While going through Mel gorman's book, I read that mem_map for NUMA systems is treated as a virtual array at PAGE_OFFSET. I have a hard time visualizing it. I could understand the the explanation as follows. mem_map[pfn] should not be accessed as it is. calculate the actual node corresponding to pfn and access the page as pglist_data[A]->node_zonelists[B]->zone_mem_map[C], where, A : node_id, calculated using pfn, B: offset in the zonelist calculated using pfn and, C : offset in the local mem_map calculated using pfn. Is my understanding correct? (Maybe one can find the page using the node_mem_map as well, but that is another question.) Now, why should the mem_map be initialized to PAGE_OFFSET? Where is it done? In page_alloc.c, I found mem_map = NODE_DATA(0)->node_mem_map; when CONFIG_FLAT_NODE_MEM_MAP is defined (non numa case). If my understanding is correct, this case should hold for NUMA as well. What am I missing? Regards, Om -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
