Re: [PATCH] memcg: make threshold index in the right position

["Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>]

On Thu, Feb 02, 2012 at 05:45:19PM +0800, Sha Zhengju wrote:
> From: Sha Zhengju <handai.szj-3b8fjiQLQpfQT0dZR+AlfA@public.gmane.org>
> 
> Index current_threshold may point to threshold that just equal to
> usage after __mem_cgroup_threshold is triggerd.

I don't see it. Could you describe conditions?

> But after registering
> a new event, it will change (pointing to threshold just below usage).
> So make it consistent here.
> 
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> Cc: Kirill A. Shutemov <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
> Signed-off-by: Sha Zhengju <handai.szj-3b8fjiQLQpfQT0dZR+AlfA@public.gmane.org>
> ---
>  mm/memcontrol.c |    7 ++++---
>  1 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 22d94f5..79f4a58 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -183,7 +183,7 @@ struct mem_cgroup_threshold {
>  
>  /* For threshold */
>  struct mem_cgroup_threshold_ary {
> -	/* An array index points to threshold just below usage. */
> +	/* An array index points to threshold just below or equal to usage. */
>  	int current_threshold;
>  	/* Size of entries[] */
>  	unsigned int size;
> @@ -4319,14 +4319,15 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
>  	/* Find current threshold */
>  	new->current_threshold = -1;
>  	for (i = 0; i < size; i++) {
> -		if (new->entries[i].threshold < usage) {
> +		if (new->entries[i].threshold <= usage) {
>  			/*
>  			 * new->current_threshold will not be used until
>  			 * rcu_assign_pointer(), so it's safe to increment
>  			 * it here.
>  			 */
>  			++new->current_threshold;
> -		}
> +		} else
> +			break;
>  	}
>  
>  	/* Free old spare buffer and save old primary buffer as spare */
> -- 
> 1.7.4.1
> 

-- 
 Kirill A. Shutemov