Martin Pool <mbp@sourcefrog.net> writes:
> On 2 Aug 2002, Philip Martin <philip@codematters.co.uk> wrote:
> > Mix <mixtim@acm.org> writes:
> >
> > > > $ ./a.out
> > > > 43043: 374436 < 374437
> > > > 524931: 904361 < 904362
> > > > 778682: 184323 < 184324
> > > > 887643: 304306 < 304307
> > > > 1014906: 444288 < 444289
> > > > 1187703: 634262 < 634263
> > > > 1296827: 754245 < 754246
> > > > 1315004: 774241 < 774242
> > > > 1442331: 914224 < 914225
> > > > 1596600: 84201 < 84202
> > > > so yes it goes backwards.
> > >
> > >
> > > I hate to tell you guys this, but you have screwy hardware or an OS
> > > bug here as this isn't possible. I use gettimeofday() a bit at work
> > > for some performance testing and this has never happened to me.
>
> One reason why this can happen is that on machines with variable clock
> rates (e.g. Intel's SpeedStep, common on laptops), the kernel gets
> confused about the relative speeds of the realtime clock and the CPU's
> cycle counter. This happens on my T20 Thinkpad and it gives X11 fits.
Heh. My box is a Thinkpad T20. I guess that explains that.
> You might like to try using the "notsc" boot option (on 2.4.18 at
> least.) There are some other reasons why it might happen, and this
> won't fix all of them.
Cool, thanks for the info.
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Received on Sat Aug 3 19:15:09 2002