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From:   Roman Gushchin <guro@fb.com>
To:     Xunlei Pang <xlpang@linux.alibaba.com>
CC:     Michal Hocko <mhocko@suse.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 1/3] mm/memcg: Fix min/low usage in
 propagate_protected_usage()
Thread-Topic: [PATCH 1/3] mm/memcg: Fix min/low usage in
 propagate_protected_usage()
Thread-Index: AQHUit5xdIPpMr8W9kuwgrfCUim4T6VtTlAA
Date:   Mon, 3 Dec 2018 18:00:11 +0000
Message-ID: <20181203180008.GB31090@castle.DHCP.thefacebook.com>
References: <20181203080119.18989-1-xlpang@linux.alibaba.com>
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On Mon, Dec 03, 2018 at 04:01:17PM +0800, Xunlei Pang wrote:
> When usage exceeds min, min usage should be min other than 0.
> Apply the same for low.
>=20
> Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
> ---
>  mm/page_counter.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
>=20
> diff --git a/mm/page_counter.c b/mm/page_counter.c
> index de31470655f6..75d53f15f040 100644
> --- a/mm/page_counter.c
> +++ b/mm/page_counter.c
> @@ -23,11 +23,7 @@ static void propagate_protected_usage(struct page_coun=
ter *c,
>  		return;
> =20
>  	if (c->min || atomic_long_read(&c->min_usage)) {
> -		if (usage <=3D c->min)
> -			protected =3D usage;
> -		else
> -			protected =3D 0;
> -
> +		protected =3D min(usage, c->min);

This change makes sense in the combination with the patch 3, but not as a
standlone "fix". It's not a bug, it's a required thing unless you start sca=
nning
proportionally to memory.low/min excess.

Please, reflect this in the commit message. Or, even better, merge it into
the patch 3.

Also, please, make sure that cgroup kselftests are passing after your chang=
es.

Thanks!