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

[Mathew Kanner]

On Nov 28, Marc G. Fournier wrote:
> 
> 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 ...

FreeBSD 5.2 (up, no acpia):
	I get the errors only when I force heavy load and swapping.

- kern.timecounter.hardware: TSC
- FreeBSD tube.xx.xx5.2-BETA FreeBSD 5.2-BETA #6: Fri Nov 28 14:20:25 EST 2003 xx at xx i386

FreeBSD 4.8 (up):
	Didn't see the error on a nominally loaded server, I tested
for about ten minutes.

- kern.timecounter.hardware: i8254
- FreeBSD yy.yy.yy.yy4.8-STABLE FreeBSD 4.8-STABLE #0: Wed Jul 30 13:51:04 EDT 2003 xx at xx i386

	--Mat

-- 
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