linux-kernel - Re: [PATCH 14/17] mm: Do not use atomic operations when releasing pages

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Message-ID: <20140501134713.GF23420@cmpxchg.org>
Date:	Thu, 1 May 2014 09:47:13 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Vlastimil Babka <vbabka@...e.cz>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/17] mm: Do not use atomic operations when releasing
 pages

On Thu, May 01, 2014 at 02:39:38PM +0100, Mel Gorman wrote:
> On Thu, May 01, 2014 at 09:29:22AM -0400, Johannes Weiner wrote:
> > On Thu, May 01, 2014 at 09:44:45AM +0100, Mel Gorman wrote:
> > > There should be no references to it any more and a parallel mark should
> > > not be reordered against us. Use non-locked varient to clear page active.
> > > 
> > > Signed-off-by: Mel Gorman <mgorman@...e.de>
> > > ---
> > >  mm/swap.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/mm/swap.c b/mm/swap.c
> > > index f2228b7..7a5bdd7 100644
> > > --- a/mm/swap.c
> > > +++ b/mm/swap.c
> > > @@ -854,7 +854,7 @@ void release_pages(struct page **pages, int nr, bool cold)
> > >  		}
> > >  
> > >  		/* Clear Active bit in case of parallel mark_page_accessed */
> > > -		ClearPageActive(page);
> > > +		__ClearPageActive(page);
> > 
> > Shouldn't this comment be removed also?
> 
> Why? We're still clearing the active bit.

Ah, I was just confused by the "parallel mark_page_accessed" part.  It
means parallel to release_pages(), but before the put_page_testzero(),
not parallel to the active bit clearing.
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