oom: add per-zone locking

OOM killer synchronization should be done with zone granularity so that memory
policy and cpuset allocations may have their corresponding zones locked and
allow parallel kills for other OOM conditions that may exist elsewhere in the
system.  DMA allocations can be targeted at the zone level, which would not be
possible if locking was done in nodes or globally.

Synchronization shall be done with a variation of "trylocks." The goal is to
put the current task to sleep and restart the failed allocation attempt later
if the trylock fails.  Otherwise, the OOM killer is invoked.

Each zone in the zonelist that __alloc_pages() was called with is checked for
the newly-introduced ZONE_OOM_LOCKED flag.  If any zone has this flag present,
the "trylock" to serialize the OOM killer fails and returns zero.  Otherwise,
all the zones have ZONE_OOM_LOCKED set and the try_set_zone_oom() function
returns non-zero.

Cc: Andrea Arcangeli <andrea@suse.de>
Cc: 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, 5 insertions, 0 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index bad9486ee0cc..9011505e740d 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -344,6 +344,7 @@ struct zone {
 typedef enum {
         ZONE_ALL_UNRECLAIMABLE,         /* all pages pinned */
         ZONE_RECLAIM_LOCKED,            /* prevents concurrent reclaim */
+        ZONE_OOM_LOCKED,                /* zone is in OOM killer zonelist */
 } zone_flags_t;
 
 static inline void zone_set_flag(struct zone *zone, zone_flags_t flag)
@@ -363,6 +364,10 @@ static inline int zone_is_reclaim_locked(const struct zone *zone)
 {
         return test_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
 }
+static inline int zone_is_oom_locked(const struct zone *zone)
+{
+        return test_bit(ZONE_OOM_LOCKED, &zone->flags);
+}
 
 /*
  * The "priority" of VM scanning is how much of the queues we will scan in one