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SubjectXen core parking feature enable
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Sorry, forget cc kernel development list.

Core parking is a power control feature and it can co-work with NPTM to control system power budget through online/offline some CPUs in the system. These patches implement core parking feature for xen. They consist of 2 parts: dom0 patches and xen hypervisor patches.

At dom0 side, patches include
[Patch 1/3] intercept native pad (Processor Aggregator Device) logic, providing a native interface for natvie platform and a paravirt template for paravirt platform, so that os can implicitly hook to proper ops accordingly;
[Patch 2/3] redirect paravirt template to Xen pv ops;
[Patch 3/3] implement Xen pad logic, and when getting pad device notification, it hypercalls to Xen hypervisor for core parking. Due to the characteristic of xen continue_hypercall_on_cpu, dom0 seperately send/get core parking request/result;

At Xen hypervisor side, patches include
[Patch 1/2] implement hypercall through which dom0 send core parking request, and get core parking result;
[Patch 2/2] implement Xen core parking. Different core parking sequence has different power/performance result, due to cpu socket/core/thread topology. This patch provide power-first and performance-first policies, users can choose core parking policy on their own demand, considering power and performance tradeoff.

cc Shaohua, core parking feature author at linux kernel side.

Thanks,
Jinsong

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