From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762366Ab2DLJcN (ORCPT ); Thu, 12 Apr 2012 05:32:13 -0400 Received: from cantor2.suse.de ([195.135.220.15]:42810 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762320Ab2DLJcM (ORCPT ); Thu, 12 Apr 2012 05:32:12 -0400 Date: Thu, 12 Apr 2012 10:32:09 +0100 From: Mel Gorman To: Rik van Riel Cc: Andrew Morton , Konstantin Khlebnikov , Hugh Dickins , Ying Han , Linux-MM , LKML Subject: Re: [PATCH 0/3] Removal of lumpy reclaim V2 Message-ID: <20120412093209.GM3789@suse.de> References: <1334162298-18942-1-git-send-email-mgorman@suse.de> <4F85BC8E.3020400@redhat.com> <20120411175215.GI3789@suse.de> <4F85C813.2050206@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <4F85C813.2050206@redhat.com> 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 On Wed, Apr 11, 2012 at 02:06:11PM -0400, Rik van Riel wrote: > On 04/11/2012 01:52 PM, Mel Gorman wrote: > >On Wed, Apr 11, 2012 at 01:17:02PM -0400, Rik van Riel wrote: > > >>Next step: get rid of __GFP_NO_KSWAPD for THP, first > >>in the -mm kernel > >> > > > >Initially the flag was introduced because kswapd reclaimed too > >aggressively. One would like to believe that it would be less of a problem > >now but we must avoid a situation where the CPU and reclaim cost of kswapd > >exceeds the benefit of allocating a THP. > > Since kswapd and the direct reclaim code now use > the same conditionals for calling compaction, > the cost ought to be identical. > kswapd has different retry logic for reclaim and can stay awake if there are continual calls to wakeup_kswapd() setting pgdat->kswapd_max_order and kswapd makes forward progress. It's not identical enough that I would express 100% confidence that it will be free of problems. -- Mel Gorman SUSE Labs