linux-kernel - Re: [PATCH] mm: vmscan: fix memcg-aware shrinkers not called on global reclaim

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Date:	Mon, 1 Aug 2016 15:18:40 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Minchan Kim <minchan@...nel.org>,
	Rik van Riel <riel@...riel.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: vmscan: fix memcg-aware shrinkers not called on
 global reclaim

On Mon 01-08-16 16:03:10, Vladimir Davydov wrote:
> We must call shrink_slab() for each memory cgroup on both global and
> memcg reclaim in shrink_node_memcg(). Commit d71df22b55099 accidentally
> changed that so that now shrink_slab() is only called with memcg != NULL
> on memcg reclaim. As a result, memcg-aware shrinkers (including
> dentry/inode) are never invoked on global reclaim. Fix that.
> 
> Fixes: d71df22b55099 ("mm, vmscan: begin reclaiming pages on a per-node basis")

I guess you meant b2e18757f2c9. I do not see d71df22b55099 anywhere.

> Signed-off-by: Vladimir Davydov <vdavydov@...tuozzo.com>

The fix looks ok to me otherwise

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

> ---
>  mm/vmscan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 650d26832569..374d95d04178 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2561,7 +2561,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
>  			shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
>  			node_lru_pages += lru_pages;
>  
> -			if (!global_reclaim(sc))
> +			if (memcg)
>  				shrink_slab(sc->gfp_mask, pgdat->node_id,
>  					    memcg, sc->nr_scanned - scanned,
>  					    lru_pages);
> -- 
> 2.1.4
> 
> --
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-- 
Michal Hocko
SUSE Labs