linux-kernel - Re: [PATCH -mm 3/4] fork: charge threadinfo to memcg explicitly

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Date:	Wed, 26 Mar 2014 15:00:51 -0700
From:	Michal Hocko <mhocko@...e.cz>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	akpm@...ux-foundation.org, hannes@...xchg.org, glommer@...il.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, devel@...nvz.org
Subject: Re: [PATCH -mm 3/4] fork: charge threadinfo to memcg explicitly

On Wed 26-03-14 19:28:06, Vladimir Davydov wrote:
> We have only a few places where we actually want to charge kmem so
> instead of intruding into the general page allocation path with
> __GFP_KMEMCG it's better to explictly charge kmem there. All kmem
> charges will be easier to follow that way.
> 
> This is a step toward removing __GFP_KMEMCG. It makes fork charge task
> threadinfo pages explicitly instead of passing __GFP_KMEMCG to
> alloc_pages.

Looks good from a quick glance. I would also remove
THREADINFO_GFP_ACCOUNTED in this patch.

> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...e.cz>
> Cc: Glauber Costa <glommer@...il.com>
> ---
>  kernel/fork.c |   13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c
> index f4b09bc15f3a..8209780cf732 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -150,15 +150,22 @@ void __weak arch_release_thread_info(struct thread_info *ti)
>  static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
>  						  int node)
>  {
> -	struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
> -					     THREAD_SIZE_ORDER);
> +	struct page *page;
> +	struct mem_cgroup *memcg = NULL;
>  
> +	if (!memcg_kmem_newpage_charge(THREADINFO_GFP_ACCOUNTED, &memcg,
> +				       THREAD_SIZE_ORDER))
> +		return NULL;
> +	page = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
> +	memcg_kmem_commit_charge(page, memcg, THREAD_SIZE_ORDER);
>  	return page ? page_address(page) : NULL;
>  }
>  
>  static inline void free_thread_info(struct thread_info *ti)
>  {
> -	free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
> +	if (ti)
> +		memcg_kmem_uncharge_pages(virt_to_page(ti), THREAD_SIZE_ORDER);
> +	free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
>  }
>  # else
>  static struct kmem_cache *thread_info_cache;
> -- 
> 1.7.10.4
> 

-- 
Michal Hocko
SUSE Labs
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