nat: ED: global session LRU list

Maintain a global session LRU allowing reuse of expired session instead
of relying on a scavenging mechanism to periodically walk sessions.
Whenever a new session is being allocated in slow path, also attempt to
free an expired session from global LRU list.

Type: improvement

Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: I9edde9ec138de67c9a4888e915b0490ec16415fa

1 files changed, 40 insertions, 6 deletions

diff --git a/src/plugins/nat/nat_inlines.h b/src/plugins/nat/nat_inlines.h
index bdcfd39dfb7..e5f2d96b33f 100644
--- a/src/plugins/nat/nat_inlines.h
+++ b/src/plugins/nat/nat_inlines.h
@@ -286,8 +286,9 @@ nat44_delete_user_with_no_session (snat_main_t * sm, snat_user_t * u,
 }
 
 always_inline void
-nat44_delete_session (snat_main_t * sm, snat_session_t * ses,
-		      u32 thread_index)
+nat44_delete_session_internal (snat_main_t * sm, snat_session_t * ses,
+			       u32 thread_index, int global_lru_delete
+			       /* delete from global LRU list */ )
 {
   snat_main_per_thread_data_t *tsm = vec_elt_at_index (sm->per_thread_data,
 						       thread_index);
@@ -301,6 +302,11 @@ nat44_delete_session (snat_main_t * sm, snat_session_t * ses,
 
   clib_dlist_remove (tsm->list_pool, ses->per_user_index);
   pool_put_index (tsm->list_pool, ses->per_user_index);
+  if (global_lru_delete)
+    {
+      clib_dlist_remove (tsm->global_lru_pool, ses->global_lru_index);
+    }
+  pool_put_index (tsm->global_lru_pool, ses->global_lru_index);
   pool_put (tsm->sessions, ses);
   vlib_set_simple_counter (&sm->total_sessions, thread_index, 0,
 			   pool_elts (tsm->sessions));
@@ -318,6 +324,22 @@ nat44_delete_session (snat_main_t * sm, snat_session_t * ses,
     }
 }
 
+always_inline void
+nat44_delete_session (snat_main_t * sm, snat_session_t * ses,
+		      u32 thread_index)
+{
+  return nat44_delete_session_internal (sm, ses, thread_index, 1);
+}
+
+always_inline void
+nat44_ed_delete_session (snat_main_t * sm, snat_session_t * ses,
+			 u32 thread_index, int global_lru_delete
+			 /* delete from global LRU list */ )
+{
+  return nat44_delete_session_internal (sm, ses, thread_index,
+					global_lru_delete);
+}
+
 /** \brief Set TCP session state.
     @return 1 if session was closed, otherwise 0
 */
@@ -430,10 +452,22 @@ always_inline void
 nat44_session_update_lru (snat_main_t * sm, snat_session_t * s,
 			  u32 thread_index)
 {
-  clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
-		     s->per_user_index);
-  clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
-		      s->per_user_list_head_index, s->per_user_index);
+  /* don't update too often - timeout is in a magnitude of seconds anyway */
+  if (s->last_heard > s->last_lru_update + 1)
+    {
+      clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
+			 s->per_user_index);
+      clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
+			  s->per_user_list_head_index, s->per_user_index);
+
+      clib_dlist_remove (sm->per_thread_data[thread_index].global_lru_pool,
+			 s->global_lru_index);
+      clib_dlist_addtail (sm->per_thread_data[thread_index].global_lru_pool,
+			  sm->
+			  per_thread_data[thread_index].global_lru_head_index,
+			  s->global_lru_index);
+      s->last_lru_update = s->last_heard;
+    }
 }
 
 always_inline void