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Commit 513de11b authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatarDavid S. Miller <davem@davemloft.net>
parent accc5b4f

net/core/dev.c

+6 −2
Original line number Diff line number Diff line
@@ -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;