Too many users requested semaphore undo, increase SEMMNU. (1081)

[ajk_5]

Dear all,

Regarding my rp5470 machine, I got the message "Too many users requested semaphore undo, increase SEMMNU. (1081)" in the first day of live-run yesterday. The current value of SEMMNU is 250. Please help! Thanks a lot!



Best Regards
Ajk

[Steven E. Protter · Accepted solution]

The message might not be right but in order to increase semmnu you have to build yourself a new kernel

The fast way is:

sam

kernel

configurable parameters

find semmnu and increase its value.

You might want to take a look at overall performance tuning on this link:
http://www2.itrc.hp.com/service/cki/search.do?category=c0&docType=Security&docType=Patch&docType=EngineerNotes&docType=BugReports&docType=Hardware&docType=ReferenceMaterials&docType=ThirdParty&searchString=UPERFKBAN00000726&search.y=8&search.x=28&mode=id&admit=-1335382922+1057965897014+28353475&searchCrit=allwords

You might want to collect a bit of performance data because more than likely this is not your only problem.

I'm attaching a script.

SEP

[Steven E. Protter]

Allow me to provide complete instructions. I apologize for letting my mind and fingers wander back there(nobody pick on me).


The fast way is:

sam

kernel configuration

configurable parameters

find semmnu and increase its value.

Actions modify configurable parameter

You will find this one has no linked formulas.

Actions

Process new kernel

Your machine will boot.

Hope in combination these two posts will help.

SEP

[Tim Adamson_1]

Hi Ajk,

Increase SEMMNU. It is pretty normal that problems occur when things go live as volume testing is typically missed.

Depending on what you are running, I would consider doubling it at the very least.

As mentioned above, if you don't know how to make the changes manually, use SAM.


Cheers!

[ajk_5]

I do use your script, but I still can not find what the problem is. Could you please see the attached files? Thanks.

Ajk

[ajk_5]

Attached file 2

[ajk_5]

Attached file 3

[ajk_5]

Attached file 4

[ajk_5]

Attached file 5

[ajk_5]

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[ajk_5]

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[ajk_5]

Attached file 8

[Con O'Kelly]

Hi Ajk

By your response I'm not sure wether you have increased the semmnu kernel parameter. As Steven & Tim have said, your problem is likely to be that semmnu kernel parameter needs to be increased.
Check value of paramteter with:
# kmtune -q semmnu

Increase it to 1500 (currently its only 250) and follow the steps provided by Steven. You need to be aware that this will require a system reboot.

The link below provides information on tunable kernel params for HP-UX.

http://docs.hp.com/hpux/onlinedocs/939/KCParms/KCparams.OverviewAll.html


Cheers
Con

[Steven E. Protter]

In all the months I've been posting up that script, I have never been asked to interpret the results.

Here goes:

You have enough swap space. Your report shows some swap has been reserved but none is actually in use.

Your system is not being pushed really hard.

There seems to be a fair amount of disk i/o but nothing out of the ordinary.

I would in these circumstances proceed with caution.

1) I would follow the procedure to update the kernel, raising semmnu to 500. That will boot the box so you'll have to pick your time based on factors such as your cron schedule, yada, yada yada.

I see you have pvlinks, thats good, and your volume groups and lvm structure has no real problems.

CPU usage is reasonable, and the box seems to be tuned reasonably.

You might want to tell us about what applications you are running that don't show up in swinstall.

You might also want to make sure the June 2003 Gold Pack and Hardware Enablement are installed.

You are a bit behind on that, over two years.

Patching is necessary for good machine operation on HP-UX.

The reason I would do one thing at a time, is you want to know what action solves the problem. Then the next time it happens, you know what to check first.

I'd like to hear from others on what they think of the performance data posted.

Regards,

SEP

[Con O'Kelly]

Hi again

I meant to post detailed kernel steps but hit submit by accident.
If you have not increased a kernel paramter before use SAM as Steven said OR the following command line :

I'd look at increasing semmnu to at least 1500, though others may disagree.

# cd /stand/build
# /usr/lbin/sysadm/system_prep -v -s system
# kmtune -s semmnu=1550 -S /stand/build/system
# /usr/sbin/mk_kernel -s /stand/build/system
# mv /stand/system /stand/system.prev
# mv /stand/build/system /stand
# kmupdate
# shutdown -ry 0

Once you have done the above this should fix the problem.

Cheers
Con

[Steven E. Protter]

Fabulous doc Con, Top notch.

I did my analysis while you only had 4 items posted. The last 4 do not change my conclusions.

Go ahead and do semmnu to at least 500, take the boot and see what happens.

SEP

[Con O'Kelly]

Sorry another post!
I'll revise what I said about size of semmnu. As your nproc is 980 you can't increase semmnu to 1500.
Tim & Steven have the right idea with 500. If you still get the same error, then maybe revise it upwards.

Cheers
Con