From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755041AbbINJAf (ORCPT ); Mon, 14 Sep 2015 05:00:35 -0400 Received: from relay.parallels.com ([195.214.232.42]:60641 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753272AbbINJAe (ORCPT ); Mon, 14 Sep 2015 05:00:34 -0400 Date: Mon, 14 Sep 2015 12:00:10 +0300 From: Vladimir Davydov To: Raghavendra K T CC: , , , , , , , , , , , , Subject: Re: [PATCH 1/2] mm: Replace nr_node_ids for loop with for_each_node in list lru Message-ID: <20150914090010.GB30743@esperanza> References: <1441737107-23103-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <1441737107-23103-2-git-send-email-raghavendra.kt@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1441737107-23103-2-git-send-email-raghavendra.kt@linux.vnet.ibm.com> X-ClientProxiedBy: US-EXCH2.sw.swsoft.com (10.255.249.46) To MSK-EXCH1.sw.swsoft.com (10.67.48.55) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Wed, Sep 09, 2015 at 12:01:46AM +0530, Raghavendra K T wrote: > The functions used in the patch are in slowpath, which gets called > whenever alloc_super is called during mounts. > > Though this should not make difference for the architectures with > sequential numa node ids, for the powerpc which can potentially have > sparse node ids (for e.g., 4 node system having numa ids, 0,1,16,17 > is common), this patch saves some unnecessary allocations for > non existing numa nodes. > > Even without that saving, perhaps patch makes code more readable. Do I understand correctly that node 0 must always be in node_possible_map? I ask, because we currently test lru->node[0].memcg_lrus to determine if the list is memcg aware. > > Signed-off-by: Raghavendra K T > --- > mm/list_lru.c | 23 +++++++++++++++-------- > 1 file changed, 15 insertions(+), 8 deletions(-) > > diff --git a/mm/list_lru.c b/mm/list_lru.c > index 909eca2..5a97f83 100644 > --- a/mm/list_lru.c > +++ b/mm/list_lru.c > @@ -377,7 +377,7 @@ static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware) > { > int i; > > - for (i = 0; i < nr_node_ids; i++) { > + for_each_node(i) { > if (!memcg_aware) > lru->node[i].memcg_lrus = NULL; So, we don't explicitly initialize memcg_lrus for nodes that are not in node_possible_map. That's OK, because we allocate lru->node using kzalloc. However, this partial nullifying in case !memcg_aware looks confusing IMO. Let's drop it, I mean something like this: static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware) { int i; if (!memcg_aware) return 0; for_each_node(i) { if (memcg_init_list_lru_node(&lru->node[i])) goto fail; } Thanks, Vladimir