On Wed, 2011-09-21 at 15:17 +0200, Michal Nazarewicz wrote: > > This 'struct page *'++ stuff is OK, but only for small, aligned areas. > > For at least some of the sparsemem modes (non-VMEMMAP), you could walk > > off of the end of the section_mem_map[] when you cross a MAX_ORDER > > boundary. I'd feel a little bit more comfortable if pfn_to_page() was > > being done each time, or only occasionally when you cross a section > > boundary. > > I'm fine with that. I've used pointer arithmetic for performance reasons > but if that may potentially lead to bugs then obviously pfn_to_page() > should be used pfn_to_page() on x86 these days is usually: #define __pfn_to_page(pfn) (vmemmap + (pfn)) Even for the non-vmemmap sparsemem it stays pretty quick because the section array is in cache as you run through the loop. There are ways to _minimize_ the number of pfn_to_page() calls by checking when you cross a section boundary, or even at a MAX_ORDER_NR_PAGES boundary. But, I don't think it's worth the trouble. -- Dave -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>