Re: [PATCH 4/9] mm: remove unnecessary reclaimability check from NUMA balancing target

From: Michal Hocko <mhocko@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Jia He <hejianet@gmail.com>, Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH 4/9] mm: remove unnecessary reclaimability check from NUMA balancing target
Date: Wed, 1 Mar 2017 16:14:32 +0100	[thread overview]
Message-ID: <20170301151432.GD11730@dhcp22.suse.cz> (raw)
In-Reply-To: <20170228214007.5621-5-hannes@cmpxchg.org>

On Tue 28-02-17 16:40:02, Johannes Weiner wrote:
> NUMA balancing already checks the watermarks of the target node to
> decide whether it's a suitable balancing target. Whether the node is
> reclaimable or not is irrelevant when we don't intend to reclaim.

I guess the original intention was to skip nodes which are under strong
memory pressure but I agree that this is questionable heuristic.

> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

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

> ---
>  mm/migrate.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 2c63ac06791b..45a18be27b1a 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1718,9 +1718,6 @@ static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
>  {
>  	int z;
>  
> -	if (!pgdat_reclaimable(pgdat))
> -		return false;
> -
>  	for (z = pgdat->nr_zones - 1; z >= 0; z--) {
>  		struct zone *zone = pgdat->node_zones + z;
>  
> -- 
> 2.11.1

-- 
Michal Hocko
SUSE Labs