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authorVladimir Davydov <vdavydov@parallels.com>2015-02-12 14:59:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-12 18:54:09 -0800
commitf7ce3190c4a35bf887adb7a1aa1ba899b679872d (patch)
tree8a40d93f1e796e1007d59e67541ce3044430b927 /include/linux/slab.h
parent49e7e7ff8d551b5b1e2f8da8497b9058cfa25672 (diff)
downloadop-kernel-dev-f7ce3190c4a35bf887adb7a1aa1ba899b679872d.zip
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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>
Diffstat (limited to 'include/linux/slab.h')
-rw-r--r--include/linux/slab.h17
1 files changed, 7 insertions, 10 deletions
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 2e3b448..1e03c11 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -473,14 +473,14 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
#ifndef ARCH_SLAB_MINALIGN
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif
+
+struct memcg_cache_array {
+ struct rcu_head rcu;
+ struct kmem_cache *entries[0];
+};
+
/*
* This is the main placeholder for memcg-related information in kmem caches.
- * struct kmem_cache will hold a pointer to it, so the memory cost while
- * disabled is 1 pointer. The runtime cost while enabled, gets bigger than it
- * would otherwise be if that would be bundled in kmem_cache: we'll need an
- * extra pointer chase. But the trade off clearly lays in favor of not
- * penalizing non-users.
- *
* Both the root cache and the child caches will have it. For the root cache,
* this will hold a dynamically allocated array large enough to hold
* information about the currently limited memcgs in the system. To allow the
@@ -495,10 +495,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
struct memcg_cache_params {
bool is_root_cache;
union {
- struct {
- struct rcu_head rcu_head;
- struct kmem_cache *memcg_caches[0];
- };
+ struct memcg_cache_array __rcu *memcg_caches;
struct {
struct mem_cgroup *memcg;
struct kmem_cache *root_cache;
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