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    SubjectRe: [RFC PATCH] ia64: convert to dynamic percpu allocator
    Yu, Fenghua wrote:
    >> Yu, Fenghua wrote:
    >>> After cloning from
    >>> git://, kernel
    >>> built with CONFIG_DISCONTIGMEM=y boots ok.
    >>> After pulling from review-ia64, kernel built with
    >>> CONFIG_DISCONTIGMEM=y can not boot on ia64. After loading kernel and
    >>> initrd, system hangs and doesn't show anything on serial port.
    >> Heh, I didn't really expect it to work that easily either. The code
    >> builds but is completely untested (I can't test them). Can you try to
    >> track it down? Serial console should be up and running at that point,
    >> no?
    >> Thanks.
    > IA64 kernel boots hit this in mm/percpu.c
    > BUG_ON(ai->unit_size < size_sum);
    > ai->unit_size is PERCPU_PAGE_SIZE which is 64K on IA64. size_sum is
    > relatively smaller than 64K.
    > PAGE_SIZE or the bigger one between the current definition and
    > PAGE_SIZE?


    * Is ai->reserved_size necessary for ia64? This is necessary if
    there's linking range restriction when loading modules.
    ai->reserved_size guarantees that all static module percpu variables
    are allocated in the first chunk which will be in the linear address
    range and very close to __per_cpu_start. If ai->reserved_size is
    not set, these areas are likely to end up high in the vmalloc area.

    For example, x86_64 assumes 32bit relocations should be enough to
    link module symbols and thus needs to set reserved_size but x86_32
    can link to the whole 32bit space and thus can leave reserved_size
    at zero.

    * After determining the above, we can set ai->dyn_size to be

    ai->dyn_size = min(ai->unit_size - ai->static_size - ai->reserved_size,

    Would the above work?

    > Even with the above PAGE_SIZE changes, the kernel still reports
    > warning from 952: WARN_ON(chunk->immutable) and then panic.

    Hah... strange. Can you please attach full boot log? This is
    dicontig configuration, right?



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