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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 <davem@davemloft.net>
This commit is contained in:
David S. Miller 2009-05-03 14:43:10 -07:00
parent accc5b4f90
commit 513de11bba
1 changed files with 6 additions and 2 deletions
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8
net/core/dev.c
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@ -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;