mm: vmscan: convert global reclaim to per-memcg LRU lists

The global per-zone LRU lists are about to go away on memcg-enabled
kernels, global reclaim must be able to find its pages on the per-memcg
LRU lists.

Since the LRU pages of a zone are distributed over all existing memory
cgroups, a scan target for a zone is complete when all memory cgroups
are scanned for their proportional share of a zone's memory.

The forced scanning of small scan targets from kswapd is limited to
zones marked unreclaimable, otherwise kswapd can quickly overreclaim by
force-scanning the LRU lists of multiple memory cgroups.

Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Ying Han <yinghan@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 17 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 136c7eb0ad88..024168cfdcb0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1886,7 +1886,7 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
          * latencies, so it's better to scan a minimum amount there as
          * well.
          */
-        if (current_is_kswapd())
+        if (current_is_kswapd() && mz->zone->all_unreclaimable)
                 force_scan = true;
         if (!global_reclaim(sc))
                 force_scan = true;
@@ -2111,16 +2111,6 @@ static void shrink_zone(int priority, struct zone *zone,
         };
         struct mem_cgroup *memcg;
 
-        if (global_reclaim(sc)) {
-                struct mem_cgroup_zone mz = {
-                        .mem_cgroup = NULL,
-                        .zone = zone,
-                };
-
-                shrink_mem_cgroup_zone(priority, &mz, sc);
-                return;
-        }
-
         memcg = mem_cgroup_iter(root, NULL, &reclaim);
         do {
                 struct mem_cgroup_zone mz = {
@@ -2134,6 +2124,10 @@ static void shrink_zone(int priority, struct zone *zone,
                  * scanned it with decreasing priority levels until
                  * nr_to_reclaim had been reclaimed.  This priority
                  * cycle is thus over after a single memcg.
+                 *
+                 * Direct reclaim and kswapd, on the other hand, have
+                 * to scan all memory cgroups to fulfill the overall
+                 * scan target for the zone.
                  */
                 if (!global_reclaim(sc)) {
                         mem_cgroup_iter_break(root, memcg);
@@ -2478,13 +2472,24 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
 static void age_active_anon(struct zone *zone, struct scan_control *sc,
                             int priority)
 {
-        struct mem_cgroup_zone mz = {
-                .mem_cgroup = NULL,
-                .zone = zone,
-        };
+        struct mem_cgroup *memcg;
 
-        if (inactive_anon_is_low(&mz))
-                shrink_active_list(SWAP_CLUSTER_MAX, &mz, sc, priority, 0);
+        if (!total_swap_pages)
+                return;
+
+        memcg = mem_cgroup_iter(NULL, NULL, NULL);
+        do {
+                struct mem_cgroup_zone mz = {
+                        .mem_cgroup = memcg,
+                        .zone = zone,
+                };
+
+                if (inactive_anon_is_low(&mz))
+                        shrink_active_list(SWAP_CLUSTER_MAX, &mz,
+                                           sc, priority, 0);
+
+                memcg = mem_cgroup_iter(NULL, memcg, NULL);
+        } while (memcg);
 }
 
 /*