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From: Michal Hocko <mhocko@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Minchan Kim <minchan@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch v2] mm, vmscan: avoid thrashing anon lru when free + file is low
Date: Thu, 4 May 2017 13:43:58 +0200	[thread overview]
Message-ID: <20170504114358.GD31540@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.10.1705031547360.50439@chino.kir.corp.google.com>

On Wed 03-05-17 15:52:04, David Rientjes wrote:
> On Wed, 3 May 2017, Michal Hocko wrote:
[...]
> >  	/*
> > -	 * If there is enough inactive page cache, i.e. if the size of the
> > -	 * inactive list is greater than that of the active list *and* the
> > -	 * inactive list actually has some pages to scan on this priority, we
> > -	 * do not reclaim anything from the anonymous working set right now.
> > -	 * Without the second condition we could end up never scanning an
> > -	 * lruvec even if it has plenty of old anonymous pages unless the
> > -	 * system is under heavy pressure.
> > +	 * Make sure there are enough pages on the biased LRU before we go
> > +	 * and do an exclusive reclaim from that list, i.e. if the
> > +	 * size of the inactive list is greater than that of the active list
> > +	 * *and* the inactive list actually has some pages to scan on this
> > +	 * priority.
> > +	 * Without the second condition we could end up never scanning other
> > +	 * lruvecs even if they have plenty of old pages unless the system is
> > +	 * under heavy pressure.
> >  	 */
> > -	if (!inactive_list_is_low(lruvec, true, memcg, sc, false) &&
> > -	    lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) {
> > -		scan_balance = SCAN_FILE;
> > +	lru = LRU_INACTIVE_ANON + LRU_FILE * (scan_balance == SCAN_FILE);
> 
> This part seems to complicate the logic since it determines the lru under 
> test based on the current setting of scan_balance.  I think I prefer 
> individual heuristics with well written comments, but others may feel 
> differently about this.

I do not claim the code would more obvious than before but it gets rid
of the duplication which is usually a good thing. This size check has
the same reasoning regardless of the type of the LRU. But I am not going
to insist...
 
> > +	if (!inactive_list_is_low(lruvec, is_file_lru(lru), memcg, sc, false) &&
> > +	    lruvec_lru_size(lruvec, lru, sc->reclaim_idx) >> sc->priority)
> >  		goto out;
> > -	}
> >  
> >  	scan_balance = SCAN_FRACT;
> >  

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2017-05-04 11:44 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18  0:06 [patch] " David Rientjes
2017-04-18  1:36 ` Minchan Kim
2017-04-18 21:32   ` David Rientjes
2017-04-19  0:14     ` Minchan Kim
2017-04-19 23:24       ` David Rientjes
2017-04-20  6:09         ` Minchan Kim
2017-05-01 21:34           ` [patch v2] " David Rientjes
2017-05-02  8:02             ` Michal Hocko
2017-05-02 20:41               ` David Rientjes
2017-05-03  6:15                 ` Michal Hocko
2017-05-03  7:06                   ` Michal Hocko
2017-05-03  8:49                     ` Michal Hocko
2017-05-03 22:52                       ` David Rientjes
2017-05-04 11:43                         ` Michal Hocko [this message]
2017-05-31 15:20             ` Michal Hocko
2017-06-02 20:36             ` Andrew Morton
2017-06-04 22:27               ` David Rientjes
2017-04-19  7:04     ` [patch] " Michal Hocko
2017-04-18  7:11 ` Michal Hocko

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