From patchwork Thu May 12 22:15:06 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johannes Weiner X-Patchwork-Id: 95392 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 074D1B6F11 for ; Fri, 13 May 2011 08:15:45 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932757Ab1ELWP1 (ORCPT ); Thu, 12 May 2011 18:15:27 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:40824 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932095Ab1ELWP0 (ORCPT ); Thu, 12 May 2011 18:15:26 -0400 Received: from 178-25-166-97-dynip.superkabel.de ([178.25.166.97] helo=dexter.home.cmpxchg.org) by zene.cmpxchg.org with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.72) (envelope-from ) id 1QKeA3-0001Uu-7y; Thu, 12 May 2011 22:15:11 +0000 Date: Fri, 13 May 2011 00:15:06 +0200 From: Johannes Weiner To: James Bottomley Cc: Pekka Enberg , Christoph Lameter , Mel Gorman , 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: <20110512221506.GM16531@cmpxchg.org> References: <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> <1305237882.2575.100.camel@mulgrave.site> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1305237882.2575.100.camel@mulgrave.site> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org 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? --- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html 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; }