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Commit 1aa13254 authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
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memcg, slab: clean up memcg cache initialization/destruction 



Currently, we have rather a messy function set relating to per-memcg
kmem cache initialization/destruction.

Per-memcg caches are created in memcg_create_kmem_cache().  This
function calls kmem_cache_create_memcg() to allocate and initialize a
kmem cache and then "registers" the new cache in the
memcg_params::memcg_caches array of the parent cache.

During its work-flow, kmem_cache_create_memcg() executes the following
memcg-related functions:

 - memcg_alloc_cache_params(), to initialize memcg_params of the newly
   created cache;
 - memcg_cache_list_add(), to add the new cache to the memcg_slab_caches
   list.

On the other hand, kmem_cache_destroy() called on a cache destruction
only calls memcg_release_cache(), which does all the work: it cleans the
reference to the cache in its parent's memcg_params::memcg_caches,
removes the cache from the memcg_slab_caches list, and frees
memcg_params.

Such an inconsistency between destruction and initialization paths make
the code difficult to read, so let's clean this up a bit.

This patch moves all the code relating to registration of per-memcg
caches (adding to memcg list, setting the pointer to a cache from its
parent) to the newly created memcg_register_cache() and
memcg_unregister_cache() functions making the initialization and
destruction paths look symmetrical.

Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 363a044f

include/linux/memcontrol.h

+4 −5
Original line number Diff line number Diff line
@@ -500,8 +500,8 @@ int memcg_cache_id(struct mem_cgroup *memcg); 
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);

void memcg_release_cache(struct kmem_cache *cachep);

void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep);

void memcg_register_cache(struct kmem_cache *s);

void memcg_unregister_cache(struct kmem_cache *s);



int memcg_update_cache_size(struct kmem_cache *s, int num_groups);

void memcg_update_array_size(int num_groups);
@@ -651,12 +651,11 @@ static inline void memcg_free_cache_params(struct kmem_cache *s) 
{

}



static inline void memcg_release_cache(struct kmem_cache *cachep)

static inline void memcg_register_cache(struct kmem_cache *s)

{

}



static inline void memcg_cache_list_add(struct mem_cgroup *memcg,

					struct kmem_cache *s)

static inline void memcg_unregister_cache(struct kmem_cache *s)

{

}

mm/memcontrol.c

+30 −34
Original line number Diff line number Diff line
@@ -3095,16 +3095,6 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size) 
		css_put(&memcg->css);

}



void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)

{

	if (!memcg)

		return;



	mutex_lock(&memcg->slab_caches_mutex);

	list_add(&cachep->memcg_params->list, &memcg->memcg_slab_caches);

	mutex_unlock(&memcg->slab_caches_mutex);

}



/*

 * helper for acessing a memcg's index. It will be used as an index in the

 * child cache array in kmem_cache, and also to derive its name. This function
@@ -3265,21 +3255,41 @@ void memcg_free_cache_params(struct kmem_cache *s) 
	kfree(s->memcg_params);

}



void memcg_release_cache(struct kmem_cache *s)

void memcg_register_cache(struct kmem_cache *s)

{

	struct kmem_cache *root;

	struct mem_cgroup *memcg;

	int id;



	if (is_root_cache(s))

		return;



	root = s->memcg_params->root_cache;

	memcg = s->memcg_params->memcg;

	id = memcg_cache_id(memcg);



	css_get(&memcg->css);



	mutex_lock(&memcg->slab_caches_mutex);

	list_add(&s->memcg_params->list, &memcg->memcg_slab_caches);

	mutex_unlock(&memcg->slab_caches_mutex);



	root->memcg_params->memcg_caches[id] = s;

	/*

	 * This happens, for instance, when a root cache goes away before we

	 * add any memcg.

	 * the readers won't lock, make sure everybody sees the updated value,

	 * so they won't put stuff in the queue again for no reason

	 */

	if (!s->memcg_params)

		return;

	wmb();

}



	if (s->memcg_params->is_root_cache)

		goto out;

void memcg_unregister_cache(struct kmem_cache *s)

{

	struct kmem_cache *root;

	struct mem_cgroup *memcg;

	int id;



	if (is_root_cache(s))

		return;



	memcg = s->memcg_params->memcg;

	id  = memcg_cache_id(memcg);
@@ -3292,8 +3302,6 @@ void memcg_release_cache(struct kmem_cache *s) 
	mutex_unlock(&memcg->slab_caches_mutex);



	css_put(&memcg->css);

out:

	memcg_free_cache_params(s);

}



/*
@@ -3451,26 +3459,13 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg, 


	mutex_lock(&memcg_cache_mutex);

	new_cachep = cache_from_memcg_idx(cachep, idx);

	if (new_cachep) {

		css_put(&memcg->css);

	if (new_cachep)

		goto out;

	}



	new_cachep = kmem_cache_dup(memcg, cachep);

	if (new_cachep == NULL) {

	if (new_cachep == NULL)

		new_cachep = cachep;

		css_put(&memcg->css);

		goto out;

	}



	atomic_set(&new_cachep->memcg_params->nr_pages , 0);



	cachep->memcg_params->memcg_caches[idx] = new_cachep;

	/*

	 * the readers won't lock, make sure everybody sees the updated value,

	 * so they won't put stuff in the queue again for no reason

	 */

	wmb();

out:

	mutex_unlock(&memcg_cache_mutex);

	return new_cachep;
@@ -3550,6 +3545,7 @@ static void memcg_create_cache_work_func(struct work_struct *w) 


	cw = container_of(w, struct create_work, work);

	memcg_create_kmem_cache(cw->memcg, cw->cachep);

	css_put(&cw->memcg->css);

	kfree(cw);

}

mm/slab_common.c

+3 −2
Original line number Diff line number Diff line
@@ -215,7 +215,7 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size, 


	s->refcount = 1;

	list_add(&s->list, &slab_caches);

	memcg_cache_list_add(memcg, s);

	memcg_register_cache(s);



out_unlock:

	mutex_unlock(&slab_mutex);
@@ -265,7 +265,8 @@ void kmem_cache_destroy(struct kmem_cache *s) 
			if (s->flags & SLAB_DESTROY_BY_RCU)

				rcu_barrier();



			memcg_release_cache(s);

			memcg_unregister_cache(s);

			memcg_free_cache_params(s);

			kfree(s->name);

			kmem_cache_free(kmem_cache, s);

		} else {