linux-kernel - Re: [patch 2/2] mm, compaction: return failed migration target pages back to freelist

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Date:	Thu, 1 May 2014 14:02:00 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	vbabka@...e.cz, iamjoonsoo.kim@....com, gthelen@...gle.com,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch 2/2] mm, compaction: return failed migration target pages
 back to freelist

On Thu, 1 May 2014, Naoya Horiguchi wrote:

> > diff --git a/mm/compaction.c b/mm/compaction.c
> > --- a/mm/compaction.c
> > +++ b/mm/compaction.c
> > @@ -797,6 +797,19 @@ static struct page *compaction_alloc(struct page *migratepage,
> >  }
> >  
> >  /*
> > + * This is a migrate-callback that "frees" freepages back to the isolated
> > + * freelist.  All pages on the freelist are from the same zone, so there is no
> > + * special handling needed for NUMA.
> > + */
> > +static void compaction_free(struct page *page, unsigned long data)
> > +{
> > +	struct compact_control *cc = (struct compact_control *)data;
> > +
> > +	list_add(&page->lru, &cc->freepages);
> > +	cc->nr_freepages++;
> 
> With this change, migration_page() handles cc->nr_freepages consistently, so
> we don't have to run over freelist to update this count in update_nr_listpages()?
> 

Good optimization, I'll add it!
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