Re: [PART3 Patch 00/14] introduce N_MEMORY

[David Rientjes]

On Wed, 31 Oct 2012, Wen Congyang wrote:

> From: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> 
> This patch is part3 of the following patchset:
>     https://lkml.org/lkml/2012/10/29/319
> 
> Part1 is here:
>     https://lkml.org/lkml/2012/10/31/30
> 
> Part2 is here:
>     http://marc.info/?l=linux-kernel&m=135166705909544&w=2
> 
> You can apply this patchset without the other parts.
> 
> we need a node which only contains movable memory. This feature is very
> important for node hotplug. So we will add a new nodemask
> for all memory. N_MEMORY contains movable memory but N_HIGH_MEMORY
> doesn't contain it.
> 
> We don't remove N_HIGH_MEMORY because it can be used to search which
> nodes contains memory that the kernel can use.
> 

This doesn't describe why we need the new node state, unfortunately.  It 
makes sense to boot with node(s) containing only ZONE_MOVABLE, but it 
doesn't show why we need a nodemask to specify such nodes and such 
information should be available from the kernel log or /proc/zoneinfo.

Node hotplug should fail if all memory cannot be offlined, so why do we 
need another nodemask?  Only offline the node if all memory is offlined.
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