Re: gettimeofday problem

From: Matti Aarnio (
Date: Mon Jun 24 2002 - 07:46:20 EST

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
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