Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751589AbaBSXGJ (ORCPT ); Wed, 19 Feb 2014 18:06:09 -0500 Received: from e37.co.us.ibm.com ([32.97.110.158]:57228 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080AbaBSXGH (ORCPT ); Wed, 19 Feb 2014 18:06:07 -0500 Date: Wed, 19 Feb 2014 15:05:58 -0800 From: Nishanth Aravamudan To: David Rientjes Cc: Michal Hocko , linux-mm@kvack.org, LKML Subject: Re: [RFC PATCH] mm: exclude memory less nodes from zone_reclaim Message-ID: <20140219230558.GA28062@linux.vnet.ibm.com> References: <20140219082313.GB14783@dhcp22.suse.cz> <1392829383-4125-1-git-send-email-mhocko@suse.cz> <20140219175339.GG27108@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux 3.11.0-15-generic (x86_64) User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021923-7164-0000-0000-0000063BD107 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19.02.2014 [13:56:00 -0800], David Rientjes wrote: > On Wed, 19 Feb 2014, Nishanth Aravamudan wrote: > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 3e953f07edb0..4a44bdc7a8cf 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1855,7 +1855,7 @@ static void __paginginit init_zone_allows_reclaim(int nid) > > > { > > > int i; > > > > > > - for_each_online_node(i) > > > + for_each_node_state(i, N_HIGH_MEMORY) > > > if (node_distance(nid, i) <= RECLAIM_DISTANCE) > > > node_set(i, NODE_DATA(nid)->reclaim_nodes); > > > else > > > @@ -4901,7 +4901,8 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size, > > > > > > pgdat->node_id = nid; > > > pgdat->node_start_pfn = node_start_pfn; > > > - init_zone_allows_reclaim(nid); > > > + if (node_state(nid, N_HIGH_MEMORY)) > > > + init_zone_allows_reclaim(nid); > > > > I'm still new to this code, but isn't this saying that if a node has no > > memory, then it shouldn't reclaim from any node? But, for a memoryless > > node to ensure progress later if reclaim is necessary, it *must* reclaim > > from other nodes? So wouldn't we want to set reclaim_nodes() in that > > case to node_states[N_MEMORY]? > > > > The only time when pgdat->reclaim_nodes or zone_reclaim_mode matters is > when iterating through a zonelist for page allocation and a memoryless > node should never appear in a zonelist for page allocation, so this is > just preventing setting zone_reclaim_mode unnecessarily because the only > nodes with > RECLAIM_DISTANCE to another node are memoryless. So this > patch is fine as long as it gets s/N_HIGH_MEMORY/N_MEMORY/. Ah yes, sorry, I've been looking at this code perhaps too much and going a bit cross-eyed! I wonder if we should also put some comments in? But Acked-by: Nishanth Aravamudan Tested-by: Nishanth Aravamudan Thanks, Nish -- 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/