revert "memcg, vmscan: integrate soft reclaim tighter with zone shrinking code"

Revert commit 3b38722efd9f ("memcg, vmscan: integrate soft reclaim
tighter with zone shrinking code")

I merged this prematurely - Michal and Johannes still disagree about the
overall design direction and the future remains unclear.

Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 36 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0e081cada4ba..beb35778c69f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -139,21 +139,11 @@ static bool global_reclaim(struct scan_control *sc)
 {
         return !sc->target_mem_cgroup;
 }
-
-static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc)
-{
-        return !mem_cgroup_disabled() && global_reclaim(sc);
-}
 #else
 static bool global_reclaim(struct scan_control *sc)
 {
         return true;
 }
-
-static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc)
-{
-        return false;
-}
 #endif
 
 unsigned long zone_reclaimable_pages(struct zone *zone)
@@ -2174,8 +2164,7 @@ static inline bool should_continue_reclaim(struct zone *zone,
         }
 }
 
-static void
-__shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
+static void shrink_zone(struct zone *zone, struct scan_control *sc)
 {
         unsigned long nr_reclaimed, nr_scanned;
 
@@ -2194,12 +2183,6 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
                 do {
                         struct lruvec *lruvec;
 
-                        if (soft_reclaim &&
-                            !mem_cgroup_soft_reclaim_eligible(memcg)) {
-                                memcg = mem_cgroup_iter(root, memcg, &reclaim);
-                                continue;
-                        }
-
                         lruvec = mem_cgroup_zone_lruvec(zone, memcg);
 
                         shrink_lruvec(lruvec, sc);
@@ -2230,24 +2213,6 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
                                          sc->nr_scanned - nr_scanned, sc));
 }
 
-
-static void shrink_zone(struct zone *zone, struct scan_control *sc)
-{
-        bool do_soft_reclaim = mem_cgroup_should_soft_reclaim(sc);
-        unsigned long nr_scanned = sc->nr_scanned;
-
-        __shrink_zone(zone, sc, do_soft_reclaim);
-
-        /*
-         * No group is over the soft limit or those that are do not have
-         * pages in the zone we are reclaiming so we have to reclaim everybody
-         */
-        if (do_soft_reclaim && (sc->nr_scanned == nr_scanned)) {
-                __shrink_zone(zone, sc, false);
-                return;
-        }
-}
-
 /* Returns true if compaction should go ahead for a high-order request */
 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
 {
@@ -2309,6 +2274,8 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 {
         struct zoneref *z;
         struct zone *zone;
+        unsigned long nr_soft_reclaimed;
+        unsigned long nr_soft_scanned;
         bool aborted_reclaim = false;
 
         /*
@@ -2348,6 +2315,18 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
                                         continue;
                                 }
                         }
+                        /*
+                         * This steals pages from memory cgroups over softlimit
+                         * and returns the number of reclaimed pages and
+                         * scanned pages. This works for global memory pressure
+                         * and balancing, not for a memcg's limit.
+                         */
+                        nr_soft_scanned = 0;
+                        nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+                                                sc->order, sc->gfp_mask,
+                                                &nr_soft_scanned);
+                        sc->nr_reclaimed += nr_soft_reclaimed;
+                        sc->nr_scanned += nr_soft_scanned;
                         /* need some check for avoid more shrink_zone() */
                 }
 
@@ -2941,6 +2920,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
 {
         int i;
         int end_zone = 0;       /* Inclusive.  0 = ZONE_DMA */
+        unsigned long nr_soft_reclaimed;
+        unsigned long nr_soft_scanned;
         struct scan_control sc = {
                 .gfp_mask = GFP_KERNEL,
                 .priority = DEF_PRIORITY,
@@ -3055,6 +3036,15 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
 
                         sc.nr_scanned = 0;
 
+                        nr_soft_scanned = 0;
+                        /*
+                         * Call soft limit reclaim before calling shrink_zone.
+                         */
+                        nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+                                                        order, sc.gfp_mask,
+                                                        &nr_soft_scanned);
+                        sc.nr_reclaimed += nr_soft_reclaimed;
+
                         /*
                          * There should be no need to raise the scanning
                          * priority if enough pages are already being scanned