optimize portclock.  unused stats cost ~100 cycles/tick/processor
(about 8-10%) on an 8 core machine.

Reference: /n/atom/patch/applied2013/portclockopt
Date: Sat Dec 28 16:55:21 CET 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/port/portfns.h	Sat Dec 28 16:48:24 2013
+++ /sys/src/nix/port/portfns.h	Sat Dec 28 16:48:24 2013
@@ -351,7 +351,7 @@
 void		sysprocsetup(Proc*);
 void		timeradd(Timer*);
 void		timerdel(Timer*);
-void		timerintr(Ureg*, vlong);
+void		timerintr(Ureg*, void*);
 void		timerset(uvlong);
 void		timersinit(void);
 ulong		tk2ms(ulong);
--- /sys/src/nix/port/portclock.c	Sat Dec 28 16:48:25 2013
+++ /sys/src/nix/port/portclock.c	Sat Dec 28 16:48:26 2013
@@ -14,9 +14,6 @@
 
 static Timers timers[MACHMAX];
 
-ulong intrcount[MACHMAX];
-ulong fcallcount[MACHMAX];
-
 static vlong
 tadd(Timers *tt, Timer *nt)
 {
@@ -182,14 +179,13 @@
 }
 
 void
-timerintr(Ureg *u, vlong)
+timerintr(Ureg *u, void*)
 {
 	Timer *t;
 	Timers *tt;
 	vlong when, now;
 	int callhzclock;
 
-	intrcount[m->machno]++;
 	callhzclock = 0;
 	tt = &timers[m->machno];
 	now = fastticks(nil);
@@ -212,7 +208,6 @@
 		tt->head = t->tnext;
 		assert(t->tt == tt);
 		t->tt = nil;
-		fcallcount[m->machno]++;
 		iunlock(tt);
 		if(t->tf)
 			(*t->tf)(u, t);
--- /sys/src/nix/k10/lapic.c	Sat Dec 28 16:48:27 2013
+++ /sys/src/nix/k10/lapic.c	Sat Dec 28 16:48:27 2013
@@ -249,12 +249,6 @@
 		lapicdump0(xlapic + i, i);
 }
 
-static void
-apictimer(Ureg* ureg, void*)
-{
-	timerintr(ureg, 0);
-}
-
 int
 lapiconline(void)
 {
@@ -380,9 +374,8 @@
 	 */
 	microdelay((TK2MS(1)*1000/lapmachno) * m->machno);
 	lapicrput(Tic, apic->max);
-
 	if(apic->machno == 0)
-		intrenable(IdtTIMER, apictimer, 0, -1, "APIC timer");
+		intrenable(IdtTIMER, timerintr, nil, -1, "APIC timer");
 	lapicrput(Tlvt, Periodic|IrqTIMER);
 	if(m->machno == 0)
 		lapicrput(Tp, 0);