Re: tmpfs round-robin NUMA allocation

["Martin J. Bligh" <mbligh@aracnet.com>]

> 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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