topic Paging Contd... in Operating System - HP-UX

Paging Contd...

joe_91 — Tue, 03 Dec 2002 19:42:01 GMT

Team:

Please refer this discussion.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x5a7a85079106d71190050090279cd0f9,00.html

Additional Info:
It is paging out. But the po value in vmstat is 3.
I have attached the glance report of the PID with high memory usage. Can you pl. tell me whether this Application has a memory leak?
Also another strange information is that the Page out happens in the night between 1 am to 9 am (this is the master server and this may be the time when the backups are run. The master server has to back itself up and also other 3 servers. The backup tool is veritas netbackup). Any ideas?

Thanks
Joe.

Re: Paging Contd...

joe_91 — Tue, 03 Dec 2002 20:29:37 GMT

Sorry the glance report here

Thanks
Joe

Re: Paging Contd...

John Bolene — Tue, 03 Dec 2002 20:32:03 GMT

paging out is not a problem, it is the paging back in that shows a memory problem

page outs will happen when HPUX decides that the page has not been referenced in awhile and this can happen for a lower priority process that does not get much cpu time, becuase there are higher priority processes getting the cpu

you will always have some pageins and pageouts, it is the volume of these that is bad

If you don't have at least 90% memory usage and are still having quite a few pages in and out, then you have an application that is coded to do mallocs, use it for a bit, and then release the memory. This is a real bad thing. Programs should be coded to do a malloc and then not relase it if they think they will need it again real soon.

Re: Paging Contd...

John Bolene — Tue, 03 Dec 2002 21:19:42 GMT

So what does this program do?

Looks like it is using variable amounts of shared memory (shmem), and also variable amounts of memory.

Just as I had expected, it is doing lots of malloc for both shared and normal memory and then freeing it when it is done.

This is causing your page in and out as the program grows and shrinks, HPUX has to keep moving it around in memory.