diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e91c29f..bd80c14 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -54,6 +54,7 @@ void update_xtime_cache(u64 nsec)
 }
 
 struct clocksource *clock;
+EXPORT_SYMBOL(clock);
 
 
 #ifdef CONFIG_GENERIC_TIME
diff --git a/kernel/timer.c b/kernel/timer.c
index 03bc7f1..add3a1d 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1064,6 +1064,7 @@ static inline void update_times(unsigned long ticks)
 
 void do_timer(unsigned long ticks)
 {
+	trace_mark(apic_timer_tick, "tick = %lu", ticks);
 	jiffies_64 += ticks;
 	update_times(ticks);
 }
diff --git a/samples/markers/Makefile b/samples/markers/Makefile
index 6d72312..94d2ac7 100644
--- a/samples/markers/Makefile
+++ b/samples/markers/Makefile
@@ -1,4 +1,4 @@
 # builds the kprobes example kernel modules;
 # then to use one (as root):  insmod <module_name.ko>
 
-obj-$(CONFIG_SAMPLE_MARKERS) += probe-example.o marker-example.o
+obj-$(CONFIG_SAMPLE_MARKERS) += probe-example.o marker-example.o test-apic.o
diff --git a/samples/markers/test-apic.c b/samples/markers/test-apic.c
new file mode 100644
index 0000000..a1b1107
--- /dev/null
+++ b/samples/markers/test-apic.c
@@ -0,0 +1,48 @@
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/marker.h>
+#include <asm/atomic.h>
+#include <linux/clocksource.h>
+
+extern struct clocksource *clock;
+static cycle_t cycle_prev, cycle_cur;
+
+void probe_apic_timer_event(void *data, void *call_data,
+		const char *format, va_list *args)
+{
+	unsigned long tick;
+	
+	tick = va_arg(*args, typeof(tick));
+
+	cycle_cur = clocksource_read(clock);
+	if (cycle_prev) {
+		printk(KERN_INFO "tick = %lu, apic tick timer interval is %ld\n",
+			tick, cyc2ns(clock, cycle_cur - cycle_prev));
+	}
+
+	cycle_prev = cycle_cur;
+}
+
+static int __init probe_init(void)
+{
+	int r;
+
+	r = marker_probe_register("apic_timer_tick", "tick = %lu",
+		probe_apic_timer_event, NULL);
+
+	if (r)
+		printk(KERN_INFO "Unable to register probe for apic timer tick\n");
+
+	return 0;
+}
+
+static void __exit probe_exit(void)
+{
+	marker_probe_unregister("apic_timer_tick", probe_apic_timer_event, NULL);
+}
+
+module_init(probe_init);
+module_exit(probe_exit);
+
+MODULE_LICENSE("GPL");