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Re: [Xen-devel] Core parking feature enable

I would really doubt the need to create a new interface of receiving
ACPI event and sending to user land (other than existing native
kernel) specifically for Xen. What's the benefit and why kernel people
should buy-in that?
Core parking is a platform feature, not virtualization feature.
Naturally following native approach is the most efficient. Why do you
want to create yet another interface for Xen to do that?

Shan Haitao

2012/3/1 Jan Beulich <JBeulich@xxxxxxxx>:
>>>> On 01.03.12 at 15:31, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
>> Jan Beulich wrote:
>>>>>> On 01.03.12 at 12:14, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
>>>> Unfortunately, yes, though cumbersome is not basic reason user space
>>>> approach is not preferred. Core parking is a power management staff,
>>>> based on dynamic physical details like cpu topologies and maps owned
>>>> by hypervisor. It's natural to implement
>>> CPU topology is available to user space, and as far as I recall your
>>> hypervisor patch didn't really manipulate any maps - all it did was
>>> pick what CPU to bring up/down, and then carry out that decision.
>> No. threads_per_core and cores_per_socket exposed to userspace is pointless
>> to us (and, it's questionable need fixup).
> Sure this would be insufficient. But what do you think did
> XEN_SYSCTL_topologyinfo get added for?
>> Core parking depends on following physical info (no matter where it
>> implement):
>> 1. cpu_online_map;
>> 2. cpu_present_map;
>> 3. cpu_core_mask;
>> 4. cpu_sibling_mask;
>> all of them are *dynamic*, especially, 3/4 are varied per cpu and per
>> online/offline ops.
> Afaict all of these can be reconstructed using (mostly sysctl)
> hypercalls.
> Jan
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