psuedo swap and device swap

[hua_1]

i have a system, rp8420 with 8cpu and 16G mem,
I configure 32G LV as swap deivce.and the swapmem_on is set to 1.
here is the swapinfo:

#swapinfo
Kb Kb Kb PCT START/ Kb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 32768000 0 32768000 0% 0 - 1 /dev/vg00/lvol2
reserve - 2732488 -2732488
memory 12950280 3157972 9792308 24%


the device swap is not used any more, question:
should i set the swapmem_on to off, close the psdeo_swap?
will the psuedo_swap be released after the process be started.

[Steve Steel]

Dear Sir

I would leave it as is since this machine is running well.


See
ftp://eh:spear9@hprc.external.hp.com/memory.htm

For more details

The memory is sufficient

You could reduce dbc_max_pct to the equivalent of 20% or 400MB


Steve Steel

[Kent Ostby · Accepted solution]

hua --

You do not want to turn swapmem_on to off.

One bad side effect of doing this is that you wont be able to boot into LVM maintanence mode with it turned off since that is the swap that is used for LVM maintanence mode ( -lm mode).

Your configuration of 2x swap to RAM meets the general HP recommendation for swap and RAM so I would leave it as is unless you feel the need to increase swap for performance at a later date.

Best regards,

Kent M. Ostby

[A. Clay Stephenson]

You have 2X device swap as physical memory. In your case, swapmem_on=1 serves no purpose. Pseudoswap "memory" won't be released as it doesn't exist. Pseudoswap is simply an HP-UX mechanism to allow system with large amounts of memory to not require large amounts of swap; that's why you bought all that memory in the first polace so you wouldn't swap. Pseudoswap is nothing more and nothing less than kernel bookeeping.

Without pseudoswap, if you have a system with 16GB of memory and 4GB of swap (that's perfectly OK), you could only run 4GB of processes eventhough 12GB of memory would be free. With pseudoswap, processes are allowed to count 75% of memory + any "real" swap as swap space so that more processes can be run.