Page migration.

As we described in the chapter, one important, but difficult, goal of a NUMA multiprocessor designer is maximizing the number of page accesses that can be serviced by local memory.Describe the three strategies, COMA, page migration and page replication, and discuss the advantages and disadvantages of each. What will be an ideal response?

Page migration involves moving a page to the local memory of the processor that most frequently accesses the page.The advantage of this strategy is that the coherency protocol is relatively simple, because there is still only one copy of each memory page. When employed with a heuristic to determine when and where to migrate a page, this strategy increases the percentage of memory
accesses serviced by local memory.A disadvantage is that data-access history must be stored to determine migration policy for pages.Also, page migration is more costly than remotely referencing a page, so an inefficient implementation (one in which pages are migrated needlessly) can degrade performance. Third,
false sharing can occur when two processors require access to different data
items on the same page