The Xen hypervisor offers a mechanism to balance performance and power consumption through CPU frequency scaling. Known as the Current Governor, this mechanism can lower power consumption by throttling the clock speed when a CPU is idle.
Certain versions of Oracle VM Server have the Current Governor set to
ondemand
by default, which dynamically scales
the CPU clock based on the load. Oracle recommends
that on Oracle Private Cloud Appliance compute nodes you run the Current
Governor with the performance
setting.
Particularly if you find that systems are not performing as
expected after an upgrade of Oracle VM Server, make sure that the
Current Governor is configured correctly.
To verify the Current Governor setting of a compute node, log in using SSH and enter the following command at the Oracle Linux prompt:
]# xenpm get-cpufreq-para
cpu id : 0
affected_cpus : 0
cpuinfo frequency : max [2301000] min [1200000] cur [2301000]
scaling_driver : acpi-cpufreq
scaling_avail_gov : userspace performance powersave ondemand
current_governor : performance
scaling_avail_freq : *2301000 2300000 2200000 2100000 2000000 1900000 1800000 1700000 1600000 1500000 1400000 1300000 1200000
scaling frequency : max [2301000] min [1200000] cur [2301000]
turbo mode : enabled
[...]
The command lists all CPUs in the compute node. If the
current_governor
parameter is set to anything
other than performance
, you should change the
Current Governor configuration.
To set performance mode manually, enter this command: xenpm set-scaling-governor performance.
To make this setting persistent, add it to the
grub.cfg
file.
Add the xen cpu frequency setting to the
/etc/default/grub
template file, as shown in this example:GRUB_CMDLINE_XEN="dom0_mem=max:6144M allowsuperpage dom0_vcpus_pin dom0_max_vcpus=20
cpufreq=xen:performance max_cstate=1
"Rebuild
grub.cfg
by means of the following command:# grub2-mkconfig -o /boot/grub2/grub.cfg