From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id A48CB440905 for ; Fri, 14 Jul 2017 08:39:45 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id c81so9027803wmd.10 for ; Fri, 14 Jul 2017 05:39:45 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f197si2228294wmg.81.2017.07.14.05.39.43 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 14 Jul 2017 05:39:44 -0700 (PDT) Date: Fri, 14 Jul 2017 14:39:41 +0200 From: Michal Hocko Subject: Re: [PATCH 3/9] mm, page_alloc: do not set_cpu_numa_mem on empty nodes initialization Message-ID: <20170714123940.GN2618@dhcp22.suse.cz> References: <20170714080006.7250-1-mhocko@kernel.org> <20170714080006.7250-4-mhocko@kernel.org> <20170714094810.ftthctfz33artwh2@suse.de> <20170714105003.GE2618@dhcp22.suse.cz> <20170714123242.zepgecug2kdolhky@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170714123242.zepgecug2kdolhky@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: linux-mm@kvack.org, Andrew Morton , Johannes Weiner , Vlastimil Babka , LKML On Fri 14-07-17 13:32:42, Mel Gorman wrote: > On Fri, Jul 14, 2017 at 12:50:04PM +0200, Michal Hocko wrote: > > On Fri 14-07-17 10:48:10, Mel Gorman wrote: > > > On Fri, Jul 14, 2017 at 10:00:00AM +0200, Michal Hocko wrote: > > > > From: Michal Hocko > > > > > > > > __build_all_zonelists reinitializes each online cpu local node for > > > > CONFIG_HAVE_MEMORYLESS_NODES. This makes sense because previously memory > > > > less nodes could gain some memory during memory hotplug and so the local > > > > node should be changed for CPUs close to such a node. It makes less > > > > sense to do that unconditionally for a newly creaded NUMA node which is > > > > still offline and without any memory. > > > > > > > > Let's also simplify the cpu loop and use for_each_online_cpu instead of > > > > an explicit cpu_online check for all possible cpus. > > > > > > > > Signed-off-by: Michal Hocko > > > > --- > > > > mm/page_alloc.c | 6 ++---- > > > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > > index 7746824a425d..ebc3311555b1 100644 > > > > --- a/mm/page_alloc.c > > > > +++ b/mm/page_alloc.c > > > > @@ -5096,10 +5096,8 @@ static int __build_all_zonelists(void *data) > > > > > > > > build_zonelists(pgdat); > > > > } > > > > - } > > > > > > > > #ifdef CONFIG_HAVE_MEMORYLESS_NODES > > > > - for_each_possible_cpu(cpu) { > > > > /* > > > > * We now know the "local memory node" for each node-- > > > > * i.e., the node of the first zone in the generic zonelist. > > > > @@ -5108,10 +5106,10 @@ static int __build_all_zonelists(void *data) > > > > * secondary cpus' numa_mem as they come on-line. During > > > > * node/memory hotplug, we'll fixup all on-line cpus. > > > > */ > > > > - if (cpu_online(cpu)) > > > > + for_each_online_cpu(cpu) > > > > set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu))); > > > > - } > > > > #endif > > > > + } > > > > > > > > > > This is not as clear a benefit. For each online node, we now go through > > > all online CPUs once per node. There would be some rationale for using > > > for_each_online_cpu. > > > > I am not sure I understand. I am using for_each_online_cpu... > > Yes, but within a loop that looks like > > for_each_online_node(nid) > ... > for_each_online_cpu(cpu) > > Or maybe you aren't because we are looking at different baselines. I had > minor fuzz and conflicts applying the series. The current mmotm after this patch looks like this if (self && !node_online(self->node_id)) { build_zonelists(self); } else { for_each_online_node(nid) { pg_data_t *pgdat = NODE_DATA(nid); build_zonelists(pgdat); } #ifdef CONFIG_HAVE_MEMORYLESS_NODES /* * We now know the "local memory node" for each node-- * i.e., the node of the first zone in the generic zonelist. * Set up numa_mem percpu variable for on-line cpus. During * boot, only the boot cpu should be on-line; we'll init the * secondary cpus' numa_mem as they come on-line. During * node/memory hotplug, we'll fixup all on-line cpus. */ for_each_online_cpu(cpu) set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu))); #endif } So for_each_online_cpu is called outside of the for_each_online_node. Have a look at git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git branch attempts/zonlists-build-simplification -- Michal Hocko SUSE Labs -- 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