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    SubjectRe: [PATCH] online CPU before memory failed in pcpu_alloc_pages()

    >>>> --- a/mm/percpu.c
    >>>> +++ b/mm/percpu.c
    >>>> @@ -714,13 +714,29 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
    >>>
    >>> In linux-next, Tejun has gone and moved pcpu_alloc_pages() into the new
    >>> mm/percpu-vm.c. So either
    >>
    >> This has gone into Linus' tree today ...
    >>
    >
    > Hmm, a comment here.
    >
    > Recently, Lee Schermerhorn developed
    >
    > numa-introduce-numa_mem_id-effective-local-memory-node-id-fix2.patch
    >
    > Then, you can use cpu_to_mem() instead of cpu_to_node() to find the
    > nearest available node.
    > I don't check cpu_to_mem() is synchronized with NUMA hotplug but
    > using cpu_to_mem() rather than adding
    > =
    >
    > + if ((nid == -1) ||
    > + !(node_zonelist(nid, GFP_KERNEL)->_zonerefs->zone))
    > + nid = numa_node_id();
    > +
    > ==
    >
    > is better.


    Yes. I can use cpu_to_mem(). only some little difference during
    CPU online: 1st cpu within memoryless node gets memory from current
    node or the node to which the cpu0 belongs,


    But I have a question about the patch:

    numa-slab-use-numa_mem_id-for-slab-local-memory-node.patch,




    @@ -2968,9 +2991,23 @@ static int __build_all_zonelists(void *d
    ...

    - for_each_possible_cpu(cpu)
    + for_each_possible_cpu(cpu) {
    setup_pageset(&per_cpu(boot_pageset, cpu), 0);
    ...

    +#ifdef CONFIG_HAVE_MEMORYLESS_NODES
    + if (cpu_online(cpu))
    + cpu_to_mem(cpu) = local_memory_node(cpu_to_node(cpu));
    +#endif


    Look at the last two lines, suppose that memory is onlined before CPUs,
    where will cpu_to_mem(cpu) be set to the right nodeid for the last
    onlined cpu ? Does that CPU always get memory from the node including
    cpu0 for slab allocator where cpu_to_mem() is used ?



    thanks,
    -minskey





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