Commit 2df26639 authored Jan 10, 2017 by Michal Hocko Committed by Linus Torvalds Jan 10, 2017

mm: fix remote numa hits statistics

Jia He has noticed that commit b9f00e14 ("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 b9f00e14 already.

Fixes: b9f00e14 ("mm, page_alloc: reduce branches in zone_statistics")
Link: http://lkml.kernel.org/r/20170102153057.9451-2-mhocko@kernel.org


Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Jia He <hejianet@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz> # with cbmc[1] superpowers
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f931ab47

mm/page_alloc.c

+4 −11

Original line number	Diff line number	Diff line
		@@ -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)
		{
		#ifdef CONFIG_NUMA
		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);
		#endif
		}