topic Re: Changing shmmax kernel parameter in Operating System - HP-UX

Changing shmmax kernel parameter

Indrajit Bhagat — Mon, 22 Aug 2011 10:30:37 GMT

Hi Experts

:/root#model
ia64 hp server rx6600
:/root#uname -a
HP-UX B.11.31 U ia64 3200339551 unlimited-user license

:/root#kctune -v -q shmmax

Tunable shmmax

Description Maximum size of a shared memory segment (bytes)

Module vm_asi

Current Value 1073741824 [Default]

Value at Next Boot 1073741824 [Default]

Value at Last Boot 1073741824

Default Value 1073741824

Constraints shmmax >= 2048

shmmax <= 4398046511104

Can Change Immediately or at Next Boot

I need to change the shmmax parameter to 0x40000000000

I am confused to proceed

does #kcutne shmmax=0x40000000000 will change the desired paramter. Please suggest me whehter i am correct or not

Re: Changing shmmax kernel parameter

James R. Ferguson — Mon, 22 Aug 2011 12:06:44 GMT

@Indrajit Bhagat wrote:

I need to change the shmmax parameter to 0x40000000000

does #kcutne shmmax=0x40000000000 will change the desired paramter.

So, your really have some 4TB of memory on this server? While you might want to increase your 'shmmax' from the default, it is probably absurd to jump to the maximum.

This said, yes, 'kctune shmmax=<value>' will change the tunable immediately in this case as the output of your query shows.

Regards!

...JRF...

Re: Changing shmmax kernel parameter

rariasn — Mon, 22 Aug 2011 12:14:31 GMT

Hi:

/usr/sbin/kctune -C "Reason for Change" -B shmmax="0x40000000000"

rgs,

Re: Changing shmmax kernel parameter

Indrajit Bhagat — Mon, 22 Aug 2011 12:31:27 GMT

Hi James

Currently I am having Memory of 15.97 GB, and I hope there is some change schedule for increasing the memory, according to that , I need to check the exact memory after the change happened and according to that i need to change the kernel parameter

:/root#machinfo|more
CPU info:
4 Intel(R) Itanium 2 9000 series processors (1.59 GHz, 18 MB)
532 MT/s bus, CPU version C2
8 logical processors (2 per socket)

Memory: 16351 MB (15.97 GB)

Re: Changing shmmax kernel parameter

Steven E. Protter — Mon, 22 Aug 2011 14:46:53 GMT

Shalom,

You don't need to change the number to an exact format match. That figure you have can be translated into a number, which is the minimum shmmax figure in bytes you need for the application.

You might want to look at ipcs output and see how your current use is set up.

I assume you have an application that you are installing that has minimum requirements. The details on this application would be helpful in provideing further assistance.

SEP

Re: Changing shmmax kernel parameter

Dennis Handly — Tue, 23 Aug 2011 05:23:56 GMT

>you really have some 4TB of memory on this server? ... it is probably absurd to jump to the maximum.

Right. But she could have the just announced 32 socket Superdome 2 with 4 TB memory.

Perhaps something like 50% of your 16 Gb. And what is your filecache_max(5)?

Re: Changing shmmax kernel parameter

sunil_astekar — Fri, 05 Apr 2013 05:27:09 GMT

SHMMAX kernel tunable value should be equal to installed Physical Memory in bytes, For ex : If installed memory in a server is 16GB shmmax value should be 16*1024*1024*1024=17179869184
Command
kctune shmmax=17179869184