calculate per-thread time offset

The main thread squirrels away vlib_time_now (&vlib_global_main),
worker threads use it to calculate an offset in f64 seconds from their
own vlib_time_now(vm) value. We use that offset until the next barrier
sync.

Thanks to Damjan for the suggestion.

Change-Id: If56cdfe68e5ad8ac3b0d0fc885dc3ba556cd1215
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/vlib/threads.h b/src/vlib/threads.h
index 0e9cba52103..95fcf3d83d7 100644
--- a/src/vlib/threads.h
+++ b/src/vlib/threads.h
@@ -422,6 +422,21 @@ vlib_worker_thread_barrier_check (void)
 	}
       while (*vlib_worker_threads->wait_at_barrier)
 	;
+
+      /*
+       * Recompute the offset from thread-0 time.
+       * Note that vlib_time_now adds vm->time_offset, so
+       * clear it first. Save the resulting idea of "now", to
+       * see how well we're doing. See show_clock_command_fn(...)
+       */
+      {
+	f64 now;
+	vm->time_offset = 0.0;
+	now = vlib_time_now (vm);
+	vm->time_offset = vlib_global_main.time_last_barrier_release - now;
+	vm->time_last_barrier_release = vlib_time_now (vm);
+      }
+
       if (CLIB_DEBUG > 0)
 	vm->parked_at_barrier = 0;
       clib_atomic_fetch_add (vlib_worker_threads->workers_at_barrier, -1);