+TODO list
+---------
+
+- Page migration requires the use of swap handles to preserve the
+ information of the anonymous page table entries. This means that swap
+ space is reserved but never used. The maximum number of swap handles used
+ is determined by CHUNK_SIZE (see mm/mempolicy.c) per ongoing migration.
+ Reservation of pages could be avoided by having a special type of swap
+ handle that does not require swap space and that would only track the page
+ references. Something like that was proposed by Marcelo Tosatti in the
+ past (search for migration cache on lkml or linux-mm@kvack.org).
+
+- Page migration unmaps ptes for file backed pages and requires page
+ faults to reestablish these ptes. This could be optimized by somehow
+ recording the references before migration and then reestablish them later.
+ However, there are several locking challenges that have to be overcome
+ before this is possible.
+
+- Page migration generates read ptes for anonymous pages. Dirty page
+ faults are required to make the pages writable again. It may be possible
+ to generate a pte marked dirty if it is known that the page is dirty and
+ that this process has the only reference to that page.
+
+Christoph Lameter, March 8, 2006.