[PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[Vladimir Davydov]

Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
order to just create the name of a per memcg cache, let's allocate it in
place. We only need to pass the memcg name to kmem_cache_create_memcg
for that - everything else can be done in slab_common.c.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
Initially this was a part of "memcg/kmem: cleanup naming and callflows"
patch set (https://lkml.org/lkml/2014/4/27/345).

 include/linux/memcontrol.h |    2 --
 include/linux/slab.h       |    3 ++-
 mm/memcontrol.c            |   33 +++++++++------------------------
 mm/slab_common.c           |    7 +++++--
 4 files changed, 16 insertions(+), 29 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6c59056f4bc6..7b639ab48aa8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -501,8 +501,6 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order);
 
 int memcg_cache_id(struct mem_cgroup *memcg);
 
-char *memcg_create_cache_name(struct mem_cgroup *memcg,
-			      struct kmem_cache *root_cache);
 int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
 			     struct kmem_cache *root_cache);
 void memcg_free_cache_params(struct kmem_cache *s);
diff --git a/include/linux/slab.h b/include/linux/slab.h
index ecbec9ccb80d..86e5b26fbdab 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -117,7 +117,8 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			void (*)(void *));
 #ifdef CONFIG_MEMCG_KMEM
 struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
-					   struct kmem_cache *);
+					   struct kmem_cache *,
+					   const char *);
 #endif
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f381239ab402..f401f227a099 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3101,29 +3101,6 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
 	return 0;
 }
 
-char *memcg_create_cache_name(struct mem_cgroup *memcg,
-			      struct kmem_cache *root_cache)
-{
-	static char *buf;
-
-	/*
-	 * We need a mutex here to protect the shared buffer. Since this is
-	 * expected to be called only on cache creation, we can employ the
-	 * slab_mutex for that purpose.
-	 */
-	lockdep_assert_held(&slab_mutex);
-
-	if (!buf) {
-		buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
-		if (!buf)
-			return NULL;
-	}
-
-	cgroup_name(memcg->css.cgroup, buf, NAME_MAX + 1);
-	return kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
-			 memcg_cache_id(memcg), buf);
-}
-
 int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
 			     struct kmem_cache *root_cache)
 {
@@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
 static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 				    struct kmem_cache *root_cache)
 {
+	static char *memcg_name_buf;
 	struct kmem_cache *cachep;
 	int id;
 
@@ -3179,7 +3157,14 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 	if (cache_from_memcg_idx(root_cache, id))
 		return;
 
-	cachep = kmem_cache_create_memcg(memcg, root_cache);
+	if (!memcg_name_buf) {
+		memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+		if (!memcg_name_buf)
+			return;
+	}
+
+	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
+	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
 	/*
 	 * If we could not create a memcg cache, do not complain, because
 	 * that's not critical at all as we can always proceed with the root
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7e348cff814d..32175617cb75 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -264,13 +264,15 @@ EXPORT_SYMBOL(kmem_cache_create);
  * kmem_cache_create_memcg - Create a cache for a memory cgroup.
  * @memcg: The memory cgroup the new cache is for.
  * @root_cache: The parent of the new cache.
+ * @memcg_name: The name of the memory cgroup (used for naming the new cache).
  *
  * This function attempts to create a kmem cache that will serve allocation
  * requests going from @memcg to @root_cache. The new cache inherits properties
  * from its parent.
  */
 struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
-					   struct kmem_cache *root_cache)
+					   struct kmem_cache *root_cache,
+					   const char *memcg_name)
 {
 	struct kmem_cache *s = NULL;
 	char *cache_name;
@@ -280,7 +282,8 @@ struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
 
 	mutex_lock(&slab_mutex);
 
-	cache_name = memcg_create_cache_name(memcg, root_cache);
+	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
+			       memcg_cache_id(memcg), memcg_name);
 	if (!cache_name)
 		goto out_unlock;
 
-- 
1.7.10.4

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[PATCH -mm 2/2] memcg: cleanup kmem cache creation/destruction functions naming

[Vladimir Davydov]

Current names are rather inconsistent. Let's try to improve them.

Brief change log:

** old name **                          ** new name **

kmem_cache_create_memcg                 kmem_cache_request_memcg_copy
memcg_kmem_create_cache                 memcg_copy_kmem_cache
memcg_kmem_destroy_cache                memcg_destroy_kmem_cache_copy

__kmem_cache_destroy_memcg_children     __kmem_cache_destroy_memcg_copies
kmem_cache_destroy_memcg_children       kmem_cache_destroy_memcg_copies
mem_cgroup_destroy_all_caches           memcg_destroy_kmem_cache_copies

create_work                             memcg_kmem_cache_copy_work
memcg_create_cache_work_func            memcg_kmem_cache_copy_work_func
memcg_create_cache_enqueue              memcg_schedule_kmem_cache_copy

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
Initially this was a part of "memcg/kmem: cleanup naming and callflows"
patch set (https://lkml.org/lkml/2014/4/27/345).

 include/linux/memcontrol.h |    2 +-
 include/linux/slab.h       |    6 ++---
 mm/memcontrol.c            |   58 +++++++++++++++++++++-----------------------
 mm/slab_common.c           |   29 +++++++++++-----------
 4 files changed, 45 insertions(+), 50 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 7b639ab48aa8..0958f0361af0 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -514,7 +514,7 @@ __memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);
 int __memcg_charge_slab(struct kmem_cache *cachep, gfp_t gfp, int order);
 void __memcg_uncharge_slab(struct kmem_cache *cachep, int order);
 
-int __kmem_cache_destroy_memcg_children(struct kmem_cache *s);
+int __kmem_cache_destroy_memcg_copies(struct kmem_cache *s);
 
 /**
  * memcg_kmem_newpage_charge: verify if a new kmem allocation is allowed.
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 86e5b26fbdab..e08e369d42ac 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -116,9 +116,9 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			unsigned long,
 			void (*)(void *));
 #ifdef CONFIG_MEMCG_KMEM
-struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
-					   struct kmem_cache *,
-					   const char *);
+struct kmem_cache *kmem_cache_request_memcg_copy(struct kmem_cache *,
+						 struct mem_cgroup *,
+						 const char *);
 #endif
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f401f227a099..52a31f6876ce 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3138,8 +3138,8 @@ void memcg_free_cache_params(struct kmem_cache *s)
 	kfree(s->memcg_params);
 }
 
-static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
-				    struct kmem_cache *root_cache)
+static void memcg_copy_kmem_cache(struct mem_cgroup *memcg,
+				  struct kmem_cache *root_cache)
 {
 	static char *memcg_name_buf;
 	struct kmem_cache *cachep;
@@ -3164,7 +3164,7 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 	}
 
 	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
-	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
+	cachep = kmem_cache_request_memcg_copy(root_cache, memcg, memcg_name_buf);
 	/*
 	 * If we could not create a memcg cache, do not complain, because
 	 * that's not critical at all as we can always proceed with the root
@@ -3186,7 +3186,7 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 	root_cache->memcg_params->memcg_caches[id] = cachep;
 }
 
-static void memcg_kmem_destroy_cache(struct kmem_cache *cachep)
+static void memcg_destroy_kmem_cache_copy(struct kmem_cache *cachep)
 {
 	struct kmem_cache *root_cache;
 	struct mem_cgroup *memcg;
@@ -3239,7 +3239,7 @@ static inline void memcg_resume_kmem_account(void)
 	current->memcg_kmem_skip_account--;
 }
 
-int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+int __kmem_cache_destroy_memcg_copies(struct kmem_cache *s)
 {
 	struct kmem_cache *c;
 	int i, failed = 0;
@@ -3250,7 +3250,7 @@ int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 		if (!c)
 			continue;
 
-		memcg_kmem_destroy_cache(c);
+		memcg_destroy_kmem_cache_copy(c);
 
 		if (cache_from_memcg_idx(s, i))
 			failed++;
@@ -3259,7 +3259,7 @@ int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 	return failed;
 }
 
-static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
+static void memcg_destroy_kmem_cache_copies(struct mem_cgroup *memcg)
 {
 	struct kmem_cache *cachep;
 	struct memcg_cache_params *params, *tmp;
@@ -3272,25 +3272,26 @@ static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 		cachep = memcg_params_to_cache(params);
 		kmem_cache_shrink(cachep);
 		if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
-			memcg_kmem_destroy_cache(cachep);
+			memcg_destroy_kmem_cache_copy(cachep);
 	}
 	mutex_unlock(&memcg_slab_mutex);
 }
 
-struct create_work {
+struct memcg_kmem_cache_copy_work {
 	struct mem_cgroup *memcg;
 	struct kmem_cache *cachep;
 	struct work_struct work;
 };
 
-static void memcg_create_cache_work_func(struct work_struct *w)
+static void memcg_kmem_cache_copy_work_func(struct work_struct *w)
 {
-	struct create_work *cw = container_of(w, struct create_work, work);
+	struct memcg_kmem_cache_copy_work *cw = container_of(w,
+			struct memcg_kmem_cache_copy_work, work);
 	struct mem_cgroup *memcg = cw->memcg;
 	struct kmem_cache *cachep = cw->cachep;
 
 	mutex_lock(&memcg_slab_mutex);
-	memcg_kmem_create_cache(memcg, cachep);
+	memcg_copy_kmem_cache(memcg, cachep);
 	mutex_unlock(&memcg_slab_mutex);
 
 	css_put(&memcg->css);
@@ -3300,12 +3301,12 @@ static void memcg_create_cache_work_func(struct work_struct *w)
 /*
  * Enqueue the creation of a per-memcg kmem_cache.
  */
-static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
-					 struct kmem_cache *cachep)
+static void __memcg_schedule_kmem_cache_copy(struct mem_cgroup *memcg,
+					     struct kmem_cache *cachep)
 {
-	struct create_work *cw;
+	struct memcg_kmem_cache_copy_work *cw;
 
-	cw = kmalloc(sizeof(struct create_work), GFP_NOWAIT);
+	cw = kmalloc(sizeof(*cw), GFP_NOWAIT);
 	if (cw == NULL) {
 		css_put(&memcg->css);
 		return;
@@ -3314,17 +3315,17 @@ static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
 	cw->memcg = memcg;
 	cw->cachep = cachep;
 
-	INIT_WORK(&cw->work, memcg_create_cache_work_func);
+	INIT_WORK(&cw->work, memcg_kmem_cache_copy_work_func);
 	schedule_work(&cw->work);
 }
 
-static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
-				       struct kmem_cache *cachep)
+static void memcg_schedule_kmem_cache_copy(struct mem_cgroup *memcg,
+					   struct kmem_cache *cachep)
 {
 	/*
 	 * We need to stop accounting when we kmalloc, because if the
 	 * corresponding kmalloc cache is not yet created, the first allocation
-	 * in __memcg_create_cache_enqueue will recurse.
+	 * in __memcg_schedule_kmem_cache_copy will recurse.
 	 *
 	 * However, it is better to enclose the whole function. Depending on
 	 * the debugging options enabled, INIT_WORK(), for instance, can
@@ -3333,7 +3334,7 @@ static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
 	 * the safest choice is to do it like this, wrapping the whole function.
 	 */
 	memcg_stop_kmem_account();
-	__memcg_create_cache_enqueue(memcg, cachep);
+	__memcg_schedule_kmem_cache_copy(memcg, cachep);
 	memcg_resume_kmem_account();
 }
 
@@ -3404,16 +3405,11 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
 	 *
 	 * However, there are some clashes that can arrive from locking.
 	 * For instance, because we acquire the slab_mutex while doing
-	 * kmem_cache_dup, this means no further allocation could happen
-	 * with the slab_mutex held.
-	 *
-	 * Also, because cache creation issue get_online_cpus(), this
-	 * creates a lock chain: memcg_slab_mutex -> cpu_hotplug_mutex,
-	 * that ends up reversed during cpu hotplug. (cpuset allocates
-	 * a bunch of GFP_KERNEL memory during cpuup). Due to all that,
+	 * kmem_cache_request_memcg_copy, this means no further
+	 * allocation could happen with the slab_mutex held. So it's
 	 * better to defer everything.
 	 */
-	memcg_create_cache_enqueue(memcg, cachep);
+	memcg_schedule_kmem_cache_copy(memcg, cachep);
 	return cachep;
 out:
 	rcu_read_unlock();
@@ -3537,7 +3533,7 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order)
 	memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
 }
 #else
-static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
+static inline void memcg_destroy_kmem_cache_copies(struct mem_cgroup *memcg)
 {
 }
 #endif /* CONFIG_MEMCG_KMEM */
@@ -6415,7 +6411,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
 	css_for_each_descendant_post(iter, css)
 		mem_cgroup_reparent_charges(mem_cgroup_from_css(iter));
 
-	mem_cgroup_destroy_all_caches(memcg);
+	memcg_destroy_kmem_cache_copies(memcg);
 	vmpressure_cleanup(&memcg->vmpressure);
 }
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 32175617cb75..802466c7e736 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -261,18 +261,18 @@ EXPORT_SYMBOL(kmem_cache_create);
 
 #ifdef CONFIG_MEMCG_KMEM
 /*
- * kmem_cache_create_memcg - Create a cache for a memory cgroup.
+ * kmem_cache_request_memcg_copy - Create copy of a cache for a memcg.
+ * @cachep: The cache to make a copy of.
  * @memcg: The memory cgroup the new cache is for.
- * @root_cache: The parent of the new cache.
  * @memcg_name: The name of the memory cgroup (used for naming the new cache).
  *
  * This function attempts to create a kmem cache that will serve allocation
- * requests going from @memcg to @root_cache. The new cache inherits properties
+ * requests going from @memcg to @cachep. The new cache inherits properties
  * from its parent.
  */
-struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
-					   struct kmem_cache *root_cache,
-					   const char *memcg_name)
+struct kmem_cache *kmem_cache_request_memcg_copy(struct kmem_cache *cachep,
+						 struct mem_cgroup *memcg,
+						 const char *memcg_name)
 {
 	struct kmem_cache *s = NULL;
 	char *cache_name;
@@ -282,15 +282,14 @@ struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
 
 	mutex_lock(&slab_mutex);
 
-	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
+	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", cachep->name,
 			       memcg_cache_id(memcg), memcg_name);
 	if (!cache_name)
 		goto out_unlock;
 
-	s = do_kmem_cache_create(cache_name, root_cache->object_size,
-				 root_cache->size, root_cache->align,
-				 root_cache->flags, root_cache->ctor,
-				 memcg, root_cache);
+	s = do_kmem_cache_create(cache_name, cachep->object_size, cachep->size,
+				 cachep->align, cachep->flags, cachep->ctor,
+				 memcg, cachep);
 	if (IS_ERR(s)) {
 		kfree(cache_name);
 		s = NULL;
@@ -305,7 +304,7 @@ out_unlock:
 	return s;
 }
 
-static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+static int kmem_cache_destroy_memcg_copies(struct kmem_cache *s)
 {
 	int rc;
 
@@ -314,13 +313,13 @@ static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 		return 0;
 
 	mutex_unlock(&slab_mutex);
-	rc = __kmem_cache_destroy_memcg_children(s);
+	rc = __kmem_cache_destroy_memcg_copies(s);
 	mutex_lock(&slab_mutex);
 
 	return rc;
 }
 #else
-static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+static int kmem_cache_destroy_memcg_copies(struct kmem_cache *s)
 {
 	return 0;
 }
@@ -343,7 +342,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
 	if (s->refcount)
 		goto out_unlock;
 
-	if (kmem_cache_destroy_memcg_children(s) != 0)
+	if (kmem_cache_destroy_memcg_copies(s) != 0)
 		goto out_unlock;
 
 	list_del(&s->list);
-- 
1.7.10.4

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Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[Michal Hocko]

On Wed 07-05-14 12:15:29, Vladimir Davydov wrote:
> Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
> order to just create the name of a per memcg cache, let's allocate it in
> place. We only need to pass the memcg name to kmem_cache_create_memcg
> for that - everything else can be done in slab_common.c.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

Seems good to me.
I would keep the comment about the static buffer as mentioned below.
Other than that
Acked-by: Michal Hocko <mhocko@suse.cz>

[...]
> -char *memcg_create_cache_name(struct mem_cgroup *memcg,
> -			      struct kmem_cache *root_cache)
> -{
> -	static char *buf;
> -
> -	/*
> -	 * We need a mutex here to protect the shared buffer. Since this is
> -	 * expected to be called only on cache creation, we can employ the
> -	 * slab_mutex for that purpose.
> -	 */
> -	lockdep_assert_held(&slab_mutex);
> -
> -	if (!buf) {
> -		buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
> -		if (!buf)
> -			return NULL;
> -	}
> -
> -	cgroup_name(memcg->css.cgroup, buf, NAME_MAX + 1);
> -	return kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
> -			 memcg_cache_id(memcg), buf);
> -}
> -
>  int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
>  			     struct kmem_cache *root_cache)
>  {
> @@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
>  static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  				    struct kmem_cache *root_cache)
>  {
> +	static char *memcg_name_buf;
>  	struct kmem_cache *cachep;
>  	int id;

So we are relying on memcg_slab_mutex now, right? Worth a comment I
suppose.

-- 
Michal Hocko
SUSE Labs

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Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[Vladimir Davydov]

On Wed, May 07, 2014 at 11:51:27AM +0200, Michal Hocko wrote:
> On Wed 07-05-14 12:15:29, Vladimir Davydov wrote:
> [...]
> >  static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
> >  				    struct kmem_cache *root_cache)
> >  {
> > +	static char *memcg_name_buf;
> >  	struct kmem_cache *cachep;
> >  	int id;
> 
> So we are relying on memcg_slab_mutex now, right? Worth a comment I
> suppose.

Sure. The updated version is attached below.

Thanks.
--

From: Vladimir Davydov <vdavydov@parallels.com>
Subject: [PATCH] memcg: get rid of memcg_create_cache_name

Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
order to just create the name of a per memcg cache, let's allocate it in
place. We only need to pass the memcg name to kmem_cache_create_memcg
for that - everything else can be done in slab_common.c.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6c59056f4bc6..7b639ab48aa8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -501,8 +501,6 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order);
 
 int memcg_cache_id(struct mem_cgroup *memcg);
 
-char *memcg_create_cache_name(struct mem_cgroup *memcg,
-			      struct kmem_cache *root_cache);
 int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
 			     struct kmem_cache *root_cache);
 void memcg_free_cache_params(struct kmem_cache *s);
diff --git a/include/linux/slab.h b/include/linux/slab.h
index ecbec9ccb80d..86e5b26fbdab 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -117,7 +117,8 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			void (*)(void *));
 #ifdef CONFIG_MEMCG_KMEM
 struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
-					   struct kmem_cache *);
+					   struct kmem_cache *,
+					   const char *);
 #endif
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f381239ab402..9ff3742f4154 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3101,29 +3101,6 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
 	return 0;
 }
 
-char *memcg_create_cache_name(struct mem_cgroup *memcg,
-			      struct kmem_cache *root_cache)
-{
-	static char *buf;
-
-	/*
-	 * We need a mutex here to protect the shared buffer. Since this is
-	 * expected to be called only on cache creation, we can employ the
-	 * slab_mutex for that purpose.
-	 */
-	lockdep_assert_held(&slab_mutex);
-
-	if (!buf) {
-		buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
-		if (!buf)
-			return NULL;
-	}
-
-	cgroup_name(memcg->css.cgroup, buf, NAME_MAX + 1);
-	return kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
-			 memcg_cache_id(memcg), buf);
-}
-
 int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
 			     struct kmem_cache *root_cache)
 {
@@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
 static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 				    struct kmem_cache *root_cache)
 {
+	static char *memcg_name_buf;	/* protected by memcg_slab_mutex */
 	struct kmem_cache *cachep;
 	int id;
 
@@ -3179,7 +3157,14 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 	if (cache_from_memcg_idx(root_cache, id))
 		return;
 
-	cachep = kmem_cache_create_memcg(memcg, root_cache);
+	if (!memcg_name_buf) {
+		memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+		if (!memcg_name_buf)
+			return;
+	}
+
+	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
+	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
 	/*
 	 * If we could not create a memcg cache, do not complain, because
 	 * that's not critical at all as we can always proceed with the root
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7e348cff814d..32175617cb75 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -264,13 +264,15 @@ EXPORT_SYMBOL(kmem_cache_create);
  * kmem_cache_create_memcg - Create a cache for a memory cgroup.
  * @memcg: The memory cgroup the new cache is for.
  * @root_cache: The parent of the new cache.
+ * @memcg_name: The name of the memory cgroup (used for naming the new cache).
  *
  * This function attempts to create a kmem cache that will serve allocation
  * requests going from @memcg to @root_cache. The new cache inherits properties
  * from its parent.
  */
 struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
-					   struct kmem_cache *root_cache)
+					   struct kmem_cache *root_cache,
+					   const char *memcg_name)
 {
 	struct kmem_cache *s = NULL;
 	char *cache_name;
@@ -280,7 +282,8 @@ struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
 
 	mutex_lock(&slab_mutex);
 
-	cache_name = memcg_create_cache_name(memcg, root_cache);
+	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
+			       memcg_cache_id(memcg), memcg_name);
 	if (!cache_name)
 		goto out_unlock;
 

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Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[Michal Hocko]

On Wed 07-05-14 14:45:16, Vladimir Davydov wrote:
[...]
> From: Vladimir Davydov <vdavydov@parallels.com>
> Subject: [PATCH] memcg: get rid of memcg_create_cache_name
> 
> Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
> order to just create the name of a per memcg cache, let's allocate it in
> place. We only need to pass the memcg name to kmem_cache_create_memcg
> for that - everything else can be done in slab_common.c.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

Acked-by: Michal Hocko <mhocko@suse.cz>

> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 6c59056f4bc6..7b639ab48aa8 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -501,8 +501,6 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order);
>  
>  int memcg_cache_id(struct mem_cgroup *memcg);
>  
> -char *memcg_create_cache_name(struct mem_cgroup *memcg,
> -			      struct kmem_cache *root_cache);
>  int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
>  			     struct kmem_cache *root_cache);
>  void memcg_free_cache_params(struct kmem_cache *s);
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index ecbec9ccb80d..86e5b26fbdab 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -117,7 +117,8 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
>  			void (*)(void *));
>  #ifdef CONFIG_MEMCG_KMEM
>  struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
> -					   struct kmem_cache *);
> +					   struct kmem_cache *,
> +					   const char *);
>  #endif
>  void kmem_cache_destroy(struct kmem_cache *);
>  int kmem_cache_shrink(struct kmem_cache *);
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f381239ab402..9ff3742f4154 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3101,29 +3101,6 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
>  	return 0;
>  }
>  
> -char *memcg_create_cache_name(struct mem_cgroup *memcg,
> -			      struct kmem_cache *root_cache)
> -{
> -	static char *buf;
> -
> -	/*
> -	 * We need a mutex here to protect the shared buffer. Since this is
> -	 * expected to be called only on cache creation, we can employ the
> -	 * slab_mutex for that purpose.
> -	 */
> -	lockdep_assert_held(&slab_mutex);
> -
> -	if (!buf) {
> -		buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
> -		if (!buf)
> -			return NULL;
> -	}
> -
> -	cgroup_name(memcg->css.cgroup, buf, NAME_MAX + 1);
> -	return kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
> -			 memcg_cache_id(memcg), buf);
> -}
> -
>  int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
>  			     struct kmem_cache *root_cache)
>  {
> @@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
>  static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  				    struct kmem_cache *root_cache)
>  {
> +	static char *memcg_name_buf;	/* protected by memcg_slab_mutex */
>  	struct kmem_cache *cachep;
>  	int id;
>  
> @@ -3179,7 +3157,14 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  	if (cache_from_memcg_idx(root_cache, id))
>  		return;
>  
> -	cachep = kmem_cache_create_memcg(memcg, root_cache);
> +	if (!memcg_name_buf) {
> +		memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
> +		if (!memcg_name_buf)
> +			return;
> +	}
> +
> +	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
> +	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
>  	/*
>  	 * If we could not create a memcg cache, do not complain, because
>  	 * that's not critical at all as we can always proceed with the root
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 7e348cff814d..32175617cb75 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -264,13 +264,15 @@ EXPORT_SYMBOL(kmem_cache_create);
>   * kmem_cache_create_memcg - Create a cache for a memory cgroup.
>   * @memcg: The memory cgroup the new cache is for.
>   * @root_cache: The parent of the new cache.
> + * @memcg_name: The name of the memory cgroup (used for naming the new cache).
>   *
>   * This function attempts to create a kmem cache that will serve allocation
>   * requests going from @memcg to @root_cache. The new cache inherits properties
>   * from its parent.
>   */
>  struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
> -					   struct kmem_cache *root_cache)
> +					   struct kmem_cache *root_cache,
> +					   const char *memcg_name)
>  {
>  	struct kmem_cache *s = NULL;
>  	char *cache_name;
> @@ -280,7 +282,8 @@ struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
>  
>  	mutex_lock(&slab_mutex);
>  
> -	cache_name = memcg_create_cache_name(memcg, root_cache);
> +	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
> +			       memcg_cache_id(memcg), memcg_name);
>  	if (!cache_name)
>  		goto out_unlock;
>  

-- 
Michal Hocko
SUSE Labs

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Re: [PATCH -mm 2/2] memcg: cleanup kmem cache creation/destruction functions naming

[Michal Hocko]

On Wed 07-05-14 12:15:30, Vladimir Davydov wrote:
> Current names are rather inconsistent. Let's try to improve them.

Yes the old names are a giant mess. I am not sure the new ones are
that much better however.
 
> Brief change log:
> 
> ** old name **                          ** new name **
> 
> kmem_cache_create_memcg                 kmem_cache_request_memcg_copy

Both are bad because the first suggests we are creating memcg and the second that
we are requesting a copy of memcg.

memcg_alloc_kmem_cache?

_copy suffix is a bit confusing. E.g. copy_mm and others either to
shallow or deep copy depending on the context. This one always creats a
deep copy. Also why it is imporatant to treat the created caches as
copies?

> memcg_kmem_create_cache                 memcg_copy_kmem_cache

memcg_register_kmem_cache? It also allocates so this name is a bit
awkward as well.

> memcg_kmem_destroy_cache                memcg_destroy_kmem_cache_copy

memcg_unregister_kmem_cache to match the above?

> __kmem_cache_destroy_memcg_children     __kmem_cache_destroy_memcg_copies
> kmem_cache_destroy_memcg_children       kmem_cache_destroy_memcg_copies

_children suffix is really confusing because they have different meaning in
memcg and refer to children groups.

memcg_cleanup_kmem_chache_memcg_params? It doesn't have to live in the
kmem_cache namespace because it only does only memcg kmem specific
stuff.

> mem_cgroup_destroy_all_caches           memcg_destroy_kmem_cache_copies
> 
> create_work                             memcg_kmem_cache_copy_work

memcg_register_cache_work?

> memcg_create_cache_work_func            memcg_kmem_cache_copy_work_func

memcg_register_cache_func?

> memcg_create_cache_enqueue              memcg_schedule_kmem_cache_copy

memcg_schedule_register_cache?

-- 
Michal Hocko
SUSE Labs

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Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[Andrew Morton]

On Wed, 7 May 2014 14:45:16 +0400 Vladimir Davydov <vdavydov@parallels.com> wrote:

> @@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
>  static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  				    struct kmem_cache *root_cache)
>  {
> +	static char *memcg_name_buf;	/* protected by memcg_slab_mutex */
>  	struct kmem_cache *cachep;
>  	int id;
>  
> @@ -3179,7 +3157,14 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  	if (cache_from_memcg_idx(root_cache, id))
>  		return;
>  
> -	cachep = kmem_cache_create_memcg(memcg, root_cache);
> +	if (!memcg_name_buf) {
> +		memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
> +		if (!memcg_name_buf)
> +			return;
> +	}

Does this have any meaningful advantage over the simpler

	static char memcg_name_buf[NAME_MAX + 1];

?

I guess it saves a scrap of memory if the machine never uses memcg's.

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Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name

[Vladimir Davydov]

On Wed, May 07, 2014 at 01:53:52PM -0700, Andrew Morton wrote:
> On Wed, 7 May 2014 14:45:16 +0400 Vladimir Davydov <vdavydov@parallels.com> wrote:
> 
> > @@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
> >  static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
> >  				    struct kmem_cache *root_cache)
> >  {
> > +	static char *memcg_name_buf;	/* protected by memcg_slab_mutex */
> >  	struct kmem_cache *cachep;
> >  	int id;
> >  
> > @@ -3179,7 +3157,14 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
> >  	if (cache_from_memcg_idx(root_cache, id))
> >  		return;
> >  
> > -	cachep = kmem_cache_create_memcg(memcg, root_cache);
> > +	if (!memcg_name_buf) {
> > +		memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
> > +		if (!memcg_name_buf)
> > +			return;
> > +	}
> 
> Does this have any meaningful advantage over the simpler
> 
> 	static char memcg_name_buf[NAME_MAX + 1];
> 
> ?

Don't think so. In case nobody has objections, the patch is attached
below.

Thanks.
--

From: Vladimir Davydov <vdavydov@parallels.com>
Subject: [PATCH] memcg: memcg_kmem_create_cache: make memcg_name_buf
 statically allocated

It isn't worth complicating the code by allocating it on the first
access, because it only takes 256 bytes.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9ff3742f4154..01fda17a2566 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3141,7 +3141,8 @@ void memcg_free_cache_params(struct kmem_cache *s)
 static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 				    struct kmem_cache *root_cache)
 {
-	static char *memcg_name_buf;	/* protected by memcg_slab_mutex */
+	static char memcg_name_buf[NAME_MAX + 1]; /* protected by
+						     memcg_slab_mutex */
 	struct kmem_cache *cachep;
 	int id;
 
@@ -3157,12 +3158,6 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 	if (cache_from_memcg_idx(root_cache, id))
 		return;
 
-	if (!memcg_name_buf) {
-		memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
-		if (!memcg_name_buf)
-			return;
-	}
-
 	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
 	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
 	/*

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[PATCH -mm v2] memcg: cleanup kmem cache creation/destruction functions naming

[Vladimir Davydov]

Current names are rather inconsistent. Let's try to improve them.

Brief change log:

** old name **                          ** new name **

kmem_cache_create_memcg                 memcg_create_kmem_cache
memcg_kmem_create_cache                 memcg_regsiter_cache
memcg_kmem_destroy_cache                memcg_unregister_cache

kmem_cache_destroy_memcg_children       memcg_cleanup_cache_params
mem_cgroup_destroy_all_caches           memcg_unregister_all_caches

create_work                             memcg_register_cache_work
memcg_create_cache_work_func            memcg_register_cache_func
memcg_create_cache_enqueue              memcg_schedule_register_cache

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
 include/linux/memcontrol.h |    2 +-
 include/linux/slab.h       |    2 +-
 mm/memcontrol.c            |   60 +++++++++++++++++++++-----------------------
 mm/slab_common.c           |   12 ++++-----
 4 files changed, 36 insertions(+), 40 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index aa429de275cc..c3a53cbb88eb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -514,7 +514,7 @@ __memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);
 int __memcg_charge_slab(struct kmem_cache *cachep, gfp_t gfp, int order);
 void __memcg_uncharge_slab(struct kmem_cache *cachep, int order);
 
-int __kmem_cache_destroy_memcg_children(struct kmem_cache *s);
+int __memcg_cleanup_cache_params(struct kmem_cache *s);
 
 /**
  * memcg_kmem_newpage_charge: verify if a new kmem allocation is allowed.
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 86e5b26fbdab..1d9abb7d22a0 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -116,7 +116,7 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			unsigned long,
 			void (*)(void *));
 #ifdef CONFIG_MEMCG_KMEM
-struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
+struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *,
 					   struct kmem_cache *,
 					   const char *);
 #endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f5ea266f4d9a..b12a05049f2a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3127,8 +3127,8 @@ void memcg_free_cache_params(struct kmem_cache *s)
 	kfree(s->memcg_params);
 }
 
-static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
-				    struct kmem_cache *root_cache)
+static void memcg_register_cache(struct mem_cgroup *memcg,
+				 struct kmem_cache *root_cache)
 {
 	static char memcg_name_buf[NAME_MAX + 1]; /* protected by
 						     memcg_slab_mutex */
@@ -3148,7 +3148,7 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 		return;
 
 	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
-	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
+	cachep = memcg_create_kmem_cache(memcg, root_cache, memcg_name_buf);
 	/*
 	 * If we could not create a memcg cache, do not complain, because
 	 * that's not critical at all as we can always proceed with the root
@@ -3170,7 +3170,7 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
 	root_cache->memcg_params->memcg_caches[id] = cachep;
 }
 
-static void memcg_kmem_destroy_cache(struct kmem_cache *cachep)
+static void memcg_unregister_cache(struct kmem_cache *cachep)
 {
 	struct kmem_cache *root_cache;
 	struct mem_cgroup *memcg;
@@ -3223,7 +3223,7 @@ static inline void memcg_resume_kmem_account(void)
 	current->memcg_kmem_skip_account--;
 }
 
-int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+int __memcg_cleanup_cache_params(struct kmem_cache *s)
 {
 	struct kmem_cache *c;
 	int i, failed = 0;
@@ -3234,7 +3234,7 @@ int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 		if (!c)
 			continue;
 
-		memcg_kmem_destroy_cache(c);
+		memcg_unregister_cache(c);
 
 		if (cache_from_memcg_idx(s, i))
 			failed++;
@@ -3243,7 +3243,7 @@ int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 	return failed;
 }
 
-static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
+static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
 {
 	struct kmem_cache *cachep;
 	struct memcg_cache_params *params, *tmp;
@@ -3256,25 +3256,26 @@ static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 		cachep = memcg_params_to_cache(params);
 		kmem_cache_shrink(cachep);
 		if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
-			memcg_kmem_destroy_cache(cachep);
+			memcg_unregister_cache(cachep);
 	}
 	mutex_unlock(&memcg_slab_mutex);
 }
 
-struct create_work {
+struct memcg_register_cache_work {
 	struct mem_cgroup *memcg;
 	struct kmem_cache *cachep;
 	struct work_struct work;
 };
 
-static void memcg_create_cache_work_func(struct work_struct *w)
+static void memcg_register_cache_func(struct work_struct *w)
 {
-	struct create_work *cw = container_of(w, struct create_work, work);
+	struct memcg_register_cache_work *cw =
+		container_of(w, struct memcg_register_cache_work, work);
 	struct mem_cgroup *memcg = cw->memcg;
 	struct kmem_cache *cachep = cw->cachep;
 
 	mutex_lock(&memcg_slab_mutex);
-	memcg_kmem_create_cache(memcg, cachep);
+	memcg_register_cache(memcg, cachep);
 	mutex_unlock(&memcg_slab_mutex);
 
 	css_put(&memcg->css);
@@ -3284,12 +3285,12 @@ static void memcg_create_cache_work_func(struct work_struct *w)
 /*
  * Enqueue the creation of a per-memcg kmem_cache.
  */
-static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
-					 struct kmem_cache *cachep)
+static void __memcg_schedule_register_cache(struct mem_cgroup *memcg,
+					    struct kmem_cache *cachep)
 {
-	struct create_work *cw;
+	struct memcg_register_cache_work *cw;
 
-	cw = kmalloc(sizeof(struct create_work), GFP_NOWAIT);
+	cw = kmalloc(sizeof(*cw), GFP_NOWAIT);
 	if (cw == NULL) {
 		css_put(&memcg->css);
 		return;
@@ -3298,17 +3299,17 @@ static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
 	cw->memcg = memcg;
 	cw->cachep = cachep;
 
-	INIT_WORK(&cw->work, memcg_create_cache_work_func);
+	INIT_WORK(&cw->work, memcg_register_cache_func);
 	schedule_work(&cw->work);
 }
 
-static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
-				       struct kmem_cache *cachep)
+static void memcg_schedule_register_cache(struct mem_cgroup *memcg,
+					  struct kmem_cache *cachep)
 {
 	/*
 	 * We need to stop accounting when we kmalloc, because if the
 	 * corresponding kmalloc cache is not yet created, the first allocation
-	 * in __memcg_create_cache_enqueue will recurse.
+	 * in __memcg_schedule_register_cache will recurse.
 	 *
 	 * However, it is better to enclose the whole function. Depending on
 	 * the debugging options enabled, INIT_WORK(), for instance, can
@@ -3317,7 +3318,7 @@ static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
 	 * the safest choice is to do it like this, wrapping the whole function.
 	 */
 	memcg_stop_kmem_account();
-	__memcg_create_cache_enqueue(memcg, cachep);
+	__memcg_schedule_register_cache(memcg, cachep);
 	memcg_resume_kmem_account();
 }
 
@@ -3388,16 +3389,11 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
 	 *
 	 * However, there are some clashes that can arrive from locking.
 	 * For instance, because we acquire the slab_mutex while doing
-	 * kmem_cache_dup, this means no further allocation could happen
-	 * with the slab_mutex held.
-	 *
-	 * Also, because cache creation issue get_online_cpus(), this
-	 * creates a lock chain: memcg_slab_mutex -> cpu_hotplug_mutex,
-	 * that ends up reversed during cpu hotplug. (cpuset allocates
-	 * a bunch of GFP_KERNEL memory during cpuup). Due to all that,
-	 * better to defer everything.
+	 * memcg_create_kmem_cache, this means no further allocation
+	 * could happen with the slab_mutex held. So it's better to
+	 * defer everything.
 	 */
-	memcg_create_cache_enqueue(memcg, cachep);
+	memcg_schedule_register_cache(memcg, cachep);
 	return cachep;
 out:
 	rcu_read_unlock();
@@ -3521,7 +3517,7 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order)
 	memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
 }
 #else
-static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
+static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg)
 {
 }
 #endif /* CONFIG_MEMCG_KMEM */
@@ -6399,7 +6395,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
 	css_for_each_descendant_post(iter, css)
 		mem_cgroup_reparent_charges(mem_cgroup_from_css(iter));
 
-	mem_cgroup_destroy_all_caches(memcg);
+	memcg_unregister_all_caches(memcg);
 	vmpressure_cleanup(&memcg->vmpressure);
 }
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 32175617cb75..48fafb61f35e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -261,7 +261,7 @@ EXPORT_SYMBOL(kmem_cache_create);
 
 #ifdef CONFIG_MEMCG_KMEM
 /*
- * kmem_cache_create_memcg - Create a cache for a memory cgroup.
+ * memcg_create_kmem_cache - Create a cache for a memory cgroup.
  * @memcg: The memory cgroup the new cache is for.
  * @root_cache: The parent of the new cache.
  * @memcg_name: The name of the memory cgroup (used for naming the new cache).
@@ -270,7 +270,7 @@ EXPORT_SYMBOL(kmem_cache_create);
  * requests going from @memcg to @root_cache. The new cache inherits properties
  * from its parent.
  */
-struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
+struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 					   struct kmem_cache *root_cache,
 					   const char *memcg_name)
 {
@@ -305,7 +305,7 @@ out_unlock:
 	return s;
 }
 
-static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+static int memcg_cleanup_cache_params(struct kmem_cache *s)
 {
 	int rc;
 
@@ -314,13 +314,13 @@ static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 		return 0;
 
 	mutex_unlock(&slab_mutex);
-	rc = __kmem_cache_destroy_memcg_children(s);
+	rc = __memcg_cleanup_cache_params(s);
 	mutex_lock(&slab_mutex);
 
 	return rc;
 }
 #else
-static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+static int memcg_cleanup_cache_params(struct kmem_cache *s)
 {
 	return 0;
 }
@@ -343,7 +343,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
 	if (s->refcount)
 		goto out_unlock;
 
-	if (kmem_cache_destroy_memcg_children(s) != 0)
+	if (memcg_cleanup_cache_params(s) != 0)
 		goto out_unlock;
 
 	list_del(&s->list);
-- 
1.7.10.4

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Re: [PATCH -mm v2] memcg: cleanup kmem cache creation/destruction functions naming

[Michal Hocko]

On Tue 13-05-14 19:05:51, Vladimir Davydov wrote:
> Current names are rather inconsistent. Let's try to improve them.
> 
> Brief change log:
> 
> ** old name **                          ** new name **
> 
> kmem_cache_create_memcg                 memcg_create_kmem_cache
> memcg_kmem_create_cache                 memcg_regsiter_cache
> memcg_kmem_destroy_cache                memcg_unregister_cache
> 
> kmem_cache_destroy_memcg_children       memcg_cleanup_cache_params
> mem_cgroup_destroy_all_caches           memcg_unregister_all_caches
> 
> create_work                             memcg_register_cache_work
> memcg_create_cache_work_func            memcg_register_cache_func
> memcg_create_cache_enqueue              memcg_schedule_register_cache
> 
> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

Acked-by: Michal Hocko <mhocko@suse.cz>
Thanks!

> ---
>  include/linux/memcontrol.h |    2 +-
>  include/linux/slab.h       |    2 +-
>  mm/memcontrol.c            |   60 +++++++++++++++++++++-----------------------
>  mm/slab_common.c           |   12 ++++-----
>  4 files changed, 36 insertions(+), 40 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index aa429de275cc..c3a53cbb88eb 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -514,7 +514,7 @@ __memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);
>  int __memcg_charge_slab(struct kmem_cache *cachep, gfp_t gfp, int order);
>  void __memcg_uncharge_slab(struct kmem_cache *cachep, int order);
>  
> -int __kmem_cache_destroy_memcg_children(struct kmem_cache *s);
> +int __memcg_cleanup_cache_params(struct kmem_cache *s);
>  
>  /**
>   * memcg_kmem_newpage_charge: verify if a new kmem allocation is allowed.
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 86e5b26fbdab..1d9abb7d22a0 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -116,7 +116,7 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
>  			unsigned long,
>  			void (*)(void *));
>  #ifdef CONFIG_MEMCG_KMEM
> -struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
> +struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *,
>  					   struct kmem_cache *,
>  					   const char *);
>  #endif
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f5ea266f4d9a..b12a05049f2a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3127,8 +3127,8 @@ void memcg_free_cache_params(struct kmem_cache *s)
>  	kfree(s->memcg_params);
>  }
>  
> -static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
> -				    struct kmem_cache *root_cache)
> +static void memcg_register_cache(struct mem_cgroup *memcg,
> +				 struct kmem_cache *root_cache)
>  {
>  	static char memcg_name_buf[NAME_MAX + 1]; /* protected by
>  						     memcg_slab_mutex */
> @@ -3148,7 +3148,7 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  		return;
>  
>  	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
> -	cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
> +	cachep = memcg_create_kmem_cache(memcg, root_cache, memcg_name_buf);
>  	/*
>  	 * If we could not create a memcg cache, do not complain, because
>  	 * that's not critical at all as we can always proceed with the root
> @@ -3170,7 +3170,7 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
>  	root_cache->memcg_params->memcg_caches[id] = cachep;
>  }
>  
> -static void memcg_kmem_destroy_cache(struct kmem_cache *cachep)
> +static void memcg_unregister_cache(struct kmem_cache *cachep)
>  {
>  	struct kmem_cache *root_cache;
>  	struct mem_cgroup *memcg;
> @@ -3223,7 +3223,7 @@ static inline void memcg_resume_kmem_account(void)
>  	current->memcg_kmem_skip_account--;
>  }
>  
> -int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
> +int __memcg_cleanup_cache_params(struct kmem_cache *s)
>  {
>  	struct kmem_cache *c;
>  	int i, failed = 0;
> @@ -3234,7 +3234,7 @@ int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
>  		if (!c)
>  			continue;
>  
> -		memcg_kmem_destroy_cache(c);
> +		memcg_unregister_cache(c);
>  
>  		if (cache_from_memcg_idx(s, i))
>  			failed++;
> @@ -3243,7 +3243,7 @@ int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
>  	return failed;
>  }
>  
> -static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
> +static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
>  {
>  	struct kmem_cache *cachep;
>  	struct memcg_cache_params *params, *tmp;
> @@ -3256,25 +3256,26 @@ static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
>  		cachep = memcg_params_to_cache(params);
>  		kmem_cache_shrink(cachep);
>  		if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
> -			memcg_kmem_destroy_cache(cachep);
> +			memcg_unregister_cache(cachep);
>  	}
>  	mutex_unlock(&memcg_slab_mutex);
>  }
>  
> -struct create_work {
> +struct memcg_register_cache_work {
>  	struct mem_cgroup *memcg;
>  	struct kmem_cache *cachep;
>  	struct work_struct work;
>  };
>  
> -static void memcg_create_cache_work_func(struct work_struct *w)
> +static void memcg_register_cache_func(struct work_struct *w)
>  {
> -	struct create_work *cw = container_of(w, struct create_work, work);
> +	struct memcg_register_cache_work *cw =
> +		container_of(w, struct memcg_register_cache_work, work);
>  	struct mem_cgroup *memcg = cw->memcg;
>  	struct kmem_cache *cachep = cw->cachep;
>  
>  	mutex_lock(&memcg_slab_mutex);
> -	memcg_kmem_create_cache(memcg, cachep);
> +	memcg_register_cache(memcg, cachep);
>  	mutex_unlock(&memcg_slab_mutex);
>  
>  	css_put(&memcg->css);
> @@ -3284,12 +3285,12 @@ static void memcg_create_cache_work_func(struct work_struct *w)
>  /*
>   * Enqueue the creation of a per-memcg kmem_cache.
>   */
> -static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
> -					 struct kmem_cache *cachep)
> +static void __memcg_schedule_register_cache(struct mem_cgroup *memcg,
> +					    struct kmem_cache *cachep)
>  {
> -	struct create_work *cw;
> +	struct memcg_register_cache_work *cw;
>  
> -	cw = kmalloc(sizeof(struct create_work), GFP_NOWAIT);
> +	cw = kmalloc(sizeof(*cw), GFP_NOWAIT);
>  	if (cw == NULL) {
>  		css_put(&memcg->css);
>  		return;
> @@ -3298,17 +3299,17 @@ static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
>  	cw->memcg = memcg;
>  	cw->cachep = cachep;
>  
> -	INIT_WORK(&cw->work, memcg_create_cache_work_func);
> +	INIT_WORK(&cw->work, memcg_register_cache_func);
>  	schedule_work(&cw->work);
>  }
>  
> -static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
> -				       struct kmem_cache *cachep)
> +static void memcg_schedule_register_cache(struct mem_cgroup *memcg,
> +					  struct kmem_cache *cachep)
>  {
>  	/*
>  	 * We need to stop accounting when we kmalloc, because if the
>  	 * corresponding kmalloc cache is not yet created, the first allocation
> -	 * in __memcg_create_cache_enqueue will recurse.
> +	 * in __memcg_schedule_register_cache will recurse.
>  	 *
>  	 * However, it is better to enclose the whole function. Depending on
>  	 * the debugging options enabled, INIT_WORK(), for instance, can
> @@ -3317,7 +3318,7 @@ static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
>  	 * the safest choice is to do it like this, wrapping the whole function.
>  	 */
>  	memcg_stop_kmem_account();
> -	__memcg_create_cache_enqueue(memcg, cachep);
> +	__memcg_schedule_register_cache(memcg, cachep);
>  	memcg_resume_kmem_account();
>  }
>  
> @@ -3388,16 +3389,11 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
>  	 *
>  	 * However, there are some clashes that can arrive from locking.
>  	 * For instance, because we acquire the slab_mutex while doing
> -	 * kmem_cache_dup, this means no further allocation could happen
> -	 * with the slab_mutex held.
> -	 *
> -	 * Also, because cache creation issue get_online_cpus(), this
> -	 * creates a lock chain: memcg_slab_mutex -> cpu_hotplug_mutex,
> -	 * that ends up reversed during cpu hotplug. (cpuset allocates
> -	 * a bunch of GFP_KERNEL memory during cpuup). Due to all that,
> -	 * better to defer everything.
> +	 * memcg_create_kmem_cache, this means no further allocation
> +	 * could happen with the slab_mutex held. So it's better to
> +	 * defer everything.
>  	 */
> -	memcg_create_cache_enqueue(memcg, cachep);
> +	memcg_schedule_register_cache(memcg, cachep);
>  	return cachep;
>  out:
>  	rcu_read_unlock();
> @@ -3521,7 +3517,7 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order)
>  	memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
>  }
>  #else
> -static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
> +static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg)
>  {
>  }
>  #endif /* CONFIG_MEMCG_KMEM */
> @@ -6399,7 +6395,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
>  	css_for_each_descendant_post(iter, css)
>  		mem_cgroup_reparent_charges(mem_cgroup_from_css(iter));
>  
> -	mem_cgroup_destroy_all_caches(memcg);
> +	memcg_unregister_all_caches(memcg);
>  	vmpressure_cleanup(&memcg->vmpressure);
>  }
>  
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 32175617cb75..48fafb61f35e 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -261,7 +261,7 @@ EXPORT_SYMBOL(kmem_cache_create);
>  
>  #ifdef CONFIG_MEMCG_KMEM
>  /*
> - * kmem_cache_create_memcg - Create a cache for a memory cgroup.
> + * memcg_create_kmem_cache - Create a cache for a memory cgroup.
>   * @memcg: The memory cgroup the new cache is for.
>   * @root_cache: The parent of the new cache.
>   * @memcg_name: The name of the memory cgroup (used for naming the new cache).
> @@ -270,7 +270,7 @@ EXPORT_SYMBOL(kmem_cache_create);
>   * requests going from @memcg to @root_cache. The new cache inherits properties
>   * from its parent.
>   */
> -struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
> +struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>  					   struct kmem_cache *root_cache,
>  					   const char *memcg_name)
>  {
> @@ -305,7 +305,7 @@ out_unlock:
>  	return s;
>  }
>  
> -static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
> +static int memcg_cleanup_cache_params(struct kmem_cache *s)
>  {
>  	int rc;
>  
> @@ -314,13 +314,13 @@ static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
>  		return 0;
>  
>  	mutex_unlock(&slab_mutex);
> -	rc = __kmem_cache_destroy_memcg_children(s);
> +	rc = __memcg_cleanup_cache_params(s);
>  	mutex_lock(&slab_mutex);
>  
>  	return rc;
>  }
>  #else
> -static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
> +static int memcg_cleanup_cache_params(struct kmem_cache *s)
>  {
>  	return 0;
>  }
> @@ -343,7 +343,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
>  	if (s->refcount)
>  		goto out_unlock;
>  
> -	if (kmem_cache_destroy_memcg_children(s) != 0)
> +	if (memcg_cleanup_cache_params(s) != 0)
>  		goto out_unlock;
>  
>  	list_del(&s->list);
> -- 
> 1.7.10.4
> 

-- 
Michal Hocko
SUSE Labs

--
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