mm/slub.c: wrap kmem_cache->cpu_partial in config CONFIG_SLUB_CPU_PARTIAL

kmem_cache->cpu_partial is just used when CONFIG_SLUB_CPU_PARTIAL is
set, so wrap it with config CONFIG_SLUB_CPU_PARTIAL will save some space
on 32bit arch.

This patch wraps kmem_cache->cpu_partial in config CONFIG_SLUB_CPU_PARTIAL
and wraps its sysfs too.

Link: http://lkml.kernel.org/r/20170502144533.10729-4-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 51 insertions, 31 deletions

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index a3e9492fed02..cc0faf3a90be 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -86,7 +86,9 @@ struct kmem_cache {
         int size;               /* The size of an object including meta data */
         int object_size;        /* The size of an object without meta data */
         int offset;             /* Free pointer offset. */
+#ifdef CONFIG_SLUB_CPU_PARTIAL
         int cpu_partial;        /* Number of per cpu partial objects to keep around */
+#endif
         struct kmem_cache_order_objects oo;
 
         /* Allocation and freeing of slabs */
@@ -131,6 +133,17 @@ struct kmem_cache {
         struct kmem_cache_node *node[MAX_NUMNODES];
 };
 
+#ifdef CONFIG_SLUB_CPU_PARTIAL
+#define slub_cpu_partial(s)             ((s)->cpu_partial)
+#define slub_set_cpu_partial(s, n)              \
+({                                              \
+        slub_cpu_partial(s) = (n);              \
+})
+#else
+#define slub_cpu_partial(s)             (0)
+#define slub_set_cpu_partial(s, n)
+#endif // CONFIG_SLUB_CPU_PARTIAL
+
 #ifdef CONFIG_SYSFS
 #define SLAB_SUPPORTS_SYSFS
 void sysfs_slab_release(struct kmem_cache *);
diff --git a/mm/slub.c b/mm/slub.c
index 48071c541275..388f66d1da5e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1829,7 +1829,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
                         stat(s, CPU_PARTIAL_NODE);
                 }
                 if (!kmem_cache_has_cpu_partial(s)
-                        || available > s->cpu_partial / 2)
+                        || available > slub_cpu_partial(s) / 2)
                         break;
 
         }
@@ -3404,6 +3404,39 @@ static void set_min_partial(struct kmem_cache *s, unsigned long min)
         s->min_partial = min;
 }
 
+static void set_cpu_partial(struct kmem_cache *s)
+{
+#ifdef CONFIG_SLUB_CPU_PARTIAL
+        /*
+         * cpu_partial determined the maximum number of objects kept in the
+         * per cpu partial lists of a processor.
+         *
+         * Per cpu partial lists mainly contain slabs that just have one
+         * object freed. If they are used for allocation then they can be
+         * filled up again with minimal effort. The slab will never hit the
+         * per node partial lists and therefore no locking will be required.
+         *
+         * This setting also determines
+         *
+         * A) The number of objects from per cpu partial slabs dumped to the
+         *    per node list when we reach the limit.
+         * B) The number of objects in cpu partial slabs to extract from the
+         *    per node list when we run out of per cpu objects. We only fetch
+         *    50% to keep some capacity around for frees.
+         */
+        if (!kmem_cache_has_cpu_partial(s))
+                s->cpu_partial = 0;
+        else if (s->size >= PAGE_SIZE)
+                s->cpu_partial = 2;
+        else if (s->size >= 1024)
+                s->cpu_partial = 6;
+        else if (s->size >= 256)
+                s->cpu_partial = 13;
+        else
+                s->cpu_partial = 30;
+#endif
+}
+
 /*
  * calculate_sizes() determines the order and the distribution of data within
  * a slab object.
@@ -3562,33 +3595,7 @@ static int kmem_cache_open(struct kmem_cache *s, unsigned long flags)
          */
         set_min_partial(s, ilog2(s->size) / 2);
 
-        /*
-         * cpu_partial determined the maximum number of objects kept in the
-         * per cpu partial lists of a processor.
-         *
-         * Per cpu partial lists mainly contain slabs that just have one
-         * object freed. If they are used for allocation then they can be
-         * filled up again with minimal effort. The slab will never hit the
-         * per node partial lists and therefore no locking will be required.
-         *
-         * This setting also determines
-         *
-         * A) The number of objects from per cpu partial slabs dumped to the
-         *    per node list when we reach the limit.
-         * B) The number of objects in cpu partial slabs to extract from the
-         *    per node list when we run out of per cpu objects. We only fetch
-         *    50% to keep some capacity around for frees.
-         */
-        if (!kmem_cache_has_cpu_partial(s))
-                s->cpu_partial = 0;
-        else if (s->size >= PAGE_SIZE)
-                s->cpu_partial = 2;
-        else if (s->size >= 1024)
-                s->cpu_partial = 6;
-        else if (s->size >= 256)
-                s->cpu_partial = 13;
-        else
-                s->cpu_partial = 30;
+        set_cpu_partial(s);
 
 #ifdef CONFIG_NUMA
         s->remote_node_defrag_ratio = 1000;
@@ -3975,7 +3982,7 @@ void __kmemcg_cache_deactivate(struct kmem_cache *s)
          * Disable empty slabs caching. Used to avoid pinning offline
          * memory cgroups by kmem pages that can be freed.
          */
-        s->cpu_partial = 0;
+        slub_set_cpu_partial(s, 0);
         s->min_partial = 0;
 
         /*
@@ -4915,7 +4922,7 @@ SLAB_ATTR(min_partial);
 
 static ssize_t cpu_partial_show(struct kmem_cache *s, char *buf)
 {
-        return sprintf(buf, "%u\n", s->cpu_partial);
+        return sprintf(buf, "%u\n", slub_cpu_partial(s));
 }
 
 static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf,
@@ -4930,7 +4937,7 @@ static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf,
         if (objects && !kmem_cache_has_cpu_partial(s))
                 return -EINVAL;
 
-        s->cpu_partial = objects;
+        slub_set_cpu_partial(s, objects);
         flush_all(s);
         return length;
 }