The patch titled
Subject: memcg: add rwsem to synchronize against memcg_caches arrays relocation
has been removed from the -mm tree. Its filename was
memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Subject: memcg: add rwsem to synchronize against memcg_caches arrays relocation
We need a stable value of memcg_nr_cache_ids in kmem_cache_create()
(memcg_alloc_cache_params() wants it for root caches), where we only hold
the slab_mutex and no memcg-related locks. As a result, we have to update
memcg_nr_cache_ids under the slab_mutex, which we can only take on the
slab's side (see memcg_update_array_size). This looks awkward and will
become even worse when per-memcg list_lru is introduced, which also wants
stable access to memcg_nr_cache_ids.
To get rid of this dependency between the memcg_nr_cache_ids and the
slab_mutex, this patch introduces a special rwsem. The rwsem is held for
writing during memcg_caches arrays relocation and memcg_nr_cache_ids
updates. Therefore one can take it for reading to get a stable access to
memcg_caches arrays and/or memcg_nr_cache_ids.
Currently the semaphore is taken for reading only from kmem_cache_create,
right before taking the slab_mutex, so right now there's no much point in
using rwsem instead of mutex. However, once list_lru is made per-memcg it
will allow list_lru initializations to proceed concurrently.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 12 ++++++++++--
mm/memcontrol.c | 29 +++++++++++++++++++----------
mm/slab_common.c | 9 ++++-----
3 files changed, 33 insertions(+), 17 deletions(-)
diff -puN include/linux/memcontrol.h~memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation include/linux/memcontrol.h
--- a/include/linux/memcontrol.h~memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation
+++ a/include/linux/memcontrol.h
@@ -399,6 +399,8 @@ static inline void sock_release_memcg(st
extern struct static_key memcg_kmem_enabled_key;
extern int memcg_nr_cache_ids;
+extern void memcg_get_cache_ids(void);
+extern void memcg_put_cache_ids(void);
/*
* Helper macro to loop through all memcg-specific caches. Callers must still
@@ -434,8 +436,6 @@ void __memcg_kmem_uncharge_pages(struct
int memcg_cache_id(struct mem_cgroup *memcg);
-void memcg_update_array_size(int num_groups);
-
struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep);
void __memcg_kmem_put_cache(struct kmem_cache *cachep);
@@ -569,6 +569,14 @@ static inline int memcg_cache_id(struct
return -1;
}
+static inline void memcg_get_cache_ids(void)
+{
+}
+
+static inline void memcg_put_cache_ids(void)
+{
+}
+
static inline struct kmem_cache *
memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
{
diff -puN mm/memcontrol.c~memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation
+++ a/mm/memcontrol.c
@@ -544,6 +544,19 @@ static void disarm_sock_keys(struct mem_
static DEFINE_IDA(memcg_cache_ida);
int memcg_nr_cache_ids;
+/* Protects memcg_nr_cache_ids */
+static DECLARE_RWSEM(memcg_cache_ids_sem);
+
+void memcg_get_cache_ids(void)
+{
+ down_read(&memcg_cache_ids_sem);
+}
+
+void memcg_put_cache_ids(void)
+{
+ up_read(&memcg_cache_ids_sem);
+}
+
/*
* MIN_SIZE is different than 1, because we would like to avoid going through
* the alloc/free process all the time. In a small machine, 4 kmem-limited
@@ -2549,6 +2562,7 @@ static int memcg_alloc_cache_id(void)
* There's no space for the new id in memcg_caches arrays,
* so we have to grow them.
*/
+ down_write(&memcg_cache_ids_sem);
size = 2 * (id + 1);
if (size < MEMCG_CACHES_MIN_SIZE)
@@ -2557,6 +2571,11 @@ static int memcg_alloc_cache_id(void)
size = MEMCG_CACHES_MAX_SIZE;
err = memcg_update_all_caches(size);
+ if (!err)
+ memcg_nr_cache_ids = size;
+
+ up_write(&memcg_cache_ids_sem);
+
if (err) {
ida_simple_remove(&memcg_cache_ida, id);
return err;
@@ -2569,16 +2588,6 @@ static void memcg_free_cache_id(int id)
ida_simple_remove(&memcg_cache_ida, id);
}
-/*
- * We should update the current array size iff all caches updates succeed. This
- * can only be done from the slab side. The slab mutex needs to be held when
- * calling this.
- */
-void memcg_update_array_size(int num)
-{
- memcg_nr_cache_ids = num;
-}
-
struct memcg_kmem_cache_create_work {
struct mem_cgroup *memcg;
struct kmem_cache *cachep;
diff -puN mm/slab_common.c~memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation mm/slab_common.c
--- a/mm/slab_common.c~memcg-add-rwsem-to-synchronize-against-memcg_caches-arrays-relocation
+++ a/mm/slab_common.c
@@ -169,8 +169,8 @@ int memcg_update_all_caches(int num_memc
{
struct kmem_cache *s;
int ret = 0;
- mutex_lock(&slab_mutex);
+ mutex_lock(&slab_mutex);
list_for_each_entry(s, &slab_caches, list) {
if (!is_root_cache(s))
continue;
@@ -181,11 +181,8 @@ int memcg_update_all_caches(int num_memc
* up to this point in an updated state.
*/
if (ret)
- goto out;
+ break;
}
-
- memcg_update_array_size(num_memcgs);
-out:
mutex_unlock(&slab_mutex);
return ret;
}
@@ -369,6 +366,7 @@ kmem_cache_create(const char *name, size
get_online_cpus();
get_online_mems();
+ memcg_get_cache_ids();
mutex_lock(&slab_mutex);
@@ -407,6 +405,7 @@ kmem_cache_create(const char *name, size
out_unlock:
mutex_unlock(&slab_mutex);
+ memcg_put_cache_ids();
put_online_mems();
put_online_cpus();
_
Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
origin.patch
mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
