Hi All,
currently we encountered two issues with the CPU frequency of the QEMU-KVM guest.
We pin the VCPUs of a guest to a few of the host cores and set the "cpupower governor" of these cores to "performance" mode to use the max CPU frequency. However,
- the guest displays constant CPU freuquency in /proc/cpuinfo, no matter how much of the workload is
- even the VCPUs are 100% loaded, the cores on which they are pinned show only 94% of their max CPU frequency
From the AMD SDM we leanred that CPU frequency is calculated from the values of two registers - MPERF and APERF, and is read to /proc/cpuinfo by queying a CPUID. The first issue was also seen in [1,2].
We'd like to know:
- is there a way to display the host CPU frequency correctly by the VCPUs in the guest ?
- does the power mode setting (e.g. ondemand - > performance) in a guest change the power mode of the pinned host cores ?
Thank you very much for your reply.