Index: sys/conf/NOTES
===================================================================
--- sys/conf/NOTES
+++ sys/conf/NOTES
@@ -2841,3 +2841,6 @@
 
 # Kernel support for stats(3).
 options 	STATS
+
+# Dtrace-based profiling of __predict_true/false
+# options 	PREDICT_PROFILING
Index: sys/conf/options
===================================================================
--- sys/conf/options
+++ sys/conf/options
@@ -1012,3 +1012,6 @@
 # gcov support
 GCOV		opt_global.h
 LINDEBUGFS
+
+# Dtrace-based profiling of __predict_true/false
+PREDICT_PROFILING	opt_global.h
Index: sys/kern/kern_sdt.c
===================================================================
--- sys/kern/kern_sdt.c
+++ sys/kern/kern_sdt.c
@@ -33,6 +33,9 @@
 #include <sys/sdt.h>
 
 SDT_PROVIDER_DEFINE(sdt);
+#ifdef	PREDICT_PROFILING
+SDT_PROBE_DEFINE4(sdt, profile, predict, , "int", "int", "char *", "int");
+#endif
 
 /*
  * Hook for the DTrace probe function. The SDT provider will set this to
@@ -54,3 +57,13 @@
 	printf("sdt_probe_stub: unexpectedly called\n");
 	kdb_backtrace();
 }
+
+#ifdef	PREDICT_PROFILING
+int
+sdt_predict_profile(int exp_res, int predict, const char *file, int line)
+{
+
+	SDT_PROBE4(sdt, profile, predict, , exp_res, predict, file, line);
+	return (exp_res);
+}
+#endif
Index: sys/sys/cdefs.h
===================================================================
--- sys/sys/cdefs.h
+++ sys/sys/cdefs.h
@@ -447,11 +447,19 @@
  *	  larger code.
  */
 #if __GNUC_PREREQ__(2, 96)
-#define	__predict_true(exp)     __builtin_expect((exp), 1)
-#define	__predict_false(exp)    __builtin_expect((exp), 0)
+#define	__predict_true_noprobe(exp)     __builtin_expect((exp), 1)
+#define	__predict_false_noprobe(exp)    __builtin_expect((exp), 0)
 #else
-#define	__predict_true(exp)     (exp)
-#define	__predict_false(exp)    (exp)
+#define	__predict_true_noprobe(exp)     (exp)
+#define	__predict_false_noprobe(exp)    (exp)
+#endif
+
+#ifdef PREDICT_PROFILING
+#define	__predict_true(exp)	sdt_predict_profile(exp, true, __FILE__, __LINE__)
+#define	__predict_false(exp)	sdt_predict_profile(exp, false, __FILE__, __LINE__)
+#else
+#define	__predict_true(exp)	__predict_true_noprobe(exp)
+#define	__predict_false(exp)	__predict_false_noprobe(exp)
 #endif
 
 #if __GNUC_PREREQ__(4, 0)
Index: sys/sys/lockstat.h
===================================================================
--- sys/sys/lockstat.h
+++ sys/sys/lockstat.h
@@ -116,7 +116,7 @@
 	LOCKSTAT_RECORD1(probe, lp, a);					\
 } while (0)
 
-#define	LOCKSTAT_PROFILE_ENABLED(probe)		__predict_false(lockstat_enabled)
+#define	LOCKSTAT_PROFILE_ENABLED(probe)		__predict_false_noprobe(lockstat_enabled)
 
 struct lock_object;
 uint64_t lockstat_nsecs(struct lock_object *);
Index: sys/sys/mutex.h
===================================================================
--- sys/sys/mutex.h
+++ sys/sys/mutex.h
@@ -240,7 +240,7 @@
 	uintptr_t _tid = (uintptr_t)(tid);				\
 	uintptr_t _v = MTX_UNOWNED;					\
 									\
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(adaptive__acquire) ||\
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(adaptive__acquire) ||\
 	    !_mtx_obtain_lock_fetch((mp), &_v, _tid)))			\
 		_mtx_lock_sleep((mp), _v, (opts), (file), (line));	\
 } while (0)
@@ -257,7 +257,7 @@
 	uintptr_t _v = MTX_UNOWNED;					\
 									\
 	spinlock_enter();						\
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire) ||	\
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(spin__acquire) ||	\
 	    !_mtx_obtain_lock_fetch((mp), &_v, _tid))) 			\
 		_mtx_lock_spin((mp), _v, (opts), (file), (line)); 	\
 } while (0)
@@ -308,7 +308,7 @@
 #define __mtx_unlock(mp, tid, opts, file, line) do {			\
 	uintptr_t _v = (uintptr_t)(tid);				\
 									\
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(adaptive__release) ||\
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(adaptive__release) ||\
 	    !_mtx_release_lock_fetch((mp), &_v)))			\
 		_mtx_unlock_sleep((mp), _v, (opts), (file), (line));	\
 } while (0)
Index: sys/sys/param.h
===================================================================
--- sys/sys/param.h
+++ sys/sys/param.h
@@ -40,6 +40,10 @@
 #ifndef _SYS_PARAM_H_
 #define _SYS_PARAM_H_
 
+#ifdef PREDICT_PROFILING
+int sdt_predict_profile(int, int, const char *, int);
+#endif
+
 #include <sys/_null.h>
 
 #define	BSD	199506		/* System version (year & month). */
Index: sys/sys/rwlock.h
===================================================================
--- sys/sys/rwlock.h
+++ sys/sys/rwlock.h
@@ -107,7 +107,7 @@
 	uintptr_t _tid = (uintptr_t)(tid);				\
 	uintptr_t _v = RW_UNLOCKED;					\
 									\
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) ||	\
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(rw__acquire) ||	\
 	    !_rw_write_lock_fetch((rw), &_v, _tid)))			\
 		_rw_wlock_hard((rw), _v, (file), (line));		\
 } while (0)
@@ -116,7 +116,7 @@
 #define	__rw_wunlock(rw, tid, file, line) do {				\
 	uintptr_t _v = (uintptr_t)(tid);				\
 									\
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) ||	\
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(rw__release) ||	\
 	    !_rw_write_unlock_fetch((rw), &_v)))			\
 		_rw_wunlock_hard((rw), _v, (file), (line));		\
 } while (0)
Index: sys/sys/sdt.h
===================================================================
--- sys/sys/sdt.h
+++ sys/sys/sdt.h
@@ -165,11 +165,11 @@
 #define SDT_PROBE_DECLARE(prov, mod, func, name)				\
 	extern struct sdt_probe sdt_##prov##_##mod##_##func##_##name[1]
 
-#define	SDT_PROBES_ENABLED()	__predict_false(sdt_probes_enabled)
+#define	SDT_PROBES_ENABLED()	__predict_false_noprobe(sdt_probes_enabled)
 
 #define SDT_PROBE(prov, mod, func, name, arg0, arg1, arg2, arg3, arg4)	do {	\
 	if (SDT_PROBES_ENABLED()) {						\
-		if (__predict_false(sdt_##prov##_##mod##_##func##_##name->id))	\
+		if (__predict_false_noprobe(sdt_##prov##_##mod##_##func##_##name->id))	\
 		(*sdt_probe_func)(sdt_##prov##_##mod##_##func##_##name->id,	\
 		    (uintptr_t) arg0, (uintptr_t) arg1, (uintptr_t) arg2,	\
 		    (uintptr_t) arg3, (uintptr_t) arg4);			\
@@ -427,6 +427,8 @@
 void sdt_probe_stub(uint32_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t,
     uintptr_t);
 
+int sdt_predict_trace(int exp_res, int predict, const char *file, int line);
+
 SDT_PROVIDER_DECLARE(sdt);
 
 #endif /* _KERNEL */
Index: sys/sys/sx.h
===================================================================
--- sys/sys/sx.h
+++ sys/sys/sx.h
@@ -163,7 +163,7 @@
 	uintptr_t v = SX_LOCK_UNLOCKED;
 	int error = 0;
 
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) ||
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(sx__acquire) ||
 	    !atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid)))
 		error = _sx_xlock_hard(sx, v, opts);
 
@@ -176,7 +176,7 @@
 {
 	uintptr_t x = (uintptr_t)td;
 
-	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) ||
+	if (__predict_false_noprobe(LOCKSTAT_PROFILE_ENABLED(sx__release) ||
 	    !atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, SX_LOCK_UNLOCKED)))
 		_sx_xunlock_hard(sx, x);
 }
Index: sys/sys/systm.h
===================================================================
--- sys/sys/systm.h
+++ sys/sys/systm.h
@@ -298,7 +298,7 @@
 	__compiler_membar();
 	td->td_critnest--;
 	__compiler_membar();
-	if (__predict_false(td->td_owepreempt))
+	if (__predict_false_noprobe(td->td_owepreempt))
 		critical_exit_preempt();
 
 }