net: don't bother calling list RX functions on empty lists

Generally the check should be very cheap, as the sk_buff_head is in cache.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 5e22719..7e6a2f6 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4887,7 +4887,8 @@ static void __netif_receive_skb_list(struct list_head *head)
 
                        /* Handle the previous sublist */
                        list_cut_before(&sublist, head, &skb->list);
-                       __netif_receive_skb_list_core(&sublist, pfmemalloc);
+                       if (!list_empty(&sublist))
+                               __netif_receive_skb_list_core(&sublist, pfmemalloc);
                        pfmemalloc = !pfmemalloc;
                        /* See comments in __netif_receive_skb */
                        if (pfmemalloc)
@@ -4897,7 +4898,8 @@ static void __netif_receive_skb_list(struct list_head *head)
                }
        }
        /* Handle the remaining sublist */
-       __netif_receive_skb_list_core(head, pfmemalloc);
+       if (!list_empty(head))
+               __netif_receive_skb_list_core(head, pfmemalloc);
        /* Restore pflags */
        if (pfmemalloc)
                memalloc_noreclaim_restore(noreclaim_flag);
@@ -5058,6 +5060,8 @@ void netif_receive_skb_list(struct list_head *head)
 {
        struct sk_buff *skb;
 
+       if (list_empty(head))
+               return;
        list_for_each_entry(skb, head, list)
                trace_netif_receive_skb_list_entry(skb);
        netif_receive_skb_list_internal(head);