From: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
To: David Rientjes <rientjes@google.com>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>, Tejun Heo <tj@kernel.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map
Date: Thu, 5 Mar 2015 15:20:51 -0800 [thread overview]
Message-ID: <20150305232051.GD30570@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1503051352540.25375@chino.kir.corp.google.com>
On 05.03.2015 [13:58:27 -0800], David Rientjes wrote:
> On Fri, 6 Mar 2015, Michael Ellerman wrote:
>
> > > > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> > > > index 0257a7d659ef..24de29b3651b 100644
> > > > --- a/arch/powerpc/mm/numa.c
> > > > +++ b/arch/powerpc/mm/numa.c
> > > > @@ -958,9 +958,17 @@ void __init initmem_init(void)
> > > >
> > > > memblock_dump_all();
> > > >
> > > > + /*
> > > > + * zero out the possible nodes after we parse the device-tree,
> > > > + * so that we lower the maximum NUMA node ID to what is actually
> > > > + * present.
> > > > + */
> > > > + nodes_clear(node_possible_map);
> > > > +
> > > > for_each_online_node(nid) {
> > > > unsigned long start_pfn, end_pfn;
> > > >
> > > > + node_set(nid, node_possible_map);
> > > > get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
> > > > setup_node_data(nid, start_pfn, end_pfn);
> > > > sparse_memory_present_with_active_regions(nid);
> > >
> > > This seems a bit strange, node_possible_map is supposed to be a superset
> > > of node_online_map and this loop is iterating over node_online_map to set
> > > nodes in node_possible_map.
> >
> > Yeah. Though at this point in boot I don't think it matters that the
> > two maps are out-of-sync temporarily.
> >
> > But it would simpler to just set the possible map to be the online
> > map. That would also maintain the invariant that the possible map is
> > always a superset of the online map.
> >
> > Or did I miss a detail there (sleep deprived parent mode).
> >
>
> I think reset_numa_cpu_lookup_table() which iterates over the possible
> map, and thus only a subset of nodes now, may be concerning.
I think you are confusing the CPU online map and the NUMA node online
map. reset_numa_cpu_lookup_table is a cpu->node mapping, only called at
boot-time, and iterates over the CPU online map, which is unaltered by
my patch.
> I'm not sure why this is being proposed as a powerpc patch and now a
> patch for mem_cgroup_css_alloc().
I think mem_cgroup_css_alloc() is just an example of a larger issue. I
should have made that clearer in my changelog. Even if we change
mem_cgroup_css_alloc(), I think we want to fix the node_possible_map on
powerpc to be accurate at run-time, just like x86 does.
> In other words, why do we have to allocate for all possible nodes? We
> should only be allocating for online nodes in N_MEMORY with mem
> hotplug disabled initially and then have a mem hotplug callback
> implemented to alloc_mem_cgroup_per_zone_info() for nodes that
> transition from memoryless -> memory. The extra bonus is that
> alloc_mem_cgroup_per_zone_info() need never allocate remote memory and
> the TODO in that function can be removed.
This is a good idea, and seems like it can be a follow-on parallel patch
to the one I provided (which does need an updated changelog now).
Thanks,
Nish
next prev parent reply other threads:[~2015-03-05 23:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-05 18:05 [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map Nishanth Aravamudan
2015-03-05 21:16 ` David Rientjes
2015-03-05 21:48 ` Michael Ellerman
2015-03-05 21:58 ` David Rientjes
2015-03-05 22:08 ` Tejun Heo
2015-03-05 22:18 ` Tejun Heo
2015-03-05 23:21 ` Nishanth Aravamudan
2015-03-05 23:24 ` Tejun Heo
2015-03-05 23:20 ` Nishanth Aravamudan [this message]
2015-03-05 23:17 ` Nishanth Aravamudan
2015-03-05 23:15 ` Nishanth Aravamudan
2015-03-05 23:29 ` David Rientjes
2015-03-06 5:27 ` [PATCH v2] powerpc/numa: set node_possible_map to only node_online_map during boot Nishanth Aravamudan
2015-03-06 11:29 ` Raghavendra K T
2015-03-09 23:55 ` Michael Ellerman
2015-03-10 23:50 ` [PATCH v3] " Nishanth Aravamudan
2015-03-05 22:13 ` [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map Tejun Heo
2015-03-05 23:27 ` Nishanth Aravamudan
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