From: Michal Hocko <mhocko@xxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Reported-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/oom_kill.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/oom_kill.c~mm-oom-consider-present-pages-for-the-node-size +++ a/mm/oom_kill.c @@ -287,7 +287,7 @@ static enum oom_constraint constrained_a !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_a 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; _
