[PATCH] oom: cpuset hint

cpuset_excl_nodes_overlap does not always indicate that killing a task will
not free any memory we for us.  For example, we may be asking for an
allocation from _anywhere_ in the machine, or the task in question may be
pinning memory that is outside its cpuset.  Fix this by just causing
cpuset_excl_nodes_overlap to reduce the badness rather than disallow it.

Signed-off-by: Nick Piggin <[email protected]>
Acked-by: Paul Jackson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Nick Piggin

mm/oom_kill.c

@@ -128,6 +128,14 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
 	if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO))
 		points /= 4;
 
+	/*
+	 * If p's nodes don't overlap ours, it may still help to kill p
+	 * because p may have allocated or otherwise mapped memory on
+	 * this node before. However it will be less likely.
+	 */
+	if (!cpuset_excl_nodes_overlap(p))
+		points /= 8;
+
 	/*
 	 * Adjust the score by oomkilladj.
 	 */
@@ -198,9 +206,6 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
 			continue;
 		if (p->oomkilladj == OOM_DISABLE)
 			continue;
-		/* If p's nodes don't overlap ours, it won't help to kill p. */
-		if (!cpuset_excl_nodes_overlap(p))
-			continue;
 
 		/*
 		 * This is in the process of releasing memory so wait for it