From f7ce3190c4a35bf887adb7a1aa1ba899b679872d Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Thu, 12 Feb 2015 14:59:20 -0800 Subject: 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 Cc: Johannes Weiner Cc: Michal Hocko Cc: Tejun Heo Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Dave Chinner Cc: Dan Carpenter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/slab.h | 17 +++++++---------- include/linux/slab_def.h | 2 +- include/linux/slub_def.h | 2 +- 3 files changed, 9 insertions(+), 12 deletions(-) (limited to 'include') diff --git a/include/linux/slab.h b/include/linux/slab.h index 2e3b448cfa2d..1e03c11bbfbd 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; diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h index b869d1662ba3..33d049066c3d 100644 --- a/include/linux/slab_def.h +++ b/include/linux/slab_def.h @@ -70,7 +70,7 @@ struct kmem_cache { int obj_offset; #endif /* CONFIG_DEBUG_SLAB */ #ifdef CONFIG_MEMCG_KMEM - struct memcg_cache_params *memcg_params; + struct memcg_cache_params memcg_params; #endif struct kmem_cache_node *node[MAX_NUMNODES]; diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index d82abd40a3c0..9abf04ed0999 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -85,7 +85,7 @@ struct kmem_cache { struct kobject kobj; /* For sysfs */ #endif #ifdef CONFIG_MEMCG_KMEM - struct memcg_cache_params *memcg_params; + struct memcg_cache_params memcg_params; int max_attr_size; /* for propagation, maximum size of a stored attr */ #ifdef CONFIG_SYSFS struct kset *memcg_kset; -- cgit v1.2.3-73-gaa49b