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    SubjectRe: [PATCH] eventpoll : Suppress a short lived lock from struct file
    On Mon, 11 Jul 2005, Eric Dumazet wrote:

    > Peter Zijlstra a écrit :
    >> On Mon, 2005-07-11 at 09:18 +0200, Eric Dumazet wrote:
    >> Have you tested the impact of this change on big SMP/NUMA machines?
    >> I hate to see an Altrix crashing to its knees :-)
    > I tested on a small NUMA machine (2 nodes), with a epoll enabled application,
    > that use around 100 epoll ctl per second.
    > Of course, one may write a special benchmark on a BIG SMP/NUMA machine that
    > defeat these patch, using thousands of epoll ctl per second, but, a normal
    > (well written ?)
    > epoll application doesnt constantly add/remove epoll ctl.
    > Should we waste 8 bytes per 'struct file' for a very unlikely micro benchmark
    > ?

    Eric, I can't really say I like this one. Not at least after extensive
    tests run on top of it. You are asking to add a bottleneck to save 8 bytes
    on an entity that taken alone in more than 120 bytes. Consider that when
    you have a "struct file" allocated, the cost on the system is not only the
    struct itself, but all the allocations associated with it. For example, if
    you consider that a case where you might feel a "struct file" pressure is
    when you have hundreds of thousands of network connections, the 8 bytes
    saved compared to all the buffers associated with those sockets boils down
    to basically nothing.

    - Davide
     \ /
      Last update: 2005-07-11 16:09    [W:0.019 / U:27.760 seconds]
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