oom: select task from tasklist for mempolicy ooms

The oom killer presently kills current whenever there is no more memory
free or reclaimable on its mempolicy's nodes.  There is no guarantee that
current is a memory-hogging task or that killing it will free any
substantial amount of memory, however.

In such situations, it is better to scan the tasklist for nodes that are
allowed to allocate on current's set of nodes and kill the task with the
highest badness() score.  This ensures that the most memory-hogging task,
or the one configured by the user with /proc/pid/oom_adj, is always
selected in such scenarios.

Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 7b9ef6bf45aa..31ac26ca4acf 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -210,6 +210,8 @@ extern struct zonelist *huge_zonelist(struct vm_area_struct *vma,
                                 unsigned long addr, gfp_t gfp_flags,
                                 struct mempolicy **mpol, nodemask_t **nodemask);
 extern bool init_nodemask_of_mempolicy(nodemask_t *mask);
+extern bool mempolicy_nodemask_intersects(struct task_struct *tsk,
+                                const nodemask_t *mask);
 extern unsigned slab_node(struct mempolicy *policy);
 
 extern enum zone_type policy_zone;
@@ -338,7 +340,16 @@ static inline struct zonelist *huge_zonelist(struct vm_area_struct *vma,
         return node_zonelist(0, gfp_flags);
 }
 
-static inline bool init_nodemask_of_mempolicy(nodemask_t *m) { return false; }
+static inline bool init_nodemask_of_mempolicy(nodemask_t *m)
+{
+        return false;
+}
+
+static inline bool mempolicy_nodemask_intersects(struct task_struct *tsk,
+                        const nodemask_t *mask)
+{
+        return false;
+}
 
 static inline int do_migrate_pages(struct mm_struct *mm,
                         const nodemask_t *from_nodes,