Re: [PATCH v3 08/19] mm: memcg/slab: save obj_cgroup for non-root slab objects

[Vlastimil Babka]

On 4/22/20 10:46 PM, Roman Gushchin wrote:
> Store the obj_cgroup pointer in the corresponding place of
> page->obj_cgroups for each allocated non-root slab object.
> Make sure that each allocated object holds a reference to obj_cgroup.
> 
> Objcg pointer is obtained from the memcg->objcg dereferencing
> in memcg_kmem_get_cache() and passed from pre_alloc_hook to
> post_alloc_hook. Then in case of successful allocation(s) it's
> getting stored in the page->obj_cgroups vector.
> 
> The objcg obtaining part look a bit bulky now, but it will be simplified
> by next commits in the series.
> 
> Signed-off-by: Roman Gushchin <guro@xxxxxx>

Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>

Nit below:

> diff --git a/mm/slab.h b/mm/slab.h
> index 44def57f050e..525e09e05743 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
...
> @@ -636,8 +684,8 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
>  					 s->flags, flags);
>  	}
>  
> -	if (memcg_kmem_enabled())
> -		memcg_kmem_put_cache(s);
> +	if (!is_root_cache(s))
> +		memcg_slab_post_alloc_hook(s, objcg, size, p);
>  }
>  
>  #ifndef CONFIG_SLOB

Keep also the memcg_kmem_enabled() static key check, like elsewhere?