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Date:   Tue, 28 May 2019 11:51:34 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Kirill Tkhai <ktkhai@virtuozzo.com>
Cc:     akpm@linux-foundation.org, daniel.m.jordan@oracle.com,
        mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH REBASED 1/4] mm: Move recent_rotated pages calculation to
 shrink_inactive_list()
Message-ID: <20190528155134.GA14663@cmpxchg.org>
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 <155290127956.31489.3393586616054413298.stgit@localhost.localdomain>
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On Mon, Mar 18, 2019 at 12:27:59PM +0300, Kirill Tkhai wrote:
> @@ -1945,6 +1942,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
>  		count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_DIRECT,
>  				   nr_reclaimed);
>  	}
> +	reclaim_stat->recent_rotated[0] = stat.nr_activate[0];
> +	reclaim_stat->recent_rotated[1] = stat.nr_activate[1];

Surely this should be +=, right?

Otherwise we maintain essentially no history of page rotations and
that wreaks havoc on the page cache vs. swapping reclaim balance.