net: Avoid modulus in skb_tx_hash() for forwarding case. (513de11b) · Commits · 戴 / test

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>

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;

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