[PATCH 2/4] vmscan: bailout of slab reclaim once we reach our target

[josef@xxxxxxxxxxxxxx]

From: Josef Bacik <jbacik@xxxxxx>

Following patches will greatly increase our aggressiveness in slab
reclaim, so we need checks in place to make sure we stop trying to
reclaim slab once we've hit our reclaim target.

Signed-off-by: Josef Bacik <jbacik@xxxxxx>
---
 mm/vmscan.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cf23de9..77a887a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -305,11 +305,13 @@ EXPORT_SYMBOL(unregister_shrinker);
 
 #define SHRINK_BATCH 128
 
-static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
+static unsigned long do_shrink_slab(struct scan_control *sc,
+				    struct shrink_control *shrinkctl,
 				    struct shrinker *shrinker,
 				    unsigned long nr_scanned,
 				    unsigned long nr_eligible)
 {
+	struct reclaim_state *reclaim_state = current->reclaim_state;
 	unsigned long freed = 0;
 	unsigned long long delta;
 	long total_scan;
@@ -394,14 +396,18 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 
 		shrinkctl->nr_to_scan = nr_to_scan;
 		ret = shrinker->scan_objects(shrinker, shrinkctl);
+		if (reclaim_state) {
+			sc->nr_reclaimed += reclaim_state->reclaimed_slab;
+			reclaim_state->reclaimed_slab = 0;
+		}
 		if (ret == SHRINK_STOP)
 			break;
 		freed += ret;
-
 		count_vm_events(SLABS_SCANNED, nr_to_scan);
 		total_scan -= nr_to_scan;
 		scanned += nr_to_scan;
-
+		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
+			break;
 		cond_resched();
 	}
 
@@ -452,7 +458,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
  *
  * Returns the number of reclaimed slab objects.
  */
-static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
+static unsigned long shrink_slab(struct scan_control *sc, int nid,
 				 struct mem_cgroup *memcg,
 				 unsigned long nr_scanned,
 				 unsigned long nr_eligible)
@@ -478,8 +484,8 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 	}
 
 	list_for_each_entry(shrinker, &shrinker_list, list) {
-		struct shrink_control sc = {
-			.gfp_mask = gfp_mask,
+		struct shrink_control shrinkctl = {
+			.gfp_mask = sc->gfp_mask,
 			.nid = nid,
 			.memcg = memcg,
 		};
@@ -494,9 +500,12 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 			continue;
 
 		if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
-			sc.nid = 0;
+			shrinkctl.nid = 0;
 
-		freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible);
+		freed += do_shrink_slab(sc, &shrinkctl, shrinker, nr_scanned,
+					nr_eligible);
+		if (sc->nr_to_reclaim <= sc->nr_reclaimed)
+			break;
 	}
 
 	up_read(&shrinker_rwsem);
@@ -510,11 +519,15 @@ void drop_slab_node(int nid)
 	unsigned long freed;
 
 	do {
+		struct scan_control sc = {
+			.nr_to_reclaim = -1UL,
+			.gfp_mask = GFP_KERNEL,
+		};
 		struct mem_cgroup *memcg = NULL;
 
 		freed = 0;
 		do {
-			freed += shrink_slab(GFP_KERNEL, nid, memcg,
+			freed += shrink_slab(&sc, nid, memcg,
 					     1000, 1000);
 		} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 	} while (freed > 10);
@@ -2600,7 +2613,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 			node_lru_pages += lru_pages;
 
 			if (memcg)
-				shrink_slab(sc->gfp_mask, pgdat->node_id,
+				shrink_slab(sc, pgdat->node_id,
 					    memcg, sc->nr_scanned - scanned,
 					    lru_pages);
 
@@ -2631,7 +2644,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 		 * the eligible LRU pages were scanned.
 		 */
 		if (global_reclaim(sc))
-			shrink_slab(sc->gfp_mask, pgdat->node_id, NULL,
+			shrink_slab(sc, pgdat->node_id, NULL,
 				    sc->nr_scanned - nr_scanned,
 				    node_lru_pages);
 
-- 
2.7.4

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