On 04/11/2014 04:00 AM, David Rientjes wrote:
> On Thu, 10 Apr 2014, Naoya Horiguchi wrote:
>> > Yes, that's right, but it seems to me that just node_start_pfn and
>> > node_end_pfn
>> > is not enough because there can be holes (without any page struct backed)
>> > inside
>> > [node_start_pfn, node_end_pfn), and it's not aware of memory hotplug.
>> >
> So? Who cares if there are non-addressable holes in part of the span?
> Ulrich, correct me if I'm wrong, but it seems you're looking for just a
> address-to-nodeid mapping (or pfn-to-nodeid mapping) and aren't actually
> expecting that there are no holes in a node for things like acpi or I/O or
> reserved memory.
...
> I think trying to represent holes and handling different memory models and
> hotplug in special ways is complete overkill.
This isn't just about memory hotplug or different memory models. There
are systems out there today, in production, that have layouts like this:
|------Node0-----|
|------Node1-----|
and this:
|------Node0-----|
|-Node1-|
For those systems, this interface has no meaning. Given a page in the
shared-span areas, this interface provides no way to figure out which
node it is in.
If you want a non-portable hack that just works on one system, I'd
suggest parsing the existing firmware tables.
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