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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>
This commit is contained in:
Roman Gushchin 2020-08-06 23:21:14 -07:00 committed by Linus Torvalds
parent 9855609bde
commit d797b7d054
4 changed files with 15 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/memcontrol.h
View File

@ -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);
extern struct static_key_false memcg_kmem_enabled_key;
extern struct workqueue_struct *memcg_kmem_cache_wq;
extern int memcg_nr_cache_ids;
void memcg_get_cache_ids(void);

48
mm/memcontrol.c
View File

@ -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
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);
}
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 =
container_of(w, struct memcg_kmem_cache_create_work, work);
struct kmem_cache *cachep = 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 = kmalloc(sizeof(*cw), GFP_NOWAIT | __GFP_NOWARN);
if (!cw)
return;
cw->cachep = 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)
memcg_cachep = 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;
}
@ -7022,17 +6987,6 @@ static int __init mem_cgroup_init(void)
{
int cpu, node;
#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 = 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);

2
mm/slab.h
View File

@ -45,12 +45,14 @@ struct kmem_cache {
* @memcg_cache: pointer to memcg kmem cache, used by all non-root memory
* 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;
struct kmem_cache *memcg_cache;
struct list_head __root_caches_node;
struct work_struct work;
};
#endif /* CONFIG_SLOB */

22
mm/slab_common.c
View File

@ -134,10 +134,18 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
LIST_HEAD(slab_root_caches);
static void memcg_kmem_cache_create_func(struct work_struct *work)
{
struct kmem_cache *cachep = 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 = NULL;
s->memcg_params.memcg_cache = NULL;
INIT_WORK(&s->memcg_params.work, memcg_kmem_cache_create_func);
}
static void init_memcg_params(struct kmem_cache *s,
@ -586,15 +594,9 @@ static int shutdown_memcg_caches(struct kmem_cache *s)
return 0;
}
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)
@ -602,7 +604,7 @@ static inline int shutdown_memcg_caches(struct kmem_cache *s)
return 0;
}
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 */
@ -621,7 +623,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
if (unlikely(!s))
return;
flush_memcg_workqueue(s);
cancel_memcg_cache_creation(s);
get_online_cpus();
get_online_mems();