Netmap: Fix Netmap Polling Issue

Previously, netmap node switched from interrupt to polling if
worker threads are enabled even if there was no netmap interface
running. Netmap input node consumed CPU cycles because of input
node calls but these cycles were wasted as input node did not have
any packet to process.

This patch fixes issue stated above using more intelligent way of enabling
or disabling polling based on interfaces count. But the pre-requisite
condition for polling is, worker thread(s) should be enabled.

Change-Id: I3a901823c7b040cce3393958981f439b9f290fe5
Signed-off-by: Mohsin KAZMI <sykazmi@cisco.com>

1 files changed, 31 insertions, 7 deletions

diff --git a/vnet/vnet/devices/netmap/netmap.c b/vnet/vnet/devices/netmap/netmap.c
index 653ebc203c0..7f1cadd7951 100644
--- a/vnet/vnet/devices/netmap/netmap.c
+++ b/vnet/vnet/devices/netmap/netmap.c
@@ -79,6 +79,29 @@ close_netmap_if(netmap_main_t * nm, netmap_if_t * nif)
 }
 
 int
+netmap_worker_thread_enable()
+{
+  /* if worker threads are enabled, switch to polling mode */
+  foreach_vlib_main (
+  ({
+      vlib_node_set_state(this_vlib_main, netmap_input_node.index, VLIB_NODE_STATE_POLLING);
+  }));
+
+  return 0;
+}
+
+int
+netmap_worker_thread_disable()
+{
+  foreach_vlib_main (
+  ({
+      vlib_node_set_state(this_vlib_main, netmap_input_node.index, VLIB_NODE_STATE_INTERRUPT);
+  }));
+
+  return 0;
+}
+
+int
 netmap_create_if(vlib_main_t * vm, u8 * if_name, u8 * hw_addr_set,
 		 u8 is_pipe, u8 is_master, u32 *sw_if_index)
 {
@@ -202,6 +225,9 @@ netmap_create_if(vlib_main_t * vm, u8 * if_name, u8 * hw_addr_set,
   if (sw_if_index)
     *sw_if_index = nif->sw_if_index;
 
+  if (tm->n_vlib_mains > 1 && pool_elts(nm->interfaces) == 1)
+    netmap_worker_thread_enable();
+
   return 0;
 
 error:
@@ -216,6 +242,7 @@ netmap_delete_if(vlib_main_t *vm, u8 *host_if_name)
   netmap_main_t *nm = &netmap_main;
   netmap_if_t *nif;
   uword *p;
+  vlib_thread_main_t * tm = vlib_get_thread_main();
 
   p = mhash_get(&nm->if_index_by_host_if_name, host_if_name);
   if (p == NULL) {
@@ -230,6 +257,10 @@ netmap_delete_if(vlib_main_t *vm, u8 *host_if_name)
   ethernet_delete_interface(vnm, nif->hw_if_index);
 
   close_netmap_if(nm, nif);
+
+  if (tm->n_vlib_mains > 1 && pool_elts(nm->interfaces) == 0)
+    netmap_worker_thread_disable();
+
   return 0;
 }
 
@@ -256,13 +287,6 @@ netmap_init (vlib_main_t * vm)
       nm->input_cpu_count = tr->count;
     }
 
-  /* if worker threads are enabled, switch to polling mode */
-  if (tm->n_vlib_mains > 1)
-    foreach_vlib_main (
-    ({
-        vlib_node_set_state(this_vlib_main, netmap_input_node.index, VLIB_NODE_STATE_POLLING);
-    }));
-
   mhash_init_vec_string (&nm->if_index_by_host_if_name, sizeof (uword));
 
   vec_validate_aligned (nm->rx_buffers, tm->n_vlib_mains - 1,