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tun: compute the RFS hash only if needed. 

The tun XDP sendmsg code path, unconditionally computes the symmetric
hash of each packet for RFS's sake, even when we could skip it. e.g.
when the device has a single queue.

This change adds the check already in-place for the skb sendmsg path
to avoid unneeded hashing.

The above gives small, but measurable, performance gain for VM xmit
path when zerocopy is not enabled.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2018-11-07 10:34:36 +01:00 committed by David S. Miller
parent 2e7ad56aa5
commit f29eb2a96c
1 changed files with 2 additions and 1 deletions
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3
drivers/net/tun.c
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@ -2448,7 +2448,8 @@ static int tun_xdp_one(struct tun_struct *tun,
goto out; goto out;
} }
if (!rcu_dereference(tun->steering_prog)) if (!rcu_dereference(tun->steering_prog) && tun->numqueues > 1 &&
!tfile->detached)
rxhash = __skb_get_hash_symmetric(skb); rxhash = __skb_get_hash_symmetric(skb);
netif_receive_skb(skb); netif_receive_skb(skb);