From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751725AbcGNBUs (ORCPT ); Wed, 13 Jul 2016 21:20:48 -0400 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:41761 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751574AbcGNBUr (ORCPT ); Wed, 13 Jul 2016 21:20:47 -0400 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 165.244.98.76 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 10.177.223.161 X-Original-MAILFROM: minchan@kernel.org Date: Thu, 14 Jul 2016 10:22:04 +0900 From: Minchan Kim To: Mel Gorman CC: Andrew Morton , Linux-MM , Johannes Weiner , LKML Subject: Re: [PATCH 1/4] mm, vmscan: Have kswapd reclaim from all zones if reclaiming and buffer_heads_over_limit -fix Message-ID: <20160714012204.GB23512@bbox> References: <1468404004-5085-1-git-send-email-mgorman@techsingularity.net> <1468404004-5085-2-git-send-email-mgorman@techsingularity.net> MIME-Version: 1.0 In-Reply-To: <1468404004-5085-2-git-send-email-mgorman@techsingularity.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB02/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2016/07/14 10:20:43, Serialize by Router on LGEKRMHUB02/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2016/07/14 10:20:43, Serialize complete at 2016/07/14 10:20:43 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 13, 2016 at 11:00:01AM +0100, Mel Gorman wrote: > Johannes reported that the comment about buffer_heads_over_limit in > balance_pgdat only made sense in the context of the patch. This patch > clarifies the reasoning and how it applies to 32 and 64 bit systems. > > This is a fix to the mmotm patch > mm-vmscan-have-kswapd-reclaim-from-all-zones-if-reclaiming-and-buffer_heads_over_limit.patch > > Suggested-by: Johannes Weiner > Signed-off-by: Mel Gorman > --- > mm/vmscan.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index d079210d46ee..21eae17ee730 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3131,12 +3131,13 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) > > /* > * If the number of buffer_heads exceeds the maximum allowed > - * then consider reclaiming from all zones. This is not > - * specific to highmem which may not exist but it is it is > - * expected that buffer_heads are stripped in writeback. > - * Reclaim may still not go ahead if all eligible zones > - * for the original allocation request are balanced to > - * avoid excessive reclaim from kswapd. > + * then consider reclaiming from all zones. This has a dual > + * purpose -- on 64-bit systems it is expected that > + * buffer_heads are stripped during active rotation. On 32-bit > + * systems, highmem pages can pin lowmem memory and shrinking > + * buffers can relieve lowmem pressure. Reclaim may still not It's good but I hope we can make it more clear. On 32-bit systems, highmem pages can pin lowmem pages storing buffer_heads so shrinking highmem pages can relieve lowmem pressure. If you don't think it's much readable compared to yours, feel free to drop. Thanks.