From 4a528b03358b156b776d12f27d792ea0e8f35285 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Wed, 7 Nov 2018 10:34:36 +0100 Subject: [PATCH] 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 Acked-by: Jason Wang Signed-off-by: David S. Miller --- drivers/net/tun.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 060135ceaf0e1..a65779c6d72ff 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -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); -- 2.39.5