Commit 183dea58 authored Nov 30, 2017 by Paolo Abeni Committed by David S. Miller Dec 02, 2017

openvswitch: do not propagate headroom updates to internal port



After commit 3a927bc7 ("ovs: propagate per dp max headroom to
all vports") the need_headroom for the internal vport is updated
accordingly to the max needed headroom in its datapath.

That avoids the pskb_expand_head() costs when sending/forwarding
packets towards tunnel devices, at least for some scenarios.

We still require such copy when using the ovs-preferred configuration
for vxlan tunnels:

    br_int
  /       \
tap      vxlan
           (remote_ip:X)

br_phy
     \
    NIC

where the route towards the IP 'X' is via 'br_phy'.

When forwarding traffic from the tap towards the vxlan device, we
will call pskb_expand_head() in vxlan_build_skb() because
br-phy->needed_headroom is equal to tun->needed_headroom.

With this change we avoid updating the internal vport needed_headroom,
so that in the above scenario no head copy is needed, giving 5%
performance improvement in UDP throughput test.

As a trade-off, packets sent from the internal port towards a tunnel
device will now experience the head copy overhead. The rationale is
that the latter use-case is less relevant performance-wise.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent c5f66a85

net/openvswitch/vport-internal_dev.c

+1 −8

Original line number	Diff line number	Diff line
		@@ -126,18 +126,12 @@ internal_get_stats(struct net_device dev, struct rtnl_link_stats64 stats)
		}
		}

		static void internal_set_rx_headroom(struct net_device *dev, int new_hr)
		{
		dev->needed_headroom = new_hr < 0 ? 0 : new_hr;
		}

		static const struct net_device_ops internal_dev_netdev_ops = {
		.ndo_open = internal_dev_open,
		.ndo_stop = internal_dev_stop,
		.ndo_start_xmit = internal_dev_xmit,
		.ndo_set_mac_address = eth_mac_addr,
		.ndo_get_stats64 = internal_get_stats,
		.ndo_set_rx_headroom = internal_set_rx_headroom,
		};

		static struct rtnl_link_ops internal_dev_link_ops __read_mostly = {
		@@ -154,7 +148,7 @@ static void do_setup(struct net_device *netdev)

		netdev->priv_flags &= ~IFF_TX_SKB_SHARING;
		netdev->priv_flags \|= IFF_LIVE_ADDR_CHANGE \| IFF_OPENVSWITCH \|
		IFF_PHONY_HEADROOM \| IFF_NO_QUEUE;
		IFF_NO_QUEUE;
		netdev->needs_free_netdev = true;
		netdev->priv_destructor = internal_dev_destructor;
		netdev->ethtool_ops = &internal_dev_ethtool_ops;
		@@ -195,7 +189,6 @@ static struct vport internal_dev_create(const struct vport_parms parms)
		err = -ENOMEM;
		goto error_free_netdev;
		}
		vport->dev->needed_headroom = vport->dp->max_headroom;

		dev_net_set(vport->dev, ovs_dp_get_net(vport->dp));
		internal_dev = internal_dev_priv(vport->dev);