linux-kernel - Re: [PATCH -mm] memcg: remove activate_kmem

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Date:	Mon, 20 Oct 2014 20:53:06 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm] memcg: remove activate_kmem_mutex

On Mon 20-10-14 19:11:29, Vladimir Davydov wrote:
> The activate_kmem_mutex is used to serialize memcg.kmem.limit updates,
> but we already serialize them with memcg_limit_mutex so let's remove the
> former.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>

Is this the case since bd67314586a3 (memcg, slab: simplify
synchronization scheme)?

Anyway Looks good to me.
Acked-by: Michal Hocko <mhocko@...e.cz>

> ---
>  mm/memcontrol.c |   24 +++++-------------------
>  1 file changed, 5 insertions(+), 19 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 3a203c7ec6c7..e957f0c80c6e 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2618,8 +2618,6 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
>   */
>  static DEFINE_MUTEX(memcg_slab_mutex);
>  
> -static DEFINE_MUTEX(activate_kmem_mutex);
> -
>  /*
>   * This is a bit cumbersome, but it is rarely used and avoids a backpointer
>   * in the memcg_cache_params struct.
> @@ -3756,9 +3754,8 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
>  }
>  
>  #ifdef CONFIG_MEMCG_KMEM
> -/* should be called with activate_kmem_mutex held */
> -static int __memcg_activate_kmem(struct mem_cgroup *memcg,
> -				 unsigned long nr_pages)
> +static int memcg_activate_kmem(struct mem_cgroup *memcg,
> +			       unsigned long nr_pages)
>  {
>  	int err = 0;
>  	int memcg_id;
> @@ -3820,17 +3817,6 @@ out:
>  	return err;
>  }
>  
> -static int memcg_activate_kmem(struct mem_cgroup *memcg,
> -			       unsigned long nr_pages)
> -{
> -	int ret;
> -
> -	mutex_lock(&activate_kmem_mutex);
> -	ret = __memcg_activate_kmem(memcg, nr_pages);
> -	mutex_unlock(&activate_kmem_mutex);
> -	return ret;
> -}
> -
>  static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
>  				   unsigned long limit)
>  {
> @@ -3853,14 +3839,14 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)
>  	if (!parent)
>  		return 0;
>  
> -	mutex_lock(&activate_kmem_mutex);
> +	mutex_lock(&memcg_limit_mutex);
>  	/*
>  	 * If the parent cgroup is not kmem-active now, it cannot be activated
>  	 * after this point, because it has at least one child already.
>  	 */
>  	if (memcg_kmem_is_active(parent))
> -		ret = __memcg_activate_kmem(memcg, PAGE_COUNTER_MAX);
> -	mutex_unlock(&activate_kmem_mutex);
> +		ret = memcg_activate_kmem(memcg, PAGE_COUNTER_MAX);
> +	mutex_unlock(&memcg_limit_mutex);
>  	return ret;
>  }
>  #else
> -- 
> 1.7.10.4
> 

-- 
Michal Hocko
SUSE Labs
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