On Sunday 01 April 2007 09:10, Christoph Lameter wrote: > x86_64 make SPARSE_VIRTUAL the default > > x86_64 is using 2M page table entries to map its 1-1 kernel space. > We implement the virtual memmap also using 2M page table entries. > So there is no difference at all to FLATMEM. Both schemes require > a page table and a TLB.
Hmm, this means there is at least 2MB worth of struct page on every node? Or do you have overlaps with other memory (I think you have) In that case you have to handle the overlap in change_page_attr() Also your "generic" vmemmap code doesn't look very generic, but rather x86 specific. I didn't think huge pages could be easily set up this way in many other architectures. And when you reserve virtual space somewhere you should update Documentation/x86_64/mm.txt. Also you didn't adjust the end of the vmalloc area so in theory vmalloc could run into your vmemmap. > Thus the SPARSEMEM becomes the most efficient way of handling > virt_to_page, pfn_to_page and friends for UP, SMP and NUMA. Do you have any benchmarks numbers to prove it? There seem to be a few benchmarks where the discontig virt_to_page is a problem (although I know ways to make it more efficient), and sparsemem is normally slower. Still some numbers would be good. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
