On Thu, 2010-07-29 at 19:33 +0100, Russell King - ARM Linux wrote: > And no, setting the sparse section size to 512kB doesn't work - memory is > offset by 256MB already, so you need a sparsemem section array of 1024 > entries just to cover that - with the full 256MB populated, that's 512 > unused entries followed by 512 used entries. That too is going to waste > memory like nobodies business. Sparsemem could use some work in the case where memory doesn't start at 0x0. But, it doesn't seem like it would be _too_ oppressive to add. It's literally just adding an offset to all of the places where a physical address is stuck into the system. It'll make a few of the calculations longer, of course, but it should be manageable. Could you give some full examples of how the memory is laid out on these systems? I'm having a bit of a hard time visualizing it. As Christoph mentioned, SPARSEMEM_EXTREME might be viable here, too. If you free up parts of the mem_map[] array, how does the buddy allocator still work? I thought we required at 'struct page's to be contiguous and present for at least 2^MAX_ORDER-1 pages in one go. -- Dave -- 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>