FIB walk process - wake-up rate unnecessarily high

Change-Id: I7dedf283c83c7f0e0b7642f095b68bc0b40898cf
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/fib/fib_walk.c b/src/vnet/fib/fib_walk.c
index 7018013..9429744 100644
--- a/src/vnet/fib/fib_walk.c
+++ b/src/vnet/fib/fib_walk.c
@@ -399,7 +399,17 @@
  * @brief Durations for the sleep types
  */
 static f64 fib_walk_sleep_duration[] = {
-    [FIB_WALK_LONG_SLEEP] = 1e-3,
+    /**
+     * Long sleep when there is no more work, i.e. the queues are empty.
+     * This is a sleep (as opposed to a wait for event) just to be sure we
+     * are not missing events by sleeping forever.
+     */
+    [FIB_WALK_LONG_SLEEP] = 2,
+
+    /**
+     * Short sleep. There is work left in the queues. We are yielding the CPU
+     * momentarily.
+     */
     [FIB_WALK_SHORT_SLEEP] = 1e-8,
 };