commit 2d18d2ea9f0e3d6c47d365ec135af651b14e8165
author Nitin Saxena <nsaxena@marvell.com> Sat Jan 04 12:28:42 2020 +0530
committer Florin Coras <florin.coras@gmail.com> Sat Jan 11 16:53:41 2020 +0000
tree 251f0dcd684503f1419379e4db3fb64afcb24859
parent dfb3e4106f8013d40522570362a776d096f51413

ip: avoid fib lookup for consecutive pkts having same source IP

Type: fix
Fixes: be2286b0

This patch does following:

- If terminating frame has consecutive packets with same source IP, this patch
  avoids fib lookup for those packets in ip4-local node. This drops cycle count
  for ip4-local node on both ARM and x86. It being done by enabling dead code in
  else {} case of ip4_local_check_src_x2() and ip4_local_check_src() functions.

- In case all packets in terminating frame have unique source IP (e.g:
  incrementing), ip4-local is costlier by 2 cycles (broadwell)

Change-Id: I472ddc324716cec8bfe601568b8aeb7565f97ab3
Signed-off-by: Nitin Saxena <nsaxena@marvell.com>

src/vnet/ip/ip4_forward.c

diff --git a/src/vnet/ip/ip4_forward.c b/src/vnet/ip/ip4_forward.c
index aa554ea..b8defc5 100644
--- a/src/vnet/ip/ip4_forward.c
+++ b/src/vnet/ip/ip4_forward.c
@@ -1504,8 +1504,8 @@
    * vnet_buffer()->ip.adj_index[VLIB_TX] will be set to the index of the
    *  adjacency for the source address (the remote sender's address)
    */
-  if (PREDICT_FALSE (last_check->first ||
-		     (last_check->src.as_u32 != ip0->src_address.as_u32)))
+  if (PREDICT_TRUE (last_check->src.as_u32 != ip0->src_address.as_u32) ||
+      last_check->first)
     {
       mtrie0 = &ip4_fib_get (vnet_buffer (b)->ip.fib_index)->mtrie;
       leaf0 = ip4_fib_mtrie_lookup_step_one (mtrie0, &ip0->src_address);
@@ -1542,6 +1542,7 @@
       last_check->src.as_u32 = ip0->src_address.as_u32;
       last_check->lbi = lbi0;
       last_check->error = *error0;
+      last_check->first = 0;
     }
   else
     {
@@ -1549,7 +1550,6 @@
 	vnet_buffer (b)->ip.adj_index[VLIB_TX];
       vnet_buffer (b)->ip.adj_index[VLIB_TX] = last_check->lbi;
       *error0 = last_check->error;
-      last_check->first = 0;
     }
 }
 
@@ -1584,7 +1584,7 @@
    * vnet_buffer()->ip.adj_index[VLIB_TX] will be set to the index of the
    *  adjacency for the source address (the remote sender's address)
    */
-  if (PREDICT_FALSE (not_last_hit))
+  if (PREDICT_TRUE (not_last_hit))
     {
       mtrie[0] = &ip4_fib_get (vnet_buffer (b[0])->ip.fib_index)->mtrie;
       mtrie[1] = &ip4_fib_get (vnet_buffer (b[1])->ip.fib_index)->mtrie;
@@ -1638,6 +1638,7 @@
       last_check->src.as_u32 = ip[1]->src_address.as_u32;
       last_check->lbi = lbi[1];
       last_check->error = error[1];
+      last_check->first = 0;
     }
   else
     {
@@ -1651,7 +1652,6 @@
 
       error[0] = last_check->error;
       error[1] = last_check->error;
-      last_check->first = 0;
     }
 }