Recombine diags and minimum barrier open time changes (VPP-968)

Support logging to both syslog and elog
Also include DaveB is_mp_safe fix, which had been lost

Change-Id: If82f7969e2f43c63c3fed5b1a0c7434c90c1f380
Signed-off-by: Colin Tregenza Dancer <ctd@metaswitch.com>

3 files changed, 340 insertions, 11 deletions

diff --git a/src/vlib/main.h b/src/vlib/main.h
index 4c0cde3f..fb67334e 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -199,6 +199,15 @@ typedef struct vlib_main_t
    */
   int need_vlib_worker_thread_node_runtime_update;
 
+  /*
+   * Barrier epoch - Set to current time, each time barrier_sync or
+   * barrier_release is called with zero recursion.
+   */
+  f64 barrier_epoch;
+
+  /* Earliest barrier can be closed again */
+  f64 barrier_no_close_before;
+
 } vlib_main_t;
 
 /* Global main structure. */
diff --git a/src/vlib/threads.c b/src/vlib/threads.c
index 6cd325b3..2d9ce84a 100644
--- a/src/vlib/threads.c
+++ b/src/vlib/threads.c
@@ -35,6 +35,222 @@ vl (void *p)
 vlib_worker_thread_t *vlib_worker_threads;
 vlib_thread_main_t vlib_thread_main;
 
+/*
+ * Barrier tracing can be enabled on a normal build to collect information
+ * on barrier use, including timings and call stacks.  Deliberately not
+ * keyed off CLIB_DEBUG, because that can add significant overhead which
+ * imapacts observed timings.
+ */
+
+#ifdef BARRIER_TRACING
+ /*
+  * Output of barrier tracing can be to syslog or elog as suits
+  */
+#ifdef BARRIER_TRACING_ELOG
+static u32
+elog_id_for_msg_name (const char *msg_name)
+{
+  uword *p, r;
+  static uword *h;
+  u8 *name_copy;
+
+  if (!h)
+    h = hash_create_string (0, sizeof (uword));
+
+  p = hash_get_mem (h, msg_name);
+  if (p)
+    return p[0];
+  r = elog_string (&vlib_global_main.elog_main, "%s", msg_name);
+
+  name_copy = format (0, "%s%c", msg_name, 0);
+
+  hash_set_mem (h, name_copy, r);
+
+  return r;
+}
+
+  /*
+   * elog Barrier trace functions, which are nulled out if BARRIER_TRACING isn't
+   * defined
+   */
+
+static inline void
+barrier_trace_sync (f64 t_entry, f64 t_open, f64 t_closed)
+{
+    /* *INDENT-OFF* */
+    ELOG_TYPE_DECLARE (e) =
+      {
+        .format = "barrier <%d#%s(O:%dus:%dus)(%dus)",
+        .format_args = "i4T4i4i4i4",
+      };
+    /* *INDENT-ON* */
+  struct
+  {
+    u32 count, caller, t_entry, t_open, t_closed;
+  } *ed = 0;
+
+  ed = ELOG_DATA (&vlib_global_main.elog_main, e);
+  ed->count = (int) vlib_worker_threads[0].barrier_sync_count;
+  ed->caller = elog_id_for_msg_name (vlib_worker_threads[0].barrier_caller);
+  ed->t_entry = (int) (1000000.0 * t_entry);
+  ed->t_open = (int) (1000000.0 * t_open);
+  ed->t_closed = (int) (1000000.0 * t_closed);
+}
+
+static inline void
+barrier_trace_sync_rec (f64 t_entry)
+{
+    /* *INDENT-OFF* */
+    ELOG_TYPE_DECLARE (e) =
+      {
+        .format = "barrier    <%d(%dus)%s",
+        .format_args = "i4i4T4",
+      };
+    /* *INDENT-ON* */
+  struct
+  {
+    u32 depth, t_entry, caller;
+  } *ed = 0;
+
+  ed = ELOG_DATA (&vlib_global_main.elog_main, e);
+  ed->depth = (int) vlib_worker_threads[0].recursion_level - 1;
+  ed->t_entry = (int) (1000000.0 * t_entry);
+  ed->caller = elog_id_for_msg_name (vlib_worker_threads[0].barrier_caller);
+}
+
+static inline void
+barrier_trace_release_rec (f64 t_entry)
+{
+    /* *INDENT-OFF* */
+    ELOG_TYPE_DECLARE (e) =
+      {
+        .format = "barrier      (%dus)%d>",
+        .format_args = "i4i4",
+      };
+    /* *INDENT-ON* */
+  struct
+  {
+    u32 t_entry, depth;
+  } *ed = 0;
+
+  ed = ELOG_DATA (&vlib_global_main.elog_main, e);
+  ed->t_entry = (int) (1000000.0 * t_entry);
+  ed->depth = (int) vlib_worker_threads[0].recursion_level;
+}
+
+static inline void
+barrier_trace_release (f64 t_entry, f64 t_closed_total, f64 t_update_main)
+{
+    /* *INDENT-OFF* */
+    ELOG_TYPE_DECLARE (e) =
+      {
+        .format = "barrier   (%dus){%d}(C:%dus)#%d>",
+        .format_args = "i4i4i4i4",
+      };
+    /* *INDENT-ON* */
+  struct
+  {
+    u32 t_entry, t_update_main, t_closed_total, count;
+  } *ed = 0;
+
+  ed = ELOG_DATA (&vlib_global_main.elog_main, e);
+  ed->t_entry = (int) (1000000.0 * t_entry);
+  ed->t_update_main = (int) (1000000.0 * t_update_main);
+  ed->t_closed_total = (int) (1000000.0 * t_closed_total);
+  ed->count = (int) vlib_worker_threads[0].barrier_sync_count;
+
+  /* Reset context for next trace */
+  vlib_worker_threads[0].barrier_context = NULL;
+}
+#else
+char barrier_trace[65536];
+char *btp = barrier_trace;
+
+  /*
+   * syslog Barrier trace functions, which are nulled out if BARRIER_TRACING
+   * isn't defined
+   */
+
+
+static inline void
+barrier_trace_sync (f64 t_entry, f64 t_open, f64 t_closed)
+{
+  btp += sprintf (btp, "<%u#%s",
+		  (unsigned int) vlib_worker_threads[0].barrier_sync_count,
+		  vlib_worker_threads[0].barrier_caller);
+
+  if (vlib_worker_threads[0].barrier_context)
+    {
+      btp += sprintf (btp, "[%s]", vlib_worker_threads[0].barrier_context);
+
+    }
+
+  btp += sprintf (btp, "(O:%dus:%dus)(%dus):",
+		  (int) (1000000.0 * t_entry),
+		  (int) (1000000.0 * t_open), (int) (1000000.0 * t_closed));
+
+}
+
+static inline void
+barrier_trace_sync_rec (f64 t_entry)
+{
+  btp += sprintf (btp, "<%u(%dus)%s:",
+		  (int) vlib_worker_threads[0].recursion_level - 1,
+		  (int) (1000000.0 * t_entry),
+		  vlib_worker_threads[0].barrier_caller);
+}
+
+static inline void
+barrier_trace_release_rec (f64 t_entry)
+{
+  btp += sprintf (btp, ":(%dus)%u>", (int) (1000000.0 * t_entry),
+		  (int) vlib_worker_threads[0].recursion_level);
+}
+
+static inline void
+barrier_trace_release (f64 t_entry, f64 t_closed_total, f64 t_update_main)
+{
+
+  btp += sprintf (btp, ":(%dus)", (int) (1000000.0 * t_entry));
+  if (t_update_main > 0)
+    {
+      btp += sprintf (btp, "{%dus}", (int) (1000000.0 * t_update_main));
+    }
+
+  btp += sprintf (btp, "(C:%dus)#%u>",
+		  (int) (1000000.0 * t_closed_total),
+		  (int) vlib_worker_threads[0].barrier_sync_count);
+
+  /* Dump buffer to syslog, and reset for next trace */
+  fformat (stderr, "BTRC %s\n", barrier_trace);
+  btp = barrier_trace;
+  vlib_worker_threads[0].barrier_context = NULL;
+}
+#endif
+#else
+
+  /* Null functions for default case where barrier tracing isn't used */
+static inline void
+barrier_trace_sync (f64 t_entry, f64 t_open, f64 t_closed)
+{
+}
+
+static inline void
+barrier_trace_sync_rec (f64 t_entry)
+{
+}
+
+static inline void
+barrier_trace_release_rec (f64 t_entry)
+{
+}
+
+static inline void
+barrier_trace_release (f64 t_entry, f64 t_closed_total, f64 t_update_main)
+{
+}
+#endif
+
 uword
 os_get_nthreads (void)
 {
@@ -558,6 +774,10 @@ start_workers (vlib_main_t * vm)
       *vlib_worker_threads->node_reforks_required = 0;
       vm->need_vlib_worker_thread_node_runtime_update = 0;
 
+      /* init timing */
+      vm->barrier_epoch = 0;
+      vm->barrier_no_close_before = 0;
+
       worker_thread_index = 1;
 
       for (i = 0; i < vec_len (tm->registrations); i++)
@@ -790,6 +1010,7 @@ start_workers (vlib_main_t * vm)
 
 VLIB_MAIN_LOOP_ENTER_FUNCTION (start_workers);
 
+
 static inline void
 worker_thread_node_runtime_update_internal (void)
 {
@@ -993,7 +1214,6 @@ vlib_worker_thread_node_refork (void)
   nm_clone->processes = vec_dup (nm->processes);
 }
 
-
 void
 vlib_worker_thread_node_runtime_update (void)
 {
@@ -1192,10 +1412,29 @@ vlib_worker_thread_fork_fixup (vlib_fork_fixup_t which)
   vlib_worker_thread_barrier_release (vm);
 }
 
+  /*
+   * Enforce minimum open time to minimize packet loss due to Rx overflow,
+   * based on a test based heuristic that barrier should be open for at least
+   * 3 time as long as it is closed (with an upper bound of 1ms because by that
+   *  point it is probably too late to make a difference)
+   */
+
+#ifndef BARRIER_MINIMUM_OPEN_LIMIT
+#define BARRIER_MINIMUM_OPEN_LIMIT 0.001
+#endif
+
+#ifndef BARRIER_MINIMUM_OPEN_FACTOR
+#define BARRIER_MINIMUM_OPEN_FACTOR 3
+#endif
+
 void
-vlib_worker_thread_barrier_sync (vlib_main_t * vm)
+vlib_worker_thread_barrier_sync_int (vlib_main_t * vm)
 {
   f64 deadline;
+  f64 now;
+  f64 t_entry;
+  f64 t_open;
+  f64 t_closed;
   u32 count;
 
   if (vec_len (vlib_mains) < 2)
@@ -1205,29 +1444,55 @@ vlib_worker_thread_barrier_sync (vlib_main_t * vm)
 
   count = vec_len (vlib_mains) - 1;
 
+  /* Record entry relative to last close */
+  now = vlib_time_now (vm);
+  t_entry = now - vm->barrier_epoch;
+
   /* Tolerate recursive calls */
   if (++vlib_worker_threads[0].recursion_level > 1)
-    return;
+    {
+      barrier_trace_sync_rec (t_entry);
+      return;
+    }
 
   vlib_worker_threads[0].barrier_sync_count++;
 
-  deadline = vlib_time_now (vm) + BARRIER_SYNC_TIMEOUT;
+  /* Enforce minimum barrier open time to minimize packet loss */
+  ASSERT (vm->barrier_no_close_before <= (now + BARRIER_MINIMUM_OPEN_LIMIT));
+  while ((now = vlib_time_now (vm)) < vm->barrier_no_close_before)
+    ;
+
+  /* Record time of closure */
+  t_open = now - vm->barrier_epoch;
+  vm->barrier_epoch = now;
+
+  deadline = now + BARRIER_SYNC_TIMEOUT;
 
   *vlib_worker_threads->wait_at_barrier = 1;
   while (*vlib_worker_threads->workers_at_barrier != count)
     {
-      if (vlib_time_now (vm) > deadline)
+      if ((now = vlib_time_now (vm)) > deadline)
 	{
 	  fformat (stderr, "%s: worker thread deadlock\n", __FUNCTION__);
 	  os_panic ();
 	}
     }
+
+  t_closed = now - vm->barrier_epoch;
+
+  barrier_trace_sync (t_entry, t_open, t_closed);
+
 }
 
 void
 vlib_worker_thread_barrier_release (vlib_main_t * vm)
 {
   f64 deadline;
+  f64 now;
+  f64 minimum_open;
+  f64 t_entry;
+  f64 t_closed_total;
+  f64 t_update_main = 0.0;
   int refork_needed = 0;
 
   if (vec_len (vlib_mains) < 2)
@@ -1235,8 +1500,15 @@ vlib_worker_thread_barrier_release (vlib_main_t * vm)
 
   ASSERT (vlib_get_thread_index () == 0);
 
+
+  now = vlib_time_now (vm);
+  t_entry = now - vm->barrier_epoch;
+
   if (--vlib_worker_threads[0].recursion_level > 0)
-    return;
+    {
+      barrier_trace_release_rec (t_entry);
+      return;
+    }
 
   /* Update (all) node runtimes before releasing the barrier, if needed */
   if (vm->need_vlib_worker_thread_node_runtime_update)
@@ -1249,15 +1521,17 @@ vlib_worker_thread_barrier_release (vlib_main_t * vm)
       refork_needed = 1;
       clib_smp_atomic_add (vlib_worker_threads->node_reforks_required,
 			   (vec_len (vlib_mains) - 1));
+      now = vlib_time_now (vm);
+      t_update_main = now - vm->barrier_epoch;
     }
 
-  deadline = vlib_time_now (vm) + BARRIER_SYNC_TIMEOUT;
+  deadline = now + BARRIER_SYNC_TIMEOUT;
 
   *vlib_worker_threads->wait_at_barrier = 0;
 
   while (*vlib_worker_threads->workers_at_barrier > 0)
     {
-      if (vlib_time_now (vm) > deadline)
+      if ((now = vlib_time_now (vm)) > deadline)
 	{
 	  fformat (stderr, "%s: worker thread deadlock\n", __FUNCTION__);
 	  os_panic ();
@@ -1267,11 +1541,13 @@ vlib_worker_thread_barrier_release (vlib_main_t * vm)
   /* Wait for reforks before continuing */
   if (refork_needed)
     {
-      deadline = vlib_time_now (vm) + BARRIER_SYNC_TIMEOUT;
+      now = vlib_time_now (vm);
+
+      deadline = now + BARRIER_SYNC_TIMEOUT;
 
       while (*vlib_worker_threads->node_reforks_required > 0)
 	{
-	  if (vlib_time_now (vm) > deadline)
+	  if ((now = vlib_time_now (vm)) > deadline)
 	    {
 	      fformat (stderr, "%s: worker thread refork deadlock\n",
 		       __FUNCTION__);
@@ -1279,6 +1555,23 @@ vlib_worker_thread_barrier_release (vlib_main_t * vm)
 	    }
 	}
     }
+
+  t_closed_total = now - vm->barrier_epoch;
+
+  minimum_open = t_closed_total * BARRIER_MINIMUM_OPEN_FACTOR;
+
+  if (minimum_open > BARRIER_MINIMUM_OPEN_LIMIT)
+    {
+      minimum_open = BARRIER_MINIMUM_OPEN_LIMIT;
+    }
+
+  vm->barrier_no_close_before = now + minimum_open;
+
+  /* Record barrier epoch (used to enforce minimum open time) */
+  vm->barrier_epoch = now;
+
+  barrier_trace_release (t_entry, t_closed_total, t_update_main);
+
 }
 
 /*
diff --git a/src/vlib/threads.h b/src/vlib/threads.h
index c3f1cade..72340ee1 100644
--- a/src/vlib/threads.h
+++ b/src/vlib/threads.h
@@ -18,6 +18,22 @@
 #include <vlib/main.h>
 #include <linux/sched.h>
 
+/*
+ * To enable detailed tracing of barrier usage, including call stacks and
+ * timings, define BARRIER_TRACING here or in relevant TAGS.  If also used
+ * with CLIB_DEBUG, timing will _not_ be representative of normal code
+ * execution.
+ *
+ */
+
+// #define BARRIER_TRACING 1
+
+/*
+ * Two options for barrier tracing output: syslog & elog.
+ */
+
+// #define BARRIER_TRACING_ELOG 1
+
 extern vlib_main_t **vlib_mains;
 
 void vlib_set_thread_name (char *name);
@@ -102,6 +118,10 @@ typedef struct
   vlib_thread_registration_t *registration;
   u8 *name;
   u64 barrier_sync_count;
+#ifdef BARRIER_TRACING
+  const char *barrier_caller;
+  const char *barrier_context;
+#endif
   volatile u32 *node_reforks_required;
 
   long lwp;
@@ -179,7 +199,14 @@ u32 vlib_frame_queue_main_init (u32 node_index, u32 frame_queue_nelts);
 #define BARRIER_SYNC_TIMEOUT (1.0)
 #endif
 
-void vlib_worker_thread_barrier_sync (vlib_main_t * vm);
+#ifdef BARRIER_TRACING
+#define vlib_worker_thread_barrier_sync(X) {vlib_worker_threads[0].barrier_caller=__FUNCTION__;vlib_worker_thread_barrier_sync_int(X);}
+#else
+#define vlib_worker_thread_barrier_sync(X) vlib_worker_thread_barrier_sync_int(X)
+#endif
+
+
+void vlib_worker_thread_barrier_sync_int (vlib_main_t * vm);
 void vlib_worker_thread_barrier_release (vlib_main_t * vm);
 void vlib_worker_thread_node_refork (void);