Revert "revert "mm: vmscan: do not swap anon pages just because free+file is low""

This reverts commit 623762517e2370be3b3f95f4fe08d6c063a49b06.

Ben rightly points out that commit 0bf1457f0cfc, which is what this
original commit was reverting, never ended up in 3.14-stable, but was
only for 3.15.

So revert this patch as we now have the same check twice in a row, which
is pretty pointless.  Although the comments were "prettier"...

Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 30a4b09..a9c74b4 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1916,24 +1916,6 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
        }
 
        /*
-        * Prevent the reclaimer from falling into the cache trap: as
-        * cache pages start out inactive, every cache fault will tip
-        * the scan balance towards the file LRU.  And as the file LRU
-        * shrinks, so does the window for rotation from references.
-        * This means we have a runaway feedback loop where a tiny
-        * thrashing file LRU becomes infinitely more attractive than
-        * anon pages.  Try to detect this based on file LRU size.
-        */
-       if (global_reclaim(sc)) {
-               unsigned long free = zone_page_state(zone, NR_FREE_PAGES);
-
-               if (unlikely(file + free <= high_wmark_pages(zone))) {
-                       scan_balance = SCAN_ANON;
-                       goto out;
-               }
-       }
-
-       /*
         * There is enough inactive page cache, do not reclaim
         * anything from the anonymous working set right now.
         */