Re: gettimeofday problem

[Pavel Machek]

Hi!

> > In this piece of code I convert seconds and microseconds in 
> > milliseconds. I think the problem is not in my code, in fact I wrote the 
> > following piece of code in Java, and it does not work too. In the for 
> > loop the 90% of times b > a while for 10% of times not.
> > 
> ...
> >                     long a = System.currentTimeMillis();
> >                     long b = System.currentTimeMillis();
> >                     if (a > b) {
> >                          System.out.println("Wrong!!!!!!!!!!!!!");
> >                     }
> 
> 
>    So in 10% of the cases, two successive calls yield time
>    rolling BACK ?
> 
>    I used  gettimeofday()  call, and compared the original data
>    from the code.
> 
>    At a modern uniprocessor machine I never get anything except
>    monotonously increasing time (TSC is used in betwen timer ticks
>    to supply time increase.)   At a dual processor machine, on
>    occasion I do get SAME value twice.   I have never seen time
>    rolling backwards.
> 
>    Uh..  correction:  216199245  0:-1  -- it did step backwards,
>    but only once within about 216 million gettimeofday() calls.
>    (I am running 2.4.19-pre8smp at the test box.)

Hmm, so it is buggy even for you. He probably has way crappier
hardware. Neptun chipsets and via chipsets have bugs in time
implementation.
									Pavel
-- 
(about SSSCA) "I don't say this lightly.  However, I really think that the U.S.
no longer is classifiable as a democracy, but rather as a plutocracy." --hpa