[PATCH -mm 07/14] memcg: update memcg_caches array entries on the slab side
From: Vladimir Davydov <hidden>
Date: 2014-09-21 15:18:54
Also in:
linux-mm, lkml
Subsystem:
control group - memory resource controller (memcg), memory management, slab allocator, the rest · Maintainers:
Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt, Andrew Morton, Vlastimil Babka, Harry Yoo, Linus Torvalds
I think that all manipulations on memcg_caches array must happen where
it is defined, i.e. on the slab side. The array allocation and
relocation paths as well as elements access follow this pattern (see
e.g. cache_from_memcg_idx, memcg_update_all_caches), but elements update
doesn't. We still want to setup new array elements in memcontrol.c (see
memcg_{un,}register_cache), though it may change in the future. Anyway,
let's introduce a simple function for updating the array entries,
cache_install_at_memcg_idx, to match cache_from_memcg_idx.
Signed-off-by: Vladimir Davydov <redacted>
---
mm/memcontrol.c | 15 ++++-----------
mm/slab.h | 21 ++++++++++++++++++++-
2 files changed, 24 insertions(+), 12 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 412fa220b9aa..9ae2627bd3b1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c@@ -3018,15 +3018,8 @@ static void memcg_register_cache(struct mem_cgroup *memcg, css_get(&memcg->css); list_add(&cachep->memcg_params->list, &memcg->memcg_slab_caches); - /* - * Since readers won't lock (see cache_from_memcg_idx()), we need a - * barrier here to ensure nobody will see the kmem_cache partially - * initialized. - */ - smp_wmb(); - - BUG_ON(root_cache->memcg_params->memcg_caches[id]); - root_cache->memcg_params->memcg_caches[id] = cachep; + BUG_ON(cache_from_memcg_idx(root_cache, id) != NULL); + cache_install_at_memcg_idx(root_cache, id, cachep); } static void memcg_unregister_cache(struct kmem_cache *cachep)
@@ -3043,8 +3036,8 @@ static void memcg_unregister_cache(struct kmem_cache *cachep) memcg = cachep->memcg_params->memcg; id = memcg_cache_id(memcg); - BUG_ON(root_cache->memcg_params->memcg_caches[id] != cachep); - root_cache->memcg_params->memcg_caches[id] = NULL; + BUG_ON(cache_from_memcg_idx(root_cache, id) != cachep); + cache_install_at_memcg_idx(root_cache, id, NULL); list_del(&cachep->memcg_params->list);
diff --git a/mm/slab.h b/mm/slab.h
index 52b570932ba0..da798cfe5efa 100644
--- a/mm/slab.h
+++ b/mm/slab.h@@ -201,12 +201,31 @@ cache_from_memcg_idx(struct kmem_cache *s, int idx) /* * Make sure we will access the up-to-date value. The code updating * memcg_caches issues a write barrier to match this (see - * memcg_register_cache()). + * cache_install_at_memcg_idx()). */ smp_read_barrier_depends(); return cachep; } +/* + * Update the entry at index @memcg_idx in the memcg_caches array of + * @root_cache. The caller must synchronize against concurrent updates to the + * same entry as well as guarantee that the memcg_caches array won't be + * relocated under our noses. + */ +static inline void cache_install_at_memcg_idx(struct kmem_cache *root_cache, + int memcg_idx, struct kmem_cache *memcg_cache) +{ + /* + * Since readers won't lock (see cache_from_memcg_idx()), we need a + * barrier here to ensure nobody will see the kmem_cache partially + * initialized. + */ + smp_wmb(); + + root_cache->memcg_params->memcg_caches[memcg_idx] = memcg_cache; +} + static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s) { if (is_root_cache(s))
--
1.7.10.4
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