mm, oom: consider present pages for the node size

constrained_alloc() calculates the size of the oom domain by using
node_spanned_pages which is incorrect because this is the full range of
the physical memory range that the numa node occupies rather than the
memory that backs that range which is represented by node_present_pages.

Sparsely populated nodes (e.g.  after memory hot remove or simply sparse
due to memory layout) can have really a large difference between the two.
This shouldn't really cause any real user observable problems because the
oom calculates a ratio against totalpages and used memory cannot exceed
present pages but it is confusing and wrong from code point of view.

Link: http://lkml.kernel.org/r/20190829163443.899-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 1530fccdbe4fba388c41000071e2008bfb83b0d4..c1d9496b4c4326a1fb633234cce580b5019b9e39 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -287,7 +287,7 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
            !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
                oc->totalpages = total_swap_pages;
                for_each_node_mask(nid, *oc->nodemask)
-                       oc->totalpages += node_spanned_pages(nid);
+                       oc->totalpages += node_present_pages(nid);
                return CONSTRAINT_MEMORY_POLICY;
        }
 
@@ -300,7 +300,7 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
        if (cpuset_limited) {
                oc->totalpages = total_swap_pages;
                for_each_node_mask(nid, cpuset_current_mems_allowed)
-                       oc->totalpages += node_spanned_pages(nid);
+                       oc->totalpages += node_present_pages(nid);
                return CONSTRAINT_CPUSET;
        }
        return CONSTRAINT_NONE;