On Wed 28-06-17 11:35:00, Vlastimil Babka wrote: > On 06/28/2017 11:23 AM, Michal Hocko wrote: > > On Mon 26-06-17 11:58:22, Wei Yang wrote: > >> In commit (9adb62a5df9c0fbef7) "mm/hotplug: correctly setup fallback > >> zonelists when creating new pgdat" tries to build the correct zonelist for > >> a new added node, while it is not necessary to rebuild it for already exist > >> nodes. > >> > >> In build_zonelists(), it will iterate on nodes with memory. For a new added > >> node, it will have memory until node_states_set_node() is called in > >> online_pages(). > >> > >> This patch will avoid to rebuild the zonelists for already exist nodes. > > > > It is not very clear from the changelog why that actually matters. The > > only effect I can see is that other zonelists on other online nodes will > > not learn about the currently memory less node. This is a good think > > because we do not pointlessly try to allocate from that node. > > build_zonelists_node() seems to use managed_zone(zone) checks, so it > should not include empty zones anyway. So effectively seems to me we > just avoid some pointless work under stop_machine(). Ohh, you are right. I was looking for populated_zone and didn't find any so I thought we just do not care. So, indeed the patch has no functional effect it just reduces the stop_machine overhead tiny bit. -- Michal Hocko SUSE Labs -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
