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

From: David Rientjes <rientjes@google.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, vmscan: avoid thrashing anon lru when free + file is low
Date: Wed, 19 Apr 2017 16:24:48 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.10.1704191623540.48310@chino.kir.corp.google.com> (raw)
In-Reply-To: <20170419001405.GA13364@bbox>

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.

Tested-by: David Rientjes <rientjes@google.com>