From 513de11bba246b7a67df4c314d9fc936b6a75d0e Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Sun, 3 May 2009 14:43:10 -0700 Subject: [PATCH] net: Avoid modulus in skb_tx_hash() for forwarding case. Based almost entirely upon a patch by Eric Dumazet. The common case is to have num-tx-queues <= num_rx_queues and even if num_tx_queues is larger it will not be significantly larger. Therefore, a subtraction loop is always going to be faster than modulus. Signed-off-by: David S. Miller --- net/core/dev.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 81442957c5c2..3c8073fe970a 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1735,8 +1735,12 @@ u16 skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb) { u32 hash; - if (skb_rx_queue_recorded(skb)) - return skb_get_rx_queue(skb) % dev->real_num_tx_queues; + if (skb_rx_queue_recorded(skb)) { + hash = skb_get_rx_queue(skb); + while (unlikely (hash >= dev->real_num_tx_queues)) + hash -= dev->real_num_tx_queues; + return hash; + } if (skb->sk && skb->sk->sk_hash) hash = skb->sk->sk_hash;