mm: memcontrol: report slab usage in cgroup2 memory.stat

Show how much memory is used for storing reclaimable and unreclaimable
in-kernel data structures allocated from slab caches.
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/cgroup-v2.txt

@@ -843,6 +843,11 @@ PAGE_SIZE multiple when read back.
 		Amount of memory used to cache filesystem data,
 		including tmpfs and shared memory.
 
+	  slab
+
+		Amount of memory used for storing in-kernel data
+		structures.
+
 	  sock
 
 		Amount of memory used in network transmission buffers
@@ -871,6 +876,16 @@ PAGE_SIZE multiple when read back.
 		on the internal memory management lists used by the
 		page reclaim algorithm
 
+	  slab_reclaimable
+
+		Part of "slab" that might be reclaimed, such as
+		dentries and inodes.
+
+	  slab_unreclaimable
+
+		Part of "slab" that cannot be reclaimed on memory
+		pressure.
+
 	  pgfault
 
 		Total number of page faults incurred

include/linux/memcontrol.h

@@ -53,6 +53,8 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_NSTATS,
 	/* default hierarchy stats */
 	MEMCG_SOCK = MEM_CGROUP_STAT_NSTATS,
+	MEMCG_SLAB_RECLAIMABLE,
+	MEMCG_SLAB_UNRECLAIMABLE,
 	MEMCG_NR_STAT,
 };
 
@@ -883,6 +885,20 @@ static __always_inline void memcg_kmem_put_cache(struct kmem_cache *cachep)
 	if (memcg_kmem_enabled())
 		__memcg_kmem_put_cache(cachep);
 }
+
+/**
+ * memcg_kmem_update_page_stat - update kmem page state statistics
+ * @page: the page
+ * @idx: page state item to account
+ * @val: number of pages (positive or negative)
+ */
+static inline void memcg_kmem_update_page_stat(struct page *page,
+				enum mem_cgroup_stat_index idx, int val)
+{
+	if (memcg_kmem_enabled() && page->mem_cgroup)
+		this_cpu_add(page->mem_cgroup->stat->count[idx], val);
+}
+
 #else
 #define for_each_memcg_cache_index(_idx)	\
 	for (; NULL; )
@@ -928,6 +944,11 @@ memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
 static inline void memcg_kmem_put_cache(struct kmem_cache *cachep)
 {
 }
+
+static inline void memcg_kmem_update_page_stat(struct page *page,
+				enum mem_cgroup_stat_index idx, int val)
+{
+}
 #endif /* CONFIG_MEMCG && !CONFIG_SLOB */
 
 #endif /* _LINUX_MEMCONTROL_H */

mm/memcontrol.c

@@ -5106,6 +5106,9 @@ static int memory_stat_show(struct seq_file *m, void *v)
 		   (u64)stat[MEM_CGROUP_STAT_RSS] * PAGE_SIZE);
 	seq_printf(m, "file %llu\n",
 		   (u64)stat[MEM_CGROUP_STAT_CACHE] * PAGE_SIZE);
+	seq_printf(m, "slab %llu\n",
+		   (u64)(stat[MEMCG_SLAB_RECLAIMABLE] +
+			 stat[MEMCG_SLAB_UNRECLAIMABLE]) * PAGE_SIZE);
 	seq_printf(m, "sock %llu\n",
 		   (u64)stat[MEMCG_SOCK] * PAGE_SIZE);
 
@@ -5126,6 +5129,11 @@ static int memory_stat_show(struct seq_file *m, void *v)
 			   mem_cgroup_lru_names[i], (u64)val * PAGE_SIZE);
 	}
 
+	seq_printf(m, "slab_reclaimable %llu\n",
+		   (u64)stat[MEMCG_SLAB_RECLAIMABLE] * PAGE_SIZE);
+	seq_printf(m, "slab_unreclaimable %llu\n",
+		   (u64)stat[MEMCG_SLAB_UNRECLAIMABLE] * PAGE_SIZE);
+
 	/* Accumulated memory events */
 
 	seq_printf(m, "pgfault %lu\n",

mm/slab.c

@@ -1442,9 +1442,10 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
  */
 static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
 {
-	const unsigned long nr_freed = (1 << cachep->gfporder);
+	int order = cachep->gfporder;
+	unsigned long nr_freed = (1 << order);
 
-	kmemcheck_free_shadow(page, cachep->gfporder);
+	kmemcheck_free_shadow(page, order);
 
 	if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
 		sub_zone_page_state(page_zone(page),
@@ -1461,7 +1462,8 @@ static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
 
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += nr_freed;
-	__free_kmem_pages(page, cachep->gfporder);
+	memcg_uncharge_slab(page, order, cachep);
+	__free_pages(page, order);
 }
 
 static void kmem_rcu_free(struct rcu_head *head)

mm/slab.h

@@ -246,12 +246,33 @@ static __always_inline int memcg_charge_slab(struct page *page,
 					     gfp_t gfp, int order,
 					     struct kmem_cache *s)
 {
+	int ret;
+
 	if (!memcg_kmem_enabled())
 		return 0;
 	if (is_root_cache(s))
 		return 0;
-	return __memcg_kmem_charge_memcg(page, gfp, order,
-					 s->memcg_params.memcg);
+
+	ret = __memcg_kmem_charge_memcg(page, gfp, order,
+					s->memcg_params.memcg);
+	if (ret)
+		return ret;
+
+	memcg_kmem_update_page_stat(page,
+			(s->flags & SLAB_RECLAIM_ACCOUNT) ?
+			MEMCG_SLAB_RECLAIMABLE : MEMCG_SLAB_UNRECLAIMABLE,
+			1 << order);
+	return 0;
+}
+
+static __always_inline void memcg_uncharge_slab(struct page *page, int order,
+						struct kmem_cache *s)
+{
+	memcg_kmem_update_page_stat(page,
+			(s->flags & SLAB_RECLAIM_ACCOUNT) ?
+			MEMCG_SLAB_RECLAIMABLE : MEMCG_SLAB_UNRECLAIMABLE,
+			-(1 << order));
+	memcg_kmem_uncharge(page, order);
 }
 
 extern void slab_init_memcg_params(struct kmem_cache *);
@@ -294,6 +315,11 @@ static inline int memcg_charge_slab(struct page *page, gfp_t gfp, int order,
 	return 0;
 }
 
+static inline void memcg_uncharge_slab(struct page *page, int order,
+				       struct kmem_cache *s)
+{
+}
+
 static inline void slab_init_memcg_params(struct kmem_cache *s)
 {
 }

mm/slub.c

@@ -1540,7 +1540,8 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
 	page_mapcount_reset(page);
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += pages;
-	__free_kmem_pages(page, order);
+	memcg_uncharge_slab(page, order, s);
+	__free_pages(page, order);
 }
 
 #define need_reserve_slab_rcu						\