Clean up multi-thread barrier-sync hold-down timer

Main thread: don't bother with the barrier sync hold-down timer if
none of the worker threads are busy.

Worker threads: avoid epoll_pwait (10ms timeout) when the
control-plane has been active in the last half-second.

Change-Id: I82008d09968c65e2a4af0ebb7887389992e60603
Signed-off-by: Dave Barach <dave@barachs.net>

diff --git a/src/vlib/threads.c b/src/vlib/threads.c
index 7d17c7b..52886df 100644 (file)
--- a/src/vlib/threads.c
+++ b/src/vlib/threads.c
@@ -1389,7 +1389,9 @@ vlib_worker_thread_barrier_sync_int (vlib_main_t * vm, const char *func_name)
   f64 t_entry;
   f64 t_open;
   f64 t_closed;
+  f64 max_vector_rate;
   u32 count;
+  int i;
 
   if (vec_len (vlib_mains) < 2)
     return;
@@ -1410,23 +1412,41 @@ vlib_worker_thread_barrier_sync_int (vlib_main_t * vm, const char *func_name)
       return;
     }
 
+  /*
+   * Need data to decide if we're working hard enough to honor
+   * the barrier hold-down timer.
+   */
+  max_vector_rate = 0.0;
+  for (i = 1; i < vec_len (vlib_mains); i++)
+    max_vector_rate =
+      clib_max (max_vector_rate,
+               vlib_last_vectors_per_main_loop_as_f64 (vlib_mains[i]));
+
   vlib_worker_threads[0].barrier_sync_count++;
 
   /* Enforce minimum barrier open time to minimize packet loss */
   ASSERT (vm->barrier_no_close_before <= (now + BARRIER_MINIMUM_OPEN_LIMIT));
 
-  while (1)
+  /*
+   * If any worker thread seems busy, which we define
+   * as a vector rate above 10, we enforce the barrier hold-down timer
+   */
+  if (max_vector_rate > 10.0)
     {
-      now = vlib_time_now (vm);
-      /* Barrier hold-down timer expired? */
-      if (now >= vm->barrier_no_close_before)
-       break;
-      if ((vm->barrier_no_close_before - now)
-         > (2.0 * BARRIER_MINIMUM_OPEN_LIMIT))
+      while (1)
        {
-         clib_warning ("clock change: would have waited for %.4f seconds",
-                       (vm->barrier_no_close_before - now));
-         break;
+         now = vlib_time_now (vm);
+         /* Barrier hold-down timer expired? */
+         if (now >= vm->barrier_no_close_before)
+           break;
+         if ((vm->barrier_no_close_before - now)
+             > (2.0 * BARRIER_MINIMUM_OPEN_LIMIT))
+           {
+             clib_warning
+               ("clock change: would have waited for %.4f seconds",
+                (vm->barrier_no_close_before - now));
+             break;
+           }
        }
     }
   /* Record time of closure */

diff --git a/src/vlib/unix/input.c b/src/vlib/unix/input.c
index 7f49b95..1c1cb1a 100644 (file)
--- a/src/vlib/unix/input.c
+++ b/src/vlib/unix/input.c
@@ -145,9 +145,13 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
     vlib_node_main_t *nm = &vm->node_main;
     u32 ticks_until_expiration;
     f64 timeout;
+    f64 now;
     int timeout_ms = 0, max_timeout_ms = 10;
     f64 vector_rate = vlib_last_vectors_per_main_loop (vm);
 
+    if (is_main == 0)
+      now = vlib_time_now (vm);
+
     /*
      * If we've been asked for a fixed-sleep between main loop polls,
      * do so right away.
@@ -194,8 +198,9 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
          }
        node->input_main_loops_per_call = 0;
       }
-    else if (is_main == 0 && vector_rate < 2 &&
-            nm->input_node_counts_by_state[VLIB_NODE_STATE_POLLING] == 0)
+    else if (is_main == 0 && vector_rate < 2
+            && (vlib_global_main.time_last_barrier_release + 0.5 < now)
+            && nm->input_node_counts_by_state[VLIB_NODE_STATE_POLLING] == 0)
       {
        timeout = 10e-3;
        timeout_ms = max_timeout_ms;
@@ -227,8 +232,27 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
       }
     else
       {
+       /*
+        * Worker thread, no epoll fd's, sleep for 100us at a time
+        * and check for a barrier sync request
+        */
        if (timeout_ms)
-         usleep (timeout_ms * 1000);
+         {
+           struct timespec ts, tsrem;
+           f64 limit = now + (f64) timeout_ms * 1e-3;
+
+           while (vlib_time_now (vm) < limit)
+             {
+               /* Sleep for 100us at a time */
+               ts.tv_sec = 0;
+               ts.tv_nsec = 1000 * 100;
+
+               while (nanosleep (&ts, &tsrem) < 0)
+                 ts = tsrem;
+               if (*vlib_worker_threads->wait_at_barrier)
+                 goto done;
+             }
+         }
        goto done;
       }
   }