Re: [PATCH 11/23] slub: consider a memcg parameter in kmem_create_cache

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(2012/04/21 6:57), Glauber Costa wrote:

> Allow a memcg parameter to be passed during cache creation.
> The slub allocator will only merge caches that belong to
> the same memcg.
> 
> Default function is created as a wrapper, passing NULL
> to the memcg version. We only merge caches that belong
> to the same memcg.
> 
>>From the memcontrol.c side, 3 helper functions are created:
> 
>  1) memcg_css_id: because slub needs a unique cache name
>     for sysfs. Since this is visible, but not the canonical
>     location for slab data, the cache name is not used, the
>     css_id should suffice.
> 
>  2) mem_cgroup_register_cache: is responsible for assigning
>     a unique index to each cache, and other general purpose
>     setup. The index is only assigned for the root caches. All
>     others are assigned index == -1.
> 
>  3) mem_cgroup_release_cache: can be called from the root cache
>     destruction, and will release the index for other caches.
> 
> This index mechanism was developed by Suleiman Souhlal.
> 
> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
> CC: Christoph Lameter <cl@xxxxxxxxx>
> CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
> CC: Michal Hocko <mhocko@xxxxxxx>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> CC: Johannes Weiner <hannes@xxxxxxxxxxx>
> CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
> ---
>  include/linux/memcontrol.h |   14 ++++++++++++++
>  include/linux/slab.h       |    6 ++++++
>  mm/memcontrol.c            |   29 +++++++++++++++++++++++++++++
>  mm/slub.c                  |   31 +++++++++++++++++++++++++++----
>  4 files changed, 76 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index f94efd2..99e14b9 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -26,6 +26,7 @@ struct mem_cgroup;
>  struct page_cgroup;
>  struct page;
>  struct mm_struct;
> +struct kmem_cache;
>  
>  /* Stats that can be updated by kernel. */
>  enum mem_cgroup_page_stat_item {
> @@ -440,7 +441,20 @@ struct sock;
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
>  void sock_update_memcg(struct sock *sk);
>  void sock_release_memcg(struct sock *sk);
> +int memcg_css_id(struct mem_cgroup *memcg);
> +void mem_cgroup_register_cache(struct mem_cgroup *memcg,
> +				      struct kmem_cache *s);
> +void mem_cgroup_release_cache(struct kmem_cache *cachep);
>  #else
> +static inline void mem_cgroup_register_cache(struct mem_cgroup *memcg,
> +					     struct kmem_cache *s)
> +{
> +}
> +
> +static inline void mem_cgroup_release_cache(struct kmem_cache *cachep)
> +{
> +}
> +
>  static inline void sock_update_memcg(struct sock *sk)
>  {
>  }
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index a5127e1..c7a7e05 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -321,6 +321,12 @@ extern void *__kmalloc_track_caller(size_t, gfp_t, unsigned long);
>  	__kmalloc(size, flags)
>  #endif /* DEBUG_SLAB */
>  
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +#define MAX_KMEM_CACHE_TYPES 400
> +#else
> +#define MAX_KMEM_CACHE_TYPES 0
> +#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
> +


why 400 ?


>  #ifdef CONFIG_NUMA
>  /*
>   * kmalloc_node_track_caller is a special version of kmalloc_node that
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 36f1e6b..0015ed0 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -323,6 +323,11 @@ struct mem_cgroup {
>  #endif
>  };
>  
> +int memcg_css_id(struct mem_cgroup *memcg)
> +{
> +	return css_id(&memcg->css);
> +}
> +
>  /* Stuffs for move charges at task migration. */
>  /*
>   * Types of charges to be moved. "move_charge_at_immitgrate" is treated as a
> @@ -461,6 +466,30 @@ struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
>  }
>  EXPORT_SYMBOL(tcp_proto_cgroup);
>  #endif /* CONFIG_INET */
> +
> +/* Bitmap used for allocating the cache id numbers. */
> +static DECLARE_BITMAP(cache_types, MAX_KMEM_CACHE_TYPES);
> +
> +void mem_cgroup_register_cache(struct mem_cgroup *memcg,
> +			       struct kmem_cache *cachep)
> +{
> +	int id = -1;
> +
> +	cachep->memcg_params.memcg = memcg;
> +
> +	if (!memcg) {
> +		id = find_first_zero_bit(cache_types, MAX_KMEM_CACHE_TYPES);
> +		BUG_ON(id < 0 || id >= MAX_KMEM_CACHE_TYPES);
> +		__set_bit(id, cache_types);


No lock here ? you need find_first_zero_bit_and_set_atomic() or some.
Rather than that, I think you can use lib/idr.c::ida_simple_get().

> +	} else
> +		INIT_LIST_HEAD(&cachep->memcg_params.destroyed_list);
> +	cachep->memcg_params.id = id;
> +}
> +
> +void mem_cgroup_release_cache(struct kmem_cache *cachep)
> +{
> +	__clear_bit(cachep->memcg_params.id, cache_types);
> +}
>  #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
>  
>  static void drain_all_stock_async(struct mem_cgroup *memcg);
> diff --git a/mm/slub.c b/mm/slub.c
> index 2652e7c..86e40cc 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -32,6 +32,7 @@
>  #include <linux/prefetch.h>
>  
>  #include <trace/events/kmem.h>
> +#include <linux/memcontrol.h>
>  
>  /*
>   * Lock order:
> @@ -3880,7 +3881,7 @@ static int slab_unmergeable(struct kmem_cache *s)
>  	return 0;
>  }
>  
> -static struct kmem_cache *find_mergeable(size_t size,
> +static struct kmem_cache *find_mergeable(struct mem_cgroup *memcg, size_t size,
>  		size_t align, unsigned long flags, const char *name,
>  		void (*ctor)(void *))
>  {
> @@ -3916,21 +3917,29 @@ static struct kmem_cache *find_mergeable(size_t size,
>  		if (s->size - size >= sizeof(void *))
>  			continue;
>  
> +		if (memcg && s->memcg_params.memcg != memcg)
> +			continue;
> +
>  		return s;
>  	}
>  	return NULL;
>  }
>  
> -struct kmem_cache *kmem_cache_create(const char *name, size_t size,
> -		size_t align, unsigned long flags, void (*ctor)(void *))
> +struct kmem_cache *
> +kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
> +			size_t align, unsigned long flags, void (*ctor)(void *))
>  {
>  	struct kmem_cache *s;
>  
>  	if (WARN_ON(!name))
>  		return NULL;
>  
> +#ifndef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +	WARN_ON(memcg != NULL);
> +#endif


I'm sorry what's is this warning for ?


> @@ -5265,6 +5283,11 @@ static char *create_unique_id(struct kmem_cache *s)
>  	if (p != name + 1)
>  		*p++ = '-';
>  	p += sprintf(p, "%07d", s->size);
> +
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +	if (s->memcg_params.memcg)
> +		p += sprintf(p, "-%08d", memcg_css_id(s->memcg_params.memcg));
> +#endif
>  	BUG_ON(p > name + ID_STR_LENGTH - 1);
>  	return name;
>  }


So, you use 'id' in user interface. Should we provide 'id' as memory.id file ?

Thanks,
-Kame

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