Re: [Patch V3 3/9] sgi-xp: Replace cpu_to_node() with cpu_to_mem() to support memoryless node

[David Rientjes]

On Wed, 19 Aug 2015, Jiang Liu wrote:

> > Why not simply fix build_zonelists_node() so that the __GFP_THISNODE 
> > zonelists are set up to reference the zones of cpu_to_mem() for memoryless 
> > nodes?
> > 
> > It seems much better than checking and maintaining every __GFP_THISNODE 
> > user to determine if they are using a memoryless node or not.  I don't 
> > feel that this solution is maintainable in the longterm.
> Hi David,
> 	There are some usage cases, such as memory migration,
> expect the page allocator rejecting memory allocation requests
> if there is no memory on local node. So we have:
> 1) alloc_pages_node(cpu_to_node(), __GFP_THISNODE) to only allocate
> memory from local node.
> 2) alloc_pages_node(cpu_to_mem(), __GFP_THISNODE) to allocate memory
> from local node or from nearest node if local node is memoryless.
> 

Right, so do you think it would be better to make the default zonelists be 
setup so that cpu_to_node()->zonelists == cpu_to_mem()->zonelists and then 
individual callers that want to fail for memoryless nodes check 
populated_zone() themselves?
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