VM-CPUFreq for x86: Scaling the guest frequency for performance and power savings

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" summary

VM-CPUFreq V2 ported to x86 EPYC exposes guest vCPU utilization to the hypervisor via hypercall and ACPI P‑state hints (min, mid, max). Experiments use tbench dbench cbench on 8 and 16 vCPUs and show no stable performance or power wins; idle‑polling guests force host visibility to 100% utilization and can drive ~10x higher idle power. Current VMCP uses only a lower‑bound utilization and gives guests a boost that raises effective utilization; uclamp min/max and three P‑state granularity do not fix it.

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" chapters (8)

1. 0:00Introduction to VM-CPUFreq
2. 1:08Linux CPU frequency scaling basics
3. 3:15Guest idle behavior and power issues
4. 4:45VMCP patches from Google
5. 6:15Benchmark results with VMCP
6. 8:30Summary and current status
7. 9:14Q&A session begins
8. 14:10Final remarks and feedback