If you have upgraded from an earlier release, it is possible that some of the hypervisor boot parameters for your server may need editing to ensure that newer features are enabled. To update these boot parameters, on each affected Oracle VM Server, open /boot/grub.conf in an editor. Edit the line starting with kernel /xen.gz and append the required boot parameters.

To support Huge Pages on Para-Virtualized (PV) guests

Huge page support, for PV guests, requires that the Xen hypervisor starts with the boot parameter allowsuperpage set. To allow the hypervisor to use this feature when starting up virtual machines, you must append the option to the kernel boot parameters. For example:

kernel /xen.gz console=com1,vga com1=57600,8n1 dom0_mem=1440M allowsuperpage

You must reboot the server for this setting to take effect.

For large servers with more than 20 physical CPUs

For Oracle VM Servers with more than 20 physical CPUs, performance can be improved by pinning virtual CPUs to dom0 and setting a maximum value for the number of virtual CPUs that can be used by dom0. On a new install where a system has more than 20 physical CPUs, this value is usually set to 20. To ensure that you get the best possible performance on an Oracle VM Servers with more than 20 physical CPUs, set the Xen boot parameters dom0_vcpus_pin and dom0_max_vcpus=20. For example:

kernel /xen.gz console=com1,vga com1=57600,8n1 dom0_mem=32768M allowsuperpage dom0_vcpus_pin \
  dom0_max_vcpus=20

You must reboot the server for these settings to take effect.