From: James Bottomley Subject: Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0 Date: Thu, 12 May 2011 17:04:41 -0500 Message-ID: <1305237882.2575.100.camel@mulgrave.site> References: <1305127773-10570-1-git-send-email-mgorman@suse.de> <1305127773-10570-4-git-send-email-mgorman@suse.de> <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> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Christoph Lameter , Mel Gorman , Andrew Morton , Colin King , Raghavendra D Prabhu , Jan Kara , Chris Mason , Rik van Riel , Johannes Weiner , linux-fsdevel , linux-mm , linux-kernel , linux-ext4 To: Pekka Enberg Return-path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:47645 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758736Ab1ELWE5 (ORCPT ); Thu, 12 May 2011 18:04:57 -0400 In-Reply-To: <1305230652.2575.72.camel@mulgrave.site> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 ... By the way, I stripped off all the patches, so this is a plain old 2.6.38.6 kernel with the default FC15 config. James --- diff --git a/mm/vmscan.c b/mm/vmscan.c index 0665520..1bdea7d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2255,6 +2255,8 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, if (remaining) return true; + return false; + /* Check the watermark levels */ for (i = 0; i < pgdat->nr_zones; i++) { struct zone *zone = pgdat->node_zones + i;