Add macros for ns to us,ms,s conversion

include/timestamp.h

@@ -14,6 +14,10 @@
 #define S_TO_NS(x)  x*1000000000ll
 #define MS_TO_NS(x) x*1000000ll
 #define US_TO_NS(x) x*1000ll
+#define NS_TO_US(x) x/1000ll
+#define NS_TO_MS(x) x/1000000ll
+#define NS_TO_S(x)  x/1000000000ll
+
 
 static uint64_t getTimestamp() {
   boost::posix_time::ptime epoch(boost::gregorian::date(1970,1,1));