diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index fdf2271bc8737..11afe0f5c9b8e 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -503,6 +503,8 @@ hardclock_cnt(int cnt, int usermode)
 	int i;
 #endif /* SW_WATCHDOG */
 
+	CTR3(KTR_SPARE2, "hardclock_cnt at %d:  cnt=%d pcputicks=%d",
+	    curcpu, cnt, *t);
 	/*
 	 * Update per-CPU and possibly global ticks values.
 	 */
@@ -511,6 +513,8 @@ hardclock_cnt(int cnt, int usermode)
 		global = ticks;
 		newticks = *t - global;
 		if (newticks <= 0) {
+			CTR1(KTR_SPARE2, "hardclock_cnt at %d: newticks=%d",
+			    newticks);
 			if (newticks < -1)
 				*t = global - 1;
 			newticks = 0;
@@ -518,6 +522,9 @@ hardclock_cnt(int cnt, int usermode)
 		}
 	} while (!atomic_cmpset_int(&ticks, global, *t));
 
+	CTR4(KTR_SPARE2, "hardclock_cnt at %d:  ticks: %d -> %d, newticks = %d",
+	    curcpu, 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_tc.c b/sys/kern/kern_tc.c
index 1ec1735b1ee19..50eb4ce682392 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>
@@ -1296,6 +1297,10 @@ tc_windup(void)
 	 * Update the offset fields accordingly.
 	 */
 	delta = tc_delta(th);
+	CTR4(KTR_SPARE2, "tc_windup at %d: sec=%u, frac=%lu, delta=%u",
+	    curcpu, 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 +1427,8 @@ tc_windup(void)
 	}
 #endif
 
+	CTR3(KTR_SPARE2, "tc_windup done at %d: sec=%u, frac=%lu",
+	    curcpu, th->th_offset.sec, th->th_offset.frac);
 	timehands = th;
 	timekeep_push_vdso();
 }