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From: Joonsoo Kim <js1304@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Sachin Sant <sachinp@linux.vnet.ibm.com>,
	Michal Hocko <mhocko@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Mel Gorman <mgorman@suse.de>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Andrew Morton <akpm@linux-foundation.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Christopher Lameter <cl@linux.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Kirill Tkhai <ktkhai@virtuozzo.com>,
	Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 1/3] powerpc/numa: Set numa_node for all possible cpus
Date: Mon, 16 Mar 2020 17:15:19 +0900
Message-ID: <CAAmzW4ME_WLYZPCt4+82RNKstv-H=LK5MKGGJR=6ha-ALS+FSw@mail.gmail.com> (raw)
In-Reply-To: <06be5908-9af6-2892-0333-e9558b2cf474@suse.cz>

2020년 3월 13일 (금) 오후 8:38, Vlastimil Babka <vbabka@suse.cz>님이 작성:
>
> On 3/13/20 12:04 PM, Srikar Dronamraju wrote:
> >> I lost all the memory about it. :)
> >> Anyway, how about this?
> >>
> >> 1. make node_present_pages() safer
> >> static inline node_present_pages(nid)
> >> {
> >> if (!node_online(nid)) return 0;
> >> return (NODE_DATA(nid)->node_present_pages);
> >> }
> >>
> >
> > Yes this would help.
>
> Looks good, yeah.
>
> >> 2. make node_to_mem_node() safer for all cases
> >> In ppc arch's mem_topology_setup(void)
> >> for_each_present_cpu(cpu) {
> >>  numa_setup_cpu(cpu);
> >>  mem_node = node_to_mem_node(numa_mem_id());
> >>  if (!node_present_pages(mem_node)) {
> >>   _node_numa_mem_[numa_mem_id()] = first_online_node;
> >>  }
> >> }
> >>
> >
> > But here as discussed above, we miss the case of possible but not present nodes.
> > For such nodes, the above change may not update, resulting in they still
> > having 0. And node 0 can be only possible but not present.

Oops, I don't read full thread so miss the case.

> So is there other way to do the setup so that node_to_mem_node() returns an
> online+present node when called for any possible node?

Two changes seems to be sufficient.

1. initialize all node's _node_numa_mem_[] = first_online_node in
mem_topology_setup()
2. replace the node with online+present node for _node_to_mem_node_[]
in set_cpu_numa_mem().

 static inline void set_cpu_numa_mem(int cpu, int node)
 {
        per_cpu(_numa_mem_, cpu) = node;
+       if (!node_present_pages(node))
+               node = first_online_node;
        _node_numa_mem_[cpu_to_node(cpu)] = node;
 }
 #endif

With these two change, we can safely call node_to_mem_node() anywhere.

Thanks.

  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 11:02 [PATCH 0/3] Offline memoryless cpuless node 0 Srikar Dronamraju
2020-03-11 11:02 ` [PATCH 1/3] powerpc/numa: Set numa_node for all possible cpus Srikar Dronamraju
2020-03-11 11:57   ` Michal Hocko
2020-03-12  5:27     ` Srikar Dronamraju
2020-03-12  8:23       ` Sachin Sant
2020-03-12  9:30         ` Vlastimil Babka
2020-03-12 13:14           ` Srikar Dronamraju
2020-03-12 13:51             ` Vlastimil Babka
2020-03-12 16:13               ` Srikar Dronamraju
2020-03-12 16:41                 ` Vlastimil Babka
2020-03-13  9:47                   ` Joonsoo Kim
2020-03-13 11:04                     ` Srikar Dronamraju
2020-03-13 11:38                       ` Vlastimil Babka
2020-03-16  8:15                         ` Joonsoo Kim [this message]
2020-03-13 11:22                   ` Srikar Dronamraju
2020-03-16  9:06                   ` Michal Hocko
2020-03-17 13:44                     ` Vlastimil Babka
2020-03-17 14:01                       ` Michal Hocko
2020-03-11 11:02 ` [PATCH 2/3] powerpc/numa: Prefer node id queried from vphn Srikar Dronamraju
2020-03-11 11:02 ` [PATCH 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline Srikar Dronamraju
2020-03-15 14:20   ` Christopher Lameter
2020-03-16  8:54     ` Michal Hocko
2020-03-18  7:50       ` Srikar Dronamraju
2020-03-18 18:57       ` Christopher Lameter

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