Time jumping on both 4.x and 5.x ...

From: Marc G. Fournier (scrappy_at_hub.org)
Date: 11/29/03

  • Next message: Kris Kennaway: "Re: Time jumping on both 4.x and 5.x ..." 
    Date: Fri, 28 Nov 2003 21:32:30 -0400 (AST)
To: freebsd-current@freebsd.org

    In trying to isolate an issue where the PostgreSQL 'explain analyze' is
    showing "odd results" (namely, negative time estimates on queries), Tom
    Lane wrote a quick C program to test gettimeofday() (program attached) ...
    the results on a 4.9-PRERELEASE kernel of Sep 20 14:16:48 ADT 2003 shows:

    neptune# time ./timetest
    out of order tv_sec: 1070068479 99040, prev 1070069174 725235
    out of order tv_usec: 1070068479 99040, prev 1070069174 725235
    out of order tv_sec: 1070069175 19687, prev 1070068479 99040
    out of order tv_usec: 1070069175 19687, prev 1070068479 99040
    out of order tv_sec: 1070068499 99377, prev 1070069194 625573
    out of order tv_usec: 1070068499 99377, prev 1070069194 625573
    out of order tv_sec: 1070069194 808542, prev 1070068499 99377
    ^C1.171u 23.461s 0:24.68 99.7% 5+169k 1+0io 0pf+0w

    One person on the list has tried the same script on a 5.2 kernel, and
    reports seeing similar results, but after a longer period of time (~30min)
    ...

    In most (all?) cases, the offset appears to be ~+/-695 secs ... Linux ppl
    on the list, running the same problem, seem to be able to reproduce the
    issue, except they are only finding differences of 1 microsecond, and then
    only on older kernels (2.2.x, apparently) ... those running newer Linux
    kernels are reporting a clean run ...

    Known problem? 

    ----
Marc G. Fournier           Hub.Org Networking Services (http://www.hub.org)
Email: scrappy@hub.org           Yahoo!: yscrappy              ICQ: 7615664

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  • Next message: Kris Kennaway: "Re: Time jumping on both 4.x and 5.x ..."

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