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From:	"Ralf Habacker" <Ralf DOT Habacker AT freenet DOT de>
To:	"Cygwin" <cygwin AT sources DOT redhat DOT com>
Subject:	gettimeofday() does not returns usec resolution
Date:	Wed, 23 Jan 2002 08:20:48 +0100
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Hi,

for kde2 we are building a profiler lib for profiling complex c++ applications (currently found in the cvs areas of
kde-cygwin.sf.net (http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/kde-cygwin/profiler/)
using the high resolution timer of native windows (about usec resolution).

This lib could be use for easy profiling of any c++ application and libs like cygwin.dll and so on.

While adding unix support (and cygwin) for this lib, I noticed, that the gettimeofday() function returns only a
resolution of 10ms (the time slice resolution) but mostly other unix os returns a resolution in the usec region.  I
have appended a testcase for this.

Has anyone address this problem already. I have looked int the cygwin and list and found the only topic
 http://sources.redhat.com/ml/cygwin/2001-12/msg00201.html

In http://www-106.ibm.com/developerworks/library/l-rt1/ there is a detailed instruction how to use the hugh
resolution counter. .

$ cat timeofday.c
 #include <sys/time.h>

int main()
{
        struct timeval tp;
        long a,b;

        gettimeofday(&tp,0);
        a = ((unsigned)tp.tv_sec)*1000000+((unsigned)tp.tv_usec);

        printf("timestamp (us): %d\n",a);
        usleep(1000);
        gettimeofday(&tp,0);
        b = ((unsigned)tp.tv_sec)*1000000+((unsigned)tp.tv_usec);
        printf("timestamp (us): %d (diff) %d\n",b,b-a);
}


Ralf Habacker


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