[PATCH] cpusets: confine oom_killer to mem_exclusive cpuset

Now the real motivation for this cpuset mem_exclusive patch series seems
trivial.

This patch keeps a task in or under one mem_exclusive cpuset from provoking an
oom kill of a task under a non-overlapping mem_exclusive cpuset.  Since only
interrupt and GFP_ATOMIC allocations are allowed to escape mem_exclusive
containment, there is little to gain from oom killing a task under a
non-overlapping mem_exclusive cpuset, as almost all kernel and user memory
allocation must come from disjoint memory nodes.

This patch enables configuring a system so that a runaway job under one
mem_exclusive cpuset cannot cause the killing of a job in another such cpuset
that might be using very high compute and memory resources for a prolonged
time.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/oom_kill.c

@@ -20,6 +20,7 @@
 #include <linux/swap.h>
 #include <linux/timex.h>
 #include <linux/jiffies.h>
+#include <linux/cpuset.h>
 
 /* #define DEBUG */
 
@@ -152,6 +153,10 @@ static struct task_struct * select_bad_process(void)
 			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 for wait it
 		 * to finish before killing some other task by mistake.