[PATCH] slub: avoid list_lock contention from __refill_objects_any()

[Vlastimil Babka]

Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/slub.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 7d7e1ae1922f..3458dfbab85d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3378,7 +3378,8 @@ static inline bool pfmemalloc_match(struct slab *slab, gfp_t gfpflags);
 
 static bool get_partial_node_bulk(struct kmem_cache *s,
 				  struct kmem_cache_node *n,
-				  struct partial_bulk_context *pc)
+				  struct partial_bulk_context *pc,
+				  bool allow_spin)
 {
 	struct slab *slab, *slab2;
 	unsigned int total_free = 0;
@@ -3390,7 +3391,10 @@ static bool get_partial_node_bulk(struct kmem_cache *s,
 
 	INIT_LIST_HEAD(&pc->slabs);
 
-	spin_lock_irqsave(&n->list_lock, flags);
+	if (allow_spin)
+		spin_lock_irqsave(&n->list_lock, flags);
+	else if (!spin_trylock_irqsave(&n->list_lock, flags))
+		return false;
 
 	list_for_each_entry_safe(slab, slab2, &n->partial, slab_list) {
 		struct freelist_counters flc;
@@ -6544,7 +6548,8 @@ EXPORT_SYMBOL(kmem_cache_free_bulk);
 
 static unsigned int
 __refill_objects_node(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min,
-		      unsigned int max, struct kmem_cache_node *n)
+		      unsigned int max, struct kmem_cache_node *n,
+		      bool allow_spin)
 {
 	struct partial_bulk_context pc;
 	struct slab *slab, *slab2;
@@ -6556,7 +6561,7 @@ __refill_objects_node(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int mi
 	pc.min_objects = min;
 	pc.max_objects = max;
 
-	if (!get_partial_node_bulk(s, n, &pc))
+	if (!get_partial_node_bulk(s, n, &pc, allow_spin))
 		return 0;
 
 	list_for_each_entry_safe(slab, slab2, &pc.slabs, slab_list) {
@@ -6650,7 +6655,8 @@ __refill_objects_any(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min
 					n->nr_partial <= s->min_partial)
 				continue;
 
-			r = __refill_objects_node(s, p, gfp, min, max, n);
+			r = __refill_objects_node(s, p, gfp, min, max, n,
+						  /* allow_spin = */ false);
 			refilled += r;
 
 			if (r >= min) {
@@ -6691,7 +6697,8 @@ refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min,
 		return 0;
 
 	refilled = __refill_objects_node(s, p, gfp, min, max,
-					 get_node(s, local_node));
+					 get_node(s, local_node),
+					 /* allow_spin = */ true);
 	if (refilled >= min)
 		return refilled;
 
-- 
2.52.0