kernel parameter effective_maxpid

[Simone Teles da Hora_5]

Hi,

How can i limit PID number? I have a rp3440 + 11i (HP-UX 11.11)? There is a define MAXPID on /usr/include/sys/param.h which limit Maximmum PID in 8 millions, but there is another kernel parameter which does it too!!
How can it works?

** HP-UX 11.00 this limit is 30.000!!

thanks

STH

[Steven E. Protter]

Use kmtune to limit the number. Its a formula by default in the OS install, but you can change it.

kmtune -s effective_maxpid=

Process for manually building and installing a kernel:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=105739

sam kernel, configurable parameters will also do this btw.

Frankly I am wondering about that header file.

Maybe you should change it.



SEP

[Simone Teles da Hora_5]

Steven,

I´m not complete sure, but I see process with PID great than 30.000, and my kernel parameter configurated as 30.000, look at this:

[root@fenix shora]# kmtune -q effective_maxpid
Parameter Current Dyn Planned Module Version
===============================================================================
effective_maxpid - - ((NPROC<=30000)?30000:(NPROC*5/4))

How can it be possible?

thanks

ST

[A. Clay Stephenson]

First, never change a value in a sys/ header file unless you really know what you are doing. That is an excellent way to create an unbootable or unstable machine.

What is the value of nproc?

Consider the case of a machine that had a very large nproc. 30000 could be less than nproc so that no pid's might be available.

If you don't fall into this category, simply replace the formula with a hard-coded value of 30000 and build a new kernel.

[Simone Teles da Hora_5]

Clay,

nproc = 2.500 and effective_maxpid = 30.000.

But i can see process with PID great than 30.000. how can it be possible?

[]´s

S

[A. Clay Stephenson]

Okay, it's time to ask the kernel itself what the tunable is set to:

echo "effective_maxpid/D" | adb /stand/vmunix /dev/kmem

[Kent Ostby]

Simone --

This formula:

((NPROC<=30000)?30000:(NPROC*5/4))

means that if the NPROC is <= 30000 then make it 30000.

If we fail the test of (NPROC<=30000), i.e. NPROC is > 30000, then the value is set to NPROC * 1.25.

So you would have to change the formula or assign a value to effective_maxpid.

This doesnt mean that its a good idea to do so.

Best regards,

Oz

[Simone Teles da Hora_5]

echo "effective_maxpid/D" | adb /stand/vmunix /dev/kmem
effective_maxpid:
effective_maxpid: 30000