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Date: Thu, 23 Jun 2016 09:35:01 +0100
From: Mel Gorman <mgorman@techsingularity.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>, Rik van Riel <riel@surriel.com>,
        Vlastimil Babka <vbabka@suse.cz>, Johannes Weiner <hannes@cmpxchg.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 16/27] mm: Move page mapped accounting to the node
Message-ID: <20160623083500.GO1868@techsingularity.net>
References: <1466518566-30034-1-git-send-email-mgorman@techsingularity.net>
 <1466518566-30034-17-git-send-email-mgorman@techsingularity.net>
 <20160621153206.2d72954b22dddee7f1d8b9a5@linux-foundation.org>
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On Tue, Jun 21, 2016 at 03:32:06PM -0700, Andrew Morton wrote:
> On Tue, 21 Jun 2016 15:15:55 +0100 Mel Gorman <mgorman@techsingularity.net> wrote:
> 
> > Reclaim makes decisions based on the number of pages that are mapped
> > but it's mixing node and zone information. Account NR_FILE_MAPPED and
> > NR_ANON_PAGES pages on the node.
> 
> <wading through rejects>
> 
> Boy, the difference between
> 
> 	__mod_zone_page_state(page_zone(page), ...
> 
> and
> 
> 	__mod_node_page_state(page_pgdat(page), ...
> 
> is looking subtle.  When and why to use one versus the other.  I'm not
> seeing any explanation of this in there but haven't yet looked hard.
> 

I'm not sure I see the problem. One applies for zone stats and the other
is for node. Granted, care is needed to use the correct one or a random
stat is updated instead of the one intended.


-- 
Mel Gorman
SUSE Labs

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Date: Thu, 23 Jun 2016 09:35:01 +0100
From: Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [PATCH 16/27] mm: Move page mapped accounting to the node
Message-ID: <20160623083500.GO1868@techsingularity.net>
References: <1466518566-30034-1-git-send-email-mgorman@techsingularity.net>
 <1466518566-30034-17-git-send-email-mgorman@techsingularity.net>
 <20160621153206.2d72954b22dddee7f1d8b9a5@linux-foundation.org>
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To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>, Rik van Riel <riel@surriel.com>, Vlastimil Babka <vbabka@suse.cz>, Johannes Weiner <hannes@cmpxchg.org>, LKML <linux-kernel@vger.kernel.org>

On Tue, Jun 21, 2016 at 03:32:06PM -0700, Andrew Morton wrote:
> On Tue, 21 Jun 2016 15:15:55 +0100 Mel Gorman <mgorman@techsingularity.net> wrote:
> 
> > Reclaim makes decisions based on the number of pages that are mapped
> > but it's mixing node and zone information. Account NR_FILE_MAPPED and
> > NR_ANON_PAGES pages on the node.
> 
> <wading through rejects>
> 
> Boy, the difference between
> 
> 	__mod_zone_page_state(page_zone(page), ...
> 
> and
> 
> 	__mod_node_page_state(page_pgdat(page), ...
> 
> is looking subtle.  When and why to use one versus the other.  I'm not
> seeing any explanation of this in there but haven't yet looked hard.
> 

I'm not sure I see the problem. One applies for zone stats and the other
is for node. Granted, care is needed to use the correct one or a random
stat is updated instead of the one intended.


-- 
Mel Gorman
SUSE Labs

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