mm: memcg/slab: simplify memcg cache creation
Because the number of non-root kmem_caches doesn't depend on the number of memory cgroups anymore and is generally not very big, there is no more need for a dedicated workqueue. Also, as there is no more need to pass any arguments to the memcg_create_kmem_cache() except the root kmem_cache, it's possible to just embed the work structure into the kmem_cache and avoid the dynamic allocation of the work structure. This will also simplify the synchronization: for each root kmem_cache there is only one work. So there will be no more concurrent attempts to create a non-root kmem_cache for a root kmem_cache: the second and all following attempts to queue the work will fail. On the kmem_cache destruction path there is no more need to call the expensive flush_workqueue() and wait for all pending works to be finished. Instead, cancel_work_sync() can be used to cancel/wait for only one work. Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/20200623174037.3951353-14-guro@fb.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1418,7 +1418,6 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size);
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void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size);
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extern struct static_key_false memcg_kmem_enabled_key;
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extern struct workqueue_struct *memcg_kmem_cache_wq;
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extern int memcg_nr_cache_ids;
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void memcg_get_cache_ids(void);
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@ -399,8 +399,6 @@ void memcg_put_cache_ids(void)
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*/
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DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
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EXPORT_SYMBOL(memcg_kmem_enabled_key);
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struct workqueue_struct *memcg_kmem_cache_wq;
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#endif
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static int memcg_shrinker_map_size;
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@ -2902,39 +2900,6 @@ static void memcg_free_cache_id(int id)
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ida_simple_remove(&memcg_cache_ida, id);
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}
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struct memcg_kmem_cache_create_work {
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struct kmem_cache *cachep;
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struct work_struct work;
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};
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static void memcg_kmem_cache_create_func(struct work_struct *w)
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{
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struct memcg_kmem_cache_create_work *cw =
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container_of(w, struct memcg_kmem_cache_create_work, work);
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struct kmem_cache *cachep = cw->cachep;
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memcg_create_kmem_cache(cachep);
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kfree(cw);
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}
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/*
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* Enqueue the creation of a per-memcg kmem_cache.
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*/
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static void memcg_schedule_kmem_cache_create(struct kmem_cache *cachep)
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{
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struct memcg_kmem_cache_create_work *cw;
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cw = kmalloc(sizeof(*cw), GFP_NOWAIT | __GFP_NOWARN);
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if (!cw)
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return;
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cw->cachep = cachep;
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INIT_WORK(&cw->work, memcg_kmem_cache_create_func);
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queue_work(memcg_kmem_cache_wq, &cw->work);
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}
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/**
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* memcg_kmem_get_cache: select memcg or root cache for allocation
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* @cachep: the original global kmem cache
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@ -2951,7 +2916,7 @@ struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
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memcg_cachep = READ_ONCE(cachep->memcg_params.memcg_cache);
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if (unlikely(!memcg_cachep)) {
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memcg_schedule_kmem_cache_create(cachep);
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queue_work(system_wq, &cachep->memcg_params.work);
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return cachep;
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}
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@ -7022,17 +6987,6 @@ static int __init mem_cgroup_init(void)
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{
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int cpu, node;
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#ifdef CONFIG_MEMCG_KMEM
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/*
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* Kmem cache creation is mostly done with the slab_mutex held,
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* so use a workqueue with limited concurrency to avoid stalling
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* all worker threads in case lots of cgroups are created and
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* destroyed simultaneously.
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*/
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memcg_kmem_cache_wq = alloc_workqueue("memcg_kmem_cache", 0, 1);
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BUG_ON(!memcg_kmem_cache_wq);
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#endif
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cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL,
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memcg_hotplug_cpu_dead);
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@ -45,12 +45,14 @@ struct kmem_cache {
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* @memcg_cache: pointer to memcg kmem cache, used by all non-root memory
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* cgroups.
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* @root_caches_node: list node for slab_root_caches list.
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* @work: work struct used to create the non-root cache.
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*/
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struct memcg_cache_params {
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struct kmem_cache *root_cache;
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struct kmem_cache *memcg_cache;
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struct list_head __root_caches_node;
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struct work_struct work;
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};
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#endif /* CONFIG_SLOB */
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@ -134,10 +134,18 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
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LIST_HEAD(slab_root_caches);
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static void memcg_kmem_cache_create_func(struct work_struct *work)
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{
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struct kmem_cache *cachep = container_of(work, struct kmem_cache,
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memcg_params.work);
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memcg_create_kmem_cache(cachep);
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}
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void slab_init_memcg_params(struct kmem_cache *s)
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{
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s->memcg_params.root_cache = NULL;
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s->memcg_params.memcg_cache = NULL;
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INIT_WORK(&s->memcg_params.work, memcg_kmem_cache_create_func);
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}
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static void init_memcg_params(struct kmem_cache *s,
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@ -586,15 +594,9 @@ static int shutdown_memcg_caches(struct kmem_cache *s)
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return 0;
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}
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static void flush_memcg_workqueue(struct kmem_cache *s)
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static void cancel_memcg_cache_creation(struct kmem_cache *s)
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{
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/*
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* SLAB and SLUB create memcg kmem_caches through workqueue and SLUB
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* deactivates the memcg kmem_caches through workqueue. Make sure all
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* previous workitems on workqueue are processed.
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*/
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if (likely(memcg_kmem_cache_wq))
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flush_workqueue(memcg_kmem_cache_wq);
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cancel_work_sync(&s->memcg_params.work);
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}
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#else
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static inline int shutdown_memcg_caches(struct kmem_cache *s)
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@ -602,7 +604,7 @@ static inline int shutdown_memcg_caches(struct kmem_cache *s)
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return 0;
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}
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static inline void flush_memcg_workqueue(struct kmem_cache *s)
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static inline void cancel_memcg_cache_creation(struct kmem_cache *s)
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{
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}
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#endif /* CONFIG_MEMCG_KMEM */
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@ -621,7 +623,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
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if (unlikely(!s))
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return;
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flush_memcg_workqueue(s);
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cancel_memcg_cache_creation(s);
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get_online_cpus();
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get_online_mems();
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