diff --git a/sys/alpha/alpha/machdep.c b/sys/alpha/alpha/machdep.c
index d93a86d68eec..ebf971f71e5d 100644
--- a/sys/alpha/alpha/machdep.c
+++ b/sys/alpha/alpha/machdep.c
@@ -98,6 +98,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/cpu.h>
 #include <sys/eventhandler.h>
 #include <sys/imgact.h>
 #include <sys/kdb.h>
@@ -1718,6 +1719,14 @@ cpu_boot(int howto)
 {
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+
+	return (ENXIO);
+}
+
 /*
  * Shutdown the CPU as much as possible
  */
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 16157c107311..527c61bd1dbb 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -56,8 +56,12 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
-#include <sys/sysproto.h>
-#include <sys/signalvar.h>
+#include <sys/bio.h>
+#include <sys/buf.h>
+#include <sys/bus.h>
+#include <sys/callout.h>
+#include <sys/cpu.h>
+#include <sys/eventhandler.h>
 #include <sys/imgact.h>
 #include <sys/kdb.h>
 #include <sys/kernel.h>
@@ -69,19 +73,17 @@ __FBSDID("$FreeBSD$");
 #include <sys/mutex.h>
 #include <sys/pcpu.h>
 #include <sys/proc.h>
-#include <sys/bio.h>
-#include <sys/buf.h>
 #include <sys/reboot.h>
-#include <sys/callout.h>
 #include <sys/msgbuf.h>
 #include <sys/sched.h>
+#include <sys/signalvar.h>
 #include <sys/sysent.h>
 #include <sys/sysctl.h>
+#include <sys/sysproto.h>
 #include <sys/ucontext.h>
 #include <sys/vmmeter.h>
-#include <sys/bus.h>
-#include <sys/eventhandler.h>
 
+#include <machine/clock.h>
 #include <machine/pcb.h>
 
 #include <vm/vm.h>
@@ -450,6 +452,44 @@ cpu_boot(int howto)
 {
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+	uint64_t tsc1, tsc2;
+
+	if (pcpu_find(cpu_id) == NULL || rate == NULL)
+		return (EINVAL);
+
+	/* If we're booting, trust the rate calibrated moments ago. */
+	if (cold) {
+		*rate = tsc_freq;
+		return (0);
+	}
+
+#ifdef SMP
+	/* Schedule ourselves on the indicated cpu. */
+	mtx_lock_spin(&sched_lock);
+	sched_bind(curthread, cpu_id);
+	mtx_unlock_spin(&sched_lock);
+#endif
+
+	/* Calibrate by measuring a short delay. */
+	tsc1 = rdtsc();
+	DELAY(1000);
+	tsc2 = rdtsc();
+
+#ifdef SMP
+	mtx_lock_spin(&sched_lock);
+	sched_unbind(curthread);
+	mtx_unlock_spin(&sched_lock);
+#endif
+
+	tsc_freq = (tsc2 - tsc1) * 1000;
+	*rate = tsc_freq;
+	return (0);
+}
+
 /*
  * Shutdown the CPU as much as possible
  */
diff --git a/sys/arm/arm/machdep.c b/sys/arm/arm/machdep.c
index 9a9f6150e494..06d33c382fd8 100644
--- a/sys/arm/arm/machdep.c
+++ b/sys/arm/arm/machdep.c
@@ -48,6 +48,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/cpu.h>
 #include <sys/sysproto.h>
 #include <sys/signalvar.h>
 #include <sys/imgact.h>
@@ -236,6 +237,14 @@ cpu_startup(void *dummy)
 
 SYSINIT(cpu, SI_SUB_CPU, SI_ORDER_FIRST, cpu_startup, NULL)
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+
+	return (ENXIO);
+}
+
 void
 cpu_idle(void)
 {
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 9c3b98ade7c8..ef82b80959d9 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -56,8 +56,12 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
-#include <sys/sysproto.h>
-#include <sys/signalvar.h>
+#include <sys/bio.h>
+#include <sys/buf.h>
+#include <sys/bus.h>
+#include <sys/callout.h>
+#include <sys/cpu.h>
+#include <sys/eventhandler.h>
 #include <sys/imgact.h>
 #include <sys/kdb.h>
 #include <sys/kernel.h>
@@ -66,21 +70,18 @@ __FBSDID("$FreeBSD$");
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/memrange.h>
+#include <sys/msgbuf.h>
 #include <sys/mutex.h>
 #include <sys/pcpu.h>
 #include <sys/proc.h>
-#include <sys/bio.h>
-#include <sys/buf.h>
 #include <sys/reboot.h>
-#include <sys/callout.h>
-#include <sys/msgbuf.h>
 #include <sys/sched.h>
-#include <sys/sysent.h>
+#include <sys/signalvar.h>
 #include <sys/sysctl.h>
+#include <sys/sysent.h>
+#include <sys/sysproto.h>
 #include <sys/ucontext.h>
 #include <sys/vmmeter.h>
-#include <sys/bus.h>
-#include <sys/eventhandler.h>
 
 #include <vm/vm.h>
 #include <vm/vm_param.h>
@@ -104,6 +105,7 @@ __FBSDID("$FreeBSD$");
 
 #include <net/netisr.h>
 
+#include <machine/clock.h>
 #include <machine/cpu.h>
 #include <machine/cputypes.h>
 #include <machine/reg.h>
@@ -1022,6 +1024,46 @@ cpu_boot(int howto)
 {
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+	uint64_t tsc1, tsc2;
+
+	if (pcpu_find(cpu_id) == NULL || rate == NULL)
+		return (EINVAL);
+	if (!tsc_present)
+		return (EOPNOTSUPP);
+
+	/* If we're booting, trust the rate calibrated moments ago. */
+	if (cold) {
+		*rate = tsc_freq;
+		return (0);
+	}
+
+#ifdef SMP
+	/* Schedule ourselves on the indicated cpu. */
+	mtx_lock_spin(&sched_lock);
+	sched_bind(curthread, cpu_id);
+	mtx_unlock_spin(&sched_lock);
+#endif
+
+	/* Calibrate by measuring a short delay. */
+	tsc1 = rdtsc();
+	DELAY(1000);
+	tsc2 = rdtsc();
+
+#ifdef SMP
+	mtx_lock_spin(&sched_lock);
+	sched_unbind(curthread);
+	mtx_unlock_spin(&sched_lock);
+#endif
+
+	tsc_freq = (tsc2 - tsc1) * 1000;
+	*rate = tsc_freq;
+	return (0);
+}
+
 /*
  * Shutdown the CPU as much as possible
  */
diff --git a/sys/ia64/ia64/machdep.c b/sys/ia64/ia64/machdep.c
index 608943d4f2da..289c3e1ea25a 100644
--- a/sys/ia64/ia64/machdep.c
+++ b/sys/ia64/ia64/machdep.c
@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/cpu.h>
 #include <sys/eventhandler.h>
 #include <sys/kdb.h>
 #include <sys/sysproto.h>
@@ -287,6 +288,17 @@ cpu_boot(int howto)
 	efi_reset_system();
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+
+	if (pcpu_find(cpu_id) == NULL || rate == NULL)
+		return (EINVAL);
+	*rate = processor_frequency;
+	return (0);
+}
+
 void
 cpu_halt()
 {
diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index 1748c02db1e3..c54f3363b23f 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -64,6 +64,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/cpu.h>
 #include <sys/kdb.h>
 #include <sys/eventhandler.h>
 #include <sys/imgact.h>
@@ -700,6 +701,14 @@ cpu_boot(int howto)
 {
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+
+	return (ENXIO);
+}
+
 /*
  * Shutdown the CPU as much as possible.
  */
diff --git a/sys/powerpc/powerpc/machdep.c b/sys/powerpc/powerpc/machdep.c
index 1748c02db1e3..c54f3363b23f 100644
--- a/sys/powerpc/powerpc/machdep.c
+++ b/sys/powerpc/powerpc/machdep.c
@@ -64,6 +64,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/cpu.h>
 #include <sys/kdb.h>
 #include <sys/eventhandler.h>
 #include <sys/imgact.h>
@@ -700,6 +701,14 @@ cpu_boot(int howto)
 {
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+
+	return (ENXIO);
+}
+
 /*
  * Shutdown the CPU as much as possible.
  */
diff --git a/sys/sparc64/sparc64/machdep.c b/sys/sparc64/sparc64/machdep.c
index b70ac9ab5405..7fe6acdd41f3 100644
--- a/sys/sparc64/sparc64/machdep.c
+++ b/sys/sparc64/sparc64/machdep.c
@@ -44,6 +44,7 @@
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/cons.h>
+#include <sys/cpu.h>
 #include <sys/imgact.h>
 #include <sys/kdb.h>
 #include <sys/kernel.h>
@@ -669,6 +670,14 @@ cpu_shutdown(void *args)
 	openfirmware_exit(args);
 }
 
+/* Get current clock frequency for the given cpu id. */
+int
+cpu_est_clockrate(int cpu_id, uint64_t *rate)
+{
+
+	return (ENXIO);
+}
+
 /*
  * Duplicate OF_exit() with a different firmware call function that restores
  * the trap table, otherwise a RED state exception is triggered in at least