Programming

Hi,

I have a program where I fork few child jobs and call execvp to run another jobs. I use wait to wait for any job to get complete.
Requirement is I need to know the actual time taken by child job during execution.
I thought of calculating the time just before forking and after wait, but this does not gives me the actual results. I get a difference of few milliseconds using my approach.

You can solve your problem with system call "gettimeofday" with below steps.

The steps are following:

1) The gettimeofday is called when child process begins executing.
2) The gettimeofday is called when child process finishes.
3) Then subs two results.

Best regards,
Iliyan Varshilov

Code:

     #include <sys/times.h>

      clock_t times(struct tms *buffer);
Where struct tms is:
        struct tms {
               clock_t     tms_utime;      /* user time */
               clock_t     tms_stime;      /* system time */"
               clock_t     tms_cutime;     /* user time, children */
               clock_t     tms_cstime;     /* system time, children */
           };

struct tms has times for child processes, and is the de facto standard way to get this information.

Hi...

First read time stamp just before spawning the child process.
and read the time stamp in the child process(not in parent before wait or some other places), Calculate the difference(I hope you can do it simply)...

One thing... How can you say... you are getting different results?
(There will be difference between different runnings of the program. It is dependant on the current system image... like load on system, physical memory available on the system at that time, VM present at that time etc.)

I hope you understood what is happening and what to do...

Happy programming...
Chandu.