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Tue, 23 Jun 2020 10:41:03 -0700 Received: from intmgw003.06.prn3.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Tue, 23 Jun 2020 10:40:46 -0700 Received: by devvm1291.vll0.facebook.com (Postfix, from userid 111017) id D40C4273E5EE; Tue, 23 Jun 2020 10:40:41 -0700 (PDT) Smtp-Origin-Hostprefix: devvm From: Roman Gushchin Smtp-Origin-Hostname: devvm1291.vll0.facebook.com To: Andrew Morton , Christoph Lameter CC: Johannes Weiner , Michal Hocko , Shakeel Butt , , Vlastimil Babka , , , Roman Gushchin Smtp-Origin-Cluster: vll0c01 Subject: [PATCH v7 13/19] mm: memcg/slab: simplify memcg cache creation Date: Tue, 23 Jun 2020 10:40:31 -0700 Message-ID: <20200623174037.3951353-14-guro@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200623174037.3951353-1-guro@fb.com> References: <20200623174037.3951353-1-guro@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-23_11:2020-06-23,2020-06-23 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 impostorscore=0 mlxscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 phishscore=0 malwarescore=0 mlxlogscore=999 adultscore=0 suspectscore=2 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006120000 definitions=main-2006230124 X-FB-Internal: deliver X-Rspamd-Queue-Id: 7EA5F18020B1A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Because the number of non-root kmem_caches doesn't depend on the number o= f 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 Reviewed-by: Vlastimil Babka Reviewed-by: Shakeel Butt --- include/linux/memcontrol.h | 1 - mm/memcontrol.c | 48 +------------------------------------- mm/slab.h | 2 ++ mm/slab_common.c | 22 +++++++++-------- 4 files changed, 15 insertions(+), 58 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 11fd18b3d6c6..2ac84dcfc9e5 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1418,7 +1418,6 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp= _t gfp, size_t size); void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size); =20 extern struct static_key_false memcg_kmem_enabled_key; -extern struct workqueue_struct *memcg_kmem_cache_wq; =20 extern int memcg_nr_cache_ids; void memcg_get_cache_ids(void); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 417070fb0fd0..d23c2bdeea66 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -399,8 +399,6 @@ void memcg_put_cache_ids(void) */ DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key); EXPORT_SYMBOL(memcg_kmem_enabled_key); - -struct workqueue_struct *memcg_kmem_cache_wq; #endif =20 static int memcg_shrinker_map_size; @@ -2902,39 +2900,6 @@ static void memcg_free_cache_id(int id) ida_simple_remove(&memcg_cache_ida, id); } =20 -struct memcg_kmem_cache_create_work { - struct kmem_cache *cachep; - struct work_struct work; -}; - -static void memcg_kmem_cache_create_func(struct work_struct *w) -{ - struct memcg_kmem_cache_create_work *cw =3D - container_of(w, struct memcg_kmem_cache_create_work, work); - struct kmem_cache *cachep =3D cw->cachep; - - memcg_create_kmem_cache(cachep); - - kfree(cw); -} - -/* - * Enqueue the creation of a per-memcg kmem_cache. - */ -static void memcg_schedule_kmem_cache_create(struct kmem_cache *cachep) -{ - struct memcg_kmem_cache_create_work *cw; - - cw =3D kmalloc(sizeof(*cw), GFP_NOWAIT | __GFP_NOWARN); - if (!cw) - return; - - cw->cachep =3D cachep; - INIT_WORK(&cw->work, memcg_kmem_cache_create_func); - - queue_work(memcg_kmem_cache_wq, &cw->work); -} - /** * memcg_kmem_get_cache: select memcg or root cache for allocation * @cachep: the original global kmem cache @@ -2951,7 +2916,7 @@ struct kmem_cache *memcg_kmem_get_cache(struct kmem= _cache *cachep) =20 memcg_cachep =3D READ_ONCE(cachep->memcg_params.memcg_cache); if (unlikely(!memcg_cachep)) { - memcg_schedule_kmem_cache_create(cachep); + queue_work(system_wq, &cachep->memcg_params.work); return cachep; } =20 @@ -7026,17 +6991,6 @@ static int __init mem_cgroup_init(void) { int cpu, node; =20 -#ifdef CONFIG_MEMCG_KMEM - /* - * Kmem cache creation is mostly done with the slab_mutex held, - * so use a workqueue with limited concurrency to avoid stalling - * all worker threads in case lots of cgroups are created and - * destroyed simultaneously. - */ - memcg_kmem_cache_wq =3D alloc_workqueue("memcg_kmem_cache", 0, 1); - BUG_ON(!memcg_kmem_cache_wq); -#endif - cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL, memcg_hotplug_cpu_dead); =20 diff --git a/mm/slab.h b/mm/slab.h index 673448e5cfb3..66482f8467e7 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -45,12 +45,14 @@ struct kmem_cache { * @memcg_cache: pointer to memcg kmem cache, used by all non-root memor= y * cgroups. * @root_caches_node: list node for slab_root_caches list. + * @work: work struct used to create the non-root cache. */ struct memcg_cache_params { struct kmem_cache *root_cache; =20 struct kmem_cache *memcg_cache; struct list_head __root_caches_node; + struct work_struct work; }; #endif /* CONFIG_SLOB */ =20 diff --git a/mm/slab_common.c b/mm/slab_common.c index 90c25c8db1a5..fe4f5be0e51f 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -132,10 +132,18 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, g= fp_t flags, size_t nr, =20 LIST_HEAD(slab_root_caches); =20 +static void memcg_kmem_cache_create_func(struct work_struct *work) +{ + struct kmem_cache *cachep =3D container_of(work, struct kmem_cache, + memcg_params.work); + memcg_create_kmem_cache(cachep); +} + void slab_init_memcg_params(struct kmem_cache *s) { s->memcg_params.root_cache =3D NULL; s->memcg_params.memcg_cache =3D NULL; + INIT_WORK(&s->memcg_params.work, memcg_kmem_cache_create_func); } =20 static void init_memcg_params(struct kmem_cache *s, @@ -584,15 +592,9 @@ static int shutdown_memcg_caches(struct kmem_cache *= s) return 0; } =20 -static void flush_memcg_workqueue(struct kmem_cache *s) +static void cancel_memcg_cache_creation(struct kmem_cache *s) { - /* - * SLAB and SLUB create memcg kmem_caches through workqueue and SLUB - * deactivates the memcg kmem_caches through workqueue. Make sure all - * previous workitems on workqueue are processed. - */ - if (likely(memcg_kmem_cache_wq)) - flush_workqueue(memcg_kmem_cache_wq); + cancel_work_sync(&s->memcg_params.work); } #else static inline int shutdown_memcg_caches(struct kmem_cache *s) @@ -600,7 +602,7 @@ static inline int shutdown_memcg_caches(struct kmem_c= ache *s) return 0; } =20 -static inline void flush_memcg_workqueue(struct kmem_cache *s) +static inline void cancel_memcg_cache_creation(struct kmem_cache *s) { } #endif /* CONFIG_MEMCG_KMEM */ @@ -619,7 +621,7 @@ void kmem_cache_destroy(struct kmem_cache *s) if (unlikely(!s)) return; =20 - flush_memcg_workqueue(s); + cancel_memcg_cache_creation(s); =20 get_online_cpus(); get_online_mems(); --=20 2.26.2