I looked at using the MPOL_INTERLEAVE policy to accomplish this,
however I think there's a flaw with that approach.  Since that
policy uses the vm_pgoff value (which for tmpfs is determined by
the inode swap page index) to determine the node from which to
allocate, it seems that we'll overload the first few available
nodes for interleaving instead of evenly distributing pages.
This will be particularly exacerbated if there are a large number
of small files in the tmpfs filesystem.

...

So, the big decision is whether I should put the round-robining
into tmpfs itself, or write the more general mechanism for the
NUMA memory policy code.

Doesn't really seem like a tmpfs problem - I'd think the general
mod would be more appropriate. But rather than creating another
policy, would it not be easier to just add a static "node offset"
on a per-file basis (ie make them all start on different nodes)?
Either according to the node we created the file from, or just
a random node?

M.

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