pseudo-swap question

[Chuck Ciesinski]

To all,

Please forgive me if the answer is already available as I just got tasked to find out if a patch has been released to fix known problem
# KBRC00015724.

Thanks in advance for any and all assisistance...

Chuck Ciesinski

[Patrick Wallek]

Umm...What's the problem? The Doc ID you give just answers the question "What is pseudo swap?"

What problem are you trying to solve?

If you are wanting to use pseudo-swap, just turn on (set to 1) the kernel parameter swapmem_on, recompile the kernel and reboot.

If you are looking for something else, please provide more information.

[Chuck Ciesinski]

Patrick,

We have a system which one day jumped from 45% utilization of configured memory to 92% utilization and the percentage has stayed at the high utilization level. We are exploring the excessive potential utilization of pseudo-swap and potential recovery processing. The system is an rp8400 with 11.11 v1 ( December 2004 patch level) with 24 GB of memory.

Chuck

[D Block 2]

chuck,

what is your kernel parameters:

# kmtune |grep -i dbc
dbc_max_pct 3 - 3
dbc_min_pct 1 - 1

[A. Clay Stephenson]

Pseudoswap isn't swap at all; it's simply bookkeeping and doesn't use memory. Do a swapinfo -t, the memory row lists the value for pseudoswap but it's really simply space used by processes. A very common cause of the problem you observe is unused/unattached shared memory segments. Do an ipcs -ma and note any large shmid's that have NATTCH = 0. These might possibly be safe to remove; nattach = 0 is a necessary but not necessarily sufficient condition for safe removal of a shmid via ipcrm. Shared memory segments can easily be left dangling if kill -9 has been used. You could also have very large buffer cache settings. On boxers with your amount of memory it makes much more sense to set bufpages to a non-zero value because even small percentages of dbc_xxx_pct can be quite large with 24GB of memory. In general, 800-1600MB for buffer cache is very, very generous so set bufpages to a equal to the number of desired 4KB chunks.

[Ted Buis]

Chuck,

Have you rebooted since the jump in memory utilization? Any zombies?

I can't find KBRC00015724.