On 11/27/2012 08:09 PM, Bob Liu wrote:

On Tue, Nov 27, 2012 at 4:29 PM, Tang Chen[off-list ref]  wrote:

quoted

Hi Liu,

This feature is used in memory hotplug.

In order to implement a whole node hotplug, we need to make sure the
node contains no kernel memory, because memory used by kernel could
not be migrated. (Since the kernel memory is directly mapped,
VA = PA + __PAGE_OFFSET. So the physical address could not be changed.)

User could specify all the memory on a node to be movable, so that the
node could be hot-removed.

Thank you for your explanation. It's reasonable.

But i think it's a bit duplicated with CMA, i'm not sure but maybe we
can combine it with CMA which already in mainline?

Hi Liu,

Thanks for your advice. :)

CMA is Contiguous Memory Allocator, right?  What I'm trying to do is
controlling where is the start of ZONE_MOVABLE of each node. Could
CMA do this job ?

And also, after a short investigation, CMA seems need to base on
memblock. But we need to limit memblock not to allocate memory on
ZONE_MOVABLE. As a result, we need to know the ranges before memblock
could be used. I'm afraid we still need an approach to get the ranges,
such as a boot option, or from static ACPI tables such as SRAT/MPST.

I'm don't know much about CMA for now. So if you have any better idea,
please share with us, thanks. :)


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