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 from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
