Re: [Xen-devel] Core parking feature enable

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.02.12 at 09:54, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> 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.

Does this really need to be implemented in the hypervisor? All this
boils down to is a wrapper around cpu_down() and cpu_up(), which
have hypercall interfaces already. So I'd rather see this as being
an extension to Dom0's pCPU management patches (which aren't
upstream afaict)...

Jan


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