Re: [RFC][PATCH 2/14] memcg: rewrite force_empty

[Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>]

>  /*
> - * This routine traverse page_cgroup in given list and drop them all.
> - * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
> + * This routine moves all account to root cgroup.
>   */
> -#define FORCE_UNCHARGE_BATCH	(128)
>  static void mem_cgroup_force_empty_list(struct mem_cgroup *mem,
>  			    struct mem_cgroup_per_zone *mz,
>  			    enum lru_list lru)
>  {
>  	struct page_cgroup *pc;
>  	struct page *page;
> -	int count = FORCE_UNCHARGE_BATCH;
>  	unsigned long flags;
>  	struct list_head *list;
>  
> @@ -853,22 +892,28 @@ static void mem_cgroup_force_empty_list(
>  		pc = list_entry(list->prev, struct page_cgroup, lru);
>  		page = pc->page;
>  		get_page(page);
> -		spin_unlock_irqrestore(&mz->lru_lock, flags);
> -		/*
> -		 * Check if this page is on LRU. !LRU page can be found
> -		 * if it's under page migration.
> -		 */
> -		if (PageLRU(page)) {
> -			__mem_cgroup_uncharge_common(page,
> -					MEM_CGROUP_CHARGE_TYPE_FORCE);
> +		if (!trylock_page(page)) {
> +			list_move(&pc->lru, list);
> +			put_page(page):
                                     ^^^
                                    s/:/;

Just to make sure :)


Thanks,
Daisuke Nishimura.


> +			spin_unlock_irqrestore(&mz->lru_lock, flags);
> +			yield();
> +			spin_lock_irqsave(&mz->lru_lock, flags);
> +			continue;
> +		}
> +		if (mem_cgroup_move_account(page, pc, mem, &init_mem_cgroup)) {
> +			/* some confliction */
> +			list_move(&pc->lru, list);
> +			unlock_page(page);
>  			put_page(page);
> -			if (--count <= 0) {
> -				count = FORCE_UNCHARGE_BATCH;
> -				cond_resched();
> -			}
> -		} else
> -			cond_resched();
> -		spin_lock_irqsave(&mz->lru_lock, flags);
> +			spin_unlock_irqrestore(&mz->lru_lock, flags);
> +			yield();
> +			spin_lock_irqsave(&mz->lru_lock, flags);
> +		} else {
> +			unlock_page(page);
> +			put_page(page);
> +		}
> +		if (atomic_read(&mem->css.cgroup->count) > 0)
> +			break;
>  	}
>  	spin_unlock_irqrestore(&mz->lru_lock, flags);
>  }

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