On Thu, Aug 04, 2005 at 03:19:52PM -0700, Christoph Lameter wrote:

There are three possibilites:

1. do what cpusets is doing by versioning.

2. Have the task notifier access the task_struct information.
See http://lwn.net/Articles/145232/ "A new path to the refrigerator"

3. Maybe the easiest: Require mmap_sem to be taken for all policy 
accesses. Currently its only require for vma policies. Then we need
to make a copy of the policy at some point so that alloc_pages can
access policy information lock free. This may also allow us to fix
the bind issue if we would f.e. keep a bitmap in the taskstruct or (ab)use 
the cpusets map.

None of them seem very attractive to me.  I would prefer to just
not support external accesses keeping things lean and fast.

quoted

If they cannot afford enough disk space it might be possible
to do the page migration in swap cache like Hugh proposed.

This code already exist in the memory hotplug code base and Ray already 
had a working implementation for page migration. The migration code will 
also be necessary in order to relocate pages with ECC single bit failures 
that Russ is working on (of course that will only work for some pages) and
for Mel Gorman's defragmentation approach (if we ever get the split into 
differnet types of memory chunks in).

Individual physical page migration is quite different from
address space migration.

-Andi
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