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Commit 87fd308c authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: skb_tx_hash() fix relative to skb_orphan_try() 



commit fc6055a5 (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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3a047bf8

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);