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    SubjectRe: [RFC][PATCH 6/8] mm: handle_speculative_fault()
    On Fri, 8 Jan 2010, Linus Torvalds wrote:

    > That's a huge jump. It's clear that the spinlock-based rwsem's simply
    > suck. The speculation gets rid of some additional mmap_sem contention,
    > but at least for two sockets it looks like the rwsem implementation was
    > the biggest problem by far.

    I'd say that the ticket lock sucks for short critical sections vs. a
    simple spinlock since it forces the cacheline into shared mode.

    > Of course, larger numbers of sockets will likely change the situation, but
    > at the same time I do suspect that workloads designed for hundreds of
    > cores will need to try to behave better than that benchmark anyway ;)

    Can we at least consider a typical standard business server, dual quad
    core hyperthreaded with 16 "cpus"? Cacheline contention will increase
    significantly there.

    > Because let's face it - if your workload does several million page faults
    > per second, you're just doing something fundamentally _wrong_.

    You may just want to get your app running and its trying to initialize
    its memory in parallel on all threads. Nothing wrong with that.

     \ /
      Last update: 2010-01-08 18:47    [W:0.020 / U:80.420 seconds]
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