How to change the number of processors in a 16-core machine

[Rui Tiago Matos]

On 12/11/2007, Feng Xian <feng.xian at gmail.com> wrote:
> Hi,
>
>  I am doing a scalable test on a 16-core machine (8 dual-core amd
> processors). So I need to vary the processors from 1 to 16. But I
> couldnt remove the cores from motherboard. Is there any way to achieve
> this by changing the max number of processors in the kernel? Thanks!

>From Documentation/kernel-parameters.txt in a linux source tree:

        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
                        should make use of.  maxcpus=n : n >= 0 limits the
                        kernel to using 'n' processors.  n=0 is a special case,
                        it is equivalent to "nosmp", which also disables
                        the IO APIC.

Just add that parameter on your grub config or directly on the grub shell.

Rui