Re: [PATCH] memcg: change behavior of moving charges at task move

[Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>]

On Wed, 21 Mar 2012 18:52:04 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org> wrote:

>  static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
>  			unsigned long addr, pte_t ptent, swp_entry_t *entry)
>  {
> -	int usage_count;
>  	struct page *page = NULL;
>  	swp_entry_t ent = pte_to_swp_entry(ptent);
>  
>  	if (!move_anon() || non_swap_entry(ent))
>  		return NULL;
> -	usage_count = mem_cgroup_count_swap_user(ent, &page);
> -	if (usage_count > 1) { /* we don't move shared anon */
> -		if (page)
> -			put_page(page);
> -		return NULL;
> -	}
> +#ifdef CONFIG_SWAP
> +	/*
> +	 * Avoid lookup_swap_cache() not to update statistics.
> +	 */

I don't understand this comment - what is it trying to tell us?

> +	page = find_get_page(&swapper_space, ent.val);

The code won't even compile if CONFIG_SWAP=n?

> +#endif
>  	if (do_swap_account)
>  		entry->val = ent.val;
>