param swapmem=0 => no memory line
swapmem=1 gives extra memory line...

Check using /usr/sbin/sysdef cmd


All the best
Victor

[TNT-IT]

You're right, swapmem_on=1 on server A and swapmem_on=0 on server B. What is this parameter? And should i set it to 0, or 1 or what?
L.

[Jeff Schussele]

Depends on whether you need pseudo-swap enabled.
All pseudo-swap does is allow approx 75% of memory to mimic actual swap space.
It essentially allows you to start up more processes than swap size alone would.
ALL processes must reserve swap space in case they actually need it.
You just have to pray that the space will never actually have to be used for *actual* page swapping.

Rgds,
Jeff

[Victor BERRIDGE]

Hi again,
Simply said:
You need as much swap as memory to be able to use all the memory, else if lots of RAM you can put swapmem=1 (swith swap mem on) which will use the all the memory by doing some pseudoswap

All the best
Victor

[Victor BERRIDGE]

Sorry I pressed Enter to fast...
I meant "lots of RAM" and smaller swap

Kind regards
Victor