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 <pab...@redhat.com>
---
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 @@ static int tun_xdp_one(struct tun_struct *tun,
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);
--
2.17.2
