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    SubjectRe: NFS client latencies
    Ingo Molnar <mingo@elte.hu> wrote:
    >
    >
    > * Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
    >
    > > > The 7 ms are spent in this loop:
    > >
    > > Which is basically confirming what the guys from Bull already told me,
    > > namely that the radix tree tag stuff is much less efficient that what
    > > we've got now. I never saw their patches, though, so I was curious to
    > > try it for myself.
    >
    > i think the numbers are being misinterpreted. I believe this patch is a
    > big step forward. The big thing is that nfs_list_add_request() is O(1)
    > now - while _a single request addition to the sorted list_ triggered the
    > 1+ msec latency in Lee's previous trace.

    Well. The radix-tree approach's best-case is probably quite a lot worse
    than the list-based approach's best-case. It hits a lot more cachelines
    and involves a lot more code.

    But of course the radix-tree's worst-case will be far better than list's.

    And presumably that list-based code rarely hits the worst-case, else it
    would have been changed by now.

    -
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