On Thu, 29 Jul 2010, Dave Hansen wrote: > SPARSEMEM_EXTREME would be a bit different. It's a 2-level lookup. > You'd have 16 "section roots", each representing 256MB of address space. > Each time we put memory under one of those roots, we'd fill in a > 512-section second-level table, which is designed to always fit into one > page. If you start at 256MB, you won't waste all those entries. That is certain a solution to the !MMU case and it would work very much like a page table. If you have an MMU then the vmemmap sparsemem configuration can take advantage of of that to avoid the 2 level lookup. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>