linux-kernel - Re: [PATCH 03/10] mm: vmscan: Flatten kswapd priority loop

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Date:	Thu, 21 Mar 2013 16:38:59 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linux-MM <linux-mm@...ck.org>, Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/10] mm: vmscan: Flatten kswapd priority loop

On Thu 21-03-13 15:26:02, Mel Gorman wrote:
> On Thu, Mar 21, 2013 at 03:54:58PM +0100, Michal Hocko wrote:
> > > Signed-off-by: Mel Gorman <mgorman@...e.de>
> > > ---
> > >  mm/vmscan.c | 86 ++++++++++++++++++++++++++++++-------------------------------
> > >  1 file changed, 42 insertions(+), 44 deletions(-)
> > > 
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index 182ff15..279d0c2 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -2625,8 +2625,11 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
> > >  /*
> > >   * kswapd shrinks the zone by the number of pages required to reach
> > >   * the high watermark.
> > > + *
> > > + * Returns true if kswapd scanned at least the requested number of
> > > + * pages to reclaim.
> > 
> > Maybe move the comment about not rising priority in such case here to be
> > clear what the return value means. Without that the return value could
> > be misinterpreted that kswapd_shrink_zone succeeded in shrinking might
> > be not true.
> 
> I moved the comment.

Thanks

> > Or maybe even better, leave the void there and add bool *raise_priority
> > argument here so the decision and raise_priority are at the same place.
> > 
> 
> The priority is raised if kswapd failed to reclaim from any of the unbalanced
> zone. If raise_priority is moved inside kswapd_shrink_zone then it can
> only take one zone into account.

Right you are. I am blind.

-- 
Michal Hocko
SUSE Labs
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