On Mon, 2008-07-07 at 10:09 -0500, Christoph Lameter wrote:

This will extend the number of pages that are migratable and lead to strange
semantics in the NUMA case. There suddenly vma_is migratable will forbid hotplug
to migrate certain pages. 

I think we need two functions:

vma_migratable()	General migratability

vma_policy_migratable()	Migratable under NUMA policies.

Nothing will change here for the NUMA case, this is all about making it
compile w/o NUMA and with MIGRATION. What new strange semantics do you mean?
BTW, the latest patch in this thread will not touch vma_migratable() anymore,
I haven't read your mail before, sorry.

That wont work since the migrate function takes a nodemask! The point of
the function is to move memory from node to node which is something that you
*cannot* do in a non NUMA configuration. So leave this chunk out.

Right, but I noticed that this function definition was needed to make it
compile with MIGRATION and w/o NUMA, although it would never be called in
non-NUMA config.
A better solution would probably be to put migrate_vmas(), the only caller
of vm_ops->migrate(), inside '#ifdef CONFIG_NUMA', because it will only be
called from NUMA-only mm/mempolicy.c. Does that sound reasonable?

Hmmm... Okay. I tried to make MIGRATION as independent of CONFIG_NUMA as possible so hopefully this will work.

Umm, it doesn't compile with MIGRATION and w/o NUMA, which was the reason
for this patch, because of the policy_zone reference in vma_migratable()
and the missing vm_ops->migrate() function.

Thanks,
Gerald

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