net: rps: add the shortcut for one rps_cpus

When there is only one rps_cpus, skb_get_rxhash() can be eliminated.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 3 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index efd318db11ab..cdbbea39c549 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2343,7 +2343,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
                        struct rps_dev_flow **rflowp)
 {
         struct netdev_rx_queue *rxqueue;
-        struct rps_map *map;
+        struct rps_map *map = NULL;
         struct rps_dev_flow_table *flow_table;
         struct rps_sock_flow_table *sock_flow_table;
         int cpu = -1;
@@ -2361,8 +2361,17 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
         } else
                 rxqueue = dev->_rx;
 
-        if (!rxqueue->rps_map && !rxqueue->rps_flow_table)
+        if (rxqueue->rps_map) {
+                map = rcu_dereference(rxqueue->rps_map);
+                if (map && map->len == 1) {
+                        tcpu = map->cpus[0];
+                        if (cpu_online(tcpu))
+                                cpu = tcpu;
+                        goto done;
+                }
+        } else if (!rxqueue->rps_flow_table) {
                 goto done;
+        }
 
         skb_reset_network_header(skb);
         if (!skb_get_rxhash(skb))
@@ -2407,7 +2416,6 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
                 }
         }
 
-        map = rcu_dereference(rxqueue->rps_map);
         if (map) {
                 tcpu = map->cpus[((u64) skb->rxhash * map->len) >> 32];