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    SubjectRe: async I/O seems to be blocking on 2.6.15
    On Fri, 3 Nov 2006, Jens Axboe wrote:

    > Try to time it (visual output of the app is not very telling, and it's
    > buffered) and then apply some profiling.

    OK, a little more info. I added gettimeofday() calls after each call
    to io_submit(), put the timevals in an array, and after everything was
    done computed the difference between each timeval and the program start
    time, as well as the deltas. I got this:

    0: 0.080s
    1: 0.086s 0.006s
    2: 0.102s 0.016s
    3: 0.111s 0.008s
    4: 0.118s 0.007s
    5: 0.134s 0.015s
    6: 0.141s 0.006s
    7: 0.148s 0.006s
    8: 0.158s 0.009s
    9: 0.164s 0.006s
    96: 1.036s 0.007s
    97: 1.044s 0.007s
    98: 1.147s 0.102s
    99: 1.155s 0.008s

    98 appears to be an aberration. Perhaps three of the times on an
    average run are around a tenth of a second; all of the others are
    pretty steady at 7 or 8 microseconds. So, it's basically linear in
    its time consumption.

    Does 7 microseconds seem a bit excessive for an io_submit (and a


    Brent Baccala
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