From 735fc4054b3a25034445c6713d259da0f96f8131 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Thu, 24 May 2018 16:46:12 +0200 Subject: xdp: change ndo_xdp_xmit API to support bulking This patch change the API for ndo_xdp_xmit to support bulking xdp_frames. When kernel is compiled with CONFIG_RETPOLINE, XDP sees a huge slowdown. Most of the slowdown is caused by DMA API indirect function calls, but also the net_device->ndo_xdp_xmit() call. Benchmarked patch with CONFIG_RETPOLINE, using xdp_redirect_map with single flow/core test (CPU E5-1650 v4 @ 3.60GHz), showed performance improved: for driver ixgbe: 6,042,682 pps -> 6,853,768 pps = +811,086 pps for driver i40e : 6,187,169 pps -> 6,724,519 pps = +537,350 pps With frames avail as a bulk inside the driver ndo_xdp_xmit call, further optimizations are possible, like bulk DMA-mapping for TX. Testing without CONFIG_RETPOLINE show the same performance for physical NIC drivers. The virtual NIC driver tun sees a huge performance boost, as it can avoid doing per frame producer locking, but instead amortize the locking cost over the bulk. V2: Fix compile errors reported by kbuild test robot V4: Isolated ndo, driver changes and callers. Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Alexei Starovoitov --- include/linux/netdevice.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 03ed492c4e14..debdb6286170 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1185,9 +1185,13 @@ struct dev_ifalias { * This function is used to set or query state related to XDP on the * netdevice and manage BPF offload. See definition of * enum bpf_netdev_command for details. - * int (*ndo_xdp_xmit)(struct net_device *dev, struct xdp_frame *xdp); - * This function is used to submit a XDP packet for transmit on a - * netdevice. + * int (*ndo_xdp_xmit)(struct net_device *dev, int n, struct xdp_frame **xdp); + * This function is used to submit @n XDP packets for transmit on a + * netdevice. Returns number of frames successfully transmitted, frames + * that got dropped are freed/returned via xdp_return_frame(). + * Returns negative number, means general error invoking ndo, meaning + * no frames were xmit'ed and core-caller will free all frames. + * TODO: Consider add flag to allow sending flush operation. * void (*ndo_xdp_flush)(struct net_device *dev); * This function is used to inform the driver to flush a particular * xdp tx queue. Must be called on same CPU as xdp_xmit. @@ -1375,8 +1379,8 @@ struct net_device_ops { int needed_headroom); int (*ndo_bpf)(struct net_device *dev, struct netdev_bpf *bpf); - int (*ndo_xdp_xmit)(struct net_device *dev, - struct xdp_frame *xdp); + int (*ndo_xdp_xmit)(struct net_device *dev, int n, + struct xdp_frame **xdp); void (*ndo_xdp_flush)(struct net_device *dev); }; -- cgit v1.3-18-gd494