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_common.c | 129 ++++++++++++++++++++++++++++++------------------------- 1 file changed, 71 insertions(+), 58 deletions(-) (limited to 'mm/slab_common.c') diff --git a/mm/slab_common.c b/mm/slab_common.c index 23f5fcde6043..7cc32cf126ef 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -106,62 +106,66 @@ static inline int kmem_cache_sanity_check(const char *name, size_t size) #endif #ifdef CONFIG_MEMCG_KMEM -static int memcg_alloc_cache_params(struct mem_cgroup *memcg, - struct kmem_cache *s, struct kmem_cache *root_cache) +void slab_init_memcg_params(struct kmem_cache *s) { - size_t size; + s->memcg_params.is_root_cache = true; + RCU_INIT_POINTER(s->memcg_params.memcg_caches, NULL); +} + +static int init_memcg_params(struct kmem_cache *s, + struct mem_cgroup *memcg, struct kmem_cache *root_cache) +{ + struct memcg_cache_array *arr; - if (!memcg_kmem_enabled()) + if (memcg) { + s->memcg_params.is_root_cache = false; + s->memcg_params.memcg = memcg; + s->memcg_params.root_cache = root_cache; return 0; + } - if (!memcg) { - size = offsetof(struct memcg_cache_params, memcg_caches); - size += memcg_nr_cache_ids * sizeof(void *); - } else - size = sizeof(struct memcg_cache_params); + slab_init_memcg_params(s); - s->memcg_params = kzalloc(size, GFP_KERNEL); - if (!s->memcg_params) - return -ENOMEM; + if (!memcg_nr_cache_ids) + return 0; - if (memcg) { - s->memcg_params->memcg = memcg; - s->memcg_params->root_cache = root_cache; - } else - s->memcg_params->is_root_cache = true; + arr = kzalloc(sizeof(struct memcg_cache_array) + + memcg_nr_cache_ids * sizeof(void *), + GFP_KERNEL); + if (!arr) + return -ENOMEM; + RCU_INIT_POINTER(s->memcg_params.memcg_caches, arr); return 0; } -static void memcg_free_cache_params(struct kmem_cache *s) +static void destroy_memcg_params(struct kmem_cache *s) { - kfree(s->memcg_params); + if (is_root_cache(s)) + kfree(rcu_access_pointer(s->memcg_params.memcg_caches)); } -static int memcg_update_cache_params(struct kmem_cache *s, int num_memcgs) +static int update_memcg_params(struct kmem_cache *s, int new_array_size) { - int size; - struct memcg_cache_params *new_params, *cur_params; + struct memcg_cache_array *old, *new; - BUG_ON(!is_root_cache(s)); - - size = offsetof(struct memcg_cache_params, memcg_caches); - size += num_memcgs * sizeof(void *); + if (!is_root_cache(s)) + return 0; - new_params = kzalloc(size, GFP_KERNEL); - if (!new_params) + new = kzalloc(sizeof(struct memcg_cache_array) + + new_array_size * sizeof(void *), GFP_KERNEL); + if (!new) return -ENOMEM; - cur_params = s->memcg_params; - memcpy(new_params->memcg_caches, cur_params->memcg_caches, - memcg_nr_cache_ids * sizeof(void *)); - - new_params->is_root_cache = true; - - rcu_assign_pointer(s->memcg_params, new_params); - if (cur_params) - kfree_rcu(cur_params, rcu_head); + old = rcu_dereference_protected(s->memcg_params.memcg_caches, + lockdep_is_held(&slab_mutex)); + if (old) + memcpy(new->entries, old->entries, + memcg_nr_cache_ids * sizeof(void *)); + rcu_assign_pointer(s->memcg_params.memcg_caches, new); + if (old) + kfree_rcu(old, rcu); return 0; } @@ -172,10 +176,7 @@ int memcg_update_all_caches(int num_memcgs) mutex_lock(&slab_mutex); list_for_each_entry(s, &slab_caches, list) { - if (!is_root_cache(s)) - continue; - - ret = memcg_update_cache_params(s, num_memcgs); + ret = update_memcg_params(s, num_memcgs); /* * Instead of freeing the memory, we'll just leave the caches * up to this point in an updated state. @@ -187,13 +188,13 @@ int memcg_update_all_caches(int num_memcgs) return ret; } #else -static inline int memcg_alloc_cache_params(struct mem_cgroup *memcg, - struct kmem_cache *s, struct kmem_cache *root_cache) +static inline int init_memcg_params(struct kmem_cache *s, + struct mem_cgroup *memcg, struct kmem_cache *root_cache) { return 0; } -static inline void memcg_free_cache_params(struct kmem_cache *s) +static inline void destroy_memcg_params(struct kmem_cache *s) { } #endif /* CONFIG_MEMCG_KMEM */ @@ -311,7 +312,7 @@ do_kmem_cache_create(char *name, size_t object_size, size_t size, size_t align, s->align = align; s->ctor = ctor; - err = memcg_alloc_cache_params(memcg, s, root_cache); + err = init_memcg_params(s, memcg, root_cache); if (err) goto out_free_cache; @@ -327,7 +328,7 @@ out: return s; out_free_cache: - memcg_free_cache_params(s); + destroy_memcg_params(s); kmem_cache_free(kmem_cache, s); goto out; } @@ -439,11 +440,15 @@ static int do_kmem_cache_shutdown(struct kmem_cache *s, #ifdef CONFIG_MEMCG_KMEM if (!is_root_cache(s)) { - struct kmem_cache *root_cache = s->memcg_params->root_cache; - int memcg_id = memcg_cache_id(s->memcg_params->memcg); - - BUG_ON(root_cache->memcg_params->memcg_caches[memcg_id] != s); - root_cache->memcg_params->memcg_caches[memcg_id] = NULL; + int idx; + struct memcg_cache_array *arr; + + idx = memcg_cache_id(s->memcg_params.memcg); + arr = rcu_dereference_protected(s->memcg_params.root_cache-> + memcg_params.memcg_caches, + lockdep_is_held(&slab_mutex)); + BUG_ON(arr->entries[idx] != s); + arr->entries[idx] = NULL; } #endif list_move(&s->list, release); @@ -481,27 +486,32 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg, struct kmem_cache *root_cache) { static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */ - int memcg_id = memcg_cache_id(memcg); + struct memcg_cache_array *arr; struct kmem_cache *s = NULL; char *cache_name; + int idx; get_online_cpus(); get_online_mems(); mutex_lock(&slab_mutex); + idx = memcg_cache_id(memcg); + arr = rcu_dereference_protected(root_cache->memcg_params.memcg_caches, + lockdep_is_held(&slab_mutex)); + /* * Since per-memcg caches are created asynchronously on first * allocation (see memcg_kmem_get_cache()), several threads can try to * create the same cache, but only one of them may succeed. */ - if (cache_from_memcg_idx(root_cache, memcg_id)) + if (arr->entries[idx]) goto out_unlock; cgroup_name(mem_cgroup_css(memcg)->cgroup, memcg_name_buf, sizeof(memcg_name_buf)); cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name, - memcg_cache_id(memcg), memcg_name_buf); + idx, memcg_name_buf); if (!cache_name) goto out_unlock; @@ -525,7 +535,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg, * initialized. */ smp_wmb(); - root_cache->memcg_params->memcg_caches[memcg_id] = s; + arr->entries[idx] = s; out_unlock: mutex_unlock(&slab_mutex); @@ -545,7 +555,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *memcg) mutex_lock(&slab_mutex); list_for_each_entry_safe(s, s2, &slab_caches, list) { - if (is_root_cache(s) || s->memcg_params->memcg != memcg) + if (is_root_cache(s) || s->memcg_params.memcg != memcg) continue; /* * The cgroup is about to be freed and therefore has no charges @@ -564,7 +574,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *memcg) void slab_kmem_cache_release(struct kmem_cache *s) { - memcg_free_cache_params(s); + destroy_memcg_params(s); kfree(s->name); kmem_cache_free(kmem_cache, s); } @@ -640,6 +650,9 @@ void __init create_boot_cache(struct kmem_cache *s, const char *name, size_t siz s->name = name; s->size = s->object_size = size; s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size); + + slab_init_memcg_params(s); + err = __kmem_cache_create(s, flags); if (err) @@ -980,7 +993,7 @@ int memcg_slab_show(struct seq_file *m, void *p) if (p == slab_caches.next) print_slabinfo_header(m); - if (!is_root_cache(s) && s->memcg_params->memcg == memcg) + if (!is_root_cache(s) && s->memcg_params.memcg == memcg) cache_show(s, m); return 0; } -- cgit v1.2.3-55-g7522