Index: head/sys/cam/cam_iosched.c
===================================================================
--- head/sys/cam/cam_iosched.c
+++ head/sys/cam/cam_iosched.c
@@ -883,6 +883,27 @@
 	return (error);
 }
 
+static int
+cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	int *quanta;
+	int error, value;
+
+	quanta = (unsigned *)arg1;
+	value = *quanta;
+
+	error = sysctl_handle_int(oidp, (int *)&value, 0, req);
+	if ((error != 0) || (req->newptr == NULL))
+		return (error);
+
+	if (value < 1 || value > hz)
+		return (EINVAL);
+
+	*quanta = value;
+
+	return (0);
+}
+
 static void
 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name)
 {
@@ -1104,9 +1125,9 @@
 	    &isc->read_bias, 100,
 	    "How biased towards read should we be independent of limits");
 
-	SYSCTL_ADD_INT(ctx, n,
-	    OID_AUTO, "quanta", CTLFLAG_RW,
-	    &isc->quanta, 200,
+	SYSCTL_ADD_PROC(ctx, n,
+	    OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW,
+	    &isc->quanta, 0, cam_iosched_quanta_sysctl, "I",
 	    "How many quanta per second do we slice the I/O up into");
 
 	SYSCTL_ADD_INT(ctx, n,