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

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Message-ID: <1355376960.1567.3.camel@kernel.cn.ibm.com>
Date:	Wed, 12 Dec 2012 23:36:00 -0600
From:	Simon Jeons <simon.jeons@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	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 Wed, 2012-12-12 at 16:53 -0500, Rik van Riel wrote:
> 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.

Where check enough file pages? 
if (unlikely(file + free <= high_wmark_pages(zone))), correct?

> 
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