On Tue, Jul 13, 2010 at 10:37:00AM +0100, Mel Gorman wrote: > I prefer Kamezawa's suggestion of mapping on a ZERO_PAGE-like page full > of PageReserved struct pages because it would have better performance > and be more in line with maintaining the assumptions of the memory > model. If we go in this direction, I would strongly prefer it was an > ARM-only thing. As I've said, this is not possible without doing some serious page manipulation. Plus the pages that where there become unusable as they don't correspond with a PFN or obey phys_to_virt(). So there's absolutely no point to this. Now, why do we free the holes in the mem_map - because these holes can be extremely large. Every 512K of hole equates to one page of mem_map array. Balance that against memory placed at 0xc0000000 physical on some platforms, and with PHYSMEM_BITS at 32 and SECTION_SIZE_BITS at 19 - well, you do the maths. The result is certainly not pretty. -- 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>