Re: [PATCH 09/31] mm, vmscan: by default have direct reclaim only shrink once per node

[Mel Gorman]

On Thu, Jul 07, 2016 at 10:43:22AM +0900, Joonsoo Kim wrote:
> > @@ -2600,6 +2593,16 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
> >  			classzone_idx--;
> >  
> >  		/*
> > +		 * Shrink each node in the zonelist once. If the zonelist is
> > +		 * ordered by zone (not the default) then a node may be
> > +		 * shrunk multiple times but in that case the user prefers
> > +		 * lower zones being preserved
> > +		 */
> > +		if (zone->zone_pgdat == last_pgdat)
> > +			continue;
> > +		last_pgdat = zone->zone_pgdat;
> > +
> > +		/*
> 
> After this change, compaction_ready() which uses zone information
> would be called with highest zone in node. So, if some lower zone in
> that node is compaction-ready, we cannot stop the reclaim.
> 

Yes. It only impacts direct reclaim but potentially it's an issue. I'll
fix it.

-- 
Mel Gorman
SUSE Labs