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    SubjectRe: [patch 14/22] pollfs: pollable futex
    Ulrich Drepper wrote:
    > On 5/2/07, Davi Arnaut <davi@haxent.com.br> wrote:
    >> thread A:
    >> int fd = plfutex(addr, 0);
    >> do
    >> poll(fdset+fd);
    >> process network events
    >> queue obj to thread B
    >> if fd:
    >> job processed
    >>
    >> thread B:
    >> wait_job();
    >> process_job();
    >> raise_event(addr);
    >
    > This is not the model you can implement with your changes. Because
    > every single waiter is woken you need one thread listening for the
    > jobs and then distribute the work. Otherwise you have thundering
    > herds of threads and only one gets to do some work.
    >

    NO! Every single waiter of the _file descriptor_ is waked, not of the futex.
    One can associate N fds with a single futex address. FUTEX_WAKE with
    nproc = 1 will only wake one of the file descriptors. Its up to the user
    to decide if he wants a broadcast or not.

    Have you seen the email where I told you exactly this?

    >> It simple as is, there is no need to overdesign.
    >
    > There is no reason to go with a limited, too-simple minded design if
    > we've already identified a much better design. The fact that poll is
    > used today does not excuse piling on more and more code which makes
    > additional functions which don't fit into the poll framework barely
    > work. Plus, poll/epoll itself is a problem.
    >
    epoll itself is a problem?! sorry, but i didn't know that. Care to
    elaborate?
    I really need some guidance here. I just want to unify the epoll for various
    event sources. It seems a lot of people like this, just look at the
    popularity
    of libevent and other "unifying" event loops.

    I don't think we need another epoll clone.

    > And you cannot talk about little changes and no "overdesign". You
    > have 22 patches for all this. It's not just limited to futexes, it's
    > the whole thing which IMO is unnecessary ballast going forward.
    davi@karmic:~/git/linux-2.6$ find patches/ -name *.patch |grep -v
    syscall | wc -l
    10

    davi@karmic:~/git/linux-2.6$ find patches/ -name *.patch |grep -v
    syscall |grep futex
    patches/pollfs-futex-async-wait.patch
    patches/pollfs-futex.patch

    --
    Davi Arnaut

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