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    SubjectRe: [patch 3/4] net: Percpufy frequently used variables -- proto.sockets_allocated
    Ravikiran G Thirumalai a écrit :
    > Change the atomic_t sockets_allocated member of struct proto to a
    > per-cpu counter.
    > Signed-off-by: Pravin B. Shelar <>
    > Signed-off-by: Ravikiran Thirumalai <>
    > Signed-off-by: Shai Fultheim <>
    Hi Ravikiran

    If I correctly read this patch, I think there is a scalability problem.

    On a big SMP machine, read_sockets_allocated() is going to be a real killer.

    Say we have 128 Opterons CPUS in a box.

    You'll need to bring 128 cache lines (plus 8*128 bytes to read the 128
    pointers inside percpu structure)

    I think a solution 'a la percpu_counter' is preferable, or even better a
    dedicated per_cpu with a threshold management (see mm/swap.c , function
    vm_acct_memory() to see how vm_committed_space is updated without too bad SMP

    Thank you


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      Last update: 2006-01-27 09:57    [W:0.021 / U:2.068 seconds]
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