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Commit ec581f6a authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: Fix skb_tx_hash() for forwarding workloads. 



When skb_rx_queue_recorded() is true, we dont want to use jash distribution
as the device driver exactly told us which queue was selected at RX time.
jhash makes a statistical shuffle, but this wont work with 8 static inputs.

Later improvements would be to compute reciprocal value of real_num_tx_queues
to avoid a divide here. But this computation should be done once,
when real_num_tx_queues is set. This needs a separate patch, and a new
field in struct net_device.

Reported-by: default avatarAndrew Dickinson <andrew@whydna.net>
Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7a67e56f

net/core/dev.c

+5 −4
Original line number Diff line number Diff line
@@ -1735,11 +1735,12 @@ u16 skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb) 
{

	u32 hash;



	if (skb_rx_queue_recorded(skb)) {

		hash = skb_get_rx_queue(skb);

	} else if (skb->sk && skb->sk->sk_hash) {

	if (skb_rx_queue_recorded(skb))

		return skb_get_rx_queue(skb) % dev->real_num_tx_queues;



	if (skb->sk && skb->sk->sk_hash)

		hash = skb->sk->sk_hash;

	} else

	else

		hash = skb->protocol;



	hash = jhash_1word(hash, skb_tx_hashrnd);