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    SubjectRe: [PATCH] mm/alloc: fallback to first node if the wanted node offline
    On Tue 11-12-18 16:05:58, Pingfan Liu wrote:
    > On Mon, Dec 10, 2018 at 8:37 PM Michal Hocko <mhocko@kernel.org> wrote:
    > >
    > > On Fri 07-12-18 16:56:27, Michal Hocko wrote:
    > > > On Fri 07-12-18 22:27:13, Pingfan Liu wrote:
    > > > [...]
    > > > > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
    > > > > index 1308f54..4dc497d 100644
    > > > > --- a/arch/x86/mm/numa.c
    > > > > +++ b/arch/x86/mm/numa.c
    > > > > @@ -754,18 +754,23 @@ void __init init_cpu_to_node(void)
    > > > > {
    > > > > int cpu;
    > > > > u16 *cpu_to_apicid = early_per_cpu_ptr(x86_cpu_to_apicid);
    > > > > + int node, nr;
    > > > >
    > > > > BUG_ON(cpu_to_apicid == NULL);
    > > > > + nr = cpumask_weight(cpu_possible_mask);
    > > > > +
    > > > > + /* bring up all possible node, since dev->numa_node */
    > > > > + //should check acpi works for node possible,
    > > > > + for_each_node(node)
    > > > > + if (!node_online(node))
    > > > > + init_memory_less_node(node);
    > > >
    > > > I suspect there is no change if you replace for_each_node by
    > > > for_each_node_mask(nid, node_possible_map)
    > > >
    > > > here. If that is the case then we are probably calling
    > > > free_area_init_node too early. I do not see it yet though.
    > >
    > > OK, so it is not about calling it late or soon. It is just that
    > > node_possible_map is a misnomer and it has a different semantic than
    > > I've expected. numa_nodemask_from_meminfo simply considers only nodes
    > > with some memory. So my patch didn't really make any difference and the
    > > node stayed uninialized.
    > >
    > > In other words. Does the following work? I am sorry to wildguess this
    > > way but I am not able to recreate your setups to play with this myself.
    > >
    > No problem. Yeah, in order to debug the patch, you need a numa machine
    > with a memory-less node. And unlucky, the patch can not work either by
    > grub bootup or kexec -l boot. There is nothing, just silent. I will
    > dig into numa_register_memblks() to figure out the problem.

    I do not have such a machine handy. Anyway, can you post the full serial
    console log. Maybe I can infer something. It is quite weird that this
    patch would make an existing situation any worse.
    --
    Michal Hocko
    SUSE Labs

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