diff --git a/sys/dev/acpica/acpi_hpet.c b/sys/dev/acpica/acpi_hpet.c
index 0da8bae307161..5ab8ffefe43b4 100644
--- a/sys/dev/acpica/acpi_hpet.c
+++ b/sys/dev/acpica/acpi_hpet.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/conf.h>
 #include <sys/bus.h>
 #include <sys/kernel.h>
+#include <sys/ktr.h>
 #include <sys/module.h>
 #include <sys/proc.h>
 #include <sys/rman.h>
@@ -190,6 +191,8 @@ hpet_start(struct eventtimer *et, sbintime_t first, sbintime_t period)
 	now = bus_read_4(sc->mem_res, HPET_MAIN_COUNTER);
 restart:
 	t->next = now + fdiv;
+	CTR3(KTR_SPARE2, "hpet_start: mode=%d, now=%u next=%u",
+	    t->mode, now, t->next);
 	if (t->mode == 1 && (t->caps & HPET_TCAP_PER_INT)) {
 		t->caps |= HPET_TCNF_TYPE;
 		bus_write_4(sc->mem_res, HPET_TIMER_CAP_CNF(t->num),
@@ -220,6 +223,7 @@ hpet_stop(struct eventtimer *et)
 	struct hpet_timer *t;
 	struct hpet_softc *sc = mt->sc;
 
+	CTR0(KTR_SPARE2, "hpet_stop");
 	t = (mt->pcpu_master < 0) ? mt : &sc->t[mt->pcpu_slaves[curcpu]];
 	t->mode = 0;
 	t->caps &= ~(HPET_TCNF_INT_ENB | HPET_TCNF_TYPE);
@@ -235,6 +239,7 @@ hpet_intr_single(void *arg)
 	struct hpet_softc *sc = t->sc;
 	uint32_t now;
 
+	CTR1(KTR_SPARE2, "hpet_intr_single: mode=%d", t->mode);
 	if (t->mode == 0)
 		return (FILTER_STRAY);
 	/* Check that per-CPU timer interrupt reached right CPU. */
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index fdf2271bc8737..783f9fa9954b2 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -503,6 +503,7 @@ hardclock_cnt(int cnt, int usermode)
 	int i;
 #endif /* SW_WATCHDOG */
 
+	CTR2(KTR_SPARE2, "hardclock_cnt: cnt=%d pcputicks=%d", cnt, *t);
 	/*
 	 * Update per-CPU and possibly global ticks values.
 	 */
@@ -511,6 +512,8 @@ hardclock_cnt(int cnt, int usermode)
 		global = ticks;
 		newticks = *t - global;
 		if (newticks <= 0) {
+			CTR1(KTR_SPARE2, "hardclock_cnt: newticks=%d",
+			    newticks);
 			if (newticks < -1)
 				*t = global - 1;
 			newticks = 0;
@@ -518,6 +521,9 @@ hardclock_cnt(int cnt, int usermode)
 		}
 	} while (!atomic_cmpset_int(&ticks, global, *t));
 
+	CTR3(KTR_SPARE2, "hardclock_cnt: ticks: %d -> %d, newticks = %d",
+	    global, *t, newticks);
+
 	/*
 	 * Run current process's virtual and profile time, as needed.
 	 */
diff --git a/sys/kern/kern_clocksource.c b/sys/kern/kern_clocksource.c
index cc7847c2b5de1..6b499bf9c9582 100644
--- a/sys/kern/kern_clocksource.c
+++ b/sys/kern/kern_clocksource.c
@@ -354,6 +354,8 @@ timercb(struct eventtimer *et, void *arg)
 			if (state->ipi) {
 				state->ipi = 0;
 				ipi_cpu(cpu, IPI_HARDCLOCK);
+				CTR2(KTR_SPARE2, "sending ipi at %d to %d",
+				    curcpu, cpu);
 			}
 		}
 	}
diff --git a/sys/kern/kern_et.c b/sys/kern/kern_et.c
index 979e0c5cf24aa..4f90dd955dfc6 100644
--- a/sys/kern/kern_et.c
+++ b/sys/kern/kern_et.c
@@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
+#include <sys/ktr.h>
 #include <sys/sbuf.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
@@ -187,6 +188,9 @@ et_start(struct eventtimer *et, sbintime_t first, sbintime_t period)
 		("et_start: period specified for oneshot-only timer"));
 	KASSERT((et->et_flags & ET_FLAGS_ONESHOT) || period != 0,
 		("et_start: period not specified for periodic-only timer"));
+	CTR4(KTR_SPARE2, "et_start first %d.%08x period %d.%08x",
+	    (int)(first >> 32), (u_int)(first & 0xffffffff),
+	    (int)(period >> 32), (u_int)(period & 0xffffffff));
 	if (period != 0) {
 		if (period < et->et_min_period)
 		        period = et->et_min_period;
@@ -199,6 +203,9 @@ et_start(struct eventtimer *et, sbintime_t first, sbintime_t period)
 		else if (first > et->et_max_period)
 		        first = et->et_max_period;
 	}
+	CTR4(KTR_SPARE2, "et_start first %d.%08x period %d.%08x",
+	    (int)(first >> 32), (u_int)(first & 0xffffffff),
+	    (int)(period >> 32), (u_int)(period & 0xffffffff));
 	return (et->et_start(et, first, period));
 }
 
diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index 1ec1735b1ee19..1c631f427212c 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -22,6 +22,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
+#include <sys/ktr.h>
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
@@ -187,6 +188,7 @@ tc_delta(struct timehands *th)
 	struct timecounter *tc;
 
 	tc = th->th_counter;
+	CTR1(KTR_SPARE2, "tc_delta: offset=%u", th->th_offset_count);
 	return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
 	    tc->tc_counter_mask);
 }
@@ -1296,6 +1298,10 @@ tc_windup(void)
 	 * Update the offset fields accordingly.
 	 */
 	delta = tc_delta(th);
+	CTR3(KTR_SPARE2, "tc_windup: sec=%u, frac=%lu, delta=%u",
+	    th->th_offset.sec, th->th_offset.frac, delta);
+	if (delta > th->th_counter->tc_counter_mask / 2)
+		CTR1(KTR_SPARE2, "abnormal delta 0x%x", delta);
 	if (th->th_counter != timecounter)
 		ncount = timecounter->tc_get_timecount(timecounter);
 	else
@@ -1422,6 +1428,8 @@ tc_windup(void)
 	}
 #endif
 
+	CTR2(KTR_SPARE2, "tc_windup done: sec=%u, frac=%lu",
+	    th->th_offset.sec, th->th_offset.frac);
 	timehands = th;
 	timekeep_push_vdso();
 }