Report deadtime when using a fixed delay, note how bad nanosleep is, must be a...

Report deadtime when using a fixed delay, note how bad nanosleep is, must be a major source of mismatch in our timings

swiftmpistepsim.c

@@ -95,7 +95,8 @@ static void injection_runner(int qid) {
        * are below that (we time the ticks this loop takes without any waiting
        * and use that). Otherwise we wait a while. Note we need to convert the
        * ticks of the log file into nanoseconds, that requires the original
-       * CPU frequency. */
+       * CPU frequency. Note nanosleep is not very accurate and seems to have
+       * a base line at 50us using tests on Durham COSMA. */
       if (dt > looptics) {
         struct timespec sleep;
         sleep.tv_sec = 0;
@@ -168,7 +169,7 @@ static void injection_runner(int qid) {
     message("%d injections completed, sends = %d, recvs = %d", ind_req[qid],
             nr_sends, nr_recvs);
     message("remaining sends = %d, recvs = %d", todo_send, todo_recv);
-    if (usetics) message("deadtime %.3f ms", deadtime / 1.0e6);
+    if (usetics|| waitns > 0) message("deadtime %.3f ms", deadtime / 1.0e6);
   }
   message("took %.3f %s.", clocks_from_ticks(getticks() - starttics),
           clocks_getunit());