Re: [PATCH 5/8] mm: compaction: avoid overwork in migrate sync mode

[Mel Gorman]

On Mon, Nov 21, 2011 at 04:59:36PM -0500, Rik van Riel wrote:
> On 11/19/2011 02:54 PM, Andrea Arcangeli wrote:
> >Add a lightweight sync migration (sync == 2) mode that avoids overwork
> >so more suitable to be used by compaction to provide lower latency but
> 
> >--- a/mm/compaction.c
> >+++ b/mm/compaction.c
> >@@ -552,7 +552,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
> >  		nr_migrate = cc->nr_migratepages;
> >  		err = migrate_pages(&cc->migratepages, compaction_alloc,
> >  				(unsigned long)cc, false,
> >-				cc->sync);
> >+				cc->sync ? 2 : 0);
> 
> Great idea, but it would be good if these numbers got
> a symbolic name so people trying to learn the code can
> figure it out a little easier.
> 

I took the bulk of this patch and gave them symbolic names when trying
to reconcile the two series. I didn't take all this patch such as
varying the number of passes because even if that turns out to be of
benefit, it should be a separate patch.

-- 
Mel Gorman
SUSE Labs
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