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    SubjectRe: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?
    On Tue, Feb 20, 2007 at 01:42:42PM -0500, Josef Sipek (jsipek@fsl.cs.sunysb.edu) wrote:
    > A better thing would be to use getuid - it turns into just a return with a
    > memory dereference). I ran it on my 3.06GHz P4 (HT, but only UP kernel),
    > PREEMPT, HZ=1000...
    >
    > 3.290196 0.470588 0.402614 0.396078 0.393464 0.396078 0.386928 0.386928 0.386928 0.386928
    > 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928
    > 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928
    > 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928

    I got following.

    delta for syscall: 9112 cycles = 2.977778 us
    delta for syscall: 1224 cycles = 0.400000 us
    delta for syscall: 1071 cycles = 0.350000 us
    delta for syscall: 1054 cycles = 0.344444 us
    delta for syscall: 1054 cycles = 0.344444 us

    Likely first overhead related to cache population or gamma-ray radiation.
    If it happens only one (it does in my test), then everything is ok I
    think. Bert, how frequently you get that long recvfrom()?

    --
    Evgeniy Polyakov
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