From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa0-f52.google.com (mail-oa0-f52.google.com [209.85.219.52]) by kanga.kvack.org (Postfix) with ESMTP id 07BD56B0031 for ; Wed, 19 Feb 2014 12:55:59 -0500 (EST) Received: by mail-oa0-f52.google.com with SMTP id i4so513975oah.11 for ; Wed, 19 Feb 2014 09:55:59 -0800 (PST) Received: from e33.co.us.ibm.com (e33.co.us.ibm.com. [32.97.110.151]) by mx.google.com with ESMTPS id f6si1071315obr.85.2014.02.19.09.55.59 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 19 Feb 2014 09:55:59 -0800 (PST) Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 19 Feb 2014 10:55:58 -0700 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id A28C91FF001A for ; Wed, 19 Feb 2014 10:55:55 -0700 (MST) Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by b03cxnp08025.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s1JHttqq37748972 for ; Wed, 19 Feb 2014 18:55:55 +0100 Received: from d03av02.boulder.ibm.com (localhost [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s1JHrm6h001596 for ; Wed, 19 Feb 2014 10:53:48 -0700 Date: Wed, 19 Feb 2014 09:53:39 -0800 From: Nishanth Aravamudan Subject: Re: [RFC PATCH] mm: exclude memory less nodes from zone_reclaim Message-ID: <20140219175339.GG27108@linux.vnet.ibm.com> References: <20140219082313.GB14783@dhcp22.suse.cz> <1392829383-4125-1-git-send-email-mhocko@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392829383-4125-1-git-send-email-mhocko@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, David Rientjes , LKML On 19.02.2014 [18:03:03 +0100], Michal Hocko wrote: > We had a report about strange OOM killer strikes on a PPC machine > although there was a lot of swap free and a tons of anonymous memory > which could be swapped out. In the end it turned out that the OOM was > a side effect of zone reclaim which wasn't doesn't unmap and swapp out > and so the system was pushed to the OOM. Although this sounds like a bug > somewhere in the kswapd vs. zone reclaim vs. direct reclaim interaction > numactl on the said hardware suggests that the zone reclaim should > have been set in the first place: > node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 > node 0 size: 0 MB > node 0 free: 0 MB > node 2 cpus: > node 2 size: 7168 MB > node 2 free: 6019 MB > node distances: > node 0 2 > 0: 10 40 > 2: 40 10 > > So all the CPUs are associated with Node0 which doesn't have any memory > while Node2 contains all the available memory. Node distances cause an > automatic zone_reclaim_mode enabling. > > Zone reclaim is intended to keep the allocations local but this doesn't > make any sense on the memory less nodes. So let's exlcude such nodes > for init_zone_allows_reclaim which evaluates zone reclaim behavior and > suitable reclaim_nodes. > > Signed-off-by: Michal Hocko > --- > I haven't got to testing this so I am sending this as an RFC for now. > But does this look reasonable? > > mm/page_alloc.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > 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]? Thanks, Nish -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org