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Kernel tuning

Frequent Advisor

Kernel tuning


Can you guys please help ?
I have problem in changing the kernel value as below.

NPROC = ((20+8*MAXUSERS)*2)
SEMNS = 4109

It always encountered errors as below.

ncallout >= nkthread
semmni <= semns

Attached includes the screenshot of error and current kernel values.

Gokul Chandola
Trusted Contributor

Re: Kernel tuning

I have seen the screen shot, there is clearly show that you are defining wrong parameter those are not in system.
You can change within existing parameter.
But there should be option for Customization.

Gokul Chandola
There is always some scope for improvment.
Frequent Advisor

Re: Kernel tuning

hi Gokul,

The system now is not allow me to change.
Any idea how to proceed further ?
Rita C Workman
Honored Contributor

Re: Kernel tuning

Based on the parms, I'm guessing your at 11v1 or lower.

There are a number of parms that are generated by an associated calculation that depends on the value of another parm.
If you wish, you can change that by setting the values yourself and removing the "calculation" for those parms. But here's the have to read the parms description and find out what parm affects another parm and change them in order. Confusing at times.

Example your ncallout >= nkthread
If you look at nkthread it says:
nkthread >= nproc +100
nkthread >= max_thread_proc
..and let's not forget that nproc has more than one parm that it affects, but nproc's may not be nkthread or ncallout.

So you need to adjust nproc first (personally I set these manually and also manually reset the parms it affects, but it's your choice to stick with the calcs) to what value you want. But bear in mind to make sure that what you set it to will allow you to set nkthread so it will be > greater than or = equal to ncallout.

Similar on the semaphore need to change the leading parm. For semaphores you will note that semmns and semmni have that close relationship. semmns must be greater than semmni. So if your going up in numbers make sure semmns is greater than semmni and change semmns first. If your reducing...than switch and do semmni first and then adjust the other accordingly.

Read the description on maxusers and nproc and again decide to go with calc or change manually and set accordingly.

I hope this made some sense and I didn't typo too much. Probably the best advice I can give is to ask your employer to let you take a course on Performance & Tuning. It really helps.

Hakki Aydin Ucar
Honored Contributor

Re: Kernel tuning

Easier way to do :

Go to SAM > Kernel Configuration > Configurable Parameters

to see if your adjusted parameters are available ? if yes right click on to mouse and Modify Configurable Parameters

Frequent Advisor

Re: Kernel tuning

hi all,

Thanks for those valued comments thus far.
But just one question again, since as we know kernel tuning could be done by using sam.

Is there anyway to modify /stand/system and run command to perform kernel compile ?

If it work, could eliminate of lot errors and time saving.

Johnson Punniyalingam
Honored Contributor

Re: Kernel tuning

>>Is there anyway to modify /stand/system and run command to perform kernel compile ?<<<

Answer to you above Question simple . Please try in the devlopment box than proceed to the live server.

Below are steps I usual follow with out SAM

Best Recomdation from my Expereince "SAM"

Procedures for Kernel Parameter changes
# cd /stand
# cp system system.prev.<050112>
# cp vmunix vmunix.prev.<050112>

# cd /stand/build
# /usr/lbin/sysadm/system_prep -s /stand/build/system
# vi /stand/build/system (....edit the file to make the necessary changes --> e.g. "max_thread_proc 3072")
# /usr/sbin/mk_kernel -s /stand/build/system
# mv system /stand/system
# /usr/sbin/kmupdate

Kernel update request is scheduled.

Default kernel /stand/vmunix will be updated by
newly built kernel /stand/build/vmunix_test
at next system shutdown or startup time.


Problems are common to all, but attitude makes the difference
Frequent Advisor

Re: Kernel tuning

hi Johnson,

Thanks for your input. It really helps me to resolve the problem. Very much appreciated.

Have a good day!
Frequent Advisor

Re: Kernel tuning

Solution provided by Johnson is helpful and valid.