linux-kernel - Re: [patch 1/8] mm: memcg: only evict file pages when we have plenty

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Date:	Wed, 12 Dec 2012 16:53:36 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/8] mm: memcg: only evict file pages when we have plenty

On 12/12/2012 04:43 PM, Johannes Weiner wrote:
> dc0422c "mm: vmscan: only evict file pages when we have plenty" makes
> a point of not going for anonymous memory while there is still enough
> inactive cache around.
>
> The check was added only for global reclaim, but it is just as useful
> for memory cgroup reclaim.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>   mm/vmscan.c | 19 ++++++++++---------
>   1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 157bb11..3874dcb 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1671,6 +1671,16 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
>   		denominator = 1;
>   		goto out;
>   	}
> +	/*
> +	 * There is enough inactive page cache, do not reclaim
> +	 * anything from the anonymous working set right now.
> +	 */
> +	if (!inactive_file_is_low(lruvec)) {
> +		fraction[0] = 0;
> +		fraction[1] = 1;
> +		denominator = 1;
> +		goto out;
> +	}
>
>   	anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
>   		get_lru_size(lruvec, LRU_INACTIVE_ANON);
> @@ -1688,15 +1698,6 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
>   			fraction[1] = 0;
>   			denominator = 1;
>   			goto out;
> -		} else if (!inactive_file_is_low_global(zone)) {
> -			/*
> -			 * There is enough inactive page cache, do not
> -			 * reclaim anything from the working set right now.
> -			 */
> -			fraction[0] = 0;
> -			fraction[1] = 1;
> -			denominator = 1;
> -			goto out;
>   		}
>   	}
>
>

I believe the if() block should be moved to AFTER
the check where we make sure we actually have enough
file pages.

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