[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 eff3c18..f4c560b 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;
 	}