topic Re: Not allowing a process to swap from physical mem to swap in Operating System - HP-UX

Not allowing a process to swap from physical mem to swap

Clifton Smith — Thu, 18 Dec 2003 10:31:46 GMT

We are running HP-UX 11.11 and an Oracle-based application. One of the processes seems to be very susceptible to hangs when any of its subprocesses page out to swap memory. Is there any way by using nice or some other parameter to "lock" a process and its child processes in physical memory so that they don't page out to swap?

Re: Not allowing a process to swap from physical mem to swap

Tomek Gryszkiewicz — Thu, 18 Dec 2003 10:35:08 GMT

I do not think you can do it. The only way is to set up swap in memory..

-Tomek

Re: Not allowing a process to swap from physical mem to swap

John Carr_2 — Thu, 18 Dec 2003 10:37:59 GMT

I think the application would need to changed to do this.

:-) John.

Re: Not allowing a process to swap from physical mem to swap

Mark Grant — Thu, 18 Dec 2003 10:39:19 GMT

I don't think this is possible either and I don't think it would be a very good thing to do. If a process were not swappable you could find yourself in a situation when things ran out of memory and very important processes would not be able to run. You could well trash your system.

Best thing is to have enough RAM so that you don't need to swap

Re: Not allowing a process to swap from physical mem to swap

G. Vrijhoeven — Thu, 18 Dec 2003 10:39:49 GMT

Hi,

It can only be done in the code i think. It needs to alocate lockable memory. This memory cannot be swaped out.

What you can do is install PRM v >2. You can configure memory usage and "CAPPING" by a PRM group. Check http://docs.hp.com for PRM configuration.

Hope this will help,

Gideon

Re: Not allowing a process to swap from physical mem to swap

Don Morris_1 — Thu, 18 Dec 2003 10:40:51 GMT

Within the process itself it could use mlock(2) or plock(2)... but I don't know of any command or interface outside of the process that would do that for an arbitrary process.

Re: Not allowing a process to swap from physical mem to swap

Jeff Schussele — Thu, 18 Dec 2003 10:43:34 GMT

Clifton,

I believe you need to look up the
plock() & mlock()
system calls.

Do a
man 2 plock or mlock
for further details.

HTH.
Jeff

Re: Not allowing a process to swap from physical mem to swap

doug mielke — Thu, 18 Dec 2003 10:46:43 GMT

Isn't there an Oracle concept of 'pinning' into memory? I don't know how it's done, but I thought I'd run across it before.
I'll check an Oracle manual.

Re: Not allowing a process to swap from physical mem to swap

Claudio Cilloni — Thu, 18 Dec 2003 10:48:48 GMT

Maybe you have other not-so-necessary applications/processes running that take a lot of memory; closing them or reducing their memory needs could reduce the paging activity.

Ciao
Claudio

Re: Not allowing a process to swap from physical mem to swap

doug mielke — Thu, 18 Dec 2003 11:39:54 GMT

I didn't find any doc, but our DBA tells me that you can 'pin' an object, ie: package body, tablespace, etc, imnto memory, and it's set in the database start scripts. He did't think a process could be, but any Oracle object may.

Hope this helps.

Re: Not allowing a process to swap from physical mem to swap

Alex Ostapenko — Fri, 19 Dec 2003 06:52:48 GMT

Are you sure that the problem is that the subprocess is hanging because it was paged out? HP-UX has a very robust virtual memory management system and paging mechanism, and I don't think that HP-UX would cause a process to hang just because of its normal memory management.

The process could have hung, therefore not be runnable, and then have been paged out as other runnable processes needed memory. But when you examined it, it's already paged out so it appears that it hung because of paging out. You may have the timeline reversed here: subprocess hangs, then it gets paged out.

Just a thought...

=:-) Alex