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 <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index afa55bb..6f3c0fc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -332,7 +332,7 @@
struct cg_proto tcp_mem;
#endif
#if defined(CONFIG_MEMCG_KMEM)
- /* Index in the kmem_cache->memcg_params->memcg_caches array */
+ /* Index in the kmem_cache->memcg_params.memcg_caches array */
int kmemcg_id;
#endif
@@ -531,7 +531,7 @@
#ifdef CONFIG_MEMCG_KMEM
/*
- * This will be the memcg's index in each cache's ->memcg_params->memcg_caches.
+ * This will be the memcg's index in each cache's ->memcg_params.memcg_caches.
* The main reason for not using cgroup id for this:
* this works better in sparse environments, where we have a lot of memcgs,
* but only a few kmem-limited. Or also, if we have, for instance, 200
@@ -2667,8 +2667,7 @@
struct mem_cgroup *memcg;
struct kmem_cache *memcg_cachep;
- VM_BUG_ON(!cachep->memcg_params);
- VM_BUG_ON(!cachep->memcg_params->is_root_cache);
+ VM_BUG_ON(!is_root_cache(cachep));
if (current->memcg_kmem_skip_account)
return cachep;
@@ -2702,7 +2701,7 @@
void __memcg_kmem_put_cache(struct kmem_cache *cachep)
{
if (!is_root_cache(cachep))
- css_put(&cachep->memcg_params->memcg->css);
+ css_put(&cachep->memcg_params.memcg->css);
}
/*
@@ -2778,7 +2777,7 @@
if (PageSlab(page)) {
cachep = page->slab_cache;
if (!is_root_cache(cachep))
- memcg = cachep->memcg_params->memcg;
+ memcg = cachep->memcg_params.memcg;
} else
/* page allocated by alloc_kmem_pages */
memcg = page->mem_cgroup;