Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755257Ab0LJKhC (ORCPT ); Fri, 10 Dec 2010 05:37:02 -0500 Received: from gir.skynet.ie ([193.1.99.77]:55170 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755228Ab0LJKhA (ORCPT ); Fri, 10 Dec 2010 05:37:00 -0500 Date: Fri, 10 Dec 2010 10:36:42 +0000 From: Mel Gorman To: Minchan Kim Cc: Simon Kirby , KOSAKI Motohiro , Shaohua Li , Dave Hansen , Johannes Weiner , Andrew Morton , linux-mm , linux-kernel Subject: Re: [PATCH 3/6] mm: kswapd: Use the order that kswapd was reclaiming at for sleeping_prematurely() Message-ID: <20101210103642.GK20133@csn.ul.ie> References: <1291893500-12342-1-git-send-email-mel@csn.ul.ie> <1291893500-12342-4-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3025 Lines: 79 On Fri, Dec 10, 2010 at 10:16:19AM +0900, Minchan Kim wrote: > On Thu, Dec 9, 2010 at 8:18 PM, Mel Gorman wrote: > > Before kswapd goes to sleep, it uses sleeping_prematurely() to check if > > there was a race pushing a zone below its watermark. If the race > > happened, it stays awake. However, balance_pgdat() can decide to reclaim > > at a lower order if it decides that high-order reclaim is not working as > > Could you specify "order-0" explicitly instead of "a lower order"? > It makes more clear to me. > Done. > > expected. This information is not passed back to sleeping_prematurely(). > > The impact is that kswapd remains awake reclaiming pages long after it > > should have gone to sleep. This patch passes the adjusted order to > > sleeping_prematurely and uses the same logic as balance_pgdat to decide > > if it's ok to go to sleep. > > > > Signed-off-by: Mel Gorman > Reviewed-by: Minchan Kim > > A comment below. > > > --- > > ?mm/vmscan.c | ? 14 ++++++++++---- > > ?1 files changed, 10 insertions(+), 4 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index b4472a1..52e229e 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -2132,7 +2132,7 @@ static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced) > > ?} > > > > ?/* is kswapd sleeping prematurely? */ > > -static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) > > +static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) > > ?{ > > ? ? ? ?int i; > > ? ? ? ?unsigned long balanced = 0; > > @@ -2142,7 +2142,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) > > ? ? ? ?if (remaining) > > ? ? ? ? ? ? ? ?return 1; > > > > - ? ? ? /* If after HZ/10, a zone is below the high mark, it's premature */ > > + ? ? ? /* Check the watermark levels */ > > ? ? ? ?for (i = 0; i < pgdat->nr_zones; i++) { > > ? ? ? ? ? ? ? ?struct zone *zone = pgdat->node_zones + i; > > > > @@ -2427,7 +2427,13 @@ out: > > ? ? ? ? ? ? ? ?} > > ? ? ? ?} > > > > - ? ? ? return sc.nr_reclaimed; > > + ? ? ? /* > > + ? ? ? ?* Return the order we were reclaiming at so sleeping_prematurely() > > + ? ? ? ?* makes a decision on the order we were last reclaiming at. However, > > + ? ? ? ?* if another caller entered the allocator slow path while kswapd > > + ? ? ? ?* was awake, order will remain at the higher level > > + ? ? ? ?*/ > > + ? ? ? return order; > > ?} > > Please change return value description of balance_pgdat. > "Returns the number of pages which were actually freed" > Oops, done. Thanks -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/