Re: 2.4.19pre1aa1

["Martin J. Bligh" <Martin.Bligh@us.ibm.com>]

> Not stability per se, but you have to admit the VM tends to
> behave badly when there's a shortage in just one memory zone.
> I believe NUMA will only make this situation worse.

rmap would seem to buy us (at least) two major things for NUMA:

1) We can balance between zones easier by "swapping out"
pages to another zone.

2) We can do local per-node scanning - no need to bounce
information to and fro across the interconnect just to see what's
worth swapping out.

I suspect that the performance of NUMA under memory pressure
without the rmap stuff will be truly horrific, as we decend into 
a cache-trashing page transfer war. 

I can't see any way to fix this without some sort of rmap - any
other suggestions as to how this might be done?

Thanks,

Martin.