[PATCH] out of memory notifier

Add a notifer chain to the out of memory killer.  If one of the registered
callbacks could release some memory, do not kill the process but return and
retry the allocation that forced the oom killer to run.

The purpose of the notifier is to add a safety net in the presence of
memory ballooners.  If the resource manager inflated the balloon to a size
where memory allocations can not be satisfied anymore, it is better to
deflate the balloon a bit instead of killing processes.

The implementation for the s390 ballooner is included.

[akpm@osdl.org: cleanups]
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 34a6bc3e6cf3..32db06c8ffe0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -10,6 +10,8 @@
 #include <asm/atomic.h>
 #include <asm/page.h>
 
+struct notifier_block;
+
 #define SWAP_FLAG_PREFER        0x8000  /* set if swap priority specified */
 #define SWAP_FLAG_PRIO_MASK     0x7fff
 #define SWAP_FLAG_PRIO_SHIFT    0
@@ -156,6 +158,8 @@ struct swap_list_t {
 
 /* linux/mm/oom_kill.c */
 extern void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order);
+extern int register_oom_notifier(struct notifier_block *nb);
+extern int unregister_oom_notifier(struct notifier_block *nb);
 
 /* linux/mm/memory.c */
 extern void swapin_readahead(swp_entry_t, unsigned long, struct vm_area_struct *);