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    SubjectRe: PROBLEM: select() on TCP socket sleeps for 1 tick even if data available
    OK, 2.4.0 kernel installed, and a new set of numbers:

    test kernel ping-pongs/s. @ total CPU util w/SOL_NDELAY
    sample (2 skts) 2.2.18 100 @ 0.1% 800 @ 1%
    sample (1 skt) 2.2.18 8000 @ 100% 8000 @ 50%
    real app 2.2.18 100 @ 0.1% 800 @ 1%

    sample (2 skts) 2.4.0 8000 @ 50% 8000 @ 50%
    sample (1 skt) 2.4.0 10000 @ 50% 10000 @ 50%
    real app 2.4.0 1200 @ 50% 1200 @ 50%

    real app Windows 2K 4000 @ 100%

    The two points that still seem strange to me are:

    1. The 1 socket case is still 25% faster than the 2 socket case in 2.4.0
    (in 2.2.18 the 1 socket case was 10x faster).

    2. Linux never devotes more than 50% of the CPU (average over a long
    run) to the two processes (25% to each process, with the rest of the
    time idle).

    I'd really love to show that Linux is a viable platform for our SW, and
    I think it would be doable if I could figure out how to get the other
    50% of my CPU involved. An "strace -rT" of the real app on 2.4.0 looks
    like this for each ping/pong.

    0.052371 send(7, "\0\0\0
    \177\0\0\1\3243\0\0\0\2\4\236\216\341\0\0\v\277"..., 32, 0) = 32
    <0.000529>
    0.000882 rt_sigprocmask(SIG_BLOCK, ~[], [RT_0], 8) = 0 <0.000021>
    0.000242 rt_sigprocmask(SIG_SETMASK, [RT_0], NULL, 8) = 0
    <0.000021>
    0.000173 select(8, [3 4 6 7], NULL, NULL, NULL) = 1 (in [6])
    <0.000047>
    0.000328 read(6, "\0\0\0 ", 4) = 4 <0.000031>
    0.000179 read(6,
    "\177\0\0\1\3242\0\0\0\2\4\236\216\341\0\0\7\327\177\0\0"..., 28) = 28
    <0.000075>

    --
    Mike Lindner
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