From 9855609bde03e2472b99a95e869d29ee1e78a751 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Thu, 6 Aug 2020 23:21:10 -0700 Subject: mm: memcg/slab: use a single set of kmem_caches for all accounted allocations This is fairly big but mostly red patch, which makes all accounted slab allocations use a single set of kmem_caches instead of creating a separate set for each memory cgroup. Because the number of non-root kmem_caches is now capped by the number of root kmem_caches, there is no need to shrink or destroy them prematurely. They can be perfectly destroyed together with their root counterparts. This allows to dramatically simplify the management of non-root kmem_caches and delete a ton of code. This patch performs the following changes: 1) introduces memcg_params.memcg_cache pointer to represent the kmem_cache which will be used for all non-root allocations 2) reuses the existing memcg kmem_cache creation mechanism to create memcg kmem_cache on the first allocation attempt 3) memcg kmem_caches are named -memcg, e.g. dentry-memcg 4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache or schedule it's creation and return the root cache 5) removes almost all non-root kmem_cache management code (separate refcounter, reparenting, shrinking, etc) 6) makes slab debugfs to display root_mem_cgroup css id and never show :dead and :deact flags in the memcg_slabinfo attribute. Following patches in the series will simplify the kmem_cache creation. Signed-off-by: Roman Gushchin Signed-off-by: Andrew Morton Reviewed-by: Vlastimil Babka Reviewed-by: Shakeel Butt Cc: Christoph Lameter Cc: Johannes Weiner Cc: Michal Hocko Cc: Tejun Heo Link: http://lkml.kernel.org/r/20200623174037.3951353-13-guro@fb.com Signed-off-by: Linus Torvalds --- mm/slab_common.c | 459 ++++++------------------------------------------------- 1 file changed, 47 insertions(+), 412 deletions(-) (limited to 'mm/slab_common.c') diff --git a/mm/slab_common.c b/mm/slab_common.c index f86431d0de73..e752132eb64d 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -133,141 +133,36 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr, #ifdef CONFIG_MEMCG_KMEM LIST_HEAD(slab_root_caches); -static DEFINE_SPINLOCK(memcg_kmem_wq_lock); - -static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref); void slab_init_memcg_params(struct kmem_cache *s) { s->memcg_params.root_cache = NULL; - RCU_INIT_POINTER(s->memcg_params.memcg_caches, NULL); - INIT_LIST_HEAD(&s->memcg_params.children); - s->memcg_params.dying = false; + s->memcg_params.memcg_cache = NULL; } -static int init_memcg_params(struct kmem_cache *s, - struct kmem_cache *root_cache) +static void init_memcg_params(struct kmem_cache *s, + struct kmem_cache *root_cache) { - struct memcg_cache_array *arr; - - if (root_cache) { - int ret = percpu_ref_init(&s->memcg_params.refcnt, - kmemcg_cache_shutdown, - 0, GFP_KERNEL); - if (ret) - return ret; - + if (root_cache) s->memcg_params.root_cache = root_cache; - INIT_LIST_HEAD(&s->memcg_params.children_node); - INIT_LIST_HEAD(&s->memcg_params.kmem_caches_node); - return 0; - } - - slab_init_memcg_params(s); - - if (!memcg_nr_cache_ids) - return 0; - - arr = kvzalloc(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 destroy_memcg_params(struct kmem_cache *s) -{ - if (is_root_cache(s)) { - kvfree(rcu_access_pointer(s->memcg_params.memcg_caches)); - } else { - mem_cgroup_put(s->memcg_params.memcg); - WRITE_ONCE(s->memcg_params.memcg, NULL); - percpu_ref_exit(&s->memcg_params.refcnt); - } -} - -static void free_memcg_params(struct rcu_head *rcu) -{ - struct memcg_cache_array *old; - - old = container_of(rcu, struct memcg_cache_array, rcu); - kvfree(old); -} - -static int update_memcg_params(struct kmem_cache *s, int new_array_size) -{ - struct memcg_cache_array *old, *new; - - new = kvzalloc(sizeof(struct memcg_cache_array) + - new_array_size * sizeof(void *), GFP_KERNEL); - if (!new) - return -ENOMEM; - - 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) - call_rcu(&old->rcu, free_memcg_params); - return 0; + else + slab_init_memcg_params(s); } -int memcg_update_all_caches(int num_memcgs) +void memcg_link_cache(struct kmem_cache *s) { - struct kmem_cache *s; - int ret = 0; - - mutex_lock(&slab_mutex); - list_for_each_entry(s, &slab_root_caches, root_caches_node) { - 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. - */ - if (ret) - break; - } - mutex_unlock(&slab_mutex); - return ret; -} - -void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg) -{ - if (is_root_cache(s)) { + if (is_root_cache(s)) list_add(&s->root_caches_node, &slab_root_caches); - } else { - css_get(&memcg->css); - s->memcg_params.memcg = memcg; - list_add(&s->memcg_params.children_node, - &s->memcg_params.root_cache->memcg_params.children); - list_add(&s->memcg_params.kmem_caches_node, - &s->memcg_params.memcg->kmem_caches); - } } static void memcg_unlink_cache(struct kmem_cache *s) { - if (is_root_cache(s)) { + if (is_root_cache(s)) list_del(&s->root_caches_node); - } else { - list_del(&s->memcg_params.children_node); - list_del(&s->memcg_params.kmem_caches_node); - } } #else -static inline int init_memcg_params(struct kmem_cache *s, - struct kmem_cache *root_cache) -{ - return 0; -} - -static inline void destroy_memcg_params(struct kmem_cache *s) +static inline void init_memcg_params(struct kmem_cache *s, + struct kmem_cache *root_cache) { } @@ -328,14 +223,6 @@ int slab_unmergeable(struct kmem_cache *s) if (s->refcount < 0) return 1; -#ifdef CONFIG_MEMCG_KMEM - /* - * Skip the dying kmem_cache. - */ - if (s->memcg_params.dying) - return 1; -#endif - return 0; } @@ -390,7 +277,7 @@ static struct kmem_cache *create_cache(const char *name, unsigned int object_size, unsigned int align, slab_flags_t flags, unsigned int useroffset, unsigned int usersize, void (*ctor)(void *), - struct mem_cgroup *memcg, struct kmem_cache *root_cache) + struct kmem_cache *root_cache) { struct kmem_cache *s; int err; @@ -410,24 +297,20 @@ static struct kmem_cache *create_cache(const char *name, s->useroffset = useroffset; s->usersize = usersize; - err = init_memcg_params(s, root_cache); - if (err) - goto out_free_cache; - + init_memcg_params(s, root_cache); err = __kmem_cache_create(s, flags); if (err) goto out_free_cache; s->refcount = 1; list_add(&s->list, &slab_caches); - memcg_link_cache(s, memcg); + memcg_link_cache(s); out: if (err) return ERR_PTR(err); return s; out_free_cache: - destroy_memcg_params(s); kmem_cache_free(kmem_cache, s); goto out; } @@ -514,7 +397,7 @@ kmem_cache_create_usercopy(const char *name, s = create_cache(cache_name, size, calculate_alignment(flags, align, size), - flags, useroffset, usersize, ctor, NULL, NULL); + flags, useroffset, usersize, ctor, NULL); if (IS_ERR(s)) { err = PTR_ERR(s); kfree_const(cache_name); @@ -639,51 +522,27 @@ static int shutdown_cache(struct kmem_cache *s) #ifdef CONFIG_MEMCG_KMEM /* - * memcg_create_kmem_cache - Create a cache for a memory cgroup. - * @memcg: The memory cgroup the new cache is for. + * memcg_create_kmem_cache - Create a cache for non-root memory cgroups. * @root_cache: The parent of 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. + * requests going all non-root memory cgroups to @root_cache. The new cache + * inherits properties from its parent. */ -void memcg_create_kmem_cache(struct mem_cgroup *memcg, - struct kmem_cache *root_cache) +void memcg_create_kmem_cache(struct kmem_cache *root_cache) { - static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */ - struct cgroup_subsys_state *css = &memcg->css; - 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); - /* - * The memory cgroup could have been offlined while the cache - * creation work was pending. - */ - if (memcg->kmem_state != KMEM_ONLINE) + if (root_cache->memcg_params.memcg_cache) goto out_unlock; - 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 (arr->entries[idx]) - goto out_unlock; - - cgroup_name(css->cgroup, memcg_name_buf, sizeof(memcg_name_buf)); - cache_name = kasprintf(GFP_KERNEL, "%s(%llu:%s)", root_cache->name, - css->serial_nr, memcg_name_buf); + cache_name = kasprintf(GFP_KERNEL, "%s-memcg", root_cache->name); if (!cache_name) goto out_unlock; @@ -691,7 +550,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg, root_cache->align, root_cache->flags & CACHE_CREATE_MASK, root_cache->useroffset, root_cache->usersize, - root_cache->ctor, memcg, root_cache); + root_cache->ctor, root_cache); /* * 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 @@ -708,7 +567,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg, * initialized. */ smp_wmb(); - arr->entries[idx] = s; + root_cache->memcg_params.memcg_cache = s; out_unlock: mutex_unlock(&slab_mutex); @@ -717,200 +576,18 @@ out_unlock: put_online_cpus(); } -static void kmemcg_workfn(struct work_struct *work) -{ - struct kmem_cache *s = container_of(work, struct kmem_cache, - memcg_params.work); - - get_online_cpus(); - get_online_mems(); - - mutex_lock(&slab_mutex); - s->memcg_params.work_fn(s); - mutex_unlock(&slab_mutex); - - put_online_mems(); - put_online_cpus(); -} - -static void kmemcg_rcufn(struct rcu_head *head) -{ - struct kmem_cache *s = container_of(head, struct kmem_cache, - memcg_params.rcu_head); - - /* - * We need to grab blocking locks. Bounce to ->work. The - * work item shares the space with the RCU head and can't be - * initialized earlier. - */ - INIT_WORK(&s->memcg_params.work, kmemcg_workfn); - queue_work(memcg_kmem_cache_wq, &s->memcg_params.work); -} - -static void kmemcg_cache_shutdown_fn(struct kmem_cache *s) -{ - WARN_ON(shutdown_cache(s)); -} - -static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref) -{ - struct kmem_cache *s = container_of(percpu_ref, struct kmem_cache, - memcg_params.refcnt); - unsigned long flags; - - spin_lock_irqsave(&memcg_kmem_wq_lock, flags); - if (s->memcg_params.root_cache->memcg_params.dying) - goto unlock; - - s->memcg_params.work_fn = kmemcg_cache_shutdown_fn; - INIT_WORK(&s->memcg_params.work, kmemcg_workfn); - queue_work(memcg_kmem_cache_wq, &s->memcg_params.work); - -unlock: - spin_unlock_irqrestore(&memcg_kmem_wq_lock, flags); -} - -static void kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s) -{ - __kmemcg_cache_deactivate_after_rcu(s); - percpu_ref_kill(&s->memcg_params.refcnt); -} - -static void kmemcg_cache_deactivate(struct kmem_cache *s) -{ - if (WARN_ON_ONCE(is_root_cache(s))) - return; - - __kmemcg_cache_deactivate(s); - s->flags |= SLAB_DEACTIVATED; - - /* - * memcg_kmem_wq_lock is used to synchronize memcg_params.dying - * flag and make sure that no new kmem_cache deactivation tasks - * are queued (see flush_memcg_workqueue() ). - */ - spin_lock_irq(&memcg_kmem_wq_lock); - if (s->memcg_params.root_cache->memcg_params.dying) - goto unlock; - - s->memcg_params.work_fn = kmemcg_cache_deactivate_after_rcu; - call_rcu(&s->memcg_params.rcu_head, kmemcg_rcufn); -unlock: - spin_unlock_irq(&memcg_kmem_wq_lock); -} - -void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg, - struct mem_cgroup *parent) -{ - int idx; - struct memcg_cache_array *arr; - struct kmem_cache *s, *c; - unsigned int nr_reparented; - - idx = memcg_cache_id(memcg); - - get_online_cpus(); - get_online_mems(); - - mutex_lock(&slab_mutex); - list_for_each_entry(s, &slab_root_caches, root_caches_node) { - arr = rcu_dereference_protected(s->memcg_params.memcg_caches, - lockdep_is_held(&slab_mutex)); - c = arr->entries[idx]; - if (!c) - continue; - - kmemcg_cache_deactivate(c); - arr->entries[idx] = NULL; - } - nr_reparented = 0; - list_for_each_entry(s, &memcg->kmem_caches, - memcg_params.kmem_caches_node) { - WRITE_ONCE(s->memcg_params.memcg, parent); - css_put(&memcg->css); - nr_reparented++; - } - if (nr_reparented) { - list_splice_init(&memcg->kmem_caches, - &parent->kmem_caches); - css_get_many(&parent->css, nr_reparented); - } - mutex_unlock(&slab_mutex); - - put_online_mems(); - put_online_cpus(); -} - static int shutdown_memcg_caches(struct kmem_cache *s) { - struct memcg_cache_array *arr; - struct kmem_cache *c, *c2; - LIST_HEAD(busy); - int i; - BUG_ON(!is_root_cache(s)); - /* - * First, shutdown active caches, i.e. caches that belong to online - * memory cgroups. - */ - arr = rcu_dereference_protected(s->memcg_params.memcg_caches, - lockdep_is_held(&slab_mutex)); - for_each_memcg_cache_index(i) { - c = arr->entries[i]; - if (!c) - continue; - if (shutdown_cache(c)) - /* - * The cache still has objects. Move it to a temporary - * list so as not to try to destroy it for a second - * time while iterating over inactive caches below. - */ - list_move(&c->memcg_params.children_node, &busy); - else - /* - * The cache is empty and will be destroyed soon. Clear - * the pointer to it in the memcg_caches array so that - * it will never be accessed even if the root cache - * stays alive. - */ - arr->entries[i] = NULL; - } - - /* - * Second, shutdown all caches left from memory cgroups that are now - * offline. - */ - list_for_each_entry_safe(c, c2, &s->memcg_params.children, - memcg_params.children_node) - shutdown_cache(c); - - list_splice(&busy, &s->memcg_params.children); + if (s->memcg_params.memcg_cache) + WARN_ON(shutdown_cache(s->memcg_params.memcg_cache)); - /* - * A cache being destroyed must be empty. In particular, this means - * that all per memcg caches attached to it must be empty too. - */ - if (!list_empty(&s->memcg_params.children)) - return -EBUSY; return 0; } -static void memcg_set_kmem_cache_dying(struct kmem_cache *s) -{ - spin_lock_irq(&memcg_kmem_wq_lock); - s->memcg_params.dying = true; - spin_unlock_irq(&memcg_kmem_wq_lock); -} - static void flush_memcg_workqueue(struct kmem_cache *s) { - /* - * SLAB and SLUB deactivate the kmem_caches through call_rcu. Make - * sure all registered rcu callbacks have been invoked. - */ - rcu_barrier(); - /* * SLAB and SLUB create memcg kmem_caches through workqueue and SLUB * deactivates the memcg kmem_caches through workqueue. Make sure all @@ -918,30 +595,21 @@ static void flush_memcg_workqueue(struct kmem_cache *s) */ if (likely(memcg_kmem_cache_wq)) flush_workqueue(memcg_kmem_cache_wq); - - /* - * If we're racing with children kmem_cache deactivation, it might - * take another rcu grace period to complete their destruction. - * At this moment the corresponding percpu_ref_kill() call should be - * done, but it might take another rcu grace period to complete - * switching to the atomic mode. - * Please, note that we check without grabbing the slab_mutex. It's safe - * because at this moment the children list can't grow. - */ - if (!list_empty(&s->memcg_params.children)) - rcu_barrier(); } #else static inline int shutdown_memcg_caches(struct kmem_cache *s) { return 0; } + +static inline void flush_memcg_workqueue(struct kmem_cache *s) +{ +} #endif /* CONFIG_MEMCG_KMEM */ void slab_kmem_cache_release(struct kmem_cache *s) { __kmem_cache_release(s); - destroy_memcg_params(s); kfree_const(s->name); kmem_cache_free(kmem_cache, s); } @@ -953,6 +621,8 @@ void kmem_cache_destroy(struct kmem_cache *s) if (unlikely(!s)) return; + flush_memcg_workqueue(s); + get_online_cpus(); get_online_mems(); @@ -962,22 +632,6 @@ void kmem_cache_destroy(struct kmem_cache *s) if (s->refcount) goto out_unlock; -#ifdef CONFIG_MEMCG_KMEM - memcg_set_kmem_cache_dying(s); - - mutex_unlock(&slab_mutex); - - put_online_mems(); - put_online_cpus(); - - flush_memcg_workqueue(s); - - get_online_cpus(); - get_online_mems(); - - mutex_lock(&slab_mutex); -#endif - err = shutdown_memcg_caches(s); if (!err) err = shutdown_cache(s); @@ -1019,7 +673,7 @@ int kmem_cache_shrink(struct kmem_cache *cachep) EXPORT_SYMBOL(kmem_cache_shrink); /** - * kmem_cache_shrink_all - shrink a cache and all memcg caches for root cache + * kmem_cache_shrink_all - shrink root and memcg caches * @s: The cache pointer */ void kmem_cache_shrink_all(struct kmem_cache *s) @@ -1036,21 +690,11 @@ void kmem_cache_shrink_all(struct kmem_cache *s) kasan_cache_shrink(s); __kmem_cache_shrink(s); - /* - * We have to take the slab_mutex to protect from the memcg list - * modification. - */ - mutex_lock(&slab_mutex); - for_each_memcg_cache(c, s) { - /* - * Don't need to shrink deactivated memcg caches. - */ - if (s->flags & SLAB_DEACTIVATED) - continue; + c = memcg_cache(s); + if (c) { kasan_cache_shrink(c); __kmem_cache_shrink(c); } - mutex_unlock(&slab_mutex); put_online_mems(); put_online_cpus(); } @@ -1105,7 +749,7 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name, create_boot_cache(s, name, size, flags, useroffset, usersize); list_add(&s->list, &slab_caches); - memcg_link_cache(s, NULL); + memcg_link_cache(s); s->refcount = 1; return s; } @@ -1483,7 +1127,8 @@ memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info) if (!is_root_cache(s)) return; - for_each_memcg_cache(c, s) { + c = memcg_cache(s); + if (c) { memset(&sinfo, 0, sizeof(sinfo)); get_slabinfo(c, &sinfo); @@ -1614,7 +1259,7 @@ module_init(slab_proc_init); #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_MEMCG_KMEM) /* - * Display information about kmem caches that have child memcg caches. + * Display information about kmem caches that have memcg cache. */ static int memcg_slabinfo_show(struct seq_file *m, void *unused) { @@ -1626,9 +1271,9 @@ static int memcg_slabinfo_show(struct seq_file *m, void *unused) seq_puts(m, " \n"); list_for_each_entry(s, &slab_root_caches, root_caches_node) { /* - * Skip kmem caches that don't have any memcg children. + * Skip kmem caches that don't have the memcg cache. */ - if (list_empty(&s->memcg_params.children)) + if (!s->memcg_params.memcg_cache) continue; memset(&sinfo, 0, sizeof(sinfo)); @@ -1637,23 +1282,13 @@ static int memcg_slabinfo_show(struct seq_file *m, void *unused) cache_name(s), sinfo.active_objs, sinfo.num_objs, sinfo.active_slabs, sinfo.num_slabs); - for_each_memcg_cache(c, s) { - struct cgroup_subsys_state *css; - char *status = ""; - - css = &c->memcg_params.memcg->css; - if (!(css->flags & CSS_ONLINE)) - status = ":dead"; - else if (c->flags & SLAB_DEACTIVATED) - status = ":deact"; - - memset(&sinfo, 0, sizeof(sinfo)); - get_slabinfo(c, &sinfo); - seq_printf(m, "%-17s %4d%-6s %6lu %6lu %6lu %6lu\n", - cache_name(c), css->id, status, - sinfo.active_objs, sinfo.num_objs, - sinfo.active_slabs, sinfo.num_slabs); - } + c = s->memcg_params.memcg_cache; + memset(&sinfo, 0, sizeof(sinfo)); + get_slabinfo(c, &sinfo); + seq_printf(m, "%-17s %4d %6lu %6lu %6lu %6lu\n", + cache_name(c), root_mem_cgroup->css.id, + sinfo.active_objs, sinfo.num_objs, + sinfo.active_slabs, sinfo.num_slabs); } mutex_unlock(&slab_mutex); return 0; -- cgit