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Changing shmmax kernel parameter

Regular Advisor

Changing shmmax kernel parameter

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



6 REPLIES
Acclaimed Contributor Acclaimed Contributor

Re: Changing shmmax kernel parameter


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...

Honored Contributor Honored Contributor

Re: Changing shmmax kernel parameter

Hi:

 

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

 

rgs,

Regular Advisor

Re: Changing shmmax kernel parameter

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)


Exalted Contributor Exalted Contributor

Re: Changing shmmax kernel parameter

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

Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
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Acclaimed Contributor Acclaimed Contributor

Re: Changing shmmax kernel parameter

[ Edited ]

>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)?

Highlighted
Occasional Visitor

Re: Changing shmmax kernel parameter

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