Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758302Ab1EMKaQ (ORCPT ); Fri, 13 May 2011 06:30:16 -0400 Received: from cantor.suse.de ([195.135.220.2]:37307 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757363Ab1EMKaO (ORCPT ); Fri, 13 May 2011 06:30:14 -0400 Date: Fri, 13 May 2011 11:30:09 +0100 From: Mel Gorman To: Johannes Weiner Cc: James Bottomley , Pekka Enberg , Christoph Lameter , Andrew Morton , Colin King , Raghavendra D Prabhu , Jan Kara , Chris Mason , Rik van Riel , linux-fsdevel , linux-mm , linux-kernel , linux-ext4 Subject: Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0 Message-ID: <20110513103009.GD3569@suse.de> References: <1305213359.2575.46.camel@mulgrave.site> <1305214993.2575.50.camel@mulgrave.site> <1305215742.27848.40.camel@jaguar> <1305225467.2575.66.camel@mulgrave.site> <1305229447.2575.71.camel@mulgrave.site> <1305230652.2575.72.camel@mulgrave.site> <1305237882.2575.100.camel@mulgrave.site> <20110512221506.GM16531@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20110512221506.GM16531@cmpxchg.org> 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: 2046 Lines: 51 On Fri, May 13, 2011 at 12:15:06AM +0200, Johannes Weiner wrote: > On Thu, May 12, 2011 at 05:04:41PM -0500, James Bottomley wrote: > > On Thu, 2011-05-12 at 15:04 -0500, James Bottomley wrote: > > > Confirmed, I'm afraid ... I can trigger the problem with all three > > > patches under PREEMPT. It's not a hang this time, it's just kswapd > > > taking 100% system time on 1 CPU and it won't calm down after I unload > > > the system. > > > > Just on a "if you don't know what's wrong poke about and see" basis, I > > sliced out all the complex logic in sleeping_prematurely() and, as far > > as I can tell, it cures the problem behaviour. I've loaded up the > > system, and taken the tar load generator through three runs without > > producing a spinning kswapd (this is PREEMPT). I'll try with a > > non-PREEMPT kernel shortly. > > > > What this seems to say is that there's a problem with the complex logic > > in sleeping_prematurely(). I'm pretty sure hacking up > > sleeping_prematurely() just to dump all the calculations is the wrong > > thing to do, but perhaps someone can see what the right thing is ... > > I think I see the problem: the boolean logic of sleeping_prematurely() > is odd. If it returns true, kswapd will keep running. So if > pgdat_balanced() returns true, kswapd should go to sleep. > > This? > You're right. > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 2b701e0..092d773 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2261,7 +2261,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, > * must be balanced > */ > if (order) > - return pgdat_balanced(pgdat, balanced, classzone_idx); > + return !pgdat_balanced(pgdat, balanced, classzone_idx); > else > return !all_zones_ok; > } -- Mel Gorman 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/