From f29eb2a96c56ebff6b4d9b530d5ccd61b9f538d7 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 060135ceaf0e..a65779c6d72f 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);