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

[Michal Hocko]

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@xxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxx>
> Cc: Glauber Costa <glommer@xxxxxxxxx>
> ---
>  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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