Re: [PATCH 16/27] mm: Move page mapped accounting to the node

[Mel Gorman]

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@xxxxxxxxxxxxxxxxxxx> 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