linux-kernel - Re: [patch] mm, vmscan: avoid thrashing anon lru when free + file is low

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Date:   Thu, 20 Apr 2017 15:09:04 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [patch] mm, vmscan: avoid thrashing anon lru when free + file is
 low

Hi David,

On Wed, Apr 19, 2017 at 04:24:48PM -0700, David Rientjes wrote:
> On Wed, 19 Apr 2017, Minchan Kim wrote:
> 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 24efcc20af91..5d2f3fa41e92 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2174,8 +2174,17 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
> >  		}
> >  
> >  		if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
> > -			scan_balance = SCAN_ANON;
> > -			goto out;
> > +			/*
> > +			 * force SCAN_ANON if inactive anonymous LRU lists of
> > +			 * eligible zones are enough pages. Otherwise, thrashing
> > +			 * can be happen on the small anonymous LRU list.
> > +			 */
> > +			if (!inactive_list_is_low(lruvec, false, NULL, sc, false) &&
> > +			     lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
> > +					>> sc->priority) {
> > +				scan_balance = SCAN_ANON;
> > +				goto out;
> > +			}
> >  		}
> >  	}
> >  
> 
> Hi Minchan,
> 
> This looks good and it correctly biases against SCAN_ANON for my workload 
> that was thrashing the anon lrus.  Feel free to use parts of my changelog 
> if you'd like.

Thanks for the testing!
As considering how it's hard to find such a problem, it should be totally your
credit. So you can send the patch with detailed description. Feel free to
add my suggested-by. :)

Thanks!