We don't keep a pointer to the owner kmem cache in the
memcg_cache_params struct, because we can always get the cache by
reading the slot corresponding to the owner memcg in the root cache's
memcg_caches array (see memcg_params_to_cache).
However, this means that offline css's, which can be zombieing around
for quite a long time, will occupy slots in memcg_caches arrays, making
them grow larger and larger, which doesn't sound good. Therefore I'm
going to make memcg release the slots on offline, which will render
memcg_params_to_cache invalid. So I'm removing it and adding a back
pointer to memcg_cache_params instead.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
---
include/linux/slab.h | 2 ++
mm/memcontrol.c | 20 ++++----------------
2 files changed, 6 insertions(+), 16 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 14888328e96b..e6e6ddb769c7 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -523,6 +523,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
*
* Child caches will hold extra metadata needed for its operation. Fields are:
*
+ * @cachep: cache which this struct is for
* @memcg: pointer to the memcg this cache belongs to
* @list: list_head for the list of all caches in this memcg
* @root_cache: pointer to the global, root cache, this cache was derived from
@@ -536,6 +537,7 @@ struct memcg_cache_params {
struct kmem_cache *memcg_caches[0];
};
struct {
+ struct kmem_cache *cachep;
struct mem_cgroup *memcg;
struct list_head list;
struct kmem_cache *root_cache;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index cc1064a504cc..aa3111ac3b7e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2790,19 +2790,6 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
return memcg ? memcg->kmemcg_id : -1;
}
-/*
- * This is a bit cumbersome, but it is rarely used and avoids a backpointer
- * in the memcg_cache_params struct.
- */
-static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
-{
- struct kmem_cache *cachep;
-
- VM_BUG_ON(p->is_root_cache);
- cachep = p->root_cache;
- return cache_from_memcg_idx(cachep, memcg_cache_id(p->memcg));
-}
-
#ifdef CONFIG_SLABINFO
static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)
{
@@ -2816,7 +2803,7 @@ static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)
mutex_lock(&memcg_slab_mutex);
list_for_each_entry(params, &memcg->memcg_slab_caches, list)
- cache_show(memcg_params_to_cache(params), m);
+ cache_show(params->cachep, m);
mutex_unlock(&memcg_slab_mutex);
return 0;
@@ -2979,6 +2966,7 @@ int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
return -ENOMEM;
if (memcg) {
+ s->memcg_params->cachep = s;
s->memcg_params->memcg = memcg;
s->memcg_params->root_cache = root_cache;
css_get(&memcg->css);
@@ -3124,7 +3112,6 @@ int __memcg_cleanup_cache_params(struct kmem_cache *s)
static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
{
- struct kmem_cache *cachep;
struct memcg_cache_params *params, *tmp;
if (!memcg_kmem_is_active(memcg))
@@ -3132,7 +3119,8 @@ static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
mutex_lock(&memcg_slab_mutex);
list_for_each_entry_safe(params, tmp, &memcg->memcg_slab_caches, list) {
- cachep = memcg_params_to_cache(params);
+ struct kmem_cache *cachep = params->cachep;
+
kmem_cache_shrink(cachep);
if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
memcg_unregister_cache(cachep);
--
1.7.10.4
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