Linux kernel 2.6/CentOS 4 & 5 ‘s clock source under a virtualized environment

Under Linux kernel 2.6, the default system timer is set to 1000Hz which will consumes lot of cpu cycle under a virtualized environment even it is in idle state. To run it under a virtualized environment, suitable kernel parameters should be passed to change the clock source and time divider :

for RHEL-4 32 bits: “clock=pmtmr divider=10”
for RHEL-5 32 bits: “divider=10 clocksource=acpi_pm”
for RHEL-4 64 bits: “notsc divider=10”
for RHEL-5 64 bits: “notsc divider=10”

For more information , see this Vmware KB : http://kb.vmware.com/kb/1006427