mm: remove swap token code

The swap token code no longer fits in with the current VM model.  It
does not play well with cgroups or the better NUMA placement code in
development, since we have only one swap token globally.

It also has the potential to mess with scalability of the system, by
increasing the number of non-reclaimable pages on the active and
inactive anon LRU lists.

Last but not least, the swap token code has been broken for a year
without complaints, as reported by Konstantin Khlebnikov.  This suggests
we no longer have much use for it.

The days of sub-1G memory systems with heavy use of swap are over.  If
we ever need thrashing reducing code in the future, we will have to
implement something that does scale.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Bob Picco <bpicco@meloft.net>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 6 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 33dc256033b..ca46080bb07 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2352,8 +2352,6 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 
         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
                 sc->nr_scanned = 0;
-                if (!priority)
-                        disable_swap_token(sc->target_mem_cgroup);
                 aborted_reclaim = shrink_zones(priority, zonelist, sc);
 
                 /*
@@ -2704,10 +2702,6 @@ loop_again:
                 unsigned long lru_pages = 0;
                 int has_under_min_watermark_zone = 0;
 
-                /* The swap token gets in the way of swapout... */
-                if (!priority)
-                        disable_swap_token(NULL);
-
                 all_zones_ok = 1;
                 balanced = 0;