linux-kernel - Re: [PATCH 11/23] slub: consider a memcg parameter in kmem_create

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Date:	Tue, 24 Apr 2012 16:03:31 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Glauber Costa <glommer@...allels.com>
Cc:	cgroups@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, devel@...nvz.org,
	kamezawa.hiroyu@...fujitsu.com, Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Greg Thelen <gthelen@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 11/23] slub: consider a memcg parameter in
 kmem_create_cache

On Fri, Apr 20, 2012 at 06:57:19PM -0300, Glauber Costa wrote:
> 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;
> +

This probably won't build without CONFIG_CGROUP_MEM_RES_CTLR_KMEM ?

>  		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,

Does that build without CONFIG_CGROUP_MEM_RES_CTLR ?

> +			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
> +
>  	down_write(&slub_lock);
> -	s = find_mergeable(size, align, flags, name, ctor);
> +	s = find_mergeable(memcg, size, align, flags, name, ctor);
>  	if (s) {
>  		s->refcount++;
>  		/*
> @@ -3954,12 +3963,15 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
>  				size, align, flags, ctor)) {
>  			list_add(&s->list, &slab_caches);
>  			up_write(&slub_lock);
> +			mem_cgroup_register_cache(memcg, s);

How do you handle when the memcg cgroup gets destroyed? Also that means only one
memcg cgroup can be accounted for a given slab cache? What if that memcg cgroup has
children? Hmm, perhaps this is handled in a further patch in the series, I saw a
patch title with "children" inside :)

Also my knowledge on memory allocators is near zero, so I may well be asking weird
questions...
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