net: skb_tx_hash() fix relative to skb_orphan_try() (87fd308c) · Commits · 戴 / test

commit (net: Introduce skb_orphan_try()) added early orphaning of skbs. This unfortunately added a performance regression in skb_tx_hash() in case of stacked devices (bonding, vlans, ...) Since skb->sk is now NULL, we cannot access sk->sk_hash anymore to spread tx packets to multiple NIC queues on multiqueue devices. skb_tx_hash() in this case only uses skb->protocol, same value for all flows. skb_orphan_try() can copy sk->sk_hash into skb->rxhash and skb_tx_hash() can use this saved sk_hash value to compute its internal hash value. Signed-off-by:

Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/core/dev.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -1911,9 +1911,17 @@ static int dev_gso_segment(struct sk_buff *skb)
		*/
		static inline void skb_orphan_try(struct sk_buff *skb)
		{
		if (!skb_tx(skb)->flags)
		struct sock *sk = skb->sk;

		if (sk && !skb_tx(skb)->flags) {
		/* skb_tx_hash() wont be able to get sk.
		* We copy sk_hash into skb->rxhash
		*/
		if (!skb->rxhash)
		skb->rxhash = sk->sk_hash;
		skb_orphan(skb);
		}
		}

		int dev_hard_start_xmit(struct sk_buff skb, struct net_device dev,
		struct netdev_queue *txq)
		@@ -1998,8 +2006,7 @@ u16 skb_tx_hash(const struct net_device dev, const struct sk_buff skb)
		if (skb->sk && skb->sk->sk_hash)
		hash = skb->sk->sk_hash;
		else
		hash = (__force u16) skb->protocol;

		hash = (__force u16) skb->protocol ^ skb->rxhash;
		hash = jhash_1word(hash, hashrnd);

		return (u16) (((u64) hash * dev->real_num_tx_queues) >> 32);

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