Add packet tracing hint

This avoids checking the buffer flags bit if tracing is not enabled.

Change-Id: I32e1a90b5fd10318254c611344488bc2a441c71e
Signed-off-by: Todd Foggoa (tfoggoa) <tfoggoa@cisco.com>

3 files changed, 40 insertions, 27 deletions

diff --git a/vlib/vlib/trace.c b/vlib/vlib/trace.c
index b3008644e5d..4a611ee97b1 100644
--- a/vlib/vlib/trace.c
+++ b/vlib/vlib/trace.c
@@ -121,6 +121,8 @@ clear_trace_buffer (void)
     tm = &this_vlib_main->trace_main;
     mainheap = clib_mem_set_heap (this_vlib_main->heap_base);
 
+    tm->trace_active_hint = 0;
+
     for (i = 0; i < vec_len (tm->trace_buffer_pool); i++)
       if (! pool_is_free_index (tm->trace_buffer_pool, i))
         vec_free (tm->trace_buffer_pool[i]);
@@ -369,6 +371,8 @@ cli_add_trace_buffer (vlib_main_t * vm,
     void *oldheap;
     tm = &this_vlib_main->trace_main;
 
+    tm->trace_active_hint = 1;
+
     oldheap = clib_mem_set_heap (this_vlib_main->heap_base);
 
     vec_validate (tm->nodes, node_index);
diff --git a/vlib/vlib/trace.h b/vlib/vlib/trace.h
index 50e51638fdb..fe5d7377861 100644
--- a/vlib/vlib/trace.h
+++ b/vlib/vlib/trace.h
@@ -76,6 +76,9 @@ typedef struct {
 #define FILTER_FLAG_EXCLUDE 2
   u32 filter_count;
 
+  /* set on trace add, cleared on clear trace */
+  u32 trace_active_hint;
+
   /* Per node trace counts. */
   vlib_trace_node_t * nodes;
 } vlib_trace_main_t;
diff --git a/vnet/vnet/devices/dpdk/node.c b/vnet/vnet/devices/dpdk/node.c
index 575f7f4e972..b9815706169 100644
--- a/vnet/vnet/devices/dpdk/node.c
+++ b/vnet/vnet/devices/dpdk/node.c
@@ -154,25 +154,28 @@ handoff_dispatch_node_fn (vlib_main_t * vm,
           next0 = vnet_buffer(b0)->io_handoff.next_index;
           next1 = vnet_buffer(b1)->io_handoff.next_index;
 
-          if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
+          if (PREDICT_FALSE(vm->trace_main.trace_active_hint))
             {
-              vlib_trace_buffer (vm, node, next0, b0, /* follow_chain */ 0);
-              handoff_dispatch_trace_t *t =
-                vlib_add_trace (vm, node, b0, sizeof (*t));
-              sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
-              t->sw_if_index = sw_if_index0;
-              t->next_index = next0;
-              t->buffer_index = bi0;
-            }
-          if (PREDICT_FALSE(b1->flags & VLIB_BUFFER_IS_TRACED))
-            {
-              vlib_trace_buffer (vm, node, next1, b1, /* follow_chain */ 0);
-              handoff_dispatch_trace_t *t =
-                vlib_add_trace (vm, node, b1, sizeof (*t));
-              sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_RX];
-              t->sw_if_index = sw_if_index1;
-              t->next_index = next1;
-              t->buffer_index = bi1;
+            if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
+              {
+                vlib_trace_buffer (vm, node, next0, b0, /* follow_chain */ 0);
+                handoff_dispatch_trace_t *t =
+                  vlib_add_trace (vm, node, b0, sizeof (*t));
+                sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+                t->sw_if_index = sw_if_index0;
+                t->next_index = next0;
+                t->buffer_index = bi0;
+              }
+            if (PREDICT_FALSE(b1->flags & VLIB_BUFFER_IS_TRACED))
+              {
+                vlib_trace_buffer (vm, node, next1, b1, /* follow_chain */ 0);
+                handoff_dispatch_trace_t *t =
+                  vlib_add_trace (vm, node, b1, sizeof (*t));
+                sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_RX];
+                t->sw_if_index = sw_if_index1;
+                t->next_index = next1;
+                t->buffer_index = bi1;
+              }
             }
             
           /* verify speculative enqueues, maybe switch current next frame */
@@ -200,16 +203,19 @@ handoff_dispatch_node_fn (vlib_main_t * vm,
 
           next0 = vnet_buffer(b0)->io_handoff.next_index;
 
-          if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
+          if (PREDICT_FALSE(vm->trace_main.trace_active_hint))
             {
-              vlib_trace_buffer (vm, node, next0, b0, /* follow_chain */ 0);
-              handoff_dispatch_trace_t *t =
-                vlib_add_trace (vm, node, b0, sizeof (*t));
-              sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
-              t->sw_if_index = sw_if_index0;
-              t->next_index = next0;
-              t->buffer_index = bi0;
-           }
+            if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
+              {
+                vlib_trace_buffer (vm, node, next0, b0, /* follow_chain */ 0);
+                handoff_dispatch_trace_t *t =
+                  vlib_add_trace (vm, node, b0, sizeof (*t));
+                sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+                t->sw_if_index = sw_if_index0;
+                t->next_index = next0;
+                t->buffer_index = bi0;
+              }
+            }
 
           /* verify speculative enqueue, maybe switch current next frame */
 	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index,