/*
 * from agruen - 2009 05 28
 *
 * Test time slices given to each process
 */
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/stat.h>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#undef WITH_PER_PROCESS_SLICES

struct msg {
	long mtype;
	long nivcsw;
	long utime;
};

int msqid;

void report_to_parent(int dummy) {
	static long old_nivcsw, old_utime;
	long utime;
	struct rusage usage;
	struct msg msg;

	getrusage(RUSAGE_SELF, &usage);

	utime = usage.ru_utime.tv_sec * 1000000 + usage.ru_utime.tv_usec;

	msg.mtype = 1;
	msg.nivcsw = usage.ru_nivcsw - old_nivcsw;
	msg.utime = utime - old_utime;
	msgsnd(msqid, &msg, sizeof(msg) - sizeof(long), 0);

	old_nivcsw = usage.ru_nivcsw;
	old_utime = utime;
}

void worker(void) {
	struct sigaction sa;

	sa.sa_handler = report_to_parent;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = 0;
	sigaction(SIGALRM, &sa, NULL);

	while (1)
		/* do nothing */ ;
}

void sleeper(void) {

	while (1) {
		usleep(1000);
	}
}

int main(int argc, char *argv[])
{
	int n, nproc;
	pid_t *pid;

	if (argc != 2) {
		fprintf(stderr, "Usage: %s <number-of-processes>\n", argv[0]);
		return 1;
	}
	
	msqid = msgget(IPC_PRIVATE, S_IRUSR | S_IWUSR);

	nproc = atoi(argv[1]);
	pid = malloc(nproc * sizeof(pid_t));
	for (n = 0; n < nproc; n++) {
		pid[n] = fork();
		if (pid[n] == 0)
			worker();
	}

	/* Fork sleeper(s) */
	for (n = 0; n < (nproc + 7)/8; n++)
		if (fork() == 0)
			sleeper();
	for(;;) {
		long avg_slice = 0, avg_utime = 0;

		sleep(1);
		for (n = 0; n < nproc; n++)
			kill(pid[n], SIGALRM);
		for (n = 0; n < nproc; n++) {
			struct msg msg;
			double slice;

			msgrcv(msqid, &msg, sizeof(msg) - sizeof(long), 0, 0);
			slice = 0.001 * msg.utime /
				        (msg.nivcsw ? msg.nivcsw : 1);
#ifdef WITH_PER_PROCESS_SLICES
			printf("%6.1f ", slice);
#endif

			avg_slice += slice;
			avg_utime += msg.utime;
		}

		printf("    avg slice: %5.2f utime: %f",
				(double) avg_slice / nproc,
				(double) avg_utime / nproc);
		printf("\n");
	}

	return 0;
}