Re: gettimeofday() goes backwards on FreeBSD 4.9

On Fri, 28 Nov 2003, Tom Lane wrote:

> "Nigel J. Andrews" <nandrews(at)investsystems(dot)co(dot)uk> writes:
> > On Fri, 28 Nov 2003, Tom Lane wrote:
> >> "Nigel J. Andrews" <nandrews(at)investsystems(dot)co(dot)uk> writes:
> > On an Intel Linux 2.4.18 I get them quite often, 25 in 1'45", but they
> > are all just a microsecond.
> >>
> >> What do you mean by "just a microsecond"?
>
> > I mean it's always a "out of order tv_usec..." line and the difference is
> > 1us. That is a.out gives:
>
> > out of order tv_usec: 1070065862 374978, prev 1070065862 374979
> > out of order tv_usec: 1070065867 814300, prev 1070065867 814301
>
> Fascinating. I'd call that a bug too, but evidently one with a
> different mechanism than the BSD issue we are chasing.
>
> FWIW, I have not seen any failures in a fair amount of runtime on
> a 2.4.18 (Red Hat 8.0) kernel here, running on a Dell P4. What is
> the hardware platform you're using?

Ah, I have made a mistake. It's only a 2.2.18 kernal. Dual SMP P-III, perhaps
that's the issue there.

And on the FreeBSD system I've got this:

$ time ./a.out 2>&1 | tee a.txt
out of order tv_sec: 1070066197 273140, prev 1070066195 721010
out of order tv_usec: 1070066197 273140, prev 1070066195 721010
out of order tv_sec: 1070067322 116061, prev 1070067320 440490
out of order tv_usec: 1070067322 116061, prev 1070067320 440490
out of order tv_sec: 1070067833 514969, prev 1070067831 755019
out of order tv_usec: 1070067833 514969, prev 1070067831 755019
^C

real 38m53.026s
user 6m13.953s
sys 32m6.589s

So not very often there.

--
Nigel