From: Wei Yang <richard.weiyang@xxxxxxxxx>
Subject: mm/memory_hotplug: just build zonelist for newly added node
9adb62a5df9c0fbef7 ("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@xxxxxxxxxxxxxxxxxxxx: tweak comment text]
[akpm@xxxxxxxxxxxxxxxxxxxx: coding-style tweak, per Vlastimil]
Link: http://lkml.kernel.org/r/20170626035822.50155-1-richard.weiyang@xxxxxxxxx
Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jiang Liu <liuj97@xxxxxxxxx>
Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff -puN mm/page_alloc.c~mm-memory_hotplug-just-build-zonelist-for-new-added-node mm/page_alloc.c
--- a/mm/page_alloc.c~mm-memory_hotplug-just-build-zonelist-for-new-added-node
+++ a/mm/page_alloc.c
@@ -5282,14 +5282,18 @@ static int __build_all_zonelists(void *d
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);
+ }
}
/*
_
--
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