From f7ce3190c4a35bf887adb7a1aa1ba899b679872d Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Thu, 12 Feb 2015 14:59:20 -0800 Subject: slab: embed memcg_cache_params to kmem_cache Currently, kmem_cache stores a pointer to struct memcg_cache_params instead of embedding it. The rationale is to save memory when kmem accounting is disabled. However, the memcg_cache_params has shrivelled drastically since it was first introduced: * Initially: struct memcg_cache_params { bool is_root_cache; union { struct kmem_cache *memcg_caches[0]; struct { struct mem_cgroup *memcg; struct list_head list; struct kmem_cache *root_cache; bool dead; atomic_t nr_pages; struct work_struct destroy; }; }; }; * Now: struct memcg_cache_params { bool is_root_cache; union { struct { struct rcu_head rcu_head; struct kmem_cache *memcg_caches[0]; }; struct { struct mem_cgroup *memcg; struct kmem_cache *root_cache; }; }; }; So the memory saving does not seem to be a clear win anymore. OTOH, keeping a pointer to memcg_cache_params struct instead of embedding it results in touching one more cache line on kmem alloc/free hot paths. Besides, it makes linking kmem caches in a list chained by a field of struct memcg_cache_params really painful due to a level of indirection, while I want to make them linked in the following patch. That said, let us embed it. Signed-off-by: Vladimir Davydov Cc: Johannes Weiner Cc: Michal Hocko Cc: Tejun Heo Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Dave Chinner Cc: Dan Carpenter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab.h | 48 +++++++++++++++++++++++------------------------- 1 file changed, 23 insertions(+), 25 deletions(-) (limited to 'mm/slab.h') diff --git a/mm/slab.h b/mm/slab.h index 90430d6f665e..53a623f85931 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -86,8 +86,6 @@ extern struct kmem_cache *create_kmalloc_cache(const char *name, size_t size, extern void create_boot_cache(struct kmem_cache *, const char *name, size_t size, unsigned long flags); -struct mem_cgroup; - int slab_unmergeable(struct kmem_cache *s); struct kmem_cache *find_mergeable(size_t size, size_t align, unsigned long flags, const char *name, void (*ctor)(void *)); @@ -167,14 +165,13 @@ ssize_t slabinfo_write(struct file *file, const char __user *buffer, #ifdef CONFIG_MEMCG_KMEM static inline bool is_root_cache(struct kmem_cache *s) { - return !s->memcg_params || s->memcg_params->is_root_cache; + return s->memcg_params.is_root_cache; } static inline bool slab_equal_or_root(struct kmem_cache *s, - struct kmem_cache *p) + struct kmem_cache *p) { - return (p == s) || - (s->memcg_params && (p == s->memcg_params->root_cache)); + return p == s || p == s->memcg_params.root_cache; } /* @@ -185,37 +182,30 @@ static inline bool slab_equal_or_root(struct kmem_cache *s, static inline const char *cache_name(struct kmem_cache *s) { if (!is_root_cache(s)) - return s->memcg_params->root_cache->name; + s = s->memcg_params.root_cache; return s->name; } /* * Note, we protect with RCU only the memcg_caches array, not per-memcg caches. - * That said the caller must assure the memcg's cache won't go away. Since once - * created a memcg's cache is destroyed only along with the root cache, it is - * true if we are going to allocate from the cache or hold a reference to the - * root cache by other means. Otherwise, we should hold either the slab_mutex - * or the memcg's slab_caches_mutex while calling this function and accessing - * the returned value. + * That said the caller must assure the memcg's cache won't go away by either + * taking a css reference to the owner cgroup, or holding the slab_mutex. */ static inline struct kmem_cache * cache_from_memcg_idx(struct kmem_cache *s, int idx) { struct kmem_cache *cachep; - struct memcg_cache_params *params; - - if (!s->memcg_params) - return NULL; + struct memcg_cache_array *arr; rcu_read_lock(); - params = rcu_dereference(s->memcg_params); + arr = rcu_dereference(s->memcg_params.memcg_caches); /* * Make sure we will access the up-to-date value. The code updating * memcg_caches issues a write barrier to match this (see - * memcg_register_cache()). + * memcg_create_kmem_cache()). */ - cachep = lockless_dereference(params->memcg_caches[idx]); + cachep = lockless_dereference(arr->entries[idx]); rcu_read_unlock(); return cachep; @@ -225,7 +215,7 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s) { if (is_root_cache(s)) return s; - return s->memcg_params->root_cache; + return s->memcg_params.root_cache; } static __always_inline int memcg_charge_slab(struct kmem_cache *s, @@ -235,7 +225,7 @@ static __always_inline int memcg_charge_slab(struct kmem_cache *s, return 0; if (is_root_cache(s)) return 0; - return memcg_charge_kmem(s->memcg_params->memcg, gfp, 1 << order); + return memcg_charge_kmem(s->memcg_params.memcg, gfp, 1 << order); } static __always_inline void memcg_uncharge_slab(struct kmem_cache *s, int order) @@ -244,9 +234,13 @@ static __always_inline void memcg_uncharge_slab(struct kmem_cache *s, int order) return; if (is_root_cache(s)) return; - memcg_uncharge_kmem(s->memcg_params->memcg, 1 << order); + memcg_uncharge_kmem(s->memcg_params.memcg, 1 << order); } -#else + +extern void slab_init_memcg_params(struct kmem_cache *); + +#else /* !CONFIG_MEMCG_KMEM */ + static inline bool is_root_cache(struct kmem_cache *s) { return true; @@ -282,7 +276,11 @@ static inline int memcg_charge_slab(struct kmem_cache *s, gfp_t gfp, int order) static inline void memcg_uncharge_slab(struct kmem_cache *s, int order) { } -#endif + +static inline void slab_init_memcg_params(struct kmem_cache *s) +{ +} +#endif /* CONFIG_MEMCG_KMEM */ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) { -- cgit v1.2.3-55-g7522