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Subject[PATCH AUTOSEL for 4.9 18/54] mm: fix remote numa hits statistics
From: Michal Hocko <>

[ Upstream commit 2df26639e708a88dcc22171949da638a9998f3bc ]

Jia He has noticed that commit b9f00e147f27 ("mm, page_alloc: reduce
branches in zone_statistics") has an unintentional side effect that
remote node allocation requests are accounted as NUMA_MISS rathat than
NUMA_HIT and NUMA_OTHER if such a request doesn't use __GFP_OTHER_NODE.

There are many of these potentially because the flag is used very rarely
while we have many users of __alloc_pages_node.

Fix this by simply ignoring __GFP_OTHER_NODE (it can be removed in a
follow up patch) and treat all allocations that were satisfied from the
preferred zone's node as NUMA_HITS because this is the same node we
requested the allocation from in most cases. If this is not the local
node then we just account it as NUMA_OTHER rather than NUMA_LOCAL.

One downsize would be that an allocation request for a node which is
outside of the mempolicy nodemask would be reported as a hit which is a
bit weird but that was the case before b9f00e147f27 already.

Fixes: b9f00e147f27 ("mm, page_alloc: reduce branches in zone_statistics")
Signed-off-by: Michal Hocko <>
Reported-by: Jia He <>
Reviewed-by: Vlastimil Babka <> # with cbmc[1] superpowers
Acked-by: Mel Gorman <>
Cc: Johannes Weiner <>
Cc: Joonsoo Kim <>
Cc: Taku Izumi <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Sasha Levin <>
mm/page_alloc.c | 15 ++++-----------
1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7064aae8ded7..bed0fa6125f3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2583,30 +2583,23 @@ int __isolate_free_page(struct page *page, unsigned int order)
* Update NUMA hit/miss statistics
* Must be called with interrupts disabled.
- *
- * When __GFP_OTHER_NODE is set assume the node of the preferred
- * zone is the local node. This is useful for daemons who allocate
- * memory on behalf of other processes.
static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
gfp_t flags)
- int local_nid = numa_node_id();
enum zone_stat_item local_stat = NUMA_LOCAL;

- if (unlikely(flags & __GFP_OTHER_NODE)) {
+ if (z->node != numa_node_id())
local_stat = NUMA_OTHER;
- local_nid = preferred_zone->node;
- }

- if (z->node == local_nid) {
+ if (z->node == preferred_zone->node)
__inc_zone_state(z, NUMA_HIT);
- __inc_zone_state(z, local_stat);
- } else {
+ else {
__inc_zone_state(z, NUMA_MISS);
__inc_zone_state(preferred_zone, NUMA_FOREIGN);
+ __inc_zone_state(z, local_stat);

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