Re: gettimeofday problem

Matti Aarnio
2002-06-24T12:46:22Z

On Mon, Jun 24, 2002 at 12:20:02PM +0200, Salvatore D'Angelo wrote:
> 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.)

/Matti Aarnio