[CentOS-virt] Enabling KSM with ksmctl under Centos 5.4

Are their any good guides out there on how to use ksmctl to enable and tune KSM performance on Centos/RedHat

At the moment the only guidelines I can find are from the following OLS paper, plus the Linux Kernel Docs. * http://www.kernel.org/doc/ols/2009/ols2009-pages-19-28.pdf * http://www.kernel.org/doc/Documentation/vm/ksm.txt

On a basic dual core testbed with 4GB Ram and 4-5 VMs I've tried

ksmctl start 60 5000

This resulted in a 5% system cpu load as it tried to recover shared space. Sadly I can't tell how well it is working as we don't have /sys/kernel/mm/ksm support in Centos.

Has anyone got some guidelines on how to relate number of pages + interval to number of CPUs and Ram.

Cheers

Steve