/*	nulltime.c
	Measures the time for a low priority process to execute a 
	certain number of operations.
	This is used in a pair of runs, one with an unloaded system, and 
	one with a loaded system.

	Utilization = (1 - unloaded/loaded) x 100 %

	Written by David Horton	6-Jan-92
*/

#include <unistd.h>
#include <stdio.h>
#ifndef _INCLUDE_POSIX_SOURCE
#define _INCLUDE_POSIX_SOURCE
#endif
#ifndef _INCLUDE_HPUX_SOURCE
#define _INCLUDE_HPUX_SOURCE
#endif
#include <time.h>
#include <errno.h>

#define NICE 19

main (int argc, char *argv[]) {
	int		loops = 10000000;		/* basic # loops */
	int		repeats = 1;	   	/*additional multiplier,if loops insufficient*/
	struct timeval	now;			/* time at the present moment */
	struct timeval	then;			/* when our time expires */
	struct timezone	us;				/* unused */
	int		l, r;					/* counters */

	if (argc > 3) {
		fprintf(stderr,"Usage: %s [loops [2nd_multiplier]]\n", argv[0]);
		exit (1);
	}

	if (argc >= 2) {				/* they gave us loops */
		loops = atoi(argv[1]);		
	}
	if (argc >= 3) {				/* they gave us repeat */
		repeats = atoi(argv[2]);		
	}

	if (gettimeofday(&then, &us)){	/* what was the time at the start */
		perror("gettimeofday");
		exit (errno);
	}

#	ifdef DEBUG
	printf("now %d.%6d, then %d.%6d\n", 
		now.tv_sec, now.tv_usec, then.tv_sec, then.tv_usec);
#	endif

	if (nice(NICE) < 0) {					/* set priority low */
		perror("nice");
		exit (errno);
	}

	for (r = 0; r < repeats; r++)
		for (l = 0; l < loops; l++)
			;

	if (gettimeofday(&now, &us)){	/* when is that in the future */
		perror("gettimeofday");
		exit (errno);
	}

	if (then.tv_usec > now.tv_usec) {
		now.tv_usec += 1000000;		/* avoid negatives */
		now.tv_sec--;
	}

#	ifdef DEBUG
	printf("now %d.%6d, then %d.%6d\n", 
		now.tv_sec, now.tv_usec, then.tv_sec, then.tv_usec);
#	endif

	printf("%d.%06d secs for %d x %d operations\n",
		now.tv_sec - then.tv_sec, now.tv_usec - then.tv_usec,
		repeats, loops);

	exit(0);
}