topic Re: Kernel Parameter in Operating System - HP-UX

Kernel Parameter

Rusty Sapper — Thu, 13 Dec 2001 17:23:06 GMT

I need some information on the ncallout parameter. I'm running 11.0 and one of our servers has crashed because the ncallout table was full which caused a system panic.
This is a heavily used system that has had other resource issues because of the number of applications running on it.

Any info or documents would be helpful

TIA

Rusty

Re: Kernel Parameter

Helen French — Thu, 13 Dec 2001 17:28:17 GMT

hey,

ncallout specifies the maximum number of timeouts that can be scheduled by the kernel at any given time.

Acceptable Values:
Minimum
6
Maximum
Memory limited
Default
16+Nproc+USING_ARRAY_SIZE+SERVING_ARRAY_SIZE

Timeouts are used by:

alarm() system call,
setitimer() system call,
select() system call,
drivers,
uucp processes,
process scheduling.

When the system exceeds the timeout limit, it prints the following fatal error to the system console:

panic: timeout table overflow

If the value of nproc is increased, ncallout should be increased proportionately. A general rule is that one callout per process should be allowed unless you have processes that use multiple callouts.

HTH,
Shiju

Re: Kernel Parameter

Rusty Sapper — Thu, 13 Dec 2001 17:34:03 GMT

Yes that helps.
Another question though...
When you say "timeout scheduled by the kernel" I think of some system call (like one in the list you provided) waiting for another resource for a certain period of time then timing out, is that correct?

Re: Kernel Parameter

Helen French — Thu, 13 Dec 2001 17:59:06 GMT

hey,

see this :

http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-90699/B2355-90699_top.html&con=/hpux/onlinedocs/B2355-90699/00/00/58-con.html&toc=/hpux/onlinedocs/B2355-90699/00/00/58-toc.html&searchterms=timeout&queryid=20011213-100210

http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/36217-90194/36217-90194_top.html&con=/hpux/onlinedocs/36217-90194/00/00/42-con.html&toc=/hpux/onlinedocs/36217-90194/00/00/42-toc.html&searchterms=timeout&queryid=20011213-100210

http://www.docs.hp.com/cgi-bin/otsearch/getfile?id=/hpux/onlinedocs/os/KCparam.Ncallout.html&searchterms=ncallout&queryid=20011213-100354

Shiju

Re: Kernel Parameter

Praveen Bezawada — Thu, 13 Dec 2001 18:18:41 GMT

HI

ncallout specifies the maximum number of timeouts that can be scheduled by the kernel at any given time

Default
16+Nproc+USING_ARRAY_SIZE+SERVING_ARRAY_SIZE

ncallout specifies the maximum number of timeouts that can be scheduled by the kernel at any given time. Timeouts are used by:

alarm() system call,
setitimer() system call,
select() system call,
drivers,
uucp processes,
process scheduling.

When the system exceeds the timeout limit, it prints the following fatal error to the system console:

...BPK...

Re: Kernel Parameter

Sanjay_6 — Thu, 13 Dec 2001 18:19:53 GMT

Hi Rusty,

Here is a link on the list of kernel parameters,

http://docs.hp.com//hpux/onlinedocs/os/11i/kcparams/KCparams.OverviewAll.html

Here is the detail on "ncallout"

http://docs.hp.com//hpux/onlinedocs/os/11i/kcparams/KCparam.Ncallout.html

Hope this helps.

Regds

Re: Kernel Parameter

Rusty Sapper — Thu, 13 Dec 2001 22:20:54 GMT

Actually,
Your replies are informative but not as helpful as I need. Frankly, the decription for the kernel parameter is incredibly vague.
Does anyone know anything more than the description and could explain it to someone that knows little about system timeouts?

TIA

Rusty

Re: Kernel Parameter

Steven Sim Kok Leong — Fri, 14 Dec 2001 05:08:57 GMT

Hi,

From various sources,

When the system excees the timeout limit, it prints the following fatal error to the system console:

panic: timeout table overflow

If the value of nproc is increased, ncallout should be increased proportionately. A general rule is that one callout per process should be allowed.

Change ncallout also if you are running an unusually high number of device drivers on your system.

If you are opening many sockets, many of which are waiting on I/O, you will likely run into this limit.
Set ncallout to a value greater than the sum of:

nkthread + the number of I/O devices connected to the machine

If you are running Java 1.X etc, you have to finetune your kernel parameters including ncallout.

Visit this link for more information:

http://www.hp.com/products1/unix/java/infolibrary/prog_guide/java1_3/configuration.html

Hope this helps. Regards.

Steven Sim Kok Leong
Brainbench MVP for Unix Admin
http://www.brainbench.com