From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 537066B0087 for ; Thu, 9 Dec 2010 20:16:21 -0500 (EST) Received: by iwn1 with SMTP id 1so4646400iwn.37 for ; Thu, 09 Dec 2010 17:16:19 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1291893500-12342-4-git-send-email-mel@csn.ul.ie> References: <1291893500-12342-1-git-send-email-mel@csn.ul.ie> <1291893500-12342-4-git-send-email-mel@csn.ul.ie> Date: Fri, 10 Dec 2010 10:16:19 +0900 Message-ID: Subject: Re: [PATCH 3/6] mm: kswapd: Use the order that kswapd was reclaiming at for sleeping_prematurely() From: Minchan Kim Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Simon Kirby , KOSAKI Motohiro , Shaohua Li , Dave Hansen , Johannes Weiner , Andrew Morton , linux-mm , linux-kernel List-ID: 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. > 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. > --- > =A0mm/vmscan.c | =A0 14 ++++++++++---- > =A01 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, unsign= ed long balanced) > =A0} > > =A0/* is kswapd sleeping prematurely? */ > -static int sleeping_prematurely(pg_data_t *pgdat, int order, long remain= ing) > +static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remai= ning) > =A0{ > =A0 =A0 =A0 =A0int i; > =A0 =A0 =A0 =A0unsigned long balanced =3D 0; > @@ -2142,7 +2142,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, i= nt order, long remaining) > =A0 =A0 =A0 =A0if (remaining) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0return 1; > > - =A0 =A0 =A0 /* If after HZ/10, a zone is below the high mark, it's prem= ature */ > + =A0 =A0 =A0 /* Check the watermark levels */ > =A0 =A0 =A0 =A0for (i =3D 0; i < pgdat->nr_zones; i++) { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0struct zone *zone =3D pgdat->node_zones + = i; > > @@ -2427,7 +2427,13 @@ out: > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} > =A0 =A0 =A0 =A0} > > - =A0 =A0 =A0 return sc.nr_reclaimed; > + =A0 =A0 =A0 /* > + =A0 =A0 =A0 =A0* Return the order we were reclaiming at so sleeping_pre= maturely() > + =A0 =A0 =A0 =A0* makes a decision on the order we were last reclaiming = at. However, > + =A0 =A0 =A0 =A0* if another caller entered the allocator slow path whil= e kswapd > + =A0 =A0 =A0 =A0* was awake, order will remain at the higher level > + =A0 =A0 =A0 =A0*/ > + =A0 =A0 =A0 return order; > =A0} Please change return value description of balance_pgdat. "Returns the number of pages which were actually freed" --=20 Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org