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net: skb_tx_hash() fix relative to skb_orphan_try() 

commit fc6055a5ba (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>
This commit is contained in:
Eric Dumazet 2010-07-13 05:24:20 +00:00 committed by David S. Miller
parent 3a047bf87b
commit 87fd308cfc
1 changed files with 10 additions and 3 deletions
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13
net/core/dev.c
View File

@ -1911,8 +1911,16 @@ 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,
@ -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);