From b790e01aee74c23a5d92576177934f13aa51f718 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 27 Sep 2010 23:05:47 +0000 Subject: [PATCH] ip_gre: lockless xmit GRE tunnels can benefit from lockless xmits, using NETIF_F_LLTX Note: If tunnels are created with the "oseq" option, LLTX is not enabled : Even using an atomic_t o_seq, we would increase chance for packets being out of order at receiver. Bench on a 16 cpus machine (dual E5540 cpus), 16 threads sending 10000000 UDP frames via one gre tunnel (size:200 bytes per frame) Before patch : real 3m0.094s user 0m9.365s sys 47m50.103s After patch: real 0m29.756s user 0m11.097s sys 7m33.012s Last problem to solve is the contention on dst : 38660.00 21.4% __ip_route_output_key vmlinux 20786.00 11.5% dst_release vmlinux 14191.00 7.8% __xfrm_lookup vmlinux 12410.00 6.9% ip_finish_output vmlinux 4540.00 2.5% ip_push_pending_frames vmlinux 4427.00 2.4% ip_append_data vmlinux 4265.00 2.4% __alloc_skb vmlinux 4140.00 2.3% __ip_local_out vmlinux 3991.00 2.2% dev_queue_xmit vmlinux Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ip_gre.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index a1b5d5e0306..035db635003 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -1557,6 +1557,10 @@ static int ipgre_newlink(struct net *src_net, struct net_device *dev, struct nla if (!tb[IFLA_MTU]) dev->mtu = mtu; + /* Can use a lockless transmit, unless we generate output sequences */ + if (!(nt->parms.o_flags & GRE_SEQ)) + dev->features |= NETIF_F_LLTX; + err = register_netdevice(dev); if (err) goto out; -- 2.20.1