linux-kernel - Re: [PATCH] memcg: put soft limit reclaim out of way if the excess tree is empty

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Message-ID: <20160801173956.GA31957@dhcp22.suse.cz>
Date:	Mon, 1 Aug 2016 19:39:56 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Vladimir Davydov <vdavydov@...tuozzo.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: put soft limit reclaim out of way if the excess
 tree is empty

On Mon 01-08-16 13:17:17, Johannes Weiner wrote:
> On Mon, Aug 01, 2016 at 05:24:54PM +0200, Michal Hocko wrote:
> > @@ -2564,7 +2559,13 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
> >  		return 0;
> >  
> >  	mctz = soft_limit_tree_node(pgdat->node_id);
> > -	if (soft_limit_tree_empty(mctz))
> > +
> > +	/*
> > +	 * Do not even bother to check the largest node if the node
> 
>                                                                root

Fixed

> 
> > +	 * is empty. Do it lockless to prevent lock bouncing. Races
> > +	 * are acceptable as soft limit is best effort anyway.
> > +	 */
> > +	if (RB_EMPTY_ROOT(&mctz->rb_root))
> >  		return 0;
> 
> Other than that, looks good. Please retain my
> 
> Acked-by: Johannes Weiner <hannes@...xchg.org>

Thanks.

-- 
Michal Hocko
SUSE Labs