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>

6 files changed, 79 insertions, 6 deletions

diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index ff49cf901148..e4e0c1d78cee 100644
--- a/Documentation/cgroup-v2.txt
+++ b/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
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index f0c4bec6565b..e7af4834ffea 100644
--- a/include/linux/memcontrol.h
+++ b/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 */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 430266071c36..3ad64bf464fd 100644
--- a/mm/memcontrol.c
+++ b/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",
diff --git a/mm/slab.c b/mm/slab.c
index 852fc5c79829..56dd0df2a8ce 100644
--- a/mm/slab.c
+++ b/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)
diff --git a/mm/slab.h b/mm/slab.h
index b7934361f026..ff39a8fc3b3f 100644
--- a/mm/slab.h
+++ b/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)
 {
 }
diff --git a/mm/slub.c b/mm/slub.c
index 6c91324f9370..712d53474082 100644
--- a/mm/slub.c
+++ b/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                                           \