Some legacy Linux guests may cause a high CPU load even if the guest system appears to be idle. This can be caused by a high timer frequency of the guest kernel. Some older Linux distributions ship a Linux kernel configured for a timer frequency of 1000Hz. We recommend recompiling the guest kernel and selecting a timer frequency of 100Hz.

Linux kernels shipped with Red Hat Enterprise Linux, as well as kernels of related Linux distributions, such as CentOS and Oracle Linux, support a kernel parameter divider=N. Hence, such kernels support a lower timer frequency without recompilation. Add the kernel parameter divider=10 to select a guest kernel timer frequency of 100Hz.