[SOLVED] Change/Limit numbers core of CPU

tquang · 06-29-2012, 02:56 AM

Hi,

That is crazy title of thread. Really, my partner required me decrease numbers core CPU from 16 to 8. Because he say "incompatible if run 16 cores).
In Windows, i can do that with: run > msconfig > boot > advance > number cpu boot.
And in Linux, how can i do that?

Thanks alot

syg00 · 06-29-2012, 03:15 AM

You can pass a parm to the kernel via grub/lilo to limit CPUs - maxcpus=8 say in your case.
This is for the life of the boot for all users.

If you have CPU hotplug enabled you can configure CPUs offline dynamically. This might be problematic for some software. Have a read of this.

Didier Spaier · 06-29-2012, 03:15 AM

In Linux you can use the kernel parameter maxcpus.

For instance in lilo I would add a line in the relevant image section of /etc/lilo.conf:

Code:

append = "maxcpus=8"

I suppose you can do something similar with Grub.

To know more, see the file Documentation/kernel-parameters.txt.

Or you can recompile your kernel to change the value of NR_CPUS but I guess that you would prefer to change the value at runtime.

jefro · 06-29-2012, 09:27 AM

The program is faulty I'd think. Even a single core application runs on 16x systems. Fix the program?

I forget the program but it limits cpu's after boot time to an application. I am pretty sure someone here posted that a year ago and I had to look it up to believe it. I can't find it now.

tquang · 06-29-2012, 09:30 AM

Thanks syg00, Didier Spaier

I'm still use GRUB, and here

Example Original

Code:

title CentOS (2.6.18-308.4.1.el5)
        root (hd0,0)
        kernel /vmlinuz-2.6.18-308.4.1.el5 ro root=LABEL=/
        initrd /initrd-2.6.18-308.4.1.el5.img

Edit append maxcpus=8

Code:

title CentOS (2.6.18-308.4.1.el5)
        root (hd0,0)
        kernel /vmlinuz-2.6.18-308.4.1.el5 ro root=LABEL=/ maxcpus=8
        initrd /initrd-2.6.18-308.4.1.el5.img

Quote:

Originally Posted by jefro

The program is faulty I'd think. Even a single core application runs on 16x systems. Fix the program?

I forget the program but it limits cpu's after boot time to an application. I am pretty sure someone here posted that a year ago and I had to look it up to believe it. I can't find it now.

Thank you. At first time, I only provide for my partner system installed with his request. I don't managemet