slub: rework sysfs layout for memcg caches (9a41707b) · Commits · 戴 / test

Currently, we try to arrange sysfs entries for memcg caches in the same manner as for global caches. Apart from turning /sys/kernel/slab into a mess when there are a lot of kmem-active memcgs created, it actually does not work properly - we won't create more than one link to a memcg cache in case its parent is merged with another cache. For instance, if A is a root cache merged with another root cache B, we will have the following sysfs setup: X A -> X B -> X where X is some unique id (see create_unique_id()). Now if memcgs M and N start to allocate from cache A (or B, which is the same), we will get: X X:M X:N A -> X B -> X A:M -> X:M A:N -> X:N Since B is an alias for A, we won't get entries B:M and B:N, which is confusing. It is more logical to have entries for memcg caches under the corresponding root cache's sysfs directory. This would allow us to keep sysfs layout clean, and avoid such inconsistencies like one described above. This patch does the trick. It creates a "cgroup" kset in each root cache kobject to keep its children caches there. Signed-off-by:

Vladimir Davydov <vdavydov@parallels.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Rientjes <rientjes@google.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Glauber Costa <glommer@gmail.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/slub_def.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -87,6 +87,9 @@ struct kmem_cache {
		#ifdef CONFIG_MEMCG_KMEM
		struct memcg_cache_params *memcg_params;
		int max_attr_size; /* for propagation, maximum size of a stored attr */
		#ifdef CONFIG_SYSFS
		struct kset *memcg_kset;
		#endif
		#endif

		#ifdef CONFIG_NUMA

mm/slub.c

+25 −1

Original line number	Diff line number	Diff line
		@@ -5138,6 +5138,15 @@ static const struct kset_uevent_ops slab_uevent_ops = {

		static struct kset *slab_kset;

		static inline struct kset cache_kset(struct kmem_cache s)
		{
		#ifdef CONFIG_MEMCG_KMEM
		if (!is_root_cache(s))
		return s->memcg_params->root_cache->memcg_kset;
		#endif
		return slab_kset;
		}

		#define ID_STR_LENGTH 64

		/* Create a unique string id for a slab cache:
		@@ -5203,7 +5212,7 @@ static int sysfs_slab_add(struct kmem_cache *s)
		name = create_unique_id(s);
		}

		s->kobj.kset = slab_kset;
		s->kobj.kset = cache_kset(s);
		err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s", name);
		if (err) {
		kobject_put(&s->kobj);
		@@ -5216,6 +5225,18 @@ static int sysfs_slab_add(struct kmem_cache *s)
		kobject_put(&s->kobj);
		return err;
		}

		#ifdef CONFIG_MEMCG_KMEM
		if (is_root_cache(s)) {
		s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
		if (!s->memcg_kset) {
		kobject_del(&s->kobj);
		kobject_put(&s->kobj);
		return -ENOMEM;
		}
		}
		#endif

		kobject_uevent(&s->kobj, KOBJ_ADD);
		if (!unmergeable) {
		/* Setup first alias */
		@@ -5234,6 +5255,9 @@ static void sysfs_slab_remove(struct kmem_cache *s)
		*/
		return;

		#ifdef CONFIG_MEMCG_KMEM
		kset_unregister(s->memcg_kset);
		#endif
		kobject_uevent(&s->kobj, KOBJ_REMOVE);
		kobject_del(&s->kobj);
		kobject_put(&s->kobj);

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