topic Re: usage of shared memory? in Operating System - HP-UX

usage of shared memory?

usergroup.os.ux-3.4-iro — Tue, 06 May 2003 08:01:18 GMT

Hi,

I have a machine wich sometime go's "sleeping".
I think it is a memory problem, because of paging activity.

How can i detect the actual usage of shared memory ? ( is ipcs -ma the only way ?)
And second: Where in swapinfo output is the shared memory usage hidden?

Re: usage of shared memory?

Stefan Farrelly — Tue, 06 May 2003 08:18:36 GMT

To confirm you theory of paging activity then monitor if with;

vmstat 1 100

and look at the pi and po columns. If these are running >1 constantly then you are indeed paging and have run out of free memory.

ipcs -ma shows what shared memory is allocated to what user/pid. It doesnt show how much of the allocated memory is actually being used. I dont believe you can easily work this out, you would need to attach to the shared memory segment and add up whats currently being used, not easy, and requires some C programming.

swapinfo -mt does include shared memory usage, its under the memory line in the USED column. Its listed here because shared memory is locked in memory - it cant be paged out, thus its listed as used becuase it cant be used for paging activity. However, all processes locked into memory are in this column, not only shared memory.

Re: usage of shared memory?

Zeev Schultz — Tue, 06 May 2003 08:20:25 GMT

swapinfo is all about paging/swapping.it doesn't care if it's shared or regular memory segment imho.ipcs -m -p + top (see resident memory sizes) or Glance should do the task.

regards

zeev.

Re: usage of shared memory?

Armin Feller — Tue, 06 May 2003 08:27:11 GMT

Hi,

I think the command 'ipcs -a -m' and Glance are the only ways to display the current shared memory usage.

If you have a software contract with HP, please contact your local HP-Support-Center and ask for following utilities 'shminfo' and 'kmeminfo'. This unsupported tools display a lot more infos of shared memory usage.

Like I know is there no option in 'swapinfo' about shared memory, you only get informations about swap space.

Best regards ..
Armin

Re: usage of shared memory?

Zeev Schultz — Tue, 06 May 2003 08:27:48 GMT

Or obtain shminfo from:
ftp://contrib:9unsupp8@hprc.external.hp.com/sysadmin/programs/shminfo/

Re: usage of shared memory?

Mike Stroyan — Wed, 07 May 2003 14:02:36 GMT

Stefan,
Shared memory is not always locked into memory. A program with appropriate privileges can choose to lock it with shmctl(SHM_LOCK). Perhaps you use a lot of programs that choose to do that.