shmmax

[George Abraham_1]

Dear Admins..

I have a K460 running HP-UX 11.00 64bit
Memory is 2GB

the shmmax value is set : 3.75GB
shmmni is 512 and shmseg is 50.. is it ok to have shmmax so high?...

The systems is running with UNIDATA.. it works fine except that i see a bunch of defunct processes. Is this related...

please reccomend kernel changes id required..
Thanks in advance
George

[Jeff Schussele]

Hi George,

It's OK, but kind of pointless, to have it exceed the actual system RAM.

I doubt the defunct processes are related to these values in any way.

My $0.02,
Jeff

[Pete Randall]

George,

I can't imagine any relationship between a high shmmax and defunct process - they're just process that didn't clean up after themselves when they died. A reboot or killing the parent (assuming it's not 1) will clear the defunct processes.

You should be fine.

Pete

[Byron Myers · Accepted solution]

I don't believe shmmax set that high will hurt - if a program tries to grab an SHM segment when there isn't sufficient free memory, then that shmget call will just fail. The defunct processes are there because their parent(s) is not "wait"ing for them - when a child process dies, the parent must call wait to fetch the child's return status. If the parent dies, then the children are adopted by init (process 1) which is repeatedly wait'ing for its children. The only way, I see, that shmmax can in any way be related is if a parent forks a child that thinks it can grab a shm segment larger than your available memory (2 GB max), does not handle the shmget ret (fail) appropriately, dies or even exits gracefuly, and the parent does not wait for the dead child.

[John Bolene]

your shmmax at 3.75G is the max for 11.00

now if you want to go to 11.11, think much bigger

depending on how much shared memory is requested, other programs may not have memory to start in

a better number would probably be 1G