slab: introduce alien_cache

Currently, we use array_cache for alien_cache.  Although they are mostly
similar, there is one difference, that is, need for spinlock.  We don't
need spinlock for array_cache itself, but to use array_cache for
alien_cache, array_cache structure should have spinlock.  This is
needless overhead, so removing it would be better.  This patch prepare
it by introducing alien_cache and using it.  In the following patch, we
remove spinlock in array_cache.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 68 insertions, 42 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 8d9a0fff160d..de91d6f3a2a4 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -203,6 +203,11 @@ struct array_cache {
                          */
 };
 
+struct alien_cache {
+        spinlock_t lock;
+        struct array_cache ac;
+};
+
 #define SLAB_OBJ_PFMEMALLOC     1
 static inline bool is_obj_pfmemalloc(void *objp)
 {
@@ -491,7 +496,7 @@ static void slab_set_lock_classes(struct kmem_cache *cachep,
                 struct lock_class_key *l3_key, struct lock_class_key *alc_key,
                 struct kmem_cache_node *n)
 {
-        struct array_cache **alc;
+        struct alien_cache **alc;
         int r;
 
         lockdep_set_class(&n->list_lock, l3_key);
@@ -507,7 +512,7 @@ static void slab_set_lock_classes(struct kmem_cache *cachep,
                 return;
         for_each_node(r) {
                 if (alc[r])
-                        lockdep_set_class(&alc[r]->lock, alc_key);
+                        lockdep_set_class(&(alc[r]->ac.lock), alc_key);
         }
 }
 
@@ -965,12 +970,13 @@ static int transfer_objects(struct array_cache *to,
 #define drain_alien_cache(cachep, alien) do { } while (0)
 #define reap_alien(cachep, n) do { } while (0)
 
-static inline struct array_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
+static inline struct alien_cache **alloc_alien_cache(int node,
+                                                int limit, gfp_t gfp)
 {
-        return (struct array_cache **)BAD_ALIEN_MAGIC;
+        return (struct alien_cache **)BAD_ALIEN_MAGIC;
 }
 
-static inline void free_alien_cache(struct array_cache **ac_ptr)
+static inline void free_alien_cache(struct alien_cache **ac_ptr)
 {
 }
 
@@ -996,40 +1002,52 @@ static inline void *____cache_alloc_node(struct kmem_cache *cachep,
 static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
 static void *alternate_node_alloc(struct kmem_cache *, gfp_t);
 
-static struct array_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
+static struct alien_cache *__alloc_alien_cache(int node, int entries,
+                                                int batch, gfp_t gfp)
+{
+        int memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
+        struct alien_cache *alc = NULL;
+
+        alc = kmalloc_node(memsize, gfp, node);
+        init_arraycache(&alc->ac, entries, batch);
+        return alc;
+}
+
+static struct alien_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
 {
-        struct array_cache **ac_ptr;
+        struct alien_cache **alc_ptr;
         int memsize = sizeof(void *) * nr_node_ids;
         int i;
 
         if (limit > 1)
                 limit = 12;
-        ac_ptr = kzalloc_node(memsize, gfp, node);
-        if (ac_ptr) {
-                for_each_node(i) {
-                        if (i == node || !node_online(i))
-                                continue;
-                        ac_ptr[i] = alloc_arraycache(node, limit, 0xbaadf00d, gfp);
-                        if (!ac_ptr[i]) {
-                                for (i--; i >= 0; i--)
-                                        kfree(ac_ptr[i]);
-                                kfree(ac_ptr);
-                                return NULL;
-                        }
+        alc_ptr = kzalloc_node(memsize, gfp, node);
+        if (!alc_ptr)
+                return NULL;
+
+        for_each_node(i) {
+                if (i == node || !node_online(i))
+                        continue;
+                alc_ptr[i] = __alloc_alien_cache(node, limit, 0xbaadf00d, gfp);
+                if (!alc_ptr[i]) {
+                        for (i--; i >= 0; i--)
+                                kfree(alc_ptr[i]);
+                        kfree(alc_ptr);
+                        return NULL;
                 }
         }
-        return ac_ptr;
+        return alc_ptr;
 }
 
-static void free_alien_cache(struct array_cache **ac_ptr)
+static void free_alien_cache(struct alien_cache **alc_ptr)
 {
         int i;
 
-        if (!ac_ptr)
+        if (!alc_ptr)
                 return;
         for_each_node(i)
-            kfree(ac_ptr[i]);
-        kfree(ac_ptr);
+            kfree(alc_ptr[i]);
+        kfree(alc_ptr);
 }
 
 static void __drain_alien_cache(struct kmem_cache *cachep,
@@ -1063,25 +1081,31 @@ static void reap_alien(struct kmem_cache *cachep, struct kmem_cache_node *n)
         int node = __this_cpu_read(slab_reap_node);
 
         if (n->alien) {
-                struct array_cache *ac = n->alien[node];
-
-                if (ac && ac->avail && spin_trylock_irq(&ac->lock)) {
-                        __drain_alien_cache(cachep, ac, node);
-                        spin_unlock_irq(&ac->lock);
+                struct alien_cache *alc = n->alien[node];
+                struct array_cache *ac;
+
+                if (alc) {
+                        ac = &alc->ac;
+                        if (ac->avail && spin_trylock_irq(&ac->lock)) {
+                                __drain_alien_cache(cachep, ac, node);
+                                spin_unlock_irq(&ac->lock);
+                        }
                 }
         }
 }
 
 static void drain_alien_cache(struct kmem_cache *cachep,
-                                struct array_cache **alien)
+                                struct alien_cache **alien)
 {
         int i = 0;
+        struct alien_cache *alc;
         struct array_cache *ac;
         unsigned long flags;
 
         for_each_online_node(i) {
-                ac = alien[i];
-                if (ac) {
+                alc = alien[i];
+                if (alc) {
+                        ac = &alc->ac;
                         spin_lock_irqsave(&ac->lock, flags);
                         __drain_alien_cache(cachep, ac, i);
                         spin_unlock_irqrestore(&ac->lock, flags);
@@ -1093,7 +1117,8 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
 {
         int nodeid = page_to_nid(virt_to_page(objp));
         struct kmem_cache_node *n;
-        struct array_cache *alien = NULL;
+        struct alien_cache *alien = NULL;
+        struct array_cache *ac;
         int node;
         LIST_HEAD(list);
 
@@ -1110,13 +1135,14 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
         STATS_INC_NODEFREES(cachep);
         if (n->alien && n->alien[nodeid]) {
                 alien = n->alien[nodeid];
-                spin_lock(&alien->lock);
-                if (unlikely(alien->avail == alien->limit)) {
+                ac = &alien->ac;
+                spin_lock(&ac->lock);
+                if (unlikely(ac->avail == ac->limit)) {
                         STATS_INC_ACOVERFLOW(cachep);
-                        __drain_alien_cache(cachep, alien, nodeid);
+                        __drain_alien_cache(cachep, ac, nodeid);
                 }
-                ac_put_obj(cachep, alien, objp);
-                spin_unlock(&alien->lock);
+                ac_put_obj(cachep, ac, objp);
+                spin_unlock(&ac->lock);
         } else {
                 n = get_node(cachep, nodeid);
                 spin_lock(&n->list_lock);
@@ -1191,7 +1217,7 @@ static void cpuup_canceled(long cpu)
         list_for_each_entry(cachep, &slab_caches, list) {
                 struct array_cache *nc;
                 struct array_cache *shared;
-                struct array_cache **alien;
+                struct alien_cache **alien;
                 LIST_HEAD(list);
 
                 /* cpu is dead; no one can alloc from it. */
@@ -1272,7 +1298,7 @@ static int cpuup_prepare(long cpu)
         list_for_each_entry(cachep, &slab_caches, list) {
                 struct array_cache *nc;
                 struct array_cache *shared = NULL;
-                struct array_cache **alien = NULL;
+                struct alien_cache **alien = NULL;
 
                 nc = alloc_arraycache(node, cachep->limit,
                                         cachep->batchcount, GFP_KERNEL);
@@ -3762,7 +3788,7 @@ static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp)
         int node;
         struct kmem_cache_node *n;
         struct array_cache *new_shared;
-        struct array_cache **new_alien = NULL;
+        struct alien_cache **new_alien = NULL;
 
         for_each_online_node(node) {
 
diff --git a/mm/slab.h b/mm/slab.h
index 3822b65edcc2..928823e17e58 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -276,7 +276,7 @@ struct kmem_cache_node {
         unsigned int free_limit;
         unsigned int colour_next;       /* Per-node cache coloring */
         struct array_cache *shared;     /* shared per node */
-        struct array_cache **alien;     /* on other nodes */
+        struct alien_cache **alien;     /* on other nodes */
         unsigned long next_reap;        /* updated without locking */
         int free_touched;               /* updated without locking */
 #endif