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    SubjectRe: [PATCH] modules: Use a better scheme for refcounting
    Eric Dumazet wrote:
    > Rusty Russell a écrit :
    >> Hi Eric,
    >> I like this patch! The plan was always to create a proper dynamic
    >> per-cpu
    >> allocator which used the normal per-cpu offsets, but I think module
    >> refcounts
    >> are worthwhile as a special case.
    >> Any chance I can ask you look at the issue of full dynamic per-cpu
    >> allocation? The problem of allocating memory which is laid out precisely
    >> as the original per-cpu alloc is vexing on NUMA, and probably requires
    >> reserving virtual address space and remapping into it, but the rewards
    >> would be maximally-efficient per-cpu accessors, and getting rid of that
    >> boutique allocator in module.c.
    > You mean using alloc_percpu() ? Problem is that current implementation
    > is expensive, since it is using
    > an extra array of pointers (struct percpu_data). On x86_64, that means
    > at least a 200% space increase
    > over the solution of using 4 bytes in the static percpu zone. We
    > probably can change this to dynamic
    > per-cpu as soon as Mike or Christopher finish their work on new dynamic
    > per-cpu implementation ?

    Yes, the zero-based percpu variables followed by the cpu_alloc patch should
    provide this and shrink the code quite well, including in some cases removing
    locking requirements (because the resultant instructions will be atomic.)

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      Last update: 2008-05-16 15:45    [W:0.020 / U:14.808 seconds]
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