oom: add oom_kill_allocating_task sysctl

Adds a new sysctl, 'oom_kill_allocating_task', which will automatically kill
the OOM-triggering task instead of scanning through the tasklist to find a
memory-hogging target.  This is helpful for systems with an insanely large
number of tasks where scanning the tasklist significantly degrades
performance.

Cc: Andrea Arcangeli <andrea@suse.de>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 6e999c88c503..00d0bd7d6a2b 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -27,6 +27,7 @@
 #include <linux/notifier.h>
 
 int sysctl_panic_on_oom;
+int sysctl_oom_kill_allocating_task;
 static DEFINE_MUTEX(zone_scan_mutex);
 /* #define DEBUG */
 
@@ -471,14 +472,16 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
                                 "No available memory (MPOL_BIND)");
                 break;
 
-        case CONSTRAINT_CPUSET:
-                oom_kill_process(current, points,
-                                "No available memory in cpuset");
-                break;
-
         case CONSTRAINT_NONE:
                 if (sysctl_panic_on_oom)
                         panic("out of memory. panic_on_oom is selected\n");
+                /* Fall-through */
+        case CONSTRAINT_CPUSET:
+                if (sysctl_oom_kill_allocating_task) {
+                        oom_kill_process(current, points,
+                                        "Out of memory (oom_kill_allocating_task)");
+                        break;
+                }
 retry:
                 /*
                  * Rambo mode: Shoot down a process and hope it solves whatever