[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>

1 files changed, 7 insertions, 3 deletions

diff --git a/mm/thrash.c b/mm/thrash.c
index eff3c18c33a1..f4c560b4a2b7 100644
--- a/mm/thrash.c
+++ b/mm/thrash.c
@@ -57,14 +57,17 @@ void grab_swap_token(void)
         /* We have the token. Let others know we still need it. */
         if (has_swap_token(current->mm)) {
                 current->mm->recent_pagein = 1;
+                if (unlikely(!swap_token_default_timeout))
+                        disable_swap_token();
                 return;
         }
 
         if (time_after(jiffies, swap_token_check)) {
 
-                /* Can't get swapout protection if we exceed our RSS limit. */
-                // if (current->mm->rss > current->mm->rlimit_rss)
-                //      return;
+                if (!swap_token_default_timeout) {
+                        swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
+                        return;
+                }
 
                 /* ... or if we recently held the token. */
                 if (time_before(jiffies, current->mm->swap_token_time))
@@ -95,6 +98,7 @@ void __put_swap_token(struct mm_struct *mm)
 {
         spin_lock(&swap_token_lock);
         if (likely(mm == swap_token_mm)) {
+                mm->swap_token_time = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
                 swap_token_mm = &init_mm;
                 swap_token_check = jiffies;
         }