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tun: compute the RFS hash only if needed.

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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 @@ build:
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);
netif_receive_skb(skb);