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>

diff --git a/net/core/dev.c b/net/core/dev.c
index efd318db11ab3732b37defcbbb9d84266e2c0732..cdbbea39c549057693a93752edf03ea73e909938 100644 (file)
--- 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];