linux-kernel - Re: [RFC PATCH] mm: have kswapd only reclaiming use min protection on memcg

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Date:   Wed, 27 Oct 2021 09:20:35 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Huangzhaoyang <huangzhaoyang@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mm: have kswapd only reclaiming use min protection
 on memcg

On Wed 27-10-21 15:01:50, Huangzhaoyang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> For the kswapd only reclaiming, there is no chance to try again on
> this group while direct reclaim has. fix it by judging gfp flag.

There is no problem description (same as in your last submissions. Have
you looked at the patch submission documentation as recommended
previously?).

Also this patch doesn't make any sense. Both direct reclaim and kswapd
use a gfp mask which contains __GFP_DIRECT_RECLAIM (see balance_pgdat
for the kswapd part)..

> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>

Nacked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/vmscan.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 74296c2..41f5776 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2704,7 +2704,8 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
>  			unsigned long protection;
>  
>  			/* memory.low scaling, make sure we retry before OOM */
> -			if (!sc->memcg_low_reclaim && low > min) {
> +			if (!sc->memcg_low_reclaim && low > min
> +				&& sc->gfp_mask & __GFP_DIRECT_RECLAIM) {
>  				protection = low;
>  				sc->memcg_low_skipped = 1;
>  			} else {
> -- 
> 1.9.1

-- 
Michal Hocko
SUSE Labs