Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933664Ab3CUPut (ORCPT ); Thu, 21 Mar 2013 11:50:49 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38821 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755677Ab3CUPus (ORCPT ); Thu, 21 Mar 2013 11:50:48 -0400 Date: Thu, 21 Mar 2013 16:50:45 +0100 From: Michal Hocko To: Mel Gorman Cc: Linux-MM , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , Johannes Weiner , dormando , Satoru Moriya , LKML Subject: Re: [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdat based on reclaim progress Message-ID: <20130321155045.GS6094@dhcp22.suse.cz> References: <1363525456-10448-1-git-send-email-mgorman@suse.de> <1363525456-10448-5-git-send-email-mgorman@suse.de> <20130321153231.GP6094@dhcp22.suse.cz> <20130321154730.GK1878@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130321154730.GK1878@suse.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2226 Lines: 50 On Thu 21-03-13 15:47:31, Mel Gorman wrote: > On Thu, Mar 21, 2013 at 04:32:31PM +0100, Michal Hocko wrote: > > On Sun 17-03-13 13:04:10, Mel Gorman wrote: > > > In the past, kswapd makes a decision on whether to compact memory after the > > > pgdat was considered balanced. This more or less worked but it is late to > > > make such a decision and does not fit well now that kswapd makes a decision > > > whether to exit the zone scanning loop depending on reclaim progress. > > > > > > This patch will compact a pgdat if at least the requested number of pages > > > were reclaimed from unbalanced zones for a given priority. If any zone is > > > currently balanced, kswapd will not call compaction as it is expected the > > > necessary pages are already available. > > > > > > Signed-off-by: Mel Gorman > > > --- > > > mm/vmscan.c | 52 +++++++++++++++++++++------------------------------- > > > 1 file changed, 21 insertions(+), 31 deletions(-) > > > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > index 279d0c2..7513bd1 100644 > > > --- a/mm/vmscan.c > > > +++ b/mm/vmscan.c > > > @@ -2694,8 +2694,11 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > > > > > > do { > > > unsigned long lru_pages = 0; > > > + unsigned long nr_to_reclaim = 0; > > > unsigned long nr_reclaimed = sc.nr_reclaimed; > > > + unsigned long this_reclaimed; > > > bool raise_priority = true; > > > + bool pgdat_needs_compaction = true; > > > > I am confused. We don't want to compact for order == 0, do we? > > > > No, but an order check is made later which I felt it was clearer. You are > the second person to bring it up so I'll base the initialisation on order. Dohh. Yes compact_pgdat is called only if order != 0. I was so focused on pgdat_needs_compaction that I've missed it. Both checks use (order && pgdat_needs_compaction) so initialization based on order would be probably better for readability. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/