[patch 4/9] oom: cpuset hint

[Nick Piggin <npiggin@suse.de>]

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 <npiggin@suse.de>

Index: linux-2.6/mm/oom_kill.c
===================================================================
--- linux-2.6.orig/mm/oom_kill.c
+++ linux-2.6/mm/oom_kill.c
@@ -127,6 +127,14 @@ unsigned long badness(struct task_struct
 		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.
 	 */
 	if (p->oomkilladj) {
@@ -196,9 +204,6 @@ static struct task_struct *select_bad_pr
 			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

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