#include <u.h>
#include <libc.h>

enum {
	M	= 1000000,
};

extern	void	_cycles(vlong*);

static uvlong order = 0x0001020304050607ULL;

static void
be2vlong(vlong *to, uchar *f)
{
	uchar *t, *o;
	int i;

	t = (uchar*)to;
	o = (uchar*)&order;
	for(i = 0; i < sizeof order; i++)
		t[o[i]] = f[i];
}

vlong
mynsec(void)
{
	uchar b[8];
	vlong t;
	int fd;

	t = 0;
	if((fd = open("/dev/bintime", OREAD)) >= 0)
	if(pread(fd, b, sizeof b, 0) == sizeof b)
		be2vlong(&t, b);
	close(fd);
	return t;
}


void
checkwired(int mach)
{
	char buf[128];
	int fd;

	for(;;){
		sleep(1);	
		fd = open("/dev/mach", OREAD);
		if(fd == -1)
			/* old kernel; just hope */
			return;
		buf[0] = ' ';
		buf[read(fd, buf, sizeof buf)] = 0;
		close(fd);
		if(atoi(buf) == mach)
			return;
		sysfatal("wire fails");
	}
}

void
procwired(int mach)
{
	char buf[128];
	int fd;

	snprint(buf, sizeof buf, "/proc/%d/ctl", getpid());
	fd = open(buf, OWRITE);
	if(fprint(fd, "wired %d", mach) < 0)
		sysfatal("procwired: %r");
	close(fd);
	checkwired(mach);	/* don't trust kernel yet */
}

uvlong
cyclehz(void)
{
	char buf[128], *f[30];
	int fd, n;
	uvlong u;

	fd = open("/dev/cputype", OREAD);
	if(fd == -1)
		return 1;
	n = read(fd, buf, sizeof buf-1);
	if(n == -1)
		return 1;
	buf[n] = 0;
	n = tokenize(buf, f, nelem(f));
	if(n == 0)
		return 1;
	u = strtoull(f[n-1], 0, 0);
	if(u == 0)
		return 1;
	return M*u;
}

void
main(void)
{
	vlong t, v, hz;

	procwired(0);		/* don't mix rdtsc between maches */

	t = -mynsec();
	t += mynsec();
	print("nsec latency %lldns\n", t);

	t = -mynsec();
	t += mynsec();
	print("nsec latency %lldns\n", t);

	hz = cyclehz();
	print("cycle hz = %lld\n", hz);

	_cycles(&t);
	_cycles(&v);
	print("cycles latency %lld cycles; %lld ns\n", v - t, ((v-t)*M*1000)/hz);

	_cycles(&t);
	_cycles(&v);
	print("cycles latency %lld cycles; %lld ns\n", v - t, ((v-t)*M*1000)/hz);

	exits("");
}