From c11525830f92dea58353ace0f074ece5d9ef37c8 Mon Sep 17 00:00:00 2001 From: Wei Yang Date: Wed, 6 Sep 2017 16:19:33 -0700 Subject: [PATCH] mm/memory_hotplug: just build zonelist for newly added node Commit 9adb62a5df9c ("mm/hotplug: correctly setup fallback zonelists when creating new pgdat") tries to build the correct zonelist for a newly 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 newly added node, it will have memory until node_states_set_node() is called in online_pages(). This patch avoids rebuilding the zonelists for already existing nodes. build_zonelists_node() uses managed_zone(zone) checks, so it should not include empty zones anyway. So effectively we avoid some pointless work under stop_machine(). [akpm@linux-foundation.org: tweak comment text] [akpm@linux-foundation.org: coding-style tweak, per Vlastimil] Link: http://lkml.kernel.org/r/20170626035822.50155-1-richard.weiyang@gmail.com Signed-off-by: Wei Yang Acked-by: Michal Hocko Acked-by: Vlastimil Babka Cc: Jiang Liu Cc: Xishi Qiu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9327a940e373..dcc8a1cf55b6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5282,14 +5282,18 @@ static int __build_all_zonelists(void *data) memset(node_load, 0, sizeof(node_load)); #endif + /* + * This node is hotadded and no memory is yet present. So just + * building zonelists is fine - no need to touch other nodes. + */ if (self && !node_online(self->node_id)) { build_zonelists(self); - } - - for_each_online_node(nid) { - pg_data_t *pgdat = NODE_DATA(nid); + } else { + for_each_online_node(nid) { + pg_data_t *pgdat = NODE_DATA(nid); - build_zonelists(pgdat); + build_zonelists(pgdat); + } } /* -- 2.20.1