[PATCH] temporarily disable swap token on memory pressure

Some users (hi Zwane) have seen a problem when running a workload that
eats nearly all of physical memory - th system does an OOM kill, even
when there is still a lot of swap free.

The problem appears to be a very big task that is holding the swap
token, and the VM has a very hard time finding any other page in the
system that is swappable.

Instead of ignoring the swap token when sc->priority reaches 0, we could
simply take the swap token away from the memory hog and make sure we
don't give it back to the memory hog for a few seconds.

This patch resolves the problem Zwane ran into.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 8 insertions, 2 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 35b30e6c8cf8..33261f1d2239 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -89,7 +89,7 @@ static inline void page_dup_rmap(struct page *page)
 /*
  * Called from mm/vmscan.c to handle paging out
  */
-int page_referenced(struct page *, int is_locked, int ignore_token);
+int page_referenced(struct page *, int is_locked);
 int try_to_unmap(struct page *);
 
 /*
@@ -109,7 +109,7 @@ unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 #define anon_vma_prepare(vma)   (0)
 #define anon_vma_link(vma)      do {} while (0)
 
-#define page_referenced(page,l,i) TestClearPageReferenced(page)
+#define page_referenced(page,l) TestClearPageReferenced(page)
 #define try_to_unmap(page)      SWAP_FAIL
 
 #endif  /* CONFIG_MMU */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 20c975642cab..508668f840b6 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -239,6 +239,11 @@ static inline void put_swap_token(struct mm_struct *mm)
                 __put_swap_token(mm);
 }
 
+static inline void disable_swap_token(void)
+{
+        put_swap_token(swap_token_mm);
+}
+
 #else /* CONFIG_SWAP */
 
 #define total_swap_pages                        0
@@ -283,6 +288,7 @@ static inline swp_entry_t get_swap_page(void)
 #define put_swap_token(x) do { } while(0)
 #define grab_swap_token()  do { } while(0)
 #define has_swap_token(x) 0
+#define disable_swap_token() do { } while(0)
 
 #endif /* CONFIG_SWAP */
 #endif /* __KERNEL__*/