mm, oom: consider present pages for the node size
Subsystems (2)
PATCH 1/1 mm, oom: consider present pages for the node size
From: Michal Hocko <[email protected]>
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.
--- mm/oom_kill.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
mm/oom_kill.c +2 -2
@@ -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 ;
Signature · 1 line
2.20.1
Quoted 34 lines · Michal Hocko
From: Michal Hocko <[email protected]>
constrained_alloccalculates the size of the oom domain by usingnode_spanned_pageswhich 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 bynode_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.
Noticed-by David Hildenbrand <[email protected]>Signed-off-by Michal Hocko <[email protected]>--- mm/oom_kill.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)mm/oom_kill.c +1
-1@@ -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 ; }
mm/oom_kill.c static enum oom_constraint constrained_alloc(struct oom_control *oc) · line 306
Quoted 8 lines
mm/oom_kill.c +1
-1@@ -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;>
Thanks!
Signature · 3 lines
Thanks, David / dhildenb
Quoted 14 lines · Michal Hocko
From: Michal Hocko <[email protected]>
constrained_alloccalculates the size of the oom domain by usingnode_spanned_pageswhich 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 bynode_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.
Quoted 2 lines
Noticed-by David Hildenbrand <[email protected]>Signed-off-by Michal Hocko <[email protected]>